A Phase 2/3, Double-Blind, Randomized, Placebo-Controlled, Parallel Group, Multicenter Study to Evaluate the Efficacy and Safety of Ravulizumab in Adult Participants With Dermatomyositis
Phase: PHASE2
Conditions: Dermatomyositis
Sponsor: Alexion Pharmaceuticals, Inc.

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TITLE PAGE 
Protocol Title: A Phase 2/3, Double-Blind, Randomized, Placebo-Controlled, Parallel Group, 
Multicenter Study to Evaluate the Efficacy and Safety of Ravulizumab in Adult Participants with 
Dermatomyositis.  
Protocol Number: ALXN1210-DM-310 
Amendment Number: 3.0 
Compound: Ravulizumab (ALXN1210) 
Study Phase: Phase 2/3 
Brief Title: Ravulizumab versus Placebo in Adult Participants with Dermatomyositis 
Sponsor Name: Alexion Pharmaceuticals, Inc. 
Legal Registered Address: 
121 Seaport Boulevard 
Boston MA 02210 
USA 
Regulatory Agency Identifier Number(s) 
IND Number: 152551 
EudraCT: 2021-001200-15 (formerly) 
EU CT Number: 2023-503478-19-00 
Release Date: 23 Jun 2023 
Sponsor Signatory: 
Date 
Medical Monitor Name and Contact Information will be provided separately 
NCT #: NCT04999020

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INVESTIGATOR’S AGREEMENT 
I have read the study protocol and agree to conduct the study in accordance with this protocol, all 
applicable government regulations, the principles of the International Council for Harmonisation 
of Technical Requirements for Pharmaceuticals for Human Use (ICH) E6 Guideline for Good 
Clinical Practice, and the principles of the World Medical Association Declaration of Helsinki. I 
also agree to maintain the confidentiality of all information received or developed in connection 
with this protocol. 
 
 
 
 
____________________________________ 
Printed Name of Investigator 
 
_____________________________________ 
Signature of Investigator 
 
 
_______________ 
Date 

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PROTOCOL AMENDMENT SUMMARY OF CHANGES 
This summary indicates the major changes made to Protocol ALXN1210-DM-310, Amendment 
2.0. 
Amendment 3 (23 Jun 2023) 
This modification is considered to be substantial based on the criteria set forth in Article 10(a) of 
Directive 2001/20/EC and in the EU CTR 536/2014 Article 2, 2 (13). 
Overall Rationale for the Amendment: 
The primary reasons for this modification are: 
The extension of the Randomized Controlled Period (RCP) of study Part B (Phase 3) from 
26 weeks to 50 weeks. Extension for approximately 1 year will allow for prolonged assessment 
of the effects of ravulizumab versus placebo in adult participants with DM, given that DM is a 
progressive chronic condition. This extension will also be in line with regulatory authority 
requests. 
The extension of the Open-Label Extension Period (OLE) of study Part A (Phase 2) from 
74 weeks up to 130 weeks to ensure treatment continuity for patients.  
 
Additionally, modifications have been added to address the requirements for conducting a 
clinical study under the European Union Clinical Trials Regulation (EU CTR).  
Further modifications include nonsubstantial changes, minor corrections, and harmonized 
terminology. 
 
Section # and Name 
Description of Change 
Brief Rationale 
Modifications describing the extended Open-Label Extension Period (OLE) Period of study Part 
A and the extended Randomized Controlled Period (RCP) of study Part B 
Section 1.1 Synopsis 
Section 3 Objectives, 
Estimands and/or Endpoints 
Changed study Part B endpoints for the RCP 
from Week 26 to Week 50 assessments. 
Changed endpoints/estimands for the OLE 
Periods from Week 100 to Week 156 (Part A) 
and from Week 100 to Week 124 (Part B).  
Extension of Part B 
RCP to a duration of 
50 weeks based on 
regulatory authority 
(FDA) request.  
To reflect extension 
of study Part A OLE 
Period up to 
130 weeks. 

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Section # and Name 
Description of Change 
Brief Rationale 
Section 1.1 Synopsis, Overall 
Design, 
Section 1.2 Schema, 
Section 4.1 Overall Design, 
Section 4.2.1 Study 
Population and Treatment 
Duration, 
Section 6.3.2 Blinding, 
Section 6.5.3 Acute Therapy 
with Standard DM Treatment, 
Section 9 Statistical 
Considerations, 
and throughout protocol  
Changed study Part B RCP duration from 
26 weeks to 50 weeks for a total duration of 
study Part B of up to 124 weeks 
(approximately 2.5 years). 
Extension of Part B 
RCP to a duration of 
50 weeks based on 
regulatory authority 
(FDA) request. 
Section 1.1 Synopsis, Overall 
Design, 
Section 1.2 Schema, 
Section 4.1 Overall Design, 
and throughout protocol 
Changed study Part A OLE Period from 
74 weeks up to 130 weeks for a total duration 
of study Part A of up to 156 weeks 
(approximately 3 years). 
To reflect extension 
of study Part A 
OLE Period up to 
130 weeks. 
Section 1.1 Synopsis, 
Intervention Groups and 
Duration, 
Section 4.4 End of Study 
Definition 
Added additional exit options for participants 
discontinuing from the study before end of the 
OLE Period: 
Participants may continue to receive 
ravulizumab until either: 
a) The end of the respective OLE Period 
b) Ravulizumab is registered or approved 
(in accordance with country-specific 
regulations),  
c) An alternative option for example 
transition to a rollover study or an 
early access program is provided 
To provide an exit 
strategy for 
participants 
discontinuing from 
the study before end 
of the OLE Period. 
Section 1.3 Schedule of 
Activities, Table 2 
Added a separate schedule of activities (SoA) 
table for study Part B RCP to account for the 
additional study visits during the extended 
RCP. 
Extension of Part B 
RCP to a duration of 
50 weeks based on 
regulatory authority 
(FDA) request. 

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Section # and Name 
Description of Change 
Brief Rationale 
Section 1.3 Schedule of 
Activities, Table 3, Table 4, 
and Table 5 
Added 2 additional separate SoA tables for 
study Part A OLE to account for the additional 
study visits during the extended OLE Period. 
 
Updated Table 5 (Part B, OLE) to reflect 
updated study visit days. 
To reflect extension 
of study Part A OLE 
Period up to 
130 weeks. 
To reflect changed 
study visit days in 
Part B OLE based on 
extended Part B 
RCP. 
Section 6.1.1. Study 
Intervention(s) Administered, 
Table 12 and Table 13 
Adjusted study intervention dosing days to the 
extended OLE Period of study Part A and 
extended RCP of study Part B. 
To reflect extension 
of study Part B RCP 
to 50 weeks and 
extension of study 
Part A OLE Period 
up to 130 weeks. 
Requirements for conducting a clinical study under the European Union Clinical Trials 
Regulation (EU CTR) 
TITLE PAGE and Section 1.1 
Synopsis 
Added regulatory agency identifier number 
(EU CT number). 
Changed Short Title to Brief Title. 
Updated in 
accordance with EU 
CTR. 
Section 1.1 Synopsis  
Added text on Ethical Considerations and 
Benefit-Risk Assessment. 
Added Brief Summary of synopsis comprising 
study Part A and Part B. 
Updated in 
accordance with EU 
CTR. 
Section 2.3.1 Risk 
Assessment 
Updated wording on immunogenicity risk 
mitigation strategy. 
To clarify 
instructions to 
Investigators in case 
of potential 
immunogenicity 
reactions. 
Section 3.1.1 Primary 
Estimand for Part A and 
throughout protocol 
Change of terminology: “stable background 
DM treatments” to “stable allowed 
concomitant DM treatments”; modified 
throughout document. 
Updated in 
accordance with EU 
CTR.  
Section 6.1 Study 
Intervention(s) Administered 
Added AxMP = auxiliary medicinal product. 
Updated in 
accordance with EU 
CTR. 
Section 6.2 
Preparation/Handling/Storage/ 
Accountability 
Added details on study intervention 
accountability. 
Updated in 
accordance with EU 
CTR. 
Section 6.5.3 Acute Therapy 
with Standard DM Treatment 
(formerly: Rescue Therapy) 
and throughout protocol  
Change of terminology: “rescue therapy” to 
“acute therapy with standard DM 
treatment”; modified throughout document. 
Updated in 
accordance with EU 
CTR. 

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Section # and Name 
Description of Change 
Brief Rationale 
Section 8.3.4 Regulatory 
Reporting Requirements for 
SAEs,  
Section 10.4.5 Unexpected 
Events 
Described reporting requirements and 
provided definition of unexpected events, 
respectively. 
Updated in 
accordance with EU 
CTR. 
Section 8.3.5 and 
Section 10.5, Medication 
Error, Drug Abuse, and Drug 
Misuse 
Provided definition and examples of 
medication error, drug abuse, and drug misuse 
and described reporting requirements. 
Updated in 
accordance with EU 
CTR. 
Section 8.4 Treatment of 
Overdose 
Described reporting requirements. 
Updated in 
accordance with EU 
CTR. 
Section 8.5 Pharmacokinetics 
and Pharmacodynamics, 
Section 8.7.1 Blood 
Exploratory Biomarkers. 
Section 8.7.2 Additional 
Biomarker Research, 
Section 8.8 Immunogenicity 
Assessments, 
Section 10.2.1 Regulatory and 
Ethical Considerations, 
Section 10.2.5 Data 
Protection, 
Section 10.2.7 Quality Data 
Assurance 
Added additional details on data collection, 
data storage, and data protection. 
Specified that applicable regulations will 
apply. 
Specified that serious breaches will include 
data breaches compromising the integrity, 
confidentiality, or availability of the personal 
data of participants. 
Outlined measures in case of personal data 
breaches. 
Added that unique identifiers will be assigned 
to participants by a Trusted Third Party 
contracted by Alexion or by a Principal 
Investigator. 
Specified that personal study-related data will 
also be decoded (pseudonymized). 
Added paragraphs detailing data protection 
regulations and measures to protect coded 
study data. 
Added details on legal protection of 
participant data. 
Specified storage requirements for study 
data/documents (at least 30 years after study 
completion). 
Updated in 
accordance with EU 
CTR and as per RFI 
received for another 
Alexion clinical 
study with 
ravulizumab. 

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Section # and Name 
Description of Change 
Brief Rationale 
Section 10.2.1 Regulatory and 
Ethical Considerations 
Added definition and process for reporting 
serious breaches. 
 
Removed statement on UK regulations. 
 
 
Removed substantial:  The protocol, 
substantial protocol amendments … 
Updated in 
accordance with EU 
CTR. 
UK-specific 
regulations are now 
covered under 
country-specific 
regulations as per 
EU CTR. 
Section 10.2.4 Recruitment 
Strategy 
Added new section to describe recruitment 
strategy for the study. 
Updated in 
accordance with EU 
CTR. 
Section 10.2.5 Data 
Protection 
Added paragraphs which outline requirement 
for 
a) Data protection and handling 
responsibilities between Alexion and study 
site(s) to be captured in contract 
b) Information technology systems to ensure 
data protection 
Updated in 
accordance with EU 
CTR. 
10.2.7 Data Quality 
Assurance 
Specified: Records and documents, including 
signed ICFs, pertaining to the conduct of this 
study must be retained by the Investigator for 
at least 30 years after study completion or 
longer as per local regulations or institutional 
policies. 
Updated in 
accordance with EU 
CTR. 
Section 10.2.9 Study and Site 
Start and Closure 
Clarified study start date as the date on which 
the clinical study will be open for recruitment 
of participants (ie, first site activation). 
Updated in 
accordance with EU 
CTR. 
Other substantial changes, nonsubstantial changes, corrections, and harmonized terminology 
Section 1.1 Synopsis, Overall 
Design, 
Section 4.1.1 Part A (Phase 2 
Portion) 
Section 4.1.2 Part B (Phase 3 
Portion) 
Modified statement: Participants (in the OLE 
Period) who discontinue study 
interventionwill are encouraged to complete 
the visits and assessments of the OLE Period. 
For clarification. 
Section 1.3 SoA, Table 1 
Added urinalysis and clinical laboratory tests 
on Day 15 
Correction. 
Section 1.3 SoA, Table 2 
“Ravulizumab infusion” was added for 
Unscheduled Visits 
 
Addition to ensure 
consistency with 
respective footnote. 

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Section # and Name 
Description of Change 
Brief Rationale 
Section 3.1.1.1 Primary 
Analysis for Part A 
Discontinuation of study intervention due to 
death added as an intercurrent event. 
 
Ensures missing data 
following death 
would be considered 
a non-responder for 
the primary analyses 
in Parts A and B.  
Section 4.1.3 Clinical 
Worsening 
Specified that clinical worsening criteria will 
be assessed at the visits described in 
Section 1.3 until the End of Study for all parts 
of the study. 
Rearranged section. 
For clarification, 
understandability, 
and increased patient 
centricity. 
Section 4.3 Justification for 
Dose 
Specified that ravulizumab dosing regimen is 
identical to approved weight-based dosing and 
is targeting immediate, complete and sustained 
inhibition of terminal complement. 
For clarification. 
Section 5.2 Exclusion 
Criteria; 
Criteria #1  
Changed:  
“(except basal or squamous cell skin cancer or 
carcinoma in situ of the cervix that has been 
excised and cured and at least 3 months 
before Screening).” 
to 
“(except basal or squamous cell skin cancer or 
carcinoma in situ of the cervix that has been 
excised and cured for at least 3 months before 
Screening).” 
Correction. 
Section 6.1.1 Study 
Intervention(s) Administered 
Section 6.1.1.1 Part A 
Section 6.1.1.2 Part B 
Added statement that the initial loading dose 
will be administered at the beginning of the 
RCP and the OLE followed by maintenance 
dosing initiated 2 weeks after loading dose.  
Changed: “…will receive open-label 
ravulizumab … until the end of the OLE 
Period” to “…until the last scheduled dose 
at Week 148” (Part A) and “…until the last 
scheduled dose at Week 116” (Part B). 
Modified for 
clarification and to 
reflect the modified 
study design. 

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Section # and Name 
Description of Change 
Brief Rationale 
Section 6.3.2 Blinding 
 
 
 
 
 
 
Section 9.5.1 Part A Interim 
Analyses 
Unblinded information will only be accessible 
to those who need to be involved in the safety 
reporting to Health Authorities, Independent 
Ethics Committees (IECs), Institutional 
Review Boards (IRBs), and/or IDMC.  
Moved information on discontinuation of 
unblinded participants to the end of the 
section. 
Added statement on potential additional 
analyses in Part A (at the time of the interim 
analyses) which may be generated and 
reviewed by an unblinded team (independent 
of the study team). 
Correction and for 
transparency. 
Section 6.5.1.2  
Other Allowed Therapies 
Changed “below” to “above”: “However, 
participants taking the medications listed 
below above at a stable dose for at least 4 
weeks before Screening are allowed to 
continue these medications.” 
The modification is also captured in 
administrative letter 3.  
Correction. 
Section 7.1 Discontinuation of 
Study Intervention 
Specified that the Investigator’s decision to 
discontinue study intervention should be based 
on a documented safety concern or AE or lack 
of improvement.  
Added that discontinuation of study 
intervention should also be considered in case 
of Clinical Worsening. 
Corrected hyperlink to Section 6.5.3 for acute 
therapy with standard DM treatment. 
Modified for 
clarification.  
 
 
 
 
Correction. 
Section 7.2 Participant 
Discontinuation/Withdrawal 
from the Study 
Specified that consent can be withdrawn by a 
participant at any time, and removed 
possibility for participant withdrawal by the 
Investigator. 
Update based on 
FDA feedback. 
Section 8.1.11 Handheld 
Dynamometry 
Handheld dynamometry will be assessed at 
screening and timepoints specified in the SoA. 
Correction, 
alignment with SoA. 

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Section # and Name 
Description of Change 
Brief Rationale 
Section 8.1.9 
Dermatomyositis Disease 
Symptoms Questionnaire 
(DM-DSQ), 
Section 10.8.13 
Dermatomyositis Disease 
Symptoms Questionnaire 
(DM-DSQ) 
Added that DM-DSQ version 1.1 will be used 
in the Part A RCP and OLE Period while DM-
DSQ version 5.0 will be used in the Part B 
RCP and OLE Period. 
Clarification. 
Section 8.8 Immunogenicity 
Assessments 
Specified that validated rather than 
validated/qualified assays will be used. 
Correction according 
to current 
immunogenicity 
wording. 
Section 9.3 Populations for 
Analyses, Table 17; 
Section 9.4.3.2 Analysis of 
Immunogenicity 
Changed ADA Analysis Set (AAS) to 
Immunogenicity Analysis Set (IAS). 
 
Specified that immunogenicity results will be 
analyzed by summarizing the number and 
percentage of participants who develop 
confirmed positive ADAs according to their 
ADA response status. 
Updated 
terminology. 
9.4.1.1.1. Analyses of Primary 
Efficacy Endpoint for Part A 
Revised primary analysis to remove weighted 
Generalized Estimating Equations (wGEE) 
model and replace with Barnard’s 
unconditional exact test for difference of 
proportions. 
 
Revised method 
proposed to simplify 
the statistical 
inference and to 
enable use of single 
imputation for 
missing TIS data. 
Section 9.4.1.1.2 Analyses of 
Secondary Efficacy Endpoint 
for Part A 
Removed wGEE and logistic model for 
secondary endpoints in Part A. 
To align analysis 
method for 
secondary binary 
endpoints with the 
primary endpoint 
Section 9.4.1.2.1 Analyses of 
Primary Efficacy Estimand 
and/or Endpoint for Part B 
Revised primary analysis from wGEE to a 
Cochran-Mantel Haenszel (CMH) test with 
Multiple Imputation (MI) for missing data not 
due to intercurrent events. 
Revised method to 
simplify the 
statistical inference 
and to enable use of 
multiple imputation 
for missing TIS data.  
Section 9.4.1.2.2 Sensitivity 
Analysis for the Primary 
Estimand for Part B 
Removed reference of observation weighting  
 
 
 
Edits to purpose of the sensitivity analyses.  
No longer applicable 
due to revised 
primary endpoint 
analysis,  
For clarification of 
sensitivity analyses. 

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Section # and Name 
Description of Change 
Brief Rationale 
Section 9.4.1.2.4 Analyses of 
Key Secondary Efficacy 
Endpoint(s) for Part B 
Removed adjusted baseline covariates. 
To align with revised 
approach in 9.4.1.2.1 
Section 9.4.1.2.5 Multiplicity 
Adjustment for Part B 
Minor edits. 
For clarification. 
Section 9.5.1 Part A Interim 
Analyses 
Added statement on potential additional 
analysis in Part A (at the time of the interim 
analysis which may be generated and 
reviewed by an unblinded team (independent 
of the study study). 
For clarification . 
Section 9.5.2 Part B Interim 
Analyses 
Revised the Sample Size Reestimation (SSR) 
to align with the primary endpoint and 
changed the percentage of participants from 
50% to 30%. Further clarification regarding 
SSR.  
To align with revised 
primary endpoint 
and to include 
additional details of 
SSR for clarification. 
Section 9.6 Data Monitoring 
Committee 
Corrected DMC to IDMC in 2 instances as 
IDMC is used for study. 
Correction. 
Section 10.2.6 Dissemination 
of Study Data 
Outlined that the results will be posted after 
the global end of the study. 
For clarification. 
Section 10.8 Clinical 
Outcome Assessment 
Changed appendix header from Participant-
Reported Outcome Instruments to Clinical 
Outcome Assessments 
Modified appendix 
heading to reflect 
clinical assessment 
of outcome 
measures. 
Throughout 
Specified Phase 2 for study Part A and 
Phase 3 for study Part B where applicable. 
For clarification. 
Throughout 
Orthographic corrections were made 
throughout the document.  
Correction. 
Abbreviations: ADA = antidrug antibody; AE = adverse event; DM = dermatomyositis; DMC = Data Monitoring 
Committee; ICF = informed consent form; IDMC = Independent Data Monitoring Committee; SAE = serious 
adverse event 

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TABLE OF CONTENTS 
TITLE PAGE ...................................................................................................................................1 
INVESTIGATOR’S AGREEMENT ...............................................................................................2 
PROTOCOL AMENDMENT SUMMARY OF CHANGES ..........................................................3 
TABLE OF CONTENTS ...............................................................................................................12 
LIST OF TABLES .........................................................................................................................18 
LIST OF FIGURES .......................................................................................................................19 
1. 
PROTOCOL SUMMARY ..........................................................................................20 
1.1. 
Synopsis ......................................................................................................................20 
1.2. 
Schema ........................................................................................................................28 
1.3. 
Schedule of Activities .................................................................................................29 
2. 
INTRODUCTION ......................................................................................................58 
2.1. 
Study Rationale ...........................................................................................................58 
2.2. 
Dermatomyositis Background ....................................................................................59 
2.2.1. 
Abnormal Complement Activation in DM Pathogenesis ...........................................59 
2.3. 
Benefit/Risk Assessment ............................................................................................60 
2.3.1. 
Risk Assessment .........................................................................................................61 
2.3.1.1. 
Coronavirus Disease 2019 ..........................................................................................62 
2.3.2. 
Benefit Assessment .....................................................................................................62 
2.3.3. 
Overall Benefit: Risk Conclusion ...............................................................................62 
3. 
OBJECTIVES AND ESTIMANDS AND/OR ENDPOINTS ....................................63 
3.1. 
Primary Estimand(s) ...................................................................................................71 
3.1.1. 
Primary Estimand for Part A ......................................................................................71 
3.1.2. 
Primary Estimand for Part B .......................................................................................72 
3.2. 
Secondary Estimands ..................................................................................................72 
3.3. 
Exploratory Estimands ................................................................................................72 
4. 
STUDY DESIGN .......................................................................................................73 
4.1. 
Overall Design ............................................................................................................73 
4.1.1. 
Part A (Phase 2 Portion) .............................................................................................73 
4.1.2. 
Part B (Phase 3 Portion) .............................................................................................74 
4.1.3. 
Clinical Worsening .....................................................................................................75 
4.1.4. 
Completion of Treatment ............................................................................................75 

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4.1.5. 
Completion of Randomized Controlled Period and OLE Period ...............................76 
4.2. 
Scientific Rationale for Study Design ........................................................................76 
4.2.1. 
Study Population and Treatment Duration .................................................................76 
4.2.2. 
Rationale for Primary Endpoint: International Myositis Assessment and 
Clinical Studies-Total Improvement Score (IMACS-TIS) .........................................77 
4.2.3. 
Rationale for Secondary Endpoints included in the Multiplicity Adjustment 
for Part B .....................................................................................................................78 
4.2.4. 
Participant Input into Design ......................................................................................78 
4.3. 
Justification for Dose ..................................................................................................78 
4.4. 
End of Study Definition ..............................................................................................78 
5. 
STUDY POPULATION .............................................................................................80 
5.1. 
Inclusion Criteria ........................................................................................................80 
5.2. 
Exclusion Criteria .......................................................................................................81 
5.3. 
Lifestyle Considerations .............................................................................................83 
5.3.1. 
Meals and Dietary Restrictions ...................................................................................83 
5.3.2. 
Activity .......................................................................................................................83 
5.4. 
Screen Failures ............................................................................................................83 
6. 
STUDY INTERVENTION ........................................................................................84 
6.1. 
Study Intervention(s) Administered ...........................................................................84 
6.1.1. 
Study Intervention(s) Administered ...........................................................................85 
6.1.1.1. 
Part A ..........................................................................................................................90 
6.1.1.2. 
Part B ..........................................................................................................................90 
6.2. 
Preparation/Handling/Storage/Accountability ............................................................91 
6.3. 
Measures to Minimize Bias: Randomization and Blinding ........................................92 
6.3.1. 
Randomization ............................................................................................................92 
6.3.2. 
Blinding ......................................................................................................................93 
6.4. 
Study Intervention Compliance ..................................................................................94 
6.5. 
Concomitant Therapy .................................................................................................94 
6.5.1. 
Allowed Medicine and Therapy .................................................................................94 
6.5.1.1. 
Dermatomyositis Treatment .......................................................................................94 
6.5.1.2. 
Other Allowed Therapies ............................................................................................96 
6.5.2. 
Disallowed Medicine and Therapy .............................................................................97 
6.5.3. 
Acute Therapy with Standard DM Treatment ............................................................97 

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6.6. 
Dose Modification ......................................................................................................98 
6.7. 
Intervention After the End of the Study......................................................................99 
7. 
DISCONTINUATION OF STUDY INTERVENTION AND 
PARTICIPANT DISCONTINUATION/WITHDRAWAL .....................................100 
7.1. 
Discontinuation of Study Intervention ......................................................................100 
7.2. 
Participant Discontinuation/Withdrawal from the Study..........................................101 
7.3. 
Lost to Follow-up .....................................................................................................101 
8. 
STUDY ASSESSMENTS AND PROCEDURES....................................................103 
8.1. 
Efficacy Assessments ...............................................................................................103 
8.1.1. 
International Myositis Assessment and Clinical Studies (IMACS) Core Set 
Measures (CSM) .......................................................................................................103 
8.1.1.1. 
Myositis Disease Activity Assessment Tool (MDAAT) ..........................................103 
8.1.1.2. 
Physician Global Activity Assessment .....................................................................103 
8.1.1.3. 
Patient Global Activity Assessment .........................................................................104 
8.1.1.4. 
Manual Muscle Testing 8 Muscles Group (MMT-8) ...............................................104 
8.1.1.5. 
Health Assessment Questionnaire (HAQ) ................................................................104 
8.1.1.6. 
Muscle Enzymes .......................................................................................................104 
8.1.2. 
Cutaneous Dermatomyositis Disease Area and Severity Index (CDASI) ................104 
8.1.3. 
Cutaneous Dermatomyositis Activity Physician’s Global Assessment (CDA-
IGA) ..........................................................................................................................104 
8.1.4. 
EuroQoL 5 Dimensions (EQ-5D-5L) .......................................................................105 
8.1.4.1. 
EQ-5D-5L Descriptive System .................................................................................105 
8.1.4.2. 
EQ Visual Analog Scale ...........................................................................................105 
8.1.5. 
5D-Itch Scale ............................................................................................................105 
8.1.6. 
Patient-Reported Outcomes Measurement Information System (PROMIS) 29 
v2.1 Tool ...................................................................................................................105 
8.1.7. 
Short Form Health Survey (36 Questions Version) (SF-36) ....................................105 
8.1.8. 
Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue) .......106 
8.1.9. 
Dermatomyositis Disease Symptoms Questionnaire (DM-DSQ) ............................106 
8.1.10. 
30-Second Chair Stand Test (30s CST) ....................................................................106 
8.1.11. 
Handheld Dynamometry ...........................................................................................106 
8.1.12. 
Home Electronic Patient-Reported Outcomes ..........................................................107 
8.2. 
Safety Assessments ...................................................................................................107 
8.2.1. 
Vaccine and Antibiotic Prophylaxis .........................................................................107 

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8.2.2. 
Physical Examinations ..............................................................................................107 
8.2.3. 
Height and Weight ....................................................................................................108 
8.2.4. 
Vital Signs ................................................................................................................108 
8.2.5. 
Electrocardiograms ...................................................................................................108 
8.2.6. 
Clinical Safety Laboratory Assessments ..................................................................108 
8.2.7. 
Pregnancy .................................................................................................................109 
8.2.8. 
Participant Safety Card .............................................................................................109 
8.3. 
Adverse Events and Serious Adverse Events ...........................................................110 
8.3.1. 
Time Period and Frequency for Collecting AE and SAE Information .....................110 
8.3.2. 
Method of Detecting AEs and SAEs ........................................................................110 
8.3.3. 
Follow-up of AEs and SAEs .....................................................................................110 
8.3.4. 
Regulatory Reporting Requirements for SAEs .........................................................110 
8.3.5. 
Medication Error, Drug Abuse, and Drug Misuse ....................................................111 
8.3.5.1. 
Timelines ..................................................................................................................111 
8.3.5.2. 
Medication Error .......................................................................................................111 
8.3.5.3. 
Drug Abuse ...............................................................................................................111 
8.3.5.4. 
Drug Misuse ..............................................................................................................111 
8.3.6. 
Adverse Events of Special Interest ...........................................................................111 
8.4. 
Treatment of Overdose .............................................................................................112 
8.5. 
Pharmacokinetics and Pharmacodynamics ...............................................................112 
8.6. 
Genetics ....................................................................................................................113 
8.7. 
Biomarkers ................................................................................................................113 
8.7.1. 
Blood Exploratory Biomarkers .................................................................................113 
8.7.2. 
Additional Biomarker Research................................................................................113 
8.8. 
Immunogenicity Assessments ..................................................................................113 
8.9. 
Health Economics Data and/or Medical Resource Utilization .................................114 
8.10. 
Other Assessments and Procedures ..........................................................................114 
8.10.1. 
Medical History and DM History and Diagnosis .....................................................114 
9. 
STATISTICAL CONSIDERATIONS .....................................................................115 
9.1. 
Statistical Hypotheses ...............................................................................................115 
9.2. 
Sample Size Determination ......................................................................................115 
9.2.1. 
Part A ........................................................................................................................115 
9.2.2. 
Part B ........................................................................................................................115 

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9.3. 
Populations for Analyses ..........................................................................................115 
9.4. 
Statistical Analyses ...................................................................................................116 
9.4.1. 
Efficacy Analyses .....................................................................................................116 
9.4.1.1. 
Efficacy Analysis of Part A ......................................................................................117 
9.4.1.2. 
Efficacy Analysis of Part B ......................................................................................117 
9.4.2. 
Safety Analyses ........................................................................................................119 
9.4.2.1. 
Analysis of Adverse Events ......................................................................................119 
9.4.2.2. 
Analysis of Clinical Laboratory Parameters, Vital Sign Measurements, and 
ECG Parameters ........................................................................................................120 
9.4.3. 
Other Analyses ..........................................................................................................120 
9.4.3.1. 
Pharmacokinetic/Pharmacodynamic Analysis ..........................................................120 
9.4.3.2. 
Analysis of Immunogenicity .....................................................................................120 
9.4.3.3. 
Analysis of Biomarkers ............................................................................................120 
9.4.3.4. 
Analyses of Exploratory Endpoint(s) .......................................................................120 
9.5. 
Interim Analyses .......................................................................................................121 
9.5.1. 
Part A Interim Analysis ............................................................................................121 
9.5.2. 
Part B Interim Analysis ............................................................................................121 
9.6. 
Data Monitoring Committee .....................................................................................121 
10. 
SUPPORTING DOCUMENTATION AND OPERATIONAL 
CONSIDERATIONS ................................................................................................122 
10.1. 
Management of Potential Infusion-Associated Adverse Events During Study 
Intervention Administration ......................................................................................122 
10.2. 
Regulatory, Ethical, and Study Oversight Considerations .......................................124 
10.2.1. 
Regulatory and Ethical Considerations ....................................................................124 
10.2.2. 
Financial Disclosure .................................................................................................126 
10.2.3. 
Informed Consent Process ........................................................................................126 
10.2.4. 
Recruitment Strategy ................................................................................................127 
10.2.5. 
Data Protection .........................................................................................................127 
10.2.6. 
Dissemination of Clinical Study Data ......................................................................128 
10.2.7. 
Data Quality Assurance ............................................................................................129 
10.2.8. 
Source Documents ....................................................................................................129 
10.2.9. 
Study and Site Start and Closure ..............................................................................130 
10.2.10. 
Publication Policy .....................................................................................................131 

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10.2.11. 
Good Clinical Practice Compliance ..........................................................................131 
10.3. 
Clinical Laboratory Tests .........................................................................................133 
10.4. 
Adverse Events: Definitions and Procedures for Recording, Evaluating, 
Follow-up, and Reporting .........................................................................................135 
10.4.1. 
Definition of AE .......................................................................................................135 
10.4.2. 
Definition of SAE .....................................................................................................136 
10.4.3. 
Recording and Follow-Up of AE and/or SAE ..........................................................137 
10.4.4. 
Reporting of SAEs ....................................................................................................139 
10.4.5. 
Unexpected Events ...................................................................................................139 
10.5. 
Medication Error, Drug Abuse, and Drug Misuse ....................................................140 
10.6. 
Contraceptive Guidance and Collection of Pregnancy Information .........................142 
10.6.1. 
Definitions ................................................................................................................142 
10.6.2. 
Contraception Guidance ...........................................................................................142 
10.6.2.1. 
Guidance for Female Participants .............................................................................143 
10.6.2.2. 
Guidance for Male Participants ................................................................................144 
10.6.3. 
Collection of Pregnancy Information .......................................................................144 
10.6.3.1. 
Male Participants with Partners Who Become Pregnant ..........................................145 
10.6.3.2. 
Female Participants Who Become Pregnant .............................................................145 
10.7. 
Biomarkers ................................................................................................................147 
10.8. 
Clinical Outcome Assessments .................................................................................148 
10.8.1. 
Myositis Disease Activity Assessment Tool (MDAAT) ..........................................148 
10.8.2. 
Physician Global Activity Assessment .....................................................................152 
10.8.3. 
Patient Global Activity Assessment .........................................................................153 
10.8.4. 
Manual Muscle Test (MMT-8) .................................................................................154 
10.8.5. 
Health Assessment Questionnaire (HAQ) ................................................................155 
10.8.6. 
Cutaneous Dermatomyositis Disease Area and Severity Index (CDASI) ................157 
10.8.7. 
Cutaneous Dermatomyositis Activity Physician’s Global Assessment (CDA-
IGA) ..........................................................................................................................158 
10.8.8. 
EuroQoL 5 Dimensions (EQ-5D-5L) .......................................................................159 
10.8.8.1. 
EQ-5D-5L Version for In-Clinic Use .......................................................................159 
10.8.9. 
5D-Itch Scale ............................................................................................................162 
10.8.10. 
PROMIS-29 v2.1 Tool ..............................................................................................163 
10.8.11. 
Short Form Health Survey (36 Questions Version) (SF-36) ....................................166 

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10.8.12. 
Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue) .......172 
10.8.13. 
Dermatomyositis Disease Symptoms Questionnaire (DM-DSQ) v1.1 and 
v5.0 ...........................................................................................................................173 
10.8.14. 
30-Second Chair Stand .............................................................................................177 
10.9. 
COVID-19 Risk Assessment ....................................................................................178 
10.10. 
COVID-19 Vaccine Risk Assessment ......................................................................180 
10.11. 
Abbreviations ............................................................................................................181 
10.12. 
Protocol Amendment History ...................................................................................185 
11. 
REFERENCES .........................................................................................................186 
LIST OF TABLES 
Table 1: 
Schedule of Activities: Screening Through End of the Randomized 
Controlled Period for Part A (Phase 2) .......................................................................29 
Table 2: 
Schedule of Activities: Screening Through End of the Randomized 
Controlled Period for Part B (Phase 3) .......................................................................37 
Table 3: 
Schedule of Activities: Open-Label Extension Period for Part A (Phase 2) – 
Week 26 to Week 100 .................................................................................................45 
Table 4: 
Schedule of Activities: Open-Label Extension Period for Part A (Phase 2) – 
Week 108 – Week 156 ................................................................................................49 
Table 5: 
Schedule of Activities: Open-Label Extension Period for Part B (Phase 3) ..............52 
Table 6: 
Ravulizumab Identified and Potential Risks ...............................................................61 
Table 7: 
Mapping Objectives to Endpoints for Part A (Phase 2 Portion) .................................63 
Table 8: 
Mapping Objectives to Endpoints/Estimands for Part B (Phase 3 Portion) ...............66 
Table 9: 
Mapping Objectives to Endpoints/Estimands for Open-Label Extension (Part 
A and Part B) ..............................................................................................................69 
Table 10: Study Intervention ......................................................................................................84 
Table 11: Weight-based Doses of Ravulizumab .........................................................................85 
Table 12: Reference Chart for Weight-based Dosing – Study Part A ........................................86 
Table 13: Reference Chart for Weight-based Dosing – Study Part B ........................................88 
Table 14: Allowed Concomitant DM Treatments ......................................................................95 
Table 15: Washout Periods Required Before Day 1 Visit ..........................................................95 
Table 16: Washout Periods Required Before Day 1 for Prohibited Medications .......................97 
Table 17: Study ALXN1210-DM-310 Analysis Populations ...................................................115 
Table 18: Clinical Criteria for Diagnosing Anaphylaxis ..........................................................122 

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Table 19: Laboratory Assessments ...........................................................................................133 
Table 20: Potential Risks and Mitigation Measures Due to COVID-19...................................178 
Table 21: Potential Risks and Mitigation Measures Due to COVID-19 Vaccine ....................180 
Table 22: Abbreviations and Specialist Terms .........................................................................181 
 
LIST OF FIGURES 
Figure 1: 
Study Design Schematic .............................................................................................28 
 

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1. 
PROTOCOL SUMMARY 
1.1. 
Synopsis 
Protocol Title: A Phase 2/3, Double-Blind, Randomized, Placebo-Controlled, Parallel Group, 
Multicenter Study to Evaluate the Efficacy and Safety of Ravulizumab in Adult Participants with 
Dermatomyositis. 
Brief Title: Ravulizumab versus Placebo in Adult Participants with Dermatomyositis 
Regulatory Agency Identifier Number(s): 
IND Number: 152551 
EudraCT: 2021-001200-15 (formerly) 
EU CT Number: 2023-503478-19-00 
Rationale: 
Complement-mediated injury has been implicated in the pathology of dermatomyositis (DM), a 
disorder characterized by distinct skin rashes and muscle weakness (Dalakas, 2015; Isak, 2018; 
Mahil, 2012). Patients with DM typically present with proximal muscle weakness and cutaneous 
manifestations that develop over weeks to months (Selva-O'Callaghan, 2018). Muscle biopsies 
from patients with DM reveal the presence of membrane attack complex (MAC) on the 
endothelial cells of the endomysial capillaries (Dalakas, 2020; Kissel, 1986) indicating the 
involvement of complement component 5 (C5) in DM and providing the therapeutic rationale for 
use of C5 inhibitors in DM. Currently, there are only 3 therapies approved for the treatment of 
DM: azathioprine, corticotropin injections, and glucocorticoids. Additionally, a human 
plasma-derived intravenous immunoglobulin (IVIg) was recently approved for the treatment of 
DM in the EU and US. Despite therapy, however, about a third of patients with DM are left with 
mild to severe disability (Dalakas, 2003) and half of patients considered to be stable do not 
return to previous levels of work (Marie, 2001). 
Ravulizumab is a recombinant, humanized monoclonal antibody (mAb) with high specificity 
against human C5 and blocks the cleavage of C5 into the pro-inflammatory complement 
component 5a (C5a) and the pro-inflammatory and lytic terminal complement complex (C5b-9). 
Ravulizumab has been shown to achieve immediate, complete, and sustained terminal 
complement inhibition as a chronic treatment in patients with paroxysmal nocturnal 
hemoglobinuria (PNH), in patients with atypical hemolytic uremic syndrome (aHUS), in adult 
patients with generalized myasthenia gravis (gMG), and it is currently being developed as a 
treatment in several other complement-related indications. It is expected that the same dosing 
regimen approved for PNH, aHUS, and gMG will achieve comparable inhibition of complement-
mediated damage in patients with DM. The combination of clinically relevant outcomes with 
terminal complement inhibition in other complement-mediated diseases and pharmacodynamic 
(PD) effects of ravulizumab on terminal complement provide the rationale for the hypothesis that 
ravulizumab may improve the clinical manifestations of DM in patients, and in particular, lead to 
a reduction in muscle weakness and cutaneous manifestations. 
The objective of this study is to investigate the efficacy, safety, pharmacokinetics (PK), PD, and 
immunogenicity of ravulizumab in adult participants with DM. 

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Objectives and Estimands and/or Endpoints 
Mapping Objectives to Endpoints/Estimands for Part A (Phase 2 Portion) 
Objectives 
Endpoints/Estimands 
Primary 
To determine the effect of ravulizumab 
compared with placebo in the treatment of 
DM based on improvement in Total 
Improvement Score (TIS) IMACS-TISa 
IMACS-TISa (TIS40) response at Week 26 of the 
Randomized Controlled Period as per defined 
composite estimand 
Secondary  
To assess the efficacy of ravulizumab 
compared with placebo in the treatment of 
DM based on improvement in efficacy 
endpoints 
• 
TIS at Week 26 
• 
Change from baseline in CDASI Activity Score 
at Week 26 
• 
Change from baseline in 5 IMACS core set 
measures (extra-muscular disease activity based 
on MDAAT, physician global activity 
assessment, patient global activity assessment, 
MMT-8, HAQ) at Week 26 
• 
Response related to muscle enzymes: 
- 
normalization of most abnormal baseline 
enzyme at Week 26  
• 
CDASI response (7-point improvement from 
baseline) at Week 26 
• 
CDA-IGA response (almost clear or clear) at 
Week 26 
• 
TIS20 response at Week 26 
• 
TIS60 response at Week 26 
• 
Time to First Response of TIS20, TIS40, or 
TIS60, respectively 
• 
Clinical worsening during RCP at 2 consecutive 
visits 
• 
Receipt of acute therapy with standard DM 
treatment  
PK/PD/Immunogenicity 
To characterize the PK/PD and 
immunogenicity of ravulizumab in adult 
participants with DM  
• 
Serum ravulizumab concentrations over the study 
duration 
• 
Change in serum free and total C5 concentrations 
over the study duration 
• 
Incidence and titer of ADAs over the study 
duration 

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Objectives 
Endpoints/Estimands 
Safety 
To characterize the overall safety of 
ravulizumab in participants with DM 
• 
Incidence of TEAEs, TESAEs, and TEAEs 
leading to study intervention discontinuation 
a ACR/EULAR-TIS 
Abbreviations: ACR/EULAR = American College of Rheumatology/European League Against Rheumatism; 
ADA = antidrug antibody; C5 = complement component 5; CDASI = Cutaneous Dermatomyositis Disease Area 
and Severity Index; DM = dermatomyositis; CDA-IGA = Cutaneous Dermatomyositis Activity Physician’s Global 
Assessment; HAQ = health assessment questionnaire; IMACS-TIS = International Myositis Assessment and 
Clinical Studies-Total Improvement Score; MDAAT = Myositis Disease Activity Assessment Tool; MMT-8 = 
manual muscle testing subset of 8 muscles; PD = pharmacodynamic(s); PK = pharmacokinetic(s); RCP = 
Randomized Controlled Period; TEAE = treatment-emergent adverse event; TESAE = treatment-emergent serious 
adverse event; TIS20 =TIS value ≥ 20-point improvement response on IMACS-TIS; TIS40 = TIS value ≥ 40-point 
improvement response on IMACS-TIS; TIS60 = TIS value ≥ 60-point improvement response on IMACS-TIS  

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Mapping Objectives to Endpoints/Estimands for Part B (Phase 3 Portion) 
Objectives 
Endpoints/Estimands  
Primary 
To determine the effect of ravulizumab 
compared with placebo in the treatment of 
DM based on improvement in Total 
Improvement Score (TIS) IMACS-TIS)a 
IMACS-TISa (TIS40) response at Week 50 of the 
Randomized Controlled Period as per defined 
composite estimand  
Key Secondary 
To assess the efficacy of ravulizumab 
compared with placebo in the treatment of 
DM based on improvement in components of 
IMACS and other myositis activity measures 
• 
TIS at Week 50 
• 
Change from baseline in MMT-8 at Week 50 
• 
Change from baseline in extra-muscular disease 
activity based on MDAAT at Week 50 
• 
Change from baseline in CDASI Activity Score at 
Week 50 
Secondary 
To assess the efficacy of ravulizumab 
compared with placebo in the treatment of 
DM based on other efficacy endpoints  
• 
Change from baseline in 3 IMACS core set 
measurements (physician global activity score, 
patient global activity score, HAQ) at Week 50 
• 
Response related to muscle enzymes: 
- 
normalization of most abnormal baseline 
enzyme at Week 50 
• 
CDASI response (7-point improvement from 
baseline) at Week 50 
• 
CDA-IGA response (almost clear or clear) at 
Week 50 
• 
TIS20 response at Week 50 
• 
TIS60 response at Week 50 
• 
Time to First Response of TIS20, TIS40, or 
TIS60, respectively 
• 
Clinical worsening during RCP at 2 consecutive 
visits 
• 
Receipt of acute therapy with standard DM 
treatment  

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Objectives 
Endpoints/Estimands  
PK/PD/Immunogenicity 
To characterize the PK/PD and 
immunogenicity of ravulizumab in adult 
participants with DM  
• 
Serum ravulizumab concentrations over the study 
duration 
• 
Change in serum free and total C5 concentrations 
over the study duration 
• 
Incidence and titer of ADAs over the study 
duration 
Safety  
To characterize the overall safety of 
ravulizumab in participants with DM 
• 
Incidence of TEAEs, TESAEs, and TEAEs 
leading to study intervention discontinuation 
a ACR/EULAR-TIS 
Abbreviations: ACR/EULAR = American College of Rheumatology/European League Against Rheumatism; 
ADA = antidrug antibody; C5 = complement component 5; CDASI = Cutaneous Dermatomyositis Disease Area 
and Severity Index; DM = dermatomyositis; CDA-IGA = Cutaneous Dermatomyositis Activity Physician’s Global 
Assessment; HAQ = health assessment questionnaire; IMACS-TIS = International Myositis Assessment and 
Clinical Studies-Total Improvement Score; MDAAT = Myositis Disease Activity Assessment Tool; 
MMT-8 = manual muscle testing subset of 8 muscles; PD = pharmacodynamic(s); PK = pharmacokinetic(s); 
RCP = Randomized Controlled Period; TEAE = treatment-emergent adverse event; TESAE = treatment-emergent 
serious adverse event; TIS20 = TIS value ≥ 20-point improvement response on IMACS-TIS; TIS40 = TIS 
value ≥ 40-point improvement response on IMACS-TIS; TIS60 = TIS value ≥ 60-point improvement response on 
IMACS-TIS 
 
Overall Design 
Study ALXN1210-DM-310 is an operationally seamless Phase 2/3, double-blind, randomized, 
placebo-controlled, parallel group, multicenter study to evaluate the efficacy, safety, PK, PD, and 
immunogenicity of ravulizumab IV administered q8w (regular dose) in adult participants with 
DM.  
There will be 3 periods in both Part A (Phase 2) and Part B (Phase 3) of this study: Screening 
Period, Randomized Controlled Period, and Open-Label Extension (OLE) Period. Participants 
will be screened for eligibility for up to 6 weeks during the Screening Period. Upon completing 
the last assessment of the Randomized Controlled Period at Week 26 (Part A) or Week 50 (Part 
B), participants may have the option of continuing into the OLE Period. During the OLE Period, 
participants in the ravulizumab group will continue to receive ravulizumab treatment, and 
participants in the placebo group will switch to receive ravulizumab. The study will remain 
double-blinded during the OLE Period until after data from the Randomized Controlled Period of 
the study have been cleaned, locked, and unblinded. 
The primary efficacy endpoint may be assessed in an interim analysis (Part A) (see 
Section 9.5.1). If the futility criterion is met, the Sponsor may stop further enrollment in the 
study or discontinue the study, after recommendation from an Independent Data Monitoring 
Committee (IDMC). Part B will not be initiated if Part A results in futility or is terminated due to 
safety concerns. Another interim analysis may be conducted in Part B for sample-size estimation.  
Randomized Controlled Period 

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All participants randomized into the study are expected to complete the Randomized Controlled 
Period and will be followed until the end of the Randomized Controlled Period. 
Participants who discontinue study intervention will complete the Randomized Controlled Period 
(see Section 7.1). Participants that require acute therapy with standard DM treatment (see 
Section 6.5.3) due to protocol defined Clinical Worsening and complete all remaining visits of 
the Randomized Controlled Period (see Section 4.1.3) will be permitted to enter OLE Period. 
Participants who discontinue/withdraw consent during the Randomized Controlled Period will 
not be permitted to enter the OLE Period (see Section 7.2). Participants who will not enter the 
OLE Period will not receive an infusion at Week 26 (Part A) or Week 50 (Part B). 
OLE Period 
All participants completing the OLE Period (130 weeks for Part A or 74 weeks for Part B) will 
have an End of Study (EOS) Visit at Week 156 (Part A) or Week 124 (Part B) and a follow-up 
phone call 21 weeks (± 1 week) after the participant’s last dose of study intervention to collect 
information on concomitant medications, non-pharmacologic therapies and procedures, and 
adverse events (AEs). 
Adjustments of ‘protocol allowed’ DM medications (Section 6.5.1) will be permitted throughout 
the OLE Period.  
Participants who discontinue study intervention are encouraged to complete the visits and 
assessments of the OLE Period (see Section 7.1). 
Participants who discontinue/withdraw from the study will complete an Early Termination (ET) 
Visit and a follow-up phone call (see Section 7.2). 
Participants from Part A (Phase 2) will not be enrolled in Part B of the study (Phase 3). 
Disclosure Statement: This is a blinded, parallel group intervention study with 2 treatment arms 
followed by an OLE Period. Both Part A and Part B follow this design. 
Number of Participants: Participants will be screened until enough participants have been 
enrolled to achieve an estimated total of approximately 36 participants in Part A (24 
ravulizumab:12 placebo) and approximately 114 participants in Part B (76 ravulizumab: 38 
placebo). 
Intervention Groups and Duration: Eligible participants will be enrolled into the study and 
will be randomized in a 2:1 ratio (Part A) or stratified by cutaneous manifestations CDASI 
activity score (≤ 14 and > 14) and randomized in a 2:1 ratio (Part B) to receive intravenous (IV) 
ravulizumab or placebo (Section 6.3.1) within each stratum.  
The study intervention dose for each participant will be based on body weight. The dosing 
regimen for both Parts A and B consists of a loading dose followed by maintenance doses 
administered every 8 weeks. The maintenance dosing will be initiated 2 weeks after the loading 
dose is administered.  
The Randomized Controlled Period for Part A will be 26 weeks in duration. The Randomized 
Controlled Period for Part B will be 50 weeks in duration. Participants may continue to receive 
ravulizumab or for up to 130 weeks (approximately 2.5 years) (Part A) or up to 74 weeks 
(approximately 1.5 years) (Part B) in the OLE Period, or until ravulizumab is registered or 

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approved (in accordance with country-specific regulations), or an alternative option for example 
transition to a rollover study or an early access program is provided, whichever occurs first. The 
total study treatment duration for Part A will be approximately 3 years and for Part B 
approximately 2.5 years. 
Data Monitoring Committee: This study will use an Independent Data Monitoring Committee 
(IDMC) to monitor safety and to perform the planned interim analyses of the study.  
Ethical Considerations and Benefit-Risk Assessment 
This study will be conducted as specified in this protocol and in accordance with the following: 
• Consensus ethical principles derived from international guidelines including the 
Declaration of Helsinki and Council for International Organizations of Medical 
Sciences (CIOMS) International Ethical Guidelines 
• Applicable ICH Good Clinical Practice (GCP) Guidelines 
• Applicable laws and regulations 
A thorough benefit-risk assessment has been performed for ravulizumab IV. Measures will be 
taken to minimize risk to study participants. The potential risks identified in association with 
ravulizumab IV are justified by the anticipated benefits that may be afforded to participants with 
DM. 
Brief Summary: 
Background: The complement pathway is part of the human immune defense against pathogens. 
However, if the complement pathway is abnormally activated, it may play a role in the 
development of the autoimmune disease DM, which results in muscle weakness and skin rashes. 
Ravulizumab is a treatment that blocks complement and therefore may result in improved 
symptoms in patients with DM.  
Study Population: The study will be conducted in 2 parts and will include participants with DM 
(≥ 18 years) who did not show an adequate response or are intolerant to 1 or more DM 
treatments: Part A will include approximately 36 participants randomized in a 2:1 ratio 
(24 ravulizumab:12 placebo), Part B will include approximately 114 participants randomized in a 
2:1 ratio (76 ravulizumab: 38 placebo). 
Health Measurement/Outcome: The study will evaluate the effects of ravulizumab on patients 
with IM with International Myositis Assessment and Clinical Studies Total Improvement Score 
(IMACS-TIS) as the primary endpoint. Furthermore, efficacy and safety of ravulizumab as well 
as the PK, PD and potential immune responses to ravulizumab will be assessed. The effects of 
ravulizumab will be compared to a placebo. 
Study Intervention and Intervention Form: Ravulizumab and placebo are formulated as a 
sterile liquid solution and will be administered as IV infusions. The ravulizumab or placebo dose 
for each participant will be based on body weight.  
Study/Treatment Duration: Initially a loading dose will be administered. Starting at Week 2 
maintenance doses will then be administered every 8 weeks during the 26-week Randomized 
Controlled Period (RCP) for Part A and 50-week RCP for Part B. Participants will continue to 
receive ravulizumab during the OLE Period every 8 weeks for up to 130 weeks (Part A) or up to 

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74 weeks (Part B). The total study treatment duration for Part A and Part B will be 
approximately 3 years and 2.5 years, respectively.  
Visit Frequency: The participant Screening Period covers 42 days before Study Day 1. For Part 
A, visits will be on Day 1, 15, 71, 127, and 183 during the RCP and on Day 183, 197, 253, 309, 
365, 421, 477, 533, 589, 645, 701, 757, 813, 869, 925, 981, 1037, and 1079 during the OLE. For 
Part B, visits will be on Day 1, 15, 71, 127, 183, 239, 295, and 351 during the RCP and on 
Day 351, 365, 421, 477, 533, 589, 645, 701, 757, 813, and 869 during the OLE.

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1.2. 
Schema 
Figure 1: 
Study Design Schematic 
 
Abbreviations: D = day; DM = dermatomyositis; EOS = end of study; ET = early termination; N = number of participants; q8w = once every 8 weeks; W = week 

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1.3. 
Schedule of Activities 
Table 1: 
Schedule of Activities: Screening Through End of the Randomized Controlled Period for Part A (Phase 2)  
Period/Phase 
Screening 
Randomized Controlled Period 
UV 
Notes 
Study Visit 
1 
2 
3 
4 
5 
6/ET 
 
Participants who discontinue/withdraw from the study 
should complete the study visit (if at the site for a 
scheduled visit) or return for an UV as soon as possible 
within a week and complete the ET Visit 8 weeks after 
the participant’s last dose of study intervention. In 
addition, a follow-up phone call 21 weeks (± 1 week) 
after the participant’s last dose of study intervention will 
be performed to collect information on concomitant 
medications, non-pharmacologic therapies and 
procedures, and AEs (see Section 7.2 for more details). 
Participants who will not enter the OLE Period will 
complete the assessments for Week 26 but not receive 
an infusion at Week 26 (see Section 6.1.1 for more 
details). 
Study Day 
D-42 to -1 
D1 
D15 
D71 
D127 
D183 
Window (day) 
 
 
± 2 
± 3 
± 3 
± 3 
Weeks 
Up to 
6 weeks 
 
W2 
W10 
W18 
W26 
Informed consent 
X 
 
 
 
 
 
 
 
Assessment of inclusion/ 
exclusion criteria 
X 
 
 
 
 
 
 
 
Medical history 
X 
 
 
 
 
 
 
 
DM history 
X 
 
 
 
 
 
 
 
ACR/EULAR criteria 
X 
 
 
 
 
 
 
 
Weight 
X 
X 
X 
X 
X 
X 
 
 
Height 
X 
 
 
 
 
 
 
 
HIV-(1 and 2) testing 
X 
 
 
 
 
 
 
 
Vital signs 
X 
X 
X 
X 
X 
X 
X 
On dosing days, vital signs will be taken before study 
intervention administration and after the participant has 
been resting for at least 5 minutes (see Section 8.2.4). 

Protocol Amendment 3.0  
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Alexion Confidential 
Table 1: 
Schedule of Activities: Screening Through End of the Randomized Controlled Period for Part A (Phase 2)  
Period/Phase 
Screening 
Randomized Controlled Period 
UV 
Notes 
Study Visit 
1 
2 
3 
4 
5 
6/ET 
 
Participants who discontinue/withdraw from the study 
should complete the study visit (if at the site for a 
scheduled visit) or return for an UV as soon as possible 
within a week and complete the ET Visit 8 weeks after 
the participant’s last dose of study intervention. In 
addition, a follow-up phone call 21 weeks (± 1 week) 
after the participant’s last dose of study intervention will 
be performed to collect information on concomitant 
medications, non-pharmacologic therapies and 
procedures, and AEs (see Section 7.2 for more details). 
Participants who will not enter the OLE Period will 
complete the assessments for Week 26 but not receive 
an infusion at Week 26 (see Section 6.1.1 for more 
details). 
Study Day 
D-42 to -1 
D1 
D15 
D71 
D127 
D183 
Window (day) 
 
 
± 2 
± 3 
± 3 
± 3 
Weeks 
Up to 
6 weeks 
 
W2 
W10 
W18 
W26 
Physical examination 
X 
 
 
 
 
X 
 
 
Abbreviated physical 
examination 
 
X 
X 
X 
X 
 
X 
To be performed, if necessary, based on the participant’s 
health status and the clinical judgment of the 
Investigator. 
CSMs for IMACS-TIS Determination 
 
MDAAT 
X 
X 
X 
X 
X 
X 
X 
MDAAT should be performed before the physician 
global activity assessment. 
These are the 6 IMACS core set measures that will be 
used for IMACS-TIS determination. 
 
 
 
Physician global activity 
assessment 
X 
X 
X 
X 
X 
X 
X 
Patient global activity 
assessment 
X 
X 
X 
X 
X 
X 
X 
MMT-8 
X 
X 
X 
X 
X 
X 
X 
HAQ 
X 
X 
X 
X 
X 
X 
X 
Laboratory tests for 
muscle enzymes 
X 
X 
X 
X 
X 
X 
X 

Protocol Amendment 3.0  
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23 Jun 2023 
Page 31 of 188 
Alexion Confidential 
Table 1: 
Schedule of Activities: Screening Through End of the Randomized Controlled Period for Part A (Phase 2)  
Period/Phase 
Screening 
Randomized Controlled Period 
UV 
Notes 
Study Visit 
1 
2 
3 
4 
5 
6/ET 
 
Participants who discontinue/withdraw from the study 
should complete the study visit (if at the site for a 
scheduled visit) or return for an UV as soon as possible 
within a week and complete the ET Visit 8 weeks after 
the participant’s last dose of study intervention. In 
addition, a follow-up phone call 21 weeks (± 1 week) 
after the participant’s last dose of study intervention will 
be performed to collect information on concomitant 
medications, non-pharmacologic therapies and 
procedures, and AEs (see Section 7.2 for more details). 
Participants who will not enter the OLE Period will 
complete the assessments for Week 26 but not receive 
an infusion at Week 26 (see Section 6.1.1 for more 
details). 
Study Day 
D-42 to -1 
D1 
D15 
D71 
D127 
D183 
Window (day) 
 
 
± 2 
± 3 
± 3 
± 3 
Weeks 
Up to 
6 weeks 
 
W2 
W10 
W18 
W26 
CDASI Activity and 
Damage 
X 
X 
X 
X 
X 
X 
 
 
CDA-IGA 
X 
X 
X 
X 
X 
X 
 
 
EQ-5D-5L 
X 
X 
X 
X 
X 
X 
 
 
5D-itch scale 
X 
X 
X 
X 
X 
X 
 
 
PROMIS-29 v2.1 
X 
X 
X 
X 
X 
X 
 
 
SF-36 
X 
X 
X 
X 
X 
X 
 
 
FACIT-Fatigue 
X 
X 
X 
X 
X 
X 
 
 
DM-DSQ 
X 
X 
X 
X 
X 
X 
 
Participants will complete this assessment once a day 
starting from Day 1.  
ECG 
X 
 
 
 
 
X 
 
 
30s CST 
 
X 
 
 
 
X 
 
 
Handheld dynamometry 
 
X 
 
 
 
X 
 
 

Protocol Amendment 3.0  
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23 Jun 2023 
Page 32 of 188 
Alexion Confidential 
Table 1: 
Schedule of Activities: Screening Through End of the Randomized Controlled Period for Part A (Phase 2)  
Period/Phase 
Screening 
Randomized Controlled Period 
UV 
Notes 
Study Visit 
1 
2 
3 
4 
5 
6/ET 
 
Participants who discontinue/withdraw from the study 
should complete the study visit (if at the site for a 
scheduled visit) or return for an UV as soon as possible 
within a week and complete the ET Visit 8 weeks after 
the participant’s last dose of study intervention. In 
addition, a follow-up phone call 21 weeks (± 1 week) 
after the participant’s last dose of study intervention will 
be performed to collect information on concomitant 
medications, non-pharmacologic therapies and 
procedures, and AEs (see Section 7.2 for more details). 
Participants who will not enter the OLE Period will 
complete the assessments for Week 26 but not receive 
an infusion at Week 26 (see Section 6.1.1 for more 
details). 
Study Day 
D-42 to -1 
D1 
D15 
D71 
D127 
D183 
Window (day) 
 
 
± 2 
± 3 
± 3 
± 3 
Weeks 
Up to 
6 weeks 
 
W2 
W10 
W18 
W26 
Clinical laboratory tests 
X 
X 
X 
X 
X 
X 
X 
Clinical laboratory tests will be performed at the central 
laboratory or designated third party laboratory. 
Coagulation laboratory test to be completed at Screening 
only. 
Urinalysis 
X 
X 
X 
X 
X 
X 
 
 
FSH 
X 
 
 
 
 
 
 
Performed at Screening in selected female participants 
to confirm postmenopausal status. 
Pregnancy test (WOCBP 
only) 
X 
X 
X 
X 
X 
X 
X 
Local urine testing will be standard for this study unless 
serum testing is required by local regulation or ethics 
committees. Testing will be done at indicated visits and 
when necessary at Investigator’s discretion 
(Section 8.2.7). 

Protocol Amendment 3.0  
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23 Jun 2023 
Page 33 of 188 
Alexion Confidential 
Table 1: 
Schedule of Activities: Screening Through End of the Randomized Controlled Period for Part A (Phase 2)  
Period/Phase 
Screening 
Randomized Controlled Period 
UV 
Notes 
Study Visit 
1 
2 
3 
4 
5 
6/ET 
 
Participants who discontinue/withdraw from the study 
should complete the study visit (if at the site for a 
scheduled visit) or return for an UV as soon as possible 
within a week and complete the ET Visit 8 weeks after 
the participant’s last dose of study intervention. In 
addition, a follow-up phone call 21 weeks (± 1 week) 
after the participant’s last dose of study intervention will 
be performed to collect information on concomitant 
medications, non-pharmacologic therapies and 
procedures, and AEs (see Section 7.2 for more details). 
Participants who will not enter the OLE Period will 
complete the assessments for Week 26 but not receive 
an infusion at Week 26 (see Section 6.1.1 for more 
details). 
Study Day 
D-42 to -1 
D1 
D15 
D71 
D127 
D183 
Window (day) 
 
 
± 2 
± 3 
± 3 
± 3 
Weeks 
Up to 
6 weeks 
 
W2 
W10 
W18 
W26 
PK/PD  
 
B/P 
T/P 
T/P 
T/P 
T 
X 
Baseline (B) and trough (T) blood samples for PK and 
PD will be collected predose (within 90 minutes prior to 
the start of infusion of study intervention). Peak (P) 
blood samples for PK/PD samples are to be taken within 
the 60 minutes following completion of study 
intervention infusion. B and T samples may be drawn 
through the venous access created for the dose infusion, 
prior to administration of the dose. The P samples will 
be drawn from the participant’s opposite, non-infused 
arm. On Day 183 (Week 26), the T sample is considered 
a Randomized Controlled Period assessment and the P 
sample is considered an Extension Period assessment. 
ET or UV PK/PD sample will be collected anytime. All 
collection times will be recorded in eCRF.  

Protocol Amendment 3.0  
ALXN1210-DM-310 
23 Jun 2023 
Page 34 of 188 
Alexion Confidential 
Table 1: 
Schedule of Activities: Screening Through End of the Randomized Controlled Period for Part A (Phase 2)  
Period/Phase 
Screening 
Randomized Controlled Period 
UV 
Notes 
Study Visit 
1 
2 
3 
4 
5 
6/ET 
 
Participants who discontinue/withdraw from the study 
should complete the study visit (if at the site for a 
scheduled visit) or return for an UV as soon as possible 
within a week and complete the ET Visit 8 weeks after 
the participant’s last dose of study intervention. In 
addition, a follow-up phone call 21 weeks (± 1 week) 
after the participant’s last dose of study intervention will 
be performed to collect information on concomitant 
medications, non-pharmacologic therapies and 
procedures, and AEs (see Section 7.2 for more details). 
Participants who will not enter the OLE Period will 
complete the assessments for Week 26 but not receive 
an infusion at Week 26 (see Section 6.1.1 for more 
details). 
Study Day 
D-42 to -1 
D1 
D15 
D71 
D127 
D183 
Window (day) 
 
 
± 2 
± 3 
± 3 
± 3 
Weeks 
Up to 
6 weeks 
 
W2 
W10 
W18 
W26 
ADA 
 
B 
 
T 
 
T 
X 
Baseline (B) and trough (T) blood samples for ADA will 
be collected predose (within 90 minutes prior to the start 
of infusion of study intervention). ET or UV ADA 
sample will be collected anytime. 
Blood sample for 
biomarkers  
X 
X 
X 
X 
X 
X 
X 
Blood samples for biomarkers should be collected 
predose on dosing days. Samples can be collected at any 
time on non-dosing days. 
Blood samples for Myositis-specific autoantibodies will 
be collected on Day 1 and Day 183 or ET. 
Neisseria meningitidis 
vaccination 
X 
 
 
 
 
 
 
To reduce the risk of meningococcal infection 
(N meningitidis), all participants must be vaccinated 
against meningococcal infections within 3 years prior to 
initiating study intervention as per national and local 
guidelines. Participants must receive the vaccination at 
least 2 weeks before first study intervention. The 
sponsor recommends that national and local guidelines 
for prophylactic antibiotics should also be followed. 

Protocol Amendment 3.0  
ALXN1210-DM-310 
23 Jun 2023 
Page 35 of 188 
Alexion Confidential 
Table 1: 
Schedule of Activities: Screening Through End of the Randomized Controlled Period for Part A (Phase 2)  
Period/Phase 
Screening 
Randomized Controlled Period 
UV 
Notes 
Study Visit 
1 
2 
3 
4 
5 
6/ET 
 
Participants who discontinue/withdraw from the study 
should complete the study visit (if at the site for a 
scheduled visit) or return for an UV as soon as possible 
within a week and complete the ET Visit 8 weeks after 
the participant’s last dose of study intervention. In 
addition, a follow-up phone call 21 weeks (± 1 week) 
after the participant’s last dose of study intervention will 
be performed to collect information on concomitant 
medications, non-pharmacologic therapies and 
procedures, and AEs (see Section 7.2 for more details). 
Participants who will not enter the OLE Period will 
complete the assessments for Week 26 but not receive 
an infusion at Week 26 (see Section 6.1.1 for more 
details). 
Study Day 
D-42 to -1 
D1 
D15 
D71 
D127 
D183 
Window (day) 
 
 
± 2 
± 3 
± 3 
± 3 
Weeks 
Up to 
6 weeks 
 
W2 
W10 
W18 
W26 
Participant Safety Card 
 
X 
X 
X 
X 
X 
X 
Participants will be given a Participant Safety Card prior 
to the first dose of study intervention. At each visit 
throughout the study, the study staff will ensure that the 
participant has the Participant Safety Card. 
Randomization 
 
X 
 
 
 
 
 
 
Clinical Worsening 
criteria check 
 
 
X 
X 
X 
X 
X 
Clinical Worsening criteria are described in 
Section 4.1.3. A scheduled visit or UV will occur 4 
weeks (± 7 days) later. Clinical Worsening is confirmed 
if criteria are met on 2 consecutive visits.  
Ravulizumab or placebo 
infusion 
 
X 
X 
X 
X 
 
X 
Study intervention will be administered intravenously 
via infusion after completion of all other tests and 
procedures, excluding the peak (P) blood sampling for 
PK/PD. 
Unscheduled doses should be discussed with the 
Sponsor or designee. 

Protocol Amendment 3.0  
ALXN1210-DM-310 
23 Jun 2023 
Page 36 of 188 
Alexion Confidential 
Table 1: 
Schedule of Activities: Screening Through End of the Randomized Controlled Period for Part A (Phase 2)  
Period/Phase 
Screening 
Randomized Controlled Period 
UV 
Notes 
Study Visit 
1 
2 
3 
4 
5 
6/ET 
 
Participants who discontinue/withdraw from the study 
should complete the study visit (if at the site for a 
scheduled visit) or return for an UV as soon as possible 
within a week and complete the ET Visit 8 weeks after 
the participant’s last dose of study intervention. In 
addition, a follow-up phone call 21 weeks (± 1 week) 
after the participant’s last dose of study intervention will 
be performed to collect information on concomitant 
medications, non-pharmacologic therapies and 
procedures, and AEs (see Section 7.2 for more details). 
Participants who will not enter the OLE Period will 
complete the assessments for Week 26 but not receive 
an infusion at Week 26 (see Section 6.1.1 for more 
details) 
Study Day 
D-42 to -1 
D1 
D15 
D71 
D127 
D183 
Window (day) 
 
 
± 2 
± 3 
± 3 
± 3 
Weeks 
Up to 
6 weeks 
 
W2 
W10 
W18 
W26 
Concomitant medication 
Continuous monitoring 
 
Non-drug therapy 
Continuous monitoring 
 
Adverse event 
Continuous monitoring 
 
Abbreviations: 30s CST = 30-second Chair Stand Test; ACR/EULAR = American College of Rheumatology/European League Against Rheumatism; 
ADA = antidrug antibody; AE = adverse event; CDA-IGA = Cutaneous Dermatomyositis Activity Physician’s Global Assessment; CDASI = Cutaneous 
Dermatomyositis Disease Area and Severity Index; CSM = core set measures; D = day; DM = dermatomyositis; DM-DSQ = Dermatomyositis Disease 
Symptoms Questionnaire; ECG = electrocardiogram; eCRF = electronic case report form; EQ-5D-5L = European Quality of Life Health 5-item 
questionnaire dimensions 5 level; ET = Early Termination; FACIT = Functional Assessment of Chronic Illness Therapy; FSH = follicle stimulating 
hormone; HAQ = Health Assessment Questionnaire; HIV = human immunodeficiency virus; IMACS-TIS = International Myositis Assessment and Clinical 
Studies-Total Improvement Score; MDAAT = Myositis Disease Activity Assessment Tool; MMT-8 = Manual Muscle Testing subset of 8 muscles; PD = 
pharmacodynamic(s); PK = pharmacokinetic(s); PROMIS = Patient-reported Outcomes Measurement Information System; SF-36 = Short Form Health 
Survey (36 questions version); UV = Unscheduled Visit; W = week(s); WOCBP = women of childbearing potential 

Protocol Amendment 3.0  
ALXN1210-DM-310 
23 Jun 2023 
Page 37 of 188 
Alexion Confidential 
Table 2: 
Schedule of Activities: Screening Through End of the Randomized Controlled Period for Part B (Phase 3) 
Period/Phase 
Screening 
Randomized Controlled Period 
UV 
Notes 
Study Visit 
1 
2 
3 
4 
5 
 
6 
7 
8 
9/ET 
 
 
Participants who discontinue/withdraw from the 
study should complete the study visit (if at the site 
for a scheduled visit) or return for an UV as soon as 
possible within a week and complete the ET Visit 8 
weeks after the participant’s last dose of study 
intervention. In addition, a follow-up phone call 21 
weeks (± 1 week) after the participant’s last dose of 
study intervention will be performed to collect 
information on concomitant medications, non-
pharmacologic therapies and procedures, and AEs 
(see Section 7.2 for more details). 
Participants who will not enter the OLE Period will 
complete the assessments for Week 50 but not 
receive an infusion at Week 50 (see Section 6.1.1 for 
more details). 
Study Day 
D-42 to -1 
D1 
D15 
D71 
D127 
D183 
D239 
D295 
D351 
 
Window (day) 
 
 
± 2 
± 3 
± 3 
 
± 3 
± 3 
± 3 
± 3 
Weeks 
Up to 
6 weeks 
 
W2 
W10 
W18 
W26 
W34 
W42 
W50 
Informed consent 
X 
 
 
 
 
 
 
 
 
 
 
Assessment of 
inclusion/ exclusion 
criteria 
X 
 
 
 
 
 
 
 
 
 
 
Medical history 
X 
 
 
 
 
 
 
 
 
 
 
DM history 
X 
 
 
 
 
 
 
 
 
 
 
ACR/EULAR criteria 
X 
 
 
 
 
 
 
 
 
 
 
Weight 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
Height 
X 
 
 
 
 
 
 
 
 
 
 
HIV-(1 and 2) testing 
X 
 
 
 
 
 
 
 
 
 
 
Vital signs 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
On dosing days, vital signs will be taken before 
study intervention administration and after the 
participant has been resting for at least 5 minutes 
(see Section 8.2.4). 

Protocol Amendment 3.0  
ALXN1210-DM-310 
23 Jun 2023 
Page 38 of 188 
Alexion Confidential 
Table 2: 
Schedule of Activities: Screening Through End of the Randomized Controlled Period for Part B (Phase 3) 
Period/Phase 
Screening 
Randomized Controlled Period 
UV 
Notes 
Study Visit 
1 
2 
3 
4 
5 
 
6 
7 
8 
9/ET 
 
 
Participants who discontinue/withdraw from the 
study should complete the study visit (if at the site 
for a scheduled visit) or return for an UV as soon as 
possible within a week and complete the ET Visit 8 
weeks after the participant’s last dose of study 
intervention. In addition, a follow-up phone call 21 
weeks (± 1 week) after the participant’s last dose of 
study intervention will be performed to collect 
information on concomitant medications, non-
pharmacologic therapies and procedures, and AEs 
(see Section 7.2 for more details). 
Participants who will not enter the OLE Period will 
complete the assessments for Week 50 but not 
receive an infusion at Week 50 (see Section 6.1.1 for 
more details). 
Study Day 
D-42 to -1 
D1 
D15 
D71 
D127 
D183 
D239 
D295 
D351 
 
Window (day) 
 
 
± 2 
± 3 
± 3 
 
± 3 
± 3 
± 3 
± 3 
Weeks 
Up to 
6 weeks 
 
W2 
W10 
W18 
W26 
W34 
W42 
W50 
Physical examination 
X 
 
 
 
 
 
 
 
X 
 
 
Abbreviated physical 
examination 
 
X 
X 
X 
X 
X 
X 
X 
 
X 
To be performed, if necessary, based on the 
participant’s health status and the clinical judgment 
of the Investigator. 
CSMs for IMACS-TIS Determination 
 
MDAAT 
X 
X 
X 
X 
X 
 
X 
 
X 
X 
X 
X 
MDAAT should be performed before the physician 
global activity assessment. 
These are the 6 IMACS core set measures that will 
be used for IMACS-TIS determination. 
 
 
 
Physician global 
activity assessment 
X 
X 
X 
X 
X 
 
X 
 
X 
X 
X 
X 
Patient global 
activity assessment 
X 
X 
X 
X 
X 
 
X 
 
X 
X 
X 
X 
MMT-8 
X 
X 
X 
X 
X 
 
X 
 
X 
X 
X 
X 
HAQ 
X 
X 
X 
X 
X 
 
X 
 
X 
X 
X 
X 
Laboratory tests for 
muscle enzymes 
X 
X 
X 
X 
X 
 
X 
 
X 
X 
X 
X 

Protocol Amendment 3.0  
ALXN1210-DM-310 
23 Jun 2023 
Page 39 of 188 
Alexion Confidential 
Table 2: 
Schedule of Activities: Screening Through End of the Randomized Controlled Period for Part B (Phase 3) 
Period/Phase 
Screening 
Randomized Controlled Period 
UV 
Notes 
Study Visit 
1 
2 
3 
4 
5 
 
6 
7 
8 
9/ET 
 
 
Participants who discontinue/withdraw from the 
study should complete the study visit (if at the site 
for a scheduled visit) or return for an UV as soon as 
possible within a week and complete the ET Visit 8 
weeks after the participant’s last dose of study 
intervention. In addition, a follow-up phone call 21 
weeks (± 1 week) after the participant’s last dose of 
study intervention will be performed to collect 
information on concomitant medications, non-
pharmacologic therapies and procedures, and AEs 
(see Section 7.2 for more details). 
Participants who will not enter the OLE Period will 
complete the assessments for Week 50 but not 
receive an infusion at Week 50 (see Section 6.1.1 for 
more details). 
Study Day 
D-42 to -1 
D1 
D15 
D71 
D127 
D183 
D239 
D295 
D351 
 
Window (day) 
 
 
± 2 
± 3 
± 3 
 
± 3 
± 3 
± 3 
± 3 
Weeks 
Up to 
6 weeks 
 
W2 
W10 
W18 
W26 
W34 
W42 
W50 
CDASI Activity and 
Damage 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
CDA-IGA 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
EQ-5D-5L 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
5D-itch scale 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
PROMIS-29 v2.1 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
SF-36 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
FACIT-Fatigue 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
DM-DSQ 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
ECG 
X 
 
 
 
 
 
 
 
X 
 
 
30s CST 
 
X 
 
 
 
 
 
 
X 
 
 
Handheld 
dynamometry 
 
X 
 
 
 
 
 
 
X 
 
 

Protocol Amendment 3.0  
ALXN1210-DM-310 
23 Jun 2023 
Page 40 of 188 
Alexion Confidential 
Table 2: 
Schedule of Activities: Screening Through End of the Randomized Controlled Period for Part B (Phase 3) 
Period/Phase 
Screening 
Randomized Controlled Period 
UV 
Notes 
Study Visit 
1 
2 
3 
4 
5 
 
6 
7 
8 
9/ET 
 
 
Participants who discontinue/withdraw from the 
study should complete the study visit (if at the site 
for a scheduled visit) or return for an UV as soon as 
possible within a week and complete the ET Visit 8 
weeks after the participant’s last dose of study 
intervention. In addition, a follow-up phone call 21 
weeks (± 1 week) after the participant’s last dose of 
study intervention will be performed to collect 
information on concomitant medications, non-
pharmacologic therapies and procedures, and AEs 
(see Section 7.2 for more details). 
Participants who will not enter the OLE Period will 
complete the assessments for Week 50 but not 
receive an infusion at Week 50 (see Section 6.1.1 for 
more details). 
Study Day 
D-42 to -1 
D1 
D15 
D71 
D127 
D183 
D239 
D295 
D351 
 
Window (day) 
 
 
± 2 
± 3 
± 3 
 
± 3 
± 3 
± 3 
± 3 
Weeks 
Up to 
6 weeks 
 
W2 
W10 
W18 
W26 
W34 
W42 
W50 
Clinical laboratory 
tests 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Clinical laboratory tests will be performed at the 
central laboratory or designated third party 
laboratory. Coagulation laboratory test to be 
completed at Screening only. 
Urinalysis 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
FSH 
X 
 
 
 
 
 
 
 
 
 
Performed at Screening in selected female 
participants to confirm postmenopausal status. 
Pregnancy test 
(WOCBP only) 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Local urine testing will be standard for this study 
unless serum testing is required by local regulation 
or ethics committees. Testing will be done at 
indicated visits and when necessary at Investigator’s 
discretion (Section 8.2.7). 

Protocol Amendment 3.0  
ALXN1210-DM-310 
23 Jun 2023 
Page 41 of 188 
Alexion Confidential 
Table 2: 
Schedule of Activities: Screening Through End of the Randomized Controlled Period for Part B (Phase 3) 
Period/Phase 
Screening 
Randomized Controlled Period 
UV 
Notes 
Study Visit 
1 
2 
3 
4 
5 
 
6 
7 
8 
9/ET 
 
 
Participants who discontinue/withdraw from the 
study should complete the study visit (if at the site 
for a scheduled visit) or return for an UV as soon as 
possible within a week and complete the ET Visit 8 
weeks after the participant’s last dose of study 
intervention. In addition, a follow-up phone call 21 
weeks (± 1 week) after the participant’s last dose of 
study intervention will be performed to collect 
information on concomitant medications, non-
pharmacologic therapies and procedures, and AEs 
(see Section 7.2 for more details). 
Participants who will not enter the OLE Period will 
complete the assessments for Week 50 but not 
receive an infusion at Week 50 (see Section 6.1.1 for 
more details). 
Study Day 
D-42 to -1 
D1 
D15 
D71 
D127 
D183 
D239 
D295 
D351 
 
Window (day) 
 
 
± 2 
± 3 
± 3 
 
± 3 
± 3 
± 3 
± 3 
Weeks 
Up to 
6 weeks 
 
W2 
W10 
W18 
W26 
W34 
W42 
W50 
PK/PD  
 
B/P 
T/P 
T/P 
T/P 
T/P 
T/P 
T/P 
T 
X 
Baseline (B) and trough (T) blood samples for PK 
and PD will be collected predose (within 90 minutes 
prior to the start of infusion of study intervention). 
Peak (P) blood samples for PK/PD samples are to be 
taken within the 60 minutes following completion of 
study intervention infusion. B and T samples may be 
drawn through the venous access created for the 
dose infusion, prior to administration of the dose. 
The P samples will be drawn from the participant’s 
opposite, non-infused arm. On Day 351 (Week 50), 
the T sample is considered a Randomized Controlled 
Period assessment and the P sample is considered an 
Extension Period assessment. ET or UV PK/PD 
sample will be collected anytime. All collection 
times will be recorded in eCRF.  

Protocol Amendment 3.0  
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Alexion Confidential 
Table 2: 
Schedule of Activities: Screening Through End of the Randomized Controlled Period for Part B (Phase 3) 
Period/Phase 
Screening 
Randomized Controlled Period 
UV 
Notes 
Study Visit 
1 
2 
3 
4 
5 
 
6 
7 
8 
9/ET 
 
 
Participants who discontinue/withdraw from the 
study should complete the study visit (if at the site 
for a scheduled visit) or return for an UV as soon as 
possible within a week and complete the ET Visit 8 
weeks after the participant’s last dose of study 
intervention. In addition, a follow-up phone call 21 
weeks (± 1 week) after the participant’s last dose of 
study intervention will be performed to collect 
information on concomitant medications, non-
pharmacologic therapies and procedures, and AEs 
(see Section 7.2 for more details). 
Participants who will not enter the OLE Period will 
complete the assessments for Week 50 but not 
receive an infusion at Week 50 (see Section 6.1.1 for 
more details). 
Study Day 
D-42 to -1 
D1 
D15 
D71 
D127 
D183 
D239 
D295 
D351 
 
Window (day) 
 
 
± 2 
± 3 
± 3 
 
± 3 
± 3 
± 3 
± 3 
Weeks 
Up to 
6 weeks 
 
W2 
W10 
W18 
W26 
W34 
W42 
W50 
ADA 
 
B 
 
T 
 
 
 
 
T 
X 
Baseline (B) and trough (T) blood samples for ADA 
will be collected predose (within 90 minutes prior to 
the start of infusion of study intervention). ET or UV 
ADA sample will be collected anytime. 
Blood sample for 
biomarkers  
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Blood samples for biomarkers should be collected 
predose on dosing days. Samples can be collected at 
any time on non-dosing days. 
Blood samples for Myositis-specific autoantibodies 
will be collected on Day 1 and Day 351 or ET. 
Neisseria meningitidis 
vaccination 
X 
 
 
 
 
 
 
 
 
 
To reduce the risk of meningococcal infection 
(N meningitidis), all participants must be vaccinated 
against meningococcal infections within 3 years 
prior to initiating study intervention as per national 
and local guidelines. Participants must receive the 
vaccination at least 2 weeks before first study 
intervention. The sponsor recommends that national 
and local guidelines for prophylactic antibiotics 
should also be followed. 

Protocol Amendment 3.0  
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23 Jun 2023 
Page 43 of 188 
Alexion Confidential 
Table 2: 
Schedule of Activities: Screening Through End of the Randomized Controlled Period for Part B (Phase 3) 
Period/Phase 
Screening 
Randomized Controlled Period 
UV 
Notes 
Study Visit 
1 
2 
3 
4 
5 
 
6 
7 
8 
9/ET 
 
 
Participants who discontinue/withdraw from the 
study should complete the study visit (if at the site 
for a scheduled visit) or return for an UV as soon as 
possible within a week and complete the ET Visit 8 
weeks after the participant’s last dose of study 
intervention. In addition, a follow-up phone call 21 
weeks (± 1 week) after the participant’s last dose of 
study intervention will be performed to collect 
information on concomitant medications, non-
pharmacologic therapies and procedures, and AEs 
(see Section 7.2 for more details). 
Participants who will not enter the OLE Period will 
complete the assessments for Week 50 but not 
receive an infusion at Week 50 (see Section 6.1.1 for 
more details). 
Study Day 
D-42 to -1 
D1 
D15 
D71 
D127 
D183 
D239 
D295 
D351 
 
Window (day) 
 
 
± 2 
± 3 
± 3 
 
± 3 
± 3 
± 3 
± 3 
Weeks 
Up to 
6 weeks 
 
W2 
W10 
W18 
W26 
W34 
W42 
W50 
Participant Safety 
Card 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Participants will be given a Participant Safety Card 
prior to the first dose of study intervention. At each 
visit throughout the study, the study staff will ensure 
that the participant has the Participant Safety Card. 
Randomization 
 
X 
 
 
 
 
 
 
 
 
 
Clinical Worsening 
criteria check 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
Clinical Worsening criteria are described in 
Section 4.1.3. A scheduled visit or UV will occur 4 
weeks (± 7 days) later. Clinical Worsening is 
confirmed if criteria are met on two 2 consecutive 
visits.  
Ravulizumab or 
placebo infusion 
 
X 
X 
X 
X 
X 
X 
X 
 
X 
Study intervention will be administered 
intravenously via infusion after completion of all 
other tests and procedures, excluding the peak (P) 
blood sampling for PK/PD. 
Unscheduled doses should be discussed with the 
Sponsor or designee. 

Protocol Amendment 3.0  
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23 Jun 2023 
Page 44 of 188 
Alexion Confidential 
Table 2: 
Schedule of Activities: Screening Through End of the Randomized Controlled Period for Part B (Phase 3) 
Period/Phase 
Screening 
Randomized Controlled Period 
UV 
Notes 
Study Visit 
1 
2 
3 
4 
5 
 
6 
7 
8 
9/ET 
 
 
Participants who discontinue/withdraw from the 
study should complete the study visit (if at the site 
for a scheduled visit) or return for an UV as soon as 
possible within a week and complete the ET Visit 8 
weeks after the participant’s last dose of study 
intervention. In addition, a follow-up phone call 21 
weeks (± 1 week) after the participant’s last dose of 
study intervention will be performed to collect 
information on concomitant medications, non-
pharmacologic therapies and procedures, and AEs 
(see Section 7.2 for more details). 
Participants who will not enter the OLE Period will 
complete the assessments for Week 50 but not 
receive an infusion at Week 50 (see Section 6.1.1 for 
more details) 
Study Day 
D-42 to -1 
D1 
D15 
D71 
D127 
D183 
D239 
D295 
D351 
 
Window (day) 
 
 
± 2 
± 3 
± 3 
 
± 3 
± 3 
± 3 
± 3 
Weeks 
Up to 
6 weeks 
 
W2 
W10 
W18 
W26 
W34 
W42 
W50 
Concomitant 
medication 
Continuous monitoring 
 
Non-drug therapy 
Continuous monitoring 
 
Adverse event 
Continuous monitoring 
 
Abbreviations: 30s CST = 30-second Chair Stand Test; ACR/EULAR = American College of Rheumatology/European League Against Rheumatism; 
ADA = antidrug antibody; AE = adverse event; CDA-IGA = Cutaneous Dermatomyositis Activity Physician’s Global Assessment; CDASI = Cutaneous 
Dermatomyositis Disease Area and Severity Index; CSM = core set measures; D = day; DM = dermatomyositis; DM-DSQ = Dermatomyositis Disease 
Symptoms Questionnaire; ECG = electrocardiogram; eCRF = electronic case report form; EQ-5D-5L = European Quality of Life Health 5-item 
questionnaire dimensions 5 level; ET = Early Termination; FACIT = Functional Assessment of Chronic Illness Therapy; FSH = follicle stimulating 
hormone; HAQ = Health Assessment Questionnaire; HIV = human immunodeficiency virus; IMACS-TIS = International Myositis Assessment and Clinical 
Studies-Total Improvement Score; MDAAT = Myositis Disease Activity Assessment Tool; MMT-8 = Manual Muscle Testing subset of 8 muscles; PD = 
pharmacodynamic(s); PK = pharmacokinetic(s); PROMIS = Patient-reported Outcomes Measurement Information System; SF-36 = Short Form Health 
Survey (36 questions version); UV = Unscheduled Visit; W = week(s); WOCBP = women of childbearing potential 
 

Protocol Amendment 3.0  
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23 Jun 2023 
Page 45 of 188 
Alexion Confidential 
Table 3: 
Schedule of Activities: Open-Label Extension Period for Part A (Phase 2) – Week 26 to Week 100  
Period 
Open-Label Extension Period 
Notes 
Visit 
 
6 
7 
8 
9 
10 
11 
12 
13 
14 
15 
16 
OLE Period begins at the start of dosing on Day 
183  
Participants who discontinue/ withdraw from the 
study should complete the ET Visit 8 weeks after 
the participant’s last dose of study intervention. In 
addition, a follow-up phone call 21 weeks (± 1 
week) after the participant’s last dose of study 
intervention will be performed to collect 
information on concomitant medications, non-
pharmacologic therapies and procedures, and AEs 
(see Section 7.2 for more details). 
Days 
D183 
D197 
D253 
D309 
D365 
D421 
D477 
D533 
D589 
D645 
D701 
Weeks 
W26 
W28 
W36 
W44 
W52 
W60 
W68 
W76 
W84 
W92 
W100 
Window (day) 
± 3 
± 3 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
Weight 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
Vital signs 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
On dosing days, vital signs will be taken before 
study intervention administration and after the 
participant has been resting for at least 5 minutes 
(see Section 8.2.4). 
Abbreviated 
physical 
examination 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
To be performed, if necessary, based on the 
participant’s health status and the clinical judgment 
of the Investigator. 
CSMs for IMACS-TIS Determination 
 
▪ 
MDAAT 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
MDAAT should be performed before the physician 
global activity assessment. 
These are the 6 IMACS core set measures that will 
be used for IMACS-TIS determination. 
 
 
▪ 
Physician 
global activity 
assessment 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
▪ 
Patient global 
activity 
assessment 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
▪ 
MMT-8 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
▪ 
HAQ 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
▪ 
Laboratory 
tests for muscle 
enzymes 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 

Protocol Amendment 3.0  
ALXN1210-DM-310 
23 Jun 2023 
Page 46 of 188 
Alexion Confidential 
Table 3: 
Schedule of Activities: Open-Label Extension Period for Part A (Phase 2) – Week 26 to Week 100  
Period 
Open-Label Extension Period 
Notes 
Visit 
 
6 
7 
8 
9 
10 
11 
12 
13 
14 
15 
16 
OLE Period begins at the start of dosing on Day 
183  
Participants who discontinue/ withdraw from the 
study should complete the ET Visit 8 weeks after 
the participant’s last dose of study intervention. In 
addition, a follow-up phone call 21 weeks (± 1 
week) after the participant’s last dose of study 
intervention will be performed to collect 
information on concomitant medications, non-
pharmacologic therapies and procedures, and AEs 
(see Section 7.2 for more details). 
Days 
D183 
D197 
D253 
D309 
D365 
D421 
D477 
D533 
D589 
D645 
D701 
Weeks 
W26 
W28 
W36 
W44 
W52 
W60 
W68 
W76 
W84 
W92 
W100 
Window (day) 
± 3 
± 3 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
CDASI Activity and 
Damage 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
CDA-IGA 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
EQ-5D-5L 
X 
X 
X 
X 
X 
X 
X 
X 
 
5D-itch scale 
 
 
X 
 
X 
X 
X 
X 
X 
X 
X 
 
PROMIS-29 v2.1 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
SF-36 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
FACIT-Fatigue 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
DM-DSQ 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
  
ECG 
X 
 
30s CST 
 
 
X 
 
 
 
 
 
 
 
X 
 
Handheld 
dynamometry 
 
 
 
X 
 
 
 
X 
 
 
X 
 
Clinical laboratory 
tests 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Clinical laboratory tests will be performed at the 
central laboratory or designated third party 
laboratory. 
Urinalysis 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 

Protocol Amendment 3.0  
ALXN1210-DM-310 
23 Jun 2023 
Page 47 of 188 
Alexion Confidential 
Table 3: 
Schedule of Activities: Open-Label Extension Period for Part A (Phase 2) – Week 26 to Week 100  
Period 
Open-Label Extension Period 
Notes 
Visit 
 
6 
7 
8 
9 
10 
11 
12 
13 
14 
15 
16 
OLE Period begins at the start of dosing on Day 
183  
Participants who discontinue/ withdraw from the 
study should complete the ET Visit 8 weeks after 
the participant’s last dose of study intervention. In 
addition, a follow-up phone call 21 weeks (± 1 
week) after the participant’s last dose of study 
intervention will be performed to collect 
information on concomitant medications, non-
pharmacologic therapies and procedures, and AEs 
(see Section 7.2 for more details). 
Days 
D183 
D197 
D253 
D309 
D365 
D421 
D477 
D533 
D589 
D645 
D701 
Weeks 
W26 
W28 
W36 
W44 
W52 
W60 
W68 
W76 
W84 
W92 
W100 
Window (day) 
± 3 
± 3 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
Pregnancy test 
(WOCBP only) 
 
X 
X  
X 
X  
X 
X 
X 
X 
X 
X 
Local urine testing will be standard for this study 
unless serum testing is required by local regulation 
or ethics committees. Testing will be done at 
indicated visits and when necessary at 
Investigator’s discretion (Section 8.2.7). 
PK/PD 
P 
T/P 
T/P 
T/P 
T/P 
T/P 
Trough (T) blood samples for PK and PD will be 
collected predose (within 90 minutes prior to the 
start of infusion of study intervention). Peak (P) 
blood samples for PK/PD are to be taken within the 
60 minutes following completion of study 
intervention infusion. The T samples may be drawn 
through the venous access created for the dose 
infusion, prior to administration of the dose. The P 
samples will be drawn from the participant’s 
opposite, non-infused arm. All collection times will 
be recorded in the eCRF. 
ADA 
T 
T 
T 
T 
Trough (T) blood samples for ADA will be 
collected predose (within 90 minutes prior to the 
start of infusion of study intervention).  
Blood sample for 
biomarkers  
X 
X 
X 
X 
X 
X 
Blood samples for biomarkers should be collected 
predose on dosing days. Samples can be collected 
at any time on non-dosing days. 
Participant Safety 
Card 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
At each visit throughout the study, staff will ensure 
that the participant has the Participant Safety Card. 

Protocol Amendment 3.0  
ALXN1210-DM-310 
23 Jun 2023 
Page 48 of 188 
Alexion Confidential 
Table 3: 
Schedule of Activities: Open-Label Extension Period for Part A (Phase 2) – Week 26 to Week 100  
Period 
Open-Label Extension Period 
Notes 
Visit 
 
6 
7 
8 
9 
10 
11 
12 
13 
14 
15 
16 
OLE Period begins at the start of dosing on Day 
183  
Participants who discontinue/ withdraw from the 
study should complete the ET Visit 8 weeks after 
the participant’s last dose of study intervention. In 
addition, a follow-up phone call 21 weeks (± 1 
week) after the participant’s last dose of study 
intervention will be performed to collect 
information on concomitant medications, non-
pharmacologic therapies and procedures, and AEs 
(see Section 7.2 for more details). 
Days 
D183 
D197 
D253 
D309 
D365 
D421 
D477 
D533 
D589 
D645 
D701 
Weeks 
W26 
W28 
W36 
W44 
W52 
W60 
W68 
W76 
W84 
W92 
W100 
Window (day) 
± 3 
± 3 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
Clinical Worsening 
criteria check 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Clinical Worsening criteria are described in 
Section 4.1.3. A scheduled visit or UV will occur 4 
weeks (± 7 days) later. Clinical Worsening is 
confirmed if criteria are met on 2 consecutive visits. 
Ravulizumab 
infusion 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Ravulizumab will be administered intravenously 
via infusion after completion of all predose tests 
and procedures. 
Unscheduled infusions should be discussed with the 
Medical Monitor or designee. 
Concomitant 
Medication 
Continuous monitoring 
 
Non-drug therapy 
Continuous monitoring 
 
Adverse event 
Continuous monitoring 
 
Abbreviations: 30s CST = 30-second Chair Stand Test; ADA = antidrug antibody; AE = adverse event; CDA-IGA = Cutaneous Dermatomyositis Activity 
Physician’s Global Assessment; CDASI = Cutaneous Dermatomyositis Disease Area and Severity Index; CSM = core set measures; D = day; DM-
DSQ = Dermatomyositis Disease Symptoms Questionnaire; ECG = electrocardiogram; eCRF = electronic case report form; EOS = end of study; EQ-5D-
5L = European Quality of Life Health 5-item questionnaire dimensions 5 level; ET = Early Termination; FACIT = Functional Assessment of Chronic Illness 
Therapy; HAQ = Health Assessment Questionnaire; IMACS-TIS = International Myositis Assessment and Clinical Studies-Total Improvement Score; 
MDAAT = Myositis Disease Activity Assessment Tool; MMT-8 = Manual Muscle Testing subset of 8 muscles; OLE = Open-Label Extension; 
PD = pharmacodynamic(s); PK = pharmacokinetic(s); PROMIS = Participant-reported Outcomes Measurement Information System; SF-36 = Short Form 
Health Survey (36 questions version; UV = Unscheduled Visit; W = week(s); WOCBP = women of childbearing potential 

Protocol Amendment 3.0  
ALXN1210-DM-310 
23 Jun 2023 
Page 49 of 188 
Alexion Confidential 
Table 4: 
Schedule of Activities: Open-Label Extension Period for Part A (Phase 2) – Week 108 – Week 156  
Period 
Open-Label Extension Period 
UV 
Notes 
Visit 
 
17 
18 
19 
20 
21 
22 
23/ 
ET/EOS 
 
OLE Period begins at the start of dosing on Day 183  
Participants who discontinue/withdraw from the study should complete 
the ET Visit 8 weeks after the participant’s last dose of study 
intervention. In addition, a follow-up phone call 21 weeks (± 1 week) 
after the participant’s last dose of study intervention will be performed 
to collect information on concomitant medications, non-pharmacologic 
therapies and procedures, and AEs (see Section 7.2 for more details). 
Days 
D757 
D813 
D869 
D925 
D981 
D1037 
D1079 
Weeks 
W108 
W116 
W124 
W132 
W140 
W148 
W156 
Window (day) 
± 3 
± 3 
± 7 
± 7 
± 7 
± 7 
± 7 
Weight 
X 
X 
X 
X 
X 
X 
X 
 
 
Vital signs 
X 
X 
X 
X 
X 
X 
X 
X 
On dosing days, vital signs will be taken before study intervention 
administration and after the participant has been resting for at least 
5 minutes (see Section 8.2.4). 
Physical 
Examination 
 
 
 
 
 
 
 
X 
 
Abbreviated 
physical 
examination 
X 
X 
X 
X 
X 
X 
X 
 
To be performed, if necessary, based on the participant’s health status 
and the clinical judgment of the Investigator. 
CSMs for IMACS-TIS Determination 
 
MDAAT 
X 
X 
X 
X 
X 
X 
X 
X 
MDAAT should be performed before the physician global activity 
assessment. 
These are the 6 IMACS core set measures that will be used for IMACS-
TIS determination. 
 
 
Physician global 
activity 
assessment 
X 
X 
X 
X 
X 
X 
X 
X 
Patient global 
activity 
assessment 
X 
X 
X 
X 
X 
X 
X 
X 
MMT-8 
X 
X 
X 
X 
X 
X 
X 
X 
HAQ 
X 
X 
X 
X 
X 
X 
X 
X 
Laboratory tests 
for muscle 
enzymes 
X 
X 
X 
X 
X 
X 
X 
X 
CDASI Activity and 
Damage 
X 
X 
X 
X 
X 
X 
X 
X 
 

Protocol Amendment 3.0  
ALXN1210-DM-310 
23 Jun 2023 
Page 50 of 188 
Alexion Confidential 
Table 4: 
Schedule of Activities: Open-Label Extension Period for Part A (Phase 2) – Week 108 – Week 156  
Period 
Open-Label Extension Period 
UV 
Notes 
Visit 
 
17 
18 
19 
20 
21 
22 
23/ 
ET/EOS 
 
OLE Period begins at the start of dosing on Day 183  
Participants who discontinue/withdraw from the study should complete 
the ET Visit 8 weeks after the participant’s last dose of study 
intervention. In addition, a follow-up phone call 21 weeks (± 1 week) 
after the participant’s last dose of study intervention will be performed 
to collect information on concomitant medications, non-pharmacologic 
therapies and procedures, and AEs (see Section 7.2 for more details). 
Days 
D757 
D813 
D869 
D925 
D981 
D1037 
D1079 
Weeks 
W108 
W116 
W124 
W132 
W140 
W148 
W156 
Window (day) 
± 3 
± 3 
± 7 
± 7 
± 7 
± 7 
± 7 
EQ-5D-5L 
X 
 
X 
 
X 
 
X 
 
 
SF-36 
X 
 
X 
 
X 
 
X 
 
 
DM-DSQ 
X 
X 
X 
X 
X 
X 
X 
X 
 
ECG 
X 
X 
 
Clinical laboratory 
tests 
X 
X 
X 
X 
X 
X 
X 
X 
Clinical laboratory tests will be performed at the central laboratory or 
designated third party laboratory. 
Urinalysis 
X 
X 
X 
X 
X 
X 
X 
X 
 
Pregnancy test 
(WOCBP only) 
X 
X 
X 
X 
X 
X 
X 
X 
Local urine testing will be standard for this study unless serum testing is 
required by local regulation or ethics committees. Testing will be done 
at indicated visits and when necessary at Investigator’s discretion 
(Section 8.2.7). 
PK/PD 
 
 
 
T/P 
 
 
X 
X 
Trough (T) blood samples for PK and PD will be collected predose 
(within 90 minutes prior to the start of infusion of study intervention). 
Peak (P) blood samples for PK/PD are to be taken within the 60 minutes 
following completion of study intervention infusion. The T samples 
may be drawn through the venous access created for the dose infusion, 
prior to administration of the dose. The P samples will be drawn from 
the participant’s opposite, non-infused arm. The Day 1079/ET/EOS, or 
UV PK/PD sample will be collected anytime. All collection times will 
be recorded in the eCRF. 
ADA 
 
T 
 
 
X 
X 
Trough (T) blood samples for ADA will be collected predose (within 
90 minutes prior to the start of infusion of study intervention). 
Day 1079/ET/EOS, or UV ADA sample will be collected anytime. 
Participant Safety 
Card 
X 
X 
X 
X 
X 
X 
X 
X 
At each visit throughout the study, staff will ensure that the participant 
has the Participant Safety Card. 

Protocol Amendment 3.0  
ALXN1210-DM-310 
23 Jun 2023 
Page 51 of 188 
Alexion Confidential 
Table 4: 
Schedule of Activities: Open-Label Extension Period for Part A (Phase 2) – Week 108 – Week 156  
Period 
Open-Label Extension Period 
UV 
Notes 
Visit 
 
17 
18 
19 
20 
21 
22 
23/ 
ET/EOS 
 
OLE Period begins at the start of dosing on Day 183  
Participants who discontinue/withdraw from the study should complete 
the ET Visit 8 weeks after the participant’s last dose of study 
intervention. In addition, a follow-up phone call 21 weeks (± 1 week) 
after the participant’s last dose of study intervention will be performed 
to collect information on concomitant medications, non-pharmacologic 
therapies and procedures, and AEs (see Section 7.2 for more details). 
Days 
D757 
D813 
D869 
D925 
D981 
D1037 
D1079 
Weeks 
W108 
W116 
W124 
W132 
W140 
W148 
W156 
Window (day) 
± 3 
± 3 
± 7 
± 7 
± 7 
± 7 
± 7 
Clinical Worsening 
criteria check 
X 
X 
X 
X 
X 
X 
X 
X 
Clinical Worsening criteria are described in Section 4.1.3. A scheduled 
visit or UV will occur 4 weeks (± 7 days) later. Clinical Worsening is 
confirmed if criteria are met on 2 consecutive visits. 
Ravulizumab 
infusion 
X 
X 
X 
X 
X 
X 
 
X 
Ravulizumab will be administered intravenously via infusion after 
completion of all predose tests and procedures. 
Unscheduled infusions should be discussed with the Medical Monitor or 
designee. 
Concomitant 
Medication 
Continuous monitoring 
 
Non-drug therapy 
Continuous monitoring 
 
Adverse event 
Continuous monitoring 
 
Abbreviations: 30s CST = 30-second Chair Stand Test; ADA = antidrug antibody; AE = adverse event; CDA-IGA = Cutaneous Dermatomyositis Activity 
Physician’s Global Assessment; CDASI = Cutaneous Dermatomyositis Disease Area and Severity Index; CSM = core set measures; D = day; DM-
DSQ = Dermatomyositis Disease Symptoms Questionnaire; ECG = electrocardiogram; eCRF = electronic case report form; EOS = end of study; EQ-5D-
5L = European Quality of Life Health 5-item questionnaire dimensions 5 level; ET = Early Termination; FACIT = Functional Assessment of Chronic Illness 
Therapy; HAQ = Health Assessment Questionnaire; IMACS-TIS = International Myositis Assessment and Clinical Studies-Total Improvement Score; 
MDAAT = Myositis Disease Activity Assessment Tool; MMT-8 = Manual Muscle Testing subset of 8 muscles; OLE = Open-Label Extension; 
PD = pharmacodynamic(s); PK = pharmacokinetic(s); PROMIS = Participant-reported Outcomes Measurement Information System; SF-36 = Short Form 
Health Survey (36 questions version; UV = Unscheduled Visit; W = week(s); WOCBP = women of childbearing potential 
 

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Table 5: 
Schedule of Activities: Open-Label Extension Period for Part B (Phase 3) 
Period 
Open-Label Extension Period 
UV 
Notes 
Visit 
9 
10 
11 
12 
13 
14 
15 
16 
17 
18 
19/ET/
EOS 
 
OLE Period begins at the start of dosing 
on Day 351.  
Participants who discontinue/ withdraw 
from the study should complete the ET 
Visit 8 weeks after the participant’s last 
dose of study intervention. In addition, a 
follow-up phone call 21 weeks (± 1 week) 
after the participant’s last dose of study 
intervention will be performed to collect 
information on concomitant medications, 
non-pharmacologic therapies and 
procedures, and AEs (see Section 7.2 for 
more details). 
Days 
D351 
D365 
D421 
D477 
D533 
D589 
D645 
D701 
D757 
D813 
D869 
Weeks 
W50 
W52 
W60 
W68 
W76 
W84 
W92 
W100 
W108 
W116 
W124 
Window (day) 
± 3 
± 3 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
Weight 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
Vital signs 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
On dosing days, vital signs will be taken 
before study intervention administration 
and after the participant has been resting 
for at least 5 minutes (see Section 8.2.4). 
Physical 
examination 
X 
 
 
Abbreviated 
physical 
examination 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
To be performed, if necessary, based on 
the participant’s health status and the 
clinical judgment of the Investigator. 

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Table 5: 
Schedule of Activities: Open-Label Extension Period for Part B (Phase 3) 
Period 
Open-Label Extension Period 
UV 
Notes 
Visit 
9 
10 
11 
12 
13 
14 
15 
16 
17 
18 
19/ET/
EOS 
 
OLE Period begins at the start of dosing 
on Day 351.  
Participants who discontinue/ withdraw 
from the study should complete the ET 
Visit 8 weeks after the participant’s last 
dose of study intervention. In addition, a 
follow-up phone call 21 weeks (± 1 week) 
after the participant’s last dose of study 
intervention will be performed to collect 
information on concomitant medications, 
non-pharmacologic therapies and 
procedures, and AEs (see Section 7.2 for 
more details). 
Days 
D351 
D365 
D421 
D477 
D533 
D589 
D645 
D701 
D757 
D813 
D869 
Weeks 
W50 
W52 
W60 
W68 
W76 
W84 
W92 
W100 
W108 
W116 
W124 
Window (day) 
± 3 
± 3 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
CSMs for IMACS-TIS Determination 
 
MDAAT 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
MDAAT should be performed before the 
physician global activity assessment. 
These are the 6 IMACS core set measures 
that will be used for IMACS-TIS 
determination. 
 
 
Physician global 
activity 
assessment 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Patient global 
activity 
assessment 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
MMT-8 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
HAQ 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Laboratory tests 
for muscle 
enzymes 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
CDASI Activity and 
Damage 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
CDA-IGA 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
EQ-5D-5L 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
5D-itch scale 
 
 
X 
 
X 
X 
X 
X 
X 
X 
X 
 
 
PROMIS-29 v2.1 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 

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Table 5: 
Schedule of Activities: Open-Label Extension Period for Part B (Phase 3) 
Period 
Open-Label Extension Period 
UV 
Notes 
Visit 
9 
10 
11 
12 
13 
14 
15 
16 
17 
18 
19/ET/
EOS 
 
OLE Period begins at the start of dosing 
on Day 351.  
Participants who discontinue/ withdraw 
from the study should complete the ET 
Visit 8 weeks after the participant’s last 
dose of study intervention. In addition, a 
follow-up phone call 21 weeks (± 1 week) 
after the participant’s last dose of study 
intervention will be performed to collect 
information on concomitant medications, 
non-pharmacologic therapies and 
procedures, and AEs (see Section 7.2 for 
more details). 
Days 
D351 
D365 
D421 
D477 
D533 
D589 
D645 
D701 
D757 
D813 
D869 
Weeks 
W50 
W52 
W60 
W68 
W76 
W84 
W92 
W100 
W108 
W116 
W124 
Window (day) 
± 3 
± 3 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
SF-36 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
FACIT-Fatigue 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
DM-DSQ 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
  
ECG 
X 
 
 
30s CST 
 
 
X 
 
 
 
 
 
 
 
X 
 
 
Handheld 
dynamometry 
 
 
 
X 
 
 
 
X 
 
 
X 
 
 
Clinical laboratory 
tests 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Clinical laboratory tests will be performed 
at the central laboratory or designated third 
party laboratory. 
Urinalysis 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
 
Pregnancy test 
(WOCBP only) 
 
X 
X  
X 
X  
X 
X 
X 
X 
X 
X 
X 
Local urine testing will be standard for this 
study unless serum testing is required by 
local regulation or ethics committees. 
Testing will be done at indicated visits and 
when necessary at Investigator’s discretion 
(Section 8.2.7). 

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Table 5: 
Schedule of Activities: Open-Label Extension Period for Part B (Phase 3) 
Period 
Open-Label Extension Period 
UV 
Notes 
Visit 
9 
10 
11 
12 
13 
14 
15 
16 
17 
18 
19/ET/
EOS 
 
OLE Period begins at the start of dosing 
on Day 351.  
Participants who discontinue/ withdraw 
from the study should complete the ET 
Visit 8 weeks after the participant’s last 
dose of study intervention. In addition, a 
follow-up phone call 21 weeks (± 1 week) 
after the participant’s last dose of study 
intervention will be performed to collect 
information on concomitant medications, 
non-pharmacologic therapies and 
procedures, and AEs (see Section 7.2 for 
more details). 
Days 
D351 
D365 
D421 
D477 
D533 
D589 
D645 
D701 
D757 
D813 
D869 
Weeks 
W50 
W52 
W60 
W68 
W76 
W84 
W92 
W100 
W108 
W116 
W124 
Window (day) 
± 3 
± 3 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
PK/PD 
P 
T/P 
T/P 
 
T/P 
 
 
T/P 
 
 
X 
X 
Trough (T) blood samples for PK and PD 
will be collected predose (within 
90 minutes prior to the start of infusion of 
study intervention). Peak (P) blood 
samples for PK/PD are to be taken within 
the 60 minutes following completion of 
study intervention infusion. The T samples 
may be drawn through the venous access 
created for the dose infusion, prior to 
administration of the dose. The P samples 
will be drawn from the participant’s 
opposite, non-infused arm. The Day 
869/ET/EOS, or UV PK/PD sample will 
be collected anytime. All collection times 
will be recorded in the eCRF. 

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Table 5: 
Schedule of Activities: Open-Label Extension Period for Part B (Phase 3) 
Period 
Open-Label Extension Period 
UV 
Notes 
Visit 
9 
10 
11 
12 
13 
14 
15 
16 
17 
18 
19/ET/
EOS 
 
OLE Period begins at the start of dosing 
on Day 351.  
Participants who discontinue/ withdraw 
from the study should complete the ET 
Visit 8 weeks after the participant’s last 
dose of study intervention. In addition, a 
follow-up phone call 21 weeks (± 1 week) 
after the participant’s last dose of study 
intervention will be performed to collect 
information on concomitant medications, 
non-pharmacologic therapies and 
procedures, and AEs (see Section 7.2 for 
more details). 
Days 
D351 
D365 
D421 
D477 
D533 
D589 
D645 
D701 
D757 
D813 
D869 
Weeks 
W50 
W52 
W60 
W68 
W76 
W84 
W92 
W100 
W108 
W116 
W124 
Window (day) 
± 3 
± 3 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
ADA 
 
 
T 
 
T 
 
 
T 
 
 
X 
X 
Trough (T) blood samples for ADA will 
be collected predose (within 90 minutes 
prior to the start of infusion of study 
intervention). Day 869/ET/EOS, or UV 
ADA sample will be collected anytime. 
Blood sample for 
biomarkers  
X 
X 
X 
X 
X 
X 
X 
Blood samples for biomarkers should be 
collected predose on dosing days. Samples 
can be collected at any time on non-dosing 
days. 
Blood samples for Myositis-specific 
autoantibodies will be collected on Day 
869 (contingent on first 2 tests).  
Participant Safety 
Card 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
At each visit throughout the study, staff 
will ensure that the participant has the 
Participant Safety Card. 
Clinical Worsening 
criteria check 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Clinical Worsening criteria are described 
in Section 4.1.3. A scheduled visit or UV 
will occur 4 weeks (± 7 days) later. 
Clinical Worsening is confirmed if criteria 
are met on 2 consecutive visits. 

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Table 5: 
Schedule of Activities: Open-Label Extension Period for Part B (Phase 3) 
Period 
Open-Label Extension Period 
UV 
Notes 
Visit 
9 
10 
11 
12 
13 
14 
15 
16 
17 
18 
19/ET/
EOS 
 
OLE Period begins at the start of dosing 
on Day 351.  
Participants who discontinue/ withdraw 
from the study should complete the ET 
Visit 8 weeks after the participant’s last 
dose of study intervention. In addition, a 
follow-up phone call 21 weeks (± 1 week) 
after the participant’s last dose of study 
intervention will be performed to collect 
information on concomitant medications, 
non-pharmacologic therapies and 
procedures, and AEs (see Section 7.2 for 
more details). 
Days 
D351 
D365 
D421 
D477 
D533 
D589 
D645 
D701 
D757 
D813 
D869 
Weeks 
W50 
W52 
W60 
W68 
W76 
W84 
W92 
W100 
W108 
W116 
W124 
Window (day) 
± 3 
± 3 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
± 7 
Ravulizumab 
infusion 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
 
X 
Ravulizumab will be administered 
intravenously via infusion after completion 
of all predose tests and procedures. 
Unscheduled infusions should be 
discussed with the Medical Monitor or 
designee. 
Concomitant 
Medication 
Continuous monitoring 
 
Non-drug therapy 
Continuous monitoring 
 
Adverse event 
Continuous monitoring 
 
Abbreviations: 30s CST = 30-second Chair Stand Test; ADA = antidrug antibody; AE = adverse event; CDA-IGA = Cutaneous Dermatomyositis Activity 
Physician’s Global Assessment; CDASI = Cutaneous Dermatomyositis Disease Area and Severity Index; CSM = core set measures; D = day; DM-
DSQ = Dermatomyositis Disease Symptoms Questionnaire; ECG = electrocardiogram; eCRF = electronic case report form; EOS = end of study; EQ-5D-
5L = European Quality of Life Health 5-item questionnaire dimensions 5 level; ET = Early Termination; FACIT = Functional Assessment of Chronic Illness 
Therapy; HAQ = Health Assessment Questionnaire; IMACS-TIS = International Myositis Assessment and Clinical Studies-Total Improvement Score; 
MDAAT = Myositis Disease Activity Assessment Tool; MMT-8 = Manual Muscle Testing subset of 8 muscles; OLE = Open-Label Extension; 
PD = pharmacodynamic(s); PK = pharmacokinetic(s); PROMIS = Participant-reported Outcomes Measurement Information System; SF-36 = Short Form 
Health Survey (36 questions version; UV = Unscheduled Visit; W = week(s); WOCBP = women of childbearing potential 
 

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2. 
INTRODUCTION 
2.1. 
Study Rationale 
Complement-mediated injury has been implicated in the pathology of DM as detailed in 
Section 2.2.1. Muscle biopsies from patients with DM reveal the presence of MAC on the 
endothelial cells of the endomysial capillaries (Dalakas, 2020; Kissel, 1986) indicating the 
involvement of C5 in DM and providing the therapeutic rationale for C5 inhibitor therapy. 
Immediate, complete, and sustained inhibition of terminal complement activation is efficacious 
in delivering clinically meaningful outcomes in patients with neuromyelitis optica spectrum 
disorder (NMOSD) or gMG, where neuroinflammation in the brain and spinal cord or 
neuromuscular junction, respectively, is considered an important cause of the neurodegeneration 
that underlies the pathology of these diseases. This has been demonstrated by eculizumab 
(SOLIRIS®), a C5 inhibitor approved by the US Food and Drug Administration (FDA) for the 
treatment of adult patients with NMOSD (Pittock, 2019) and gMG (Howard, 2017; Muppidi, 
2019). 
Ravulizumab is a recombinant, humanized mAb with high specificity against human C5 and 
blocks the cleavage of C5 into the pro-inflammatory C5a and the pro-inflammatory and lytic 
C5b-9. Ravulizumab was engineered by introducing 4 targeted amino acid changes into the 
sequence of the heavy chain of eculizumab, the first generation C5 inhibitor. These sequence 
modifications have resulted in an increased serum elimination half-life of ravulizumab compared 
to eculizumab, enabling an extended dosing interval. 
Ravulizumab has been shown to achieve immediate, complete, and sustained terminal 
complement inhibition in patients with PNH, in patients with aHUS, and in adult patients with 
generalized gMG (gMG), and it is currently being developed as a treatment in several other 
complement-related indications. It is expected that the same dosing regimen approved for PNH, 
aHUS, and gMG will also achieve comparable levels of complement inhibition in patients with 
DM.  The combination of clinically relevant outcomes with terminal complement inhibition in 
other complement-mediated diseases and PD effects of ravulizumab on terminal complement 
provide the rationale for the hypothesis that ravulizumab may improve the clinical manifestations 
of DM in patients, and in particular, lead to a reduction in muscle weakness and cutaneous 
manifestations. 
The primary objective of this study is to investigate the efficacy, safety, PK, PD, and 
immunogenicity of ravulizumab in adult participants with DM. To achieve this objective, this 
study will be conducted in 2 parts: 
1. Part A (Phase 2) will evaluate the safety, efficacy, PK, PD, and immunogenicity of 
ravulizumab in adult participants with DM to provide initial evidence of efficacy. 
2. Part B (Phase 3) will confirm efficacy, safety, PK, PD, and immunogenicity of 
ravulizumab in adult participants with DM. 

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2.2. 
Dermatomyositis Background 
DM is an autoimmune idiopathic inflammatory disease characterized by distinct skin rashes and 
muscle weakness (Bendewald, 2010; Bohan, 1975; Dalakas, 2015; Isak, 2018; Mahil, 2012). 
Patients with DM typically present with proximal muscle weakness and cutaneous 
manifestations that develop over weeks to months (Selva-O'Callaghan, 2018). DM affects both 
children (juvenile DM) and adults, and women more than men (Dalakas, 2003). In the US, the 
incidence of DM has been estimated as 1.1 per 100000 person-years (Kronzer, 2021), with a 
bimodal distribution peaking between the ages of 5 to 15 years and 50 to 60 years (Dalakas, 
2015; Dalakas, 2003). Patients with DM generally develop a slow weakening of muscles that 
make everyday tasks like buttoning or holding objects, combing their hair, rising from a chair, 
climbing steps, or lifting objects difficult (Dalakas, 2015; (Dalakas, 2003). 
Organ systems, such as vascular, pulmonary, gastrointestinal, and cardiac may be involved, with 
rare cases of interstitial lung disease potentially being fatal (Ernste, 2013). Adult patients with 
DM have a 9% to 32% increased risk of cancer during the first 3 to 5 years after DM diagnosis 
(Dalakas, 2015). The most common cancers in women with DM are breast and ovarian cancers; 
whereas, lung and prostate cancers are the most common in men with DM (Ernste, 2013). 
Currently, approved DM treatments are limited (Isak, 2018). Management of DM consists of 
glucocorticoids alone or in combination with immunosuppressive/immunomodulatory therapies 
(ISTs), including rituximab and IV immunoglobulin (IVIg) (Dalakas, 2015). Long-term use of 
glucocorticoids can lead to deleterious complications such as osteoporosis, compression 
fractures, and avascular necrosis, and use of ISTs can increase the risk of serious infections and 
are associated with tolerability issues as well as hepatotoxicity (Chandra, 2020; Ernste, 2013). 
Furthermore, despite therapy, about a third of patients with DM are left with mild to severe 
disability (Dalakas, 2003) and half of patients considered to be stable do not return to previous 
levels of work (Marie, 2001). With available therapies, 5-year mortality has been reduced, but is 
still approximately 25% (Rider, 2011a). 
In summary, as there are currently a limited number of treatment options available for patients 
with DM, many clinical treatment decisions are made empirically and without adequate clinical 
data. Therefore, there still exists a high unmet medical need for efficacious and safe treatment 
options for this disease. 
2.2.1. 
Abnormal Complement Activation in DM Pathogenesis 
Chronic activation of the immune system by environmental risk factors in individuals with a 
genetic predisposition is thought to be the underlying cause of DM (Rider, 2011a). 
Environmental exposures, including streptococcus, echovirus, human growth hormone, 
interferon α, interferon γ, bovine collagen implants, physical exertion, and ultraviolet radiation, 
have been implicated in the development of DM. Genetic risk factors associated with 
susceptibility of individuals to DM include gene polymorphisms known to regulate late 
responses to environmental agents (eg, polymorphisms of human leukocyte antigen [HLA], and 
cytokine and immunoglobulin genes). 
The pathogenesis of DM is thought to be triggered when autoantibodies directed against the 
endothelium of endomysial capillaries activate complement component 3 (C3) (Dalakas, 2003) 
leading to complement-mediated injury against endothelial cells in the muscle (Dalakas, 2003; 

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Mahil, 2012), as well as MAC deposition in skin and muscle tissue (Magro, 1997). This 
hypothesis is supported by activation of the complement system as an early disease manifestation 
of DM (Pinal-Fernandez, 2015). 
The complement pathways (classical, alternative, and lectin) all converge at C3. Activation of 
the terminal complement cascade is initiated by proximal complement-mediated deposition of 
C5 convertase, which activates C5 by cleaving it to produce C5a and C5b (Matis, 1995); 
ravulizumab robustly blocks this activation. C5a is one of the strongest chemoattractants and 
pro-inflammatory modulators (Sallum, 2006), recruiting B and T cells, macrophages and other 
immune cells to the inflammation site. These inappropriately activated immune cells release 
cytokines, which further potentiate the abnormal immune response with autoantibody formation 
and further tissue damage. In DM, activated complement C5a has been shown to up-regulate 
adhesion molecule expression after binding to endothelial cells, which may lead to cytokine 
induction (Sallum, 2006). 
C5b participates in the formation of the terminal complement (C5b-9) MAC (Tegla, 2011). The 
MACs are deposited on capillaries and induce perivascular inflammation in muscle fibers 
(Dalakas, 2015; Dalakas, 2003). The MAC in DM causes necrosis, reduction of the density of 
endomysial capillaries, ischemia, and muscle fiber destruction (Dalakas, 2015; Pinal-Fernandez, 
2015). Microscopic lesions in muscle fibers lead to reduced blood flow and perifascicular 
atrophy (Dalakas, 2015), which is a highly specific feature of muscle biopsies in patients with 
DM (specificity > 90%) (Suarez-Calvet, 2017). 
These data strongly indicate that abnormal complement activation is central to the pathogenesis 
of DM. 
2.3. 
Benefit/Risk Assessment  
The safety profile for ravulizumab is well established. It has been well tolerated and no 
unexpected safety concerns have been identified based on all currently available data from 
clinical development programs as well as post-marketing experience. Ravulizumab functions by 
blocking terminal complement; therefore, patients have increased susceptibility to serious 
infections, in particular Neisseria meningitidis (refer to Ravulizumab Investigator’s Brochure 
[IB]). Specific risk mitigation measures available to support the safe use of ravulizumab are 
described in Table 6. 
As with any therapeutic protein, there is potential for immunogenicity with administration of 
ravulizumab. Assessment of immunogenicity will be performed through the duration of the 
study, as described in Section 8.8. Management of potential hypersensitivity, anaphylaxis and 
serious infusion reactions is described in Section 10.1. 

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2.3.1. 
Risk Assessment 
Table 6: 
Ravulizumab Identified and Potential Risks 
Potential Risk of 
Clinical 
Significance 
Summary of Data/Rationale for Risk 
Mitigation Strategy 
Identified risk 
Meningococcal 
infection 
Complement C5 inhibition is known to 
increase the susceptibility to infections 
caused by Neisseria meningitidis.  
 
Participants must be vaccinated against 
all available serotypes of N 
meningitidis (A, C, Y, W 135, and B) 
per the inclusion criteria and Schedule 
of Activities. Participants must receive 
the vaccination at least 2 weeks before 
first study intervention. Each 
participant will be provided with a 
Participant Safety Card with signs and 
symptoms of meningococcal infection, 
instructions on when to contact a 
healthcare provider, and relevant 
contact information. The Participant 
Safety Card will be checked at each 
visit (Schedule of Activities, 
Section 1.3). 
Potential risk 
Serious infection 
Because participants with 
dermatomyositis (DM) may be 
immunosuppressed due to concomitant 
steroid and 
immunosuppressive/immunomodulatory 
therapy (IST) use, an increased risk of 
serious infections among these 
participants may occur. Apart from the 
predictable risk of infection with 
Neisseria species, which is well-known 
and directly related to its mechanism of 
action, the mechanism which might lead 
to other serious infections remains 
unclear. 
Increased awareness of healthcare 
professionals and participants about the 
potential risk of serious infection.  
 
Monitoring for signs and symptoms of 
serious infections will be conducted as 
part of the safety assessments for this 
study.  
Immunogenicity  
Treatment with any therapeutic protein 
has the potential to induce an immune 
response. Potential clinical 
consequences may include severe 
hypersensitivity type reactions, decrease 
in efficacy and potential risk of causing 
local (infusion site) and systemic 
(infusion-related) reactions (Casadevall, 
2002; Li, 2001). 
Stop infusion in the event of any drug-
related adverse events like systemic 
hypersensitivity or anaphylaxis. 
Monitoring for hypersensitivity and 
infusion-related reactions will be 
conducted as part of safety assessments 
for this study (Section 10.1). 

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Table 6: 
Ravulizumab Identified and Potential Risks 
Potential Risk of 
Clinical 
Significance 
Summary of Data/Rationale for Risk 
Mitigation Strategy 
Only 2 patients have been identified 
with treatment-emergent ADA across 
ravulizumab clinical studies in all 
indications tested to date. There was no 
association or impact of 
immunogenicity on PK, safety, or 
efficacy in either of these patients. 
Pregnancy 
exposure/lactation  
No studies of ravulizumab have been 
conducted in pregnant or breastfeeding 
women. There are no data available on 
excretion of ravulizumab in breast milk.  
Pregnant or nursing female participants 
will be excluded from this clinical 
study. Women and men enrolled in the 
study, and their spouses/partners, must 
use a highly effective or acceptable 
method of contraception during 
treatment and for a period of 8 months 
following the final dose of study 
intervention. Breastfeeding should be 
discontinued during treatment and up to 
8 months after treatment with 
ravulizumab (Section 10.5). 
2.3.1.1. 
Coronavirus Disease 2019 
The coronavirus disease 2019 (COVID-19) pandemic is active in many countries at the time of 
this protocol. Given this unique circumstance, specific consideration has been given to the risks 
and benefits of the study as they relate to COVID-19 (Section 10.8) and vaccination against the 
disease (see Section 10.9). 
2.3.2. 
Benefit Assessment 
DM is a debilitating multi-systemic disease centered around cutaneous manifestations, and 
muscle weakness and pain. Current therapies fail to provide meaningful benefit in a substantial 
number of patients; thus, discovery of new therapies is important to address this unmet medical 
need. Clinical research provides a pragmatic approach to identify effective treatments to reduce 
disease burden. Although efficacy of ravulizumab has not been previously studied in participants 
with DM, it represents an appropriate candidate for investigation due to its plausible mechanism 
of action in DM. The scientific and therapeutic hypothesis for the potential benefit in DM is 
discussed in Section 2.2.1. Of important note, ravulizumab has been found to be safe and well-
tolerated in other indications. 
2.3.3. 
Overall Benefit: Risk Conclusion 
Given the measures taken to minimize risk to participants in this study, the potential risks 
identified in association with ravulizumab are justified by the anticipated benefits that may be 
afforded to participants with DM. 

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3. 
OBJECTIVES AND ESTIMANDS AND/OR ENDPOINTS 
Table 7: 
Mapping Objectives to Endpoints for Part A (Phase 2 Portion) 
Objectives 
Endpoints/Estimands  
Primary 
To determine the effect of ravulizumab compared 
with placebo in the treatment of DM based on 
improvement in Total Improvement Score (TIS) 
IMAC-TISa  
IMACS-TISa (TIS40) response at Week 26 of the 
Randomized Controlled Period as per defined 
composite estimand (see Section 3.1) 
Secondary  
To assess the efficacy of ravulizumab compared 
with placebo in the treatment of DM based on 
improvement in efficacy endpoints 
• 
TIS at Week 26 
• 
Change from baseline in CDASI Activity 
Score at Week 26 
• 
Change from baseline in 5 IMACS core set 
measures (extra-muscular disease activity 
based on MDAAT, physician global activity 
assessment, patient global activity 
assessment, MMT-8, HAQ) at Week 26 
• 
Response related to muscle enzymes: 
- 
normalization of most abnormal baseline 
enzyme at Week 26  
• 
CDASI response (7-point improvement) at 
Week 26 
• 
CDA-IGA response (almost clear or clear) at 
Week 26 
• 
TIS20 response at Week 26 
• 
TIS60 response at Week 26 
• 
Time to First Response of TIS20, TIS40, or 
TIS60 respectively 
• 
Clinical worsening during RCP at 2 
consecutive visits 
• 
Receipt of acute therapy with standard DM 
treatment  
PK/PD/Immunogenicity 
To characterize the PK/PD and immunogenicity 
of ravulizumab in adult participants with DM  
• 
Serum ravulizumab concentrations over the 
study duration 
• 
Change in serum free and total C5 
concentrations over the study duration 
• 
Incidence and titer of ADAs over the study 
duration 

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Table 7: 
Mapping Objectives to Endpoints for Part A (Phase 2 Portion) 
Objectives 
Endpoints/Estimands  
Safety 
To characterize the overall safety of ravulizumab 
in participants with DM 
• 
Incidence of TEAEs, TESAEs, and TEAEs 
leading to study intervention discontinuation 
Exploratory  
To evaluate the effect of ravulizumab on overall 
health-related quality of life (HR-QoL) and 
participant-centered and participant-reported 
outcomes in DM 
• 
Change from baseline in EQ-5D-5L at 
Week 26 
• 
Change from baseline in PROMIS-29 v2.1 
domains at Week 26 
• 
Change from baseline in SF-36 at Week 26 
• 
Change from baseline of DM symptoms 
captured in DM-DSQ at Week 26 
• 
Change from baseline of Patient Self-
Assessment of Disease Activity (last question 
in the DM-DSQ) at Week 26 
To evaluate, complement, inflammatory, 
autoimmune, and other soluble biomarkers in 
adult participants with DM 
• 
Presence of myositis-specific autoantibodies 
(eg, anti-MDA5, anti-NXP2/MJ, and anti-
synthetase/Jo-1, anti-TIF1) in blood, and 
change from baseline in specific 
autoantibody/autoantibodies titer over the 
course of the study 
• 
Change from baseline in plasma complement 
activation (eg, sC5b-9, etc) over the course of 
the study  
• 
Change from baseline in serum inflammatory 
markers (eg, IL6, etc) and other soluble 
markers (eg, KL6, etc) over the course of the 
study 
To assess the efficacy of ravulizumab in the 
treatment of DM based on other efficacy 
endpoints  
• 
Change from baseline using scale to measure 
pruritus (5D-itch scale) at Week 26 
• 
Incidence of protocol-defined Clinical 
Worsening during RCP 
• 
Change from baseline in handheld 
dynamometry performance at Week 26 
• 
Change from baseline in 30-second Chair 
Stand Test (30s CST) at Week 26 
• 
Change from baseline in FACIT-Fatigue at 
Week 26 

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Table 7: 
Mapping Objectives to Endpoints for Part A (Phase 2 Portion) 
a ACR/EULAR-TIS 
Abbreviations: ACR/EULAR = American College of Rheumatology/European League Against Rheumatism; 
ADA = antidrug antibody; anti-MDA5 = antimelanoma differentiation-associated protein 5; 
anti-NXP2/MJ = antinuclear matrix protein 2; anti-TIF1= anti-transcription intermediary factor 1; 
C5 = complement component 5; CDA-IGA = Cutaneous Dermatomyositis Activity Physician’s Global 
Assessment; CDASI = Cutaneous Dermatomyositis Disease Area and Severity Index; DM = dermatomyositis; 
DM-DSQ = dermatomyositis disease symptoms questionnaire; EQ-5D-5L = European Quality of Life Health 5-
item questionnaire dimensions 5 level; FACIT = Functional Assessment of Chronic Illness Therapy; 
HAQ = health assessment questionnaire; IMACS-TIS = International Myositis Assessment and Clinical 
Studies-Total Improvement Score; IL6 =  interleukin 6; MDAAT = Myositis Disease Activity Assessment Tool; 
MMT-8 = manual muscle testing subset of 8 muscles; PD = pharmacodynamic(s); PK = pharmacokinetic(s); 
PROMIS = Patient-Reported Outcomes Measurement Information System; RCP = Randomized Controlled Period; 
sC5b-9 = soluble terminal complement complex; SF-36 = Short Form Health Survey (36 questions version); 
TEAE = treatment-emergent adverse event; TESAE = treatment-emergent serious adverse event; 
TIS20 = ≥ 20-point improvement response on IMACS-TIS; TIS40 = ≥ 40-point improvement response on 
IMACS-TIS; TIS60 = ≥ 60-point improvement response on IMACS-TIS

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Table 8: 
Mapping Objectives to Endpoints/Estimands for Part B (Phase 3 Portion) 
Objectives 
Endpoints/Estimands  
Primary 
To determine the effect of ravulizumab 
compared with placebo in the treatment of 
DM based on improvement in Total 
Improvement Score (TIS) IMAC-TISa 
IMACS-TISa (TIS40) response at Week 50 of the 
Randomized Controlled Period as per defined 
composite estimand (see Section 3.1) 
Key Secondary 
To assess the efficacy of ravulizumab 
compared with placebo in the treatment of 
DM based on improvement in components of 
IMACS and other myositis activity measures 
• 
TIS at Week 50 
• 
Change from baseline in MMT-8 at Week 50 
• 
Change from baseline in extra-muscular disease 
activity based on MDAAT at Week 50 
• 
Change from baseline in CDASI Activity Score at 
Week 50 
Secondary 
To assess the efficacy of ravulizumab 
compared with placebo in the treatment of 
DM based on other efficacy endpoints  
• 
Change from baseline in 3 IMACS core set 
measurements (physician global activity score, 
patient global activity score, HAQ) at Week 50 
• 
Response related to muscle enzymes: 
- 
normalization of most abnormal baseline 
enzyme at Week 50   
• 
CDASI response (7-point improvement from 
baseline) at Week 50 
• 
CDA-IGA response (almost clear or clear) at 
Week 50 
• 
TIS20 response at Week 50 
• 
TIS60 response at Week 50 
• 
Time to First Response of TIS20, TIS40, or 
TIS60, respectively 
• 
Clinical worsening during RCP at 2 consecutive 
visits 
• 
Receipt of acute therapy with standard DM 
treatment  

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Table 8: 
Mapping Objectives to Endpoints/Estimands for Part B (Phase 3 Portion) 
Objectives 
Endpoints/Estimands  
PK/PD/Immunogenicity 
To characterize the PK/PD and 
immunogenicity of ravulizumab in adult 
participants with DM  
• 
Serum ravulizumab concentration over the study 
duration 
• 
Change in serum free and total C5 concentrations 
over the study duration 
• 
Incidence and titer of ADAs over the study 
duration 
Safety 
To characterize the overall safety of 
ravulizumab in participants with DM 
• 
Incidence of TEAEs, TESAEs, and TEAEs 
leading to study intervention discontinuation 
Exploratory  
To evaluate the effect of ravulizumab 
compared with placebo on overall health-
related quality of life (HR-QoL) and 
participant-centered and participant-reported 
outcomes in DM 
• 
Change from baseline in EQ-5D-5L at Week 50 
• 
Change from baseline in PROMIS-29 v2.1 
domains at Week 50 
• 
Change from baseline in SF-36 at Week 50 
• 
Change from baseline of DM symptoms captured 
in DM-DSQ at Week 50 
• 
Change from baseline of Patient Self-Assessment 
of Disease Activity (last question in the DM-DSQ) 
at Week 50 
To evaluate, complement, inflammatory, 
autoimmune, and other soluble biomarkers in 
adult participants with DM 
• 
Presence of myositis-specific autoantibodies (eg, 
anti-MDA5, anti-NXP2/MJ, and anti-
synthetase/Jo-1, anti-TIF1) in blood, and change 
from baseline in specific 
autoantibody/autoantibodies titer over the course 
of the study 
• 
Change from baseline in plasma complement 
activation (eg, sC5b-9, etc) over the course of the 
study 
• 
Change from baseline in serum inflammatory 
markers (eg, IL6, etc) and other soluble markers 
(eg, KL6, etc) over the course of the study 

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Table 8: 
Mapping Objectives to Endpoints/Estimands for Part B (Phase 3 Portion) 
Objectives 
Endpoints/Estimands  
To assess the efficacy of ravulizumab 
compared with placebo in the treatment of 
DM based on other efficacy endpoints  
• 
Change from baseline using scale to measure 
pruritus (5D-itch scale) at Week 50 
• 
Incidence of protocol-defined Clinical Worsening 
during RCP  
• 
Change from baseline in handheld dynamometry 
performance at Week 50 
• 
Change from baseline in 30-second Chair Stand 
Test (30s CST) at Week 50 
• 
Change from baseline in FACIT-Fatigue score at 
Week 50 
a ACR/EULAR-TIS 
Abbreviations: ACR/EULAR = American College of Rheumatology/European League Against Rheumatism; 
ADA = antidrug antibody; anti-MDA5 = anti-melanoma differentiation-associated protein 5; 
anti-NXP2/MJ = antinuclear matrix protein 2; anti-TIF1= anti-transcription intermediary factor 1; 
C5 = complement component 5; CDA-IGA = Cutaneous Dermatomyositis Activity Physician’s Global 
Assessment; CDASI = Cutaneous Dermatomyositis Disease Area and Severity Index; DM = dermatomyositis; 
DM-DSQ = dermatomyositis disease symptoms questionnaire; EQ-5D-5L = European Quality of Life Health 5-
item questionnaire dimensions 5 level; FACIT = Functional Assessment of Chronic Illness Therapy; 
HAQ = Health Assessment Questionnaire; IMACS-TIS = International Myositis Assessment and Clinical 
Studies-Total Improvement Score; IL6 =  interleukin 6; MDAAT = Myositis Disease Activity Assessment Tool; 
MMT-8 = manual muscle testing subset of 8 muscles; PD = pharmacodynamic(s); PK = pharmacokinetic(s); 
PROMIS = Patient-Reported Outcomes Measurement Information System; RCP = Randomized Controlled Period; 
sC5b-9 = soluble terminal complement complex; SF-36 = Short Form Health Survey (36 questions version); 
TEAE = treatment-emergent adverse event; TESAE = treatment-emergent serious adverse event; TIS20 = ≥ 
20-point improvement response on IMACS-TIS; TIS40 = ≥ 40-point improvement response on IMACS-TIS; 
TIS60 = ≥ 60-point improvement response on IMACS-TIS 

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Table 9: 
Mapping Objectives to Endpoints/Estimands for Open-Label Extension 
(Part A and Part B) 
Objectives 
Endpoints/Estimands  
Exploratory 
To evaluate the long-term effect of 
ravulizumab treatment in participants with 
DM based on improvement in components of 
the IMACS 
• 
TIS at Week 156 (Part A) or Week 124 (Part B)  
• 
Change from baseline in MMT-8 at Week 156 
(Part A) or Week 124 (Part B)   
• 
Change from baseline in physician global activity 
assessment at Week 156 (Part A) or Week 124 
(Part B) 
• 
Change from baseline in extra-muscular disease 
activity based on MDAAT at Week 156 (Part A) 
or Week 124 (Part B) 
• 
Change from baseline in HAQ at Week 156 
(Part A) or Week 124 (Part B) 

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Table 9: 
Mapping Objectives to Endpoints/Estimands for Open-Label Extension 
(Part A and Part B) 
Objectives 
Endpoints/Estimands  
To evaluate the long-term effect of 
ravulizumab on overall health-related quality 
of life (HR-QoL) and participant-centered and 
participant-reported outcomes in DM 
• 
Change from baseline in EQ-5D-5L at Week 156 
(Part A) or Week 124 (Part B) 
• 
Change from baseline in PROMIS-29 v2.1 
domains at Week 156 (Part A) or Week 124 
(Part B) 
• 
Change from baseline in SF-36 at Week 156 
(Part A) or Week 124 (Part B) 
• 
Change from baseline of DM symptoms captured 
in DM-DSQ at Week 156 (Part A) or Week 124 
(Part B) 
• 
Change from baseline of Patient Global 
Assessment of Disease Activity (last question in 
the DM-DSQ) at Week 156 (Part A) or Week 124 
(Part B) 
To characterize the long-term safety of 
ravulizumab in participants with DM 
• 
Incidence of TEAEs, TESAEs, and TEAEs 
leading to study intervention discontinuation 
To characterize the long-term PK/PD and 
immunogenicity of ravulizumab in adult 
participants with DM  
• 
Serum ravulizumab concentration at Week 156 
(Part A) or Week 124 (Part B)   
• 
Change in serum free and total C5 concentrations 
at Week 156 (Part A) or Week 124 (Part B) 
• 
Incidence and titer of ADAs through Week 156 
(Part A) or Week 124 (Part B) 
To evaluate complement, inflammatory, 
autoimmune and other soluble biomarkers in 
adult participants with DM 
• 
Change from baseline (only in subjects positive at 
baseline) in specific autoantibody (eg, anti-MDA5, 
anti-NXP2/MJ, and anti-synthetase/Jo-1, anti-TIF-
1) titers over the course of the study 
• 
Change from baseline in plasma complement 
activation (eg, sC5b-9, etc) at Week 156 (Part A) 
or Week 124 (Part B) 
• 
Change from baseline in serum inflammatory 
markers (eg, IL6, etc) and other soluble markers 
(eg, KL6, etc) over the course of the study 

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Table 9: 
Mapping Objectives to Endpoints/Estimands for Open-Label Extension 
(Part A and Part B) 
Objectives 
Endpoints/Estimands  
To assess the long-term efficacy of 
ravulizumab in the treatment of DM based on 
other efficacy endpoints 
• 
Change from baseline using scale to measure 
pruritus (5D-itch scale) at Week 156 (Part A) or 
Week 124 (Part B) 
• 
Change from baseline in CDASI Activity Score at 
Week 156 (Part A) or Week 124 (Part B) 
• 
CDA-IGA response (almost clear or clear) at 
Week 156 (Part A) or Week 124 (Part B) 
• 
Change from baseline in handheld dynamometry 
performance at Week 156 (Part A) or Week 124 
(Part B) 
• 
Change from baseline in 30-second Chair Stand 
Test (30s CST) at Week 156 (Part A) or Week 124 
(Part B) 
• 
Change from baseline in FACIT-Fatigue score at 
Week 156 (Part A) or Week 124 (Part B) 
To evaluate the long-term use of DM 
treatment in participants with DM 
concurrently receiving ravulizumab  
• 
Percentage of participants steroid-free or minimal 
maintenance dose of 5 mg (prednisone equivalent) 
or less at the end of the OLE Period 
• 
Cumulative steroid dose from baseline 
Abbreviations: ADA = antidrug antibody; anti-MDA5 = antimelanoma differentiation-associated protein 5; 
anti-NXP2/MJ = antinuclear matrix protein; anti-TIF-1 = anti-transcription intermediary factor 1; 
C5 = complement component 5; CDA-IGA = Cutaneous Dermatomyositis Activity Physician’s Global 
Assessment; CDASI = Cutaneous Dermatomyositis Disease Area and Severity Index; DM = dermatomyositis; 
DM-DSQ = dermatomyositis disease symptoms questionnaire; EQ-5D-5L = European Quality of Life Health 5-
item questionnaire dimensions 5 level; FACIT = Functional Assessment of Chronic Illness Therapy; HAQ = 
Health Assessment Questionnaire; IMACS = International Myositis Assessment and Clinical Studies; IL6 = 
interleukin 6; MDAAT = Myositis Disease Activity Assessment Tool; MMT-8 = manual muscle testing subset of 
8 muscles; OLE = Open-Label Extension; PD = pharmacodynamic(s); PK = pharmacokinetic(s); 
PROMIS = Patient-Reported Outcomes Measurement Information System; sC5b-9 = soluble terminal complement 
complex; SF-36 = Short Form Health Survey (36 questions version); TEAE = treatment-emergent adverse event; 
TESAE = treatment-emergent serious adverse event; TIS = Total Improvement Score; Primary Estimand(s) 
3.1. 
Primary Estimand(s) 
3.1.1. 
Primary Estimand for Part A 
The five attributes for the primary estimand are described below:  
• Treatment: Ravulizumab or placebo with or without the use of stable allowed 
concomitant DM treatments  
• Population: adult DM participants who have an inadequate response or are intolerant to at 
least 1 DM treatment 
• Variable: TIS40 response at Week 26 

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• Intercurrent Events:  
o Discontinued study intervention due to death, AE, or lack of efficacy during the 
Randomized Controlled Period.  
o Received acute therapy with standard DM treatment or prohibited medications 
(Section 6.5.2 and Section 6.5.3).  
o Data handling strategy: Participants will be considered non-responders for TIS40 
after experiencing these intercurrent events (composite strategy) regardless of the 
availability of actual TIS40 responses. All available TIS40 data will be used for 
participants without these intercurrent events. 
• Population-level summary: Difference in the percentage of TIS40 response between 
ravulizumab and placebo arms 
The remaining missing data handling for TIS40 is described in Section 9.4.1.2.2. 
3.1.2. 
Primary Estimand for Part B 
The primary estimand for Part B is defined in a similar way as in Section 3.1.1. The variable is 
TIS40 at Week 50. 
3.2. 
Secondary Estimands 
This section is not applicable for this study.  
Secondary estimands are not applicable for study Part A. The key secondary estimands for Part B 
will be defined in the Statistical Analysis Plan (SAP). 
3.3. 
Exploratory Estimands 
This section is not applicable for this study.  

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4. 
STUDY DESIGN 
4.1. 
Overall Design 
Study ALXN1210-DM-310 is a Phase 2/3, double-blind, randomized, placebo-controlled, 
parallel group, multicenter study to evaluate the efficacy, safety, PK, PD, and immunogenicity of 
ravulizumab in adult participants with DM. The study will be conducted in 2 parts: Part A 
(Phase 2) described in Section 4.1.1 and Part B (Phase 3) described in Section 4.1.2. 
For the purposes of this protocol, information provided that is applicable to only Part A or Part B 
is clearly demarcated. Information without a specification as to whether it pertains to either 
Part A Part B is applicable to both parts. 
4.1.1. 
Part A (Phase 2 Portion) 
There will be 3 periods in Part A of this study: Screening Period, Randomized Controlled Period, 
and OLE Period. Participants will be screened for eligibility for up to 6 weeks during the 
Screening Period. Approximately 36 eligible participants will be randomized in a 2:1 ratio to 
receive either weight-based IV infusion of ravulizumab (Table 11) or placebo during the 
double-blind Randomized Controlled Period. Upon completing the last assessment of the 
Randomized Controlled Period at Week 26, participants may continue into the OLE Period. 
For each participant, the Randomized Controlled Period ends and the OLE Period begins at 
Week 26 (see Section 6.1.1.1 for details). During the OLE Period, participants in the 
ravulizumab group will continue to receive ravulizumab treatment, and participants in the 
placebo group will switch to receive ravulizumab treatment. Participants will receive 
ravulizumab until ravulizumab is registered or approved (in accordance with country-specific 
regulations) or for up to 130 weeks (approximately 2.5 years), whichever occurs first. 
Randomized Controlled Period 
All participants randomized into the study are expected to complete the Randomized Controlled 
Period and will be followed until the end of the Randomized Controlled Period. 
Participants who discontinue study intervention will complete the Randomized Controlled Period 
(see Section 7.1). Participants that require acute therapy with standard DM treatment (see 
Section 6.5.3) due to protocol defined Clinical Worsening (see Section 4.1.3) and complete all 
remaining visits of the Randomized Controlled Period will be permitted to enter OLE Period. 
Participants who discontinue/withdraw from the study will not be permitted to enter the OLE 
Period (see Section 7.2). Participants who will not enter the OLE Period will not receive an 
infusion at Week 26. 
 
 

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OLE Period 
All participants completing the OLE Period will have an EOS Visit at Week 156 and a follow-up 
phone call 21 weeks (± 1 week) after the participant’s last dose of study intervention to collect 
information on concomitant medications, non-pharmacologic therapies and procedures, and AEs. 
Participants who discontinue study intervention are encouraged to complete the visits and 
assessments of the OLE Period (see Section 7.1). 
Adjustments of ‘protocol allowed’ DM medications (Section 6.5.1) will be permitted throughout 
the OLE Period (Section 6.5.1). 
Participants who discontinue/withdraw from the study will complete an Early Termination (ET) 
Visit and a follow-up phone call (see Section 7.2). 
An interim analysis (Section 9.5) for Part A may be conducted when approximately 67% of 
participants have completed the Week 26 visit or discontinued prematurely from the Randomized 
Controlled Period of Part A. The unblinded interim analysis would be performed by an IDMC. 
Details are provided in the DMC Charter and the Interim Analysis Plan of Part A. 
Participants from Part A will not be enrolled in Part B (Phase 3) of the study, and therefore, will 
not contribute to the formal statistical hypothesis testing of Part B.  
4.1.2. 
Part B (Phase 3 Portion) 
There will be 3 periods in Part B of this study: Screening Period, Randomized Controlled Period, 
and OLE Period. Approximately 114 eligible participants will be stratified by cutaneous 
manifestations (Cutaneous Dermatomyositis Disease Area and Severity Index [CDASI] Activity 
Score ≤ 14 and > 14) and randomized 2:1 either to ravulizumab IV infusion or placebo IV 
infusion (Section 6.3) within each stratum. 
For each participant, the Randomized Controlled Period ends and the OLE Period begins at 
Week 50 (see Section 6.1.1.2 for details). During the OLE Period, participants in the 
ravulizumab group will continue to receive ravulizumab, and participants in the placebo group 
will switch to receive ravulizumab. Participants will receive ravulizumab until ravulizumab is 
registered or approved (in accordance with country-specific regulations) or for up to 74 weeks 
(approximately 1.5 years), whichever occurs first. 
Randomized Controlled Period 
All participants randomized into the study are expected to complete the Randomized Controlled 
Period and will be followed until the end of the Randomized Controlled Period. 
Participants who discontinue study intervention will complete the Randomized Controlled Period 
(see Section 7.1). Participants that require acute therapy with standard DM treatment (see 
Section 6.5.3) due to protocol defined Clinical Worsening (see Section 4.1.3) and complete all 
remaining visits of the Randomized Controlled Period will be permitted to enter OLE Period. 
Participants who discontinue/withdraw from the study will not be permitted to enter the OLE 
Period (see Section 7.2). Participants who will not enter the OLE Period will not receive an 
infusion at Week 50. 
 

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OLE Period 
All participants completing the OLE Period will have an EOS Visit at Week 124 and a follow-up 
phone call 21 weeks (± 1 week) after the participant’s last dose of study intervention to collect 
information on concomitant medications, non-pharmacologic therapies and procedures, and AEs. 
Participants who discontinue study intervention are encouraged to complete the visits and 
assessments of the OLE Period (see Section 7.1). 
Adjustments of ‘protocol allowed’ DM medications (Section 6.5.1) will be permitted throughout 
the OLE Period (Section 6.5.1). 
Participants who discontinue/withdraw from the study will complete an ET Visit and a follow-up 
phone call (see Section 7.2). 
One interim analysis is planned for sample-size re-estimation for Part B (Section 9.5). The 
unblinded interim analysis may be performed by an IDMC. Details would be provided in the 
DMC Charter and the Interim Analysis Plan for Part B. Treatment allocation during the 
Randomized Controlled Period will remain blinded to participants, site staff, and Alexion 
throughout the study. The interim analysis for sample size re-estimation may be conducted when 
approximately 30% of participants have completed the Week 50 visit or discontinued 
prematurely from Part B. 
4.1.3. 
Clinical Worsening 
Clinical Worsening criteria are one of the following: 
a. Physician’s global activity visual analog scale (VAS) worsening ≥ 2 cm and manual 
muscle testing subset of 8 muscles (MMT-8) worsening ≥ 20% compared to baseline 
b. Global extra muscular activity worsening ≥ 2 cm on the Myositis Disease Activity 
Assessment Tool (MDAAT) VAS compared to baseline 
c. Any 3 of 5 core set measures (CSMs) (excluding muscle enzymes) worsening by 
≥ 30% compared to baseline 
Clinical Worsening criteria will be checked at the visits described in Section 1.3. 
If Clinical Worsening criteria are met, a scheduled visit or an Unscheduled Visit will occur 
4 weeks (± 7 days) later. Clinical Worsening is confirmed if at least one of the criteria are met on 
2 consecutive visits. The same criterion does not have to be met at both visits. 
If participant meets the Clinical Worsening criteria at 2 consecutive visits, the patient may 
receive acute therapy with standard DM treatment (see Section 6.5.3) with protocol allowed 
medication(s) (see Section 6.5.1), discontinue study intervention, complete the Randomized 
Controlled Period, and will be permitted to enter the OLE Period.  
4.1.4. 
Completion of Treatment 
Participants will be considered to have completed the study treatment in the Randomized 
Controlled Period if they receive the last scheduled blinded dose at Week 18 (Part A) or 
Week 42 (Part B). All participants who discontinue the study intervention during the 
Randomized Controlled Period will be followed up for safety and efficacy assessments until the 

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end of the Randomized Controlled Period, withdrawal of consent, or lost to follow-up, whichever 
occurs earlier (see Section 7). 
Participants will be considered to have completed the study treatment in the OLE Period if they 
receive the last scheduled dose at Week 148 (Part A) or Week 116 (Part B), the participant 
terminates the study early, due to termination of the study by Alexion, or the participant 
transitions to approved product. 
4.1.5. 
Completion of Randomized Controlled Period and OLE Period 
Participants will be considered to have completed the Randomized Controlled Period of the 
study if they complete the last scheduled visit specified in the Schedule of Activities (SoA; see 
Section 1.3) for this period.  
Participants who complete Week 26 (Part A) or Week 50 (Part B) but do not receive a dose at 
that visit will be considered as discontinued from the study and will not be permitted to enter the 
OLE Period. 
Participants will be considered to have completed the OLE Period of the study if they complete 
the last scheduled visit specified in the SoA (see Section 1.3), the participant terminates the study 
early due to termination of the study by Alexion, or the participant transitions to approved 
product. 
4.2. 
Scientific Rationale for Study Design 
4.2.1. 
Study Population and Treatment Duration 
This study focuses on patients with DM who continue to show symptoms after treatment with 
presently available medications. While approved DM treatments are limited, in practice, a range 
of immunosuppressive medicines are used to mitigate symptoms of the condition (Chandra, 
2020; Ernste, 2013). While the condition in some DM patients is well-controlled, about a third of 
patients with DM are left with mild to severe disability (Dalakas, 2003) and half of patients 
considered to be stable do not return to previous levels of work (Marie, 2001). Complement 
activity is described to be a contributing factor to DM pathogenesis (Pinal-Fernandez, 2015) and 
ravulizumab, a C5 inhibitor, is expected to suppress complement activity. Thus, ravulizumab has 
the potential to provide efficacy in patients whose symptoms are not fully controlled by or who 
are intolerant to at least one DM treatment. 
This study will be conducted in 2 parts: Part A (Phase 2) and Part B (Phase 3). 
A randomized, double-blind, placebo-controlled study design was selected for both Parts A and 
B to provide the most robust evidence of the efficacy of the intervention on disease progression 
and safety. Randomization minimizes the effects of baseline characteristic differences and 
confounding factors on the study population. The use of a placebo comparator allows for the true 
treatment effect of the intervention to be established while also allowing for study management, 
drug administration, and assessments to be conducted similarly between treatment groups, thus 
minimizing the potential for bias. For Part A and Part B, a 2:1 randomization was chosen. 
Participants may continue to use allowed DM treatments described in Section 6.5.1.1. To achieve 
balance between participants receiving ravulizumab and placebo with respect of skin disease 

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activity, participants in Part B will be stratified by cutaneous manifestations (CDASI Activity 
Score ≤ 14 and > 14) for randomization. 
The Randomized Controlled Period of 26 weeks for Part A is adequate to provide proof of 
concept data on the safety and efficacy of ravulizumab in participants with DM. The 
Randomized Controlled Period of 50 weeks in Part B is adequate to demonstrate the safety and 
efficacy of ravulizumab in patients with DM. Participants in Parts A and B can then participate 
in the OLE Period. Our central hypothesis is that DM develops because of autoimmune 
membrane attack complex (MAC) deposition on affected organs (eg, muscle, skin, lungs). MAC 
deposition has been demonstrated in skin, muscle, and microvessels.  
MAC in DM may be activated through an antibody-independent classical pathway mechanism 
(Lahoria, 2016). Given that ravulizumab immediately suppresses complement activation to levels 
below detection, it is predicted to mitigate the proximal cause (MAC formation) of pathology in 
DM. 
A study design with potentially 2 interim analyses was chosen. The first interim analysis would 
be conducted for futility assessment in Part A. The second interim analysis would allow for a 
sample size re-estimation for Part B. The sample size re-estimation would enable Alexion to 
adjust the sample size to ensure adequate power in the event that the estimated treatment effect 
or variability at the interim analysis differs from the initial assumptions. 
An OLE Period was chosen to ensure that all participants in this study will have the opportunity 
to receive active treatment after the completion of the Randomized Controlled Period of the 
study. This OLE Period also allows for further evaluation of longer-term safety and efficacy of 
ravulizumab. 
4.2.2. 
Rationale for Primary Endpoint: International Myositis Assessment and Clinical 
Studies-Total Improvement Score (IMACS-TIS) 
Based on clinical instrument development in systemic lupus erythematosus (SLE) in the 
mid-1980s and over the last 2 decades, a consortium of rheumatologists, neurologists, and 
dermatologists under the umbrella of the European League Against Rheumatism (EULAR) and 
American College of Rheumatology (ACR) developed the International Myositis Assessment 
and Clinical Studies (IMACS). 
Consensus was reached for a conjoint analysis–based continuous model using absolute 
percentage change in 6 independent CSMs (physician, patient, and extra-muscular global 
activity, muscle strength, Health Assessment Questionnaire [HAQ], and muscle enzyme levels). 
A Total Improvement Score (TIS: 0–100), determined by summing scores in each CSM, was 
based on the improvement and relative weight of each CSM. Clinically meaningful thresholds 
for improvement were defined as ≥ 20-point improvement response on International Myositis 
Assessment and Clinical Studies-Total Improvement Score (IMACS-TIS) (TIS20; mild), 
≥ 40-point improvement response on IMACS-TIS (TIS40; moderate) and ≥ 60-point 
improvement response on IMACS-TIS (TIS60; severe) (Aggarwal, 2017). 

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4.2.3. 
Rationale for Secondary Endpoints included in the Multiplicity Adjustment for 
Part B 
The key secondary endpoints in Part B of the study will support the efficacy of ravulizumab in 
muscle strength and skin severity as well as the total improvement in physician’s assessment of 
the disease activity. The following tools/assessments have been validated in the DM population 
and are considered adequate for the assessment of efficacy. 
• IMACS Total Improvement Score (IMACS-TIS) 
• MMT-8 
• MDAAT 
• CDASI 
For a description of each of these tools/assessments see Section 8.1. 
4.2.4. 
Participant Input into Design 
Five patients with DM provided input through a patient insight group. Patients described their 
experiences and challenges with clinical studies and shared ideas on how to improve them. 
Patients in the insight group provided key insights on several topics including study awareness, 
care coordination between study Investigator and the patient’s clinical team, use of digital tools 
and telemedicine, travel and food reimbursement, childcare, mental health screening, and 
patient-reported outcome (PRO) questionnaires. Input provided by the patient insight group was 
incorporated accordingly. 
4.3. 
Justification for Dose  
The proposed dosing regimen of ravulizumab in this study is identical to approved weight-based 
dosing of ravulizumab in treating adult patients with other complement-mediated disorders 
(PNH, aHUS, and gMG) and is based on targeting immediate, complete and sustained inhibition 
of terminal complement in patients with DM. Additionally, this same ravulizumab dosing 
regimen is being or was investigated in several other complement-related conditions. 
Complement activation leading to MAC formation on endothelial cells in capillaries is thought to 
be a contributing factor for DM pathogenesis (Dalakas, 2011; Lahoria, 2016) (Section 2.2.1). 
Based on this hypothesis and the PK, PD, immunogenicity, efficacy, and safety data generated in 
multiple ravulizumab development programs, the approved body weight-based dosing regimen 
for treating adult patients with PNH, aHUS, and gMG has been selected for this study. This 
ravulizumab dosing regimen is expected to be beneficial in treating participants with DM 
through achieving immediate, complete, and sustained inhibition of terminal complement 
activation. 
4.4. 
End of Study Definition  
A participant is considered to have completed the study if the participant has completed all 
periods (Randomized Controlled Period and OLE Period) of the study including the last 
scheduled procedure shown in the SoA (Section 1.3). The end of the study is defined as the date 
the last participant completes the last visit shown in the SoA. 

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Participants may continue to receive ravulizumab or for up to 130 weeks (approximately 
2.5 years; Part A) or up to 74 weeks (approximately 1.5 years; Part B) in the OLE Period, or until 
ravulizumab is registered or approved (in accordance with country-specific regulations), or an 
alternative option for example transition to a rollover study or an early access program is 
provided, whichever occurs first. 

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5. 
STUDY POPULATION 
Prospective approval of protocol deviations to recruitment and enrollment criteria, also known as 
protocol waivers or exemptions, is not permitted. 
5.1. 
Inclusion Criteria 
Participants are eligible to be included in the study only if all of the following criteria apply: 
Age 
1. 18 years of age or older at the time of signing the informed consent. 
Weight 
2. Body weight ≥ 30 kg at the time of Screening. 
Sex 
3. Male or female. 
Type of Participant and Disease Characteristics 
4. Diagnosis: Meet 2017 ACR/EULAR classification criteria for definite or probable DM 
(Lundberg, 2017). 
5. Participants who have an inadequate response or are intolerant to 1 or more DM 
treatments, including systemic glucocorticoids or ISTs (eg, azathioprine, methotrexate, 
rituximab, IVIg), either in combination or as monotherapy. 
6. Participants under treatment with glucocorticoids and/or ISTs who are on stable therapy 
as described in Table 14 and who will be able to remain on stable therapy throughout the 
Randomized Controlled Period. 
OR 
Participants under treatment with glucocorticoids and/or ISTs who complete an 
appropriate washout period for these treatments before the Day 1 Visit as described in 
Table 15 (eg, 6-month washout period for rituximab; 3-month washout period for IVIg or 
subcutaneous immunoglobulin [SCIg]). 
7. Disease severity: Participants who show disease severity at Screening using the 
following criteria: 
a. MMT-8 of ≤ 142 (out of a maximum of 150) and 2 additional IMACS CSMs out of 5 
at Screening such as: 
• Patient Global Activity assessment of ≥ 2.0 cm on a 10 cm VAS 
• Physician Global Activity assessment of ≥ 2.0 cm on a 10 cm VAS  
• HAQ disability index with ≥ 0.25 
• Elevation of at least one of the muscle enzymes (which includes creatine kinase 
[CK], aldolase, lactate dehydrogenase [LDH], alanine aminotransferase [ALT], 
and aspartate aminotransferase [AST]) at ≥ 1.3 times the upper limit of normal 
(ULN) 

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• Global extramuscular disease activity score with ≥ 2.0 cm on a 10 cm VAS (this 
measure is the physician’s composite evaluation and is based on assessments of 
activity scores on the constitutional, cutaneous, skeletal, gastrointestinal, 
pulmonary, and cardiac scales of the MDAAT) 
8. Disease activity: Participants must meet one of the following criteria to ensure 
enrollment of active disease rather than weakness due to muscle damage.  
a. Muscle or skin biopsy with evidence of active pathological findings of DM within the 
last 6 months prior to or during Screening 
b. Electromyography evidence of active myositis within the last 6 months prior to or 
during Screening 
c. Magnetic resonance imaging (MRI) muscle evidence of active myositis within the 
last 6 months prior to or during Screening 
d. At least 1 muscle enzyme (CK, LDH, aldolase, AST, ALT) in the IMACS panel 
≥ 2 times ULN at Screening 
e. Active DM skin rash characterized by inflammatory changes (CDASI Activity Score 
≥ 7) at Screening 
9. Vaccinated against N meningitidis within 3 years prior to initiating ravulizumab as per 
national and local guidelines. Participants must receive the vaccination at least 2 weeks 
before first study intervention. The sponsor recommends that national and local 
guidelines for prophylactic antibiotics should also be followed. 
10. Participants who have been diagnosed with cancer within the last 3 years need to have 
appropriate negative cancer screening as per local standard of care within 6 months 
before Screening (basal or squamous cell skin cancer or carcinoma in situ of the cervix 
needs to have been excised and without evidence of residual disease for at least 3 months 
before Screening). 
Pregnancy and Contraception 
11. Female participants of childbearing potential and male participants must follow specified 
contraception guidance as described in the protocol. 
Informed Consent 
12. Capable of giving signed informed consent as described in the protocol, which includes 
compliance with the requirements and restrictions listed in the Informed Consent Form 
(ICF) and the protocol. 
5.2. 
Exclusion Criteria 
Medical Conditions 
1. Cancer-associated myositis, defined as the diagnosis of myositis within 2 years of the 
diagnosis of cancer (except basal or squamous cell skin cancer or carcinoma in situ of the 
cervix that has been excised and cured for at least 3 months before Screening). 
2. Evidence of active malignant disease or malignancies diagnosed within the previous 
3 years including hematological malignancies and solid tumors (except basal or 

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squamous cell skin cancer or carcinoma in situ of the cervix that has been excised and 
cured for at least 3 months before Screening). 
3. Participants with other forms of myositis: Clinical diagnosis of inclusion body myositis, 
polymyositis, necrotizing myopathy, drug-induced myositis/myopathy, anti-synthetase 
syndrome without DM, cancer-associated myositis (myositis diagnosed within 2 years 
either before or after a diagnosis of malignancy except squamous cell cancer of skin, 
basal cell cancer, or cervical carcinoma in situ), myositis with overlap connective tissue 
disease such as SLE, rheumatoid arthritis, or systemic sclerosis. Participants with 
secondary Sjogren’s syndrome are allowed. 
4. As per Investigator’s discretion, participants with significant muscle damage (eg, severe 
muscle atrophy, end-stage muscle disease, MRI with severe atrophy or fibrofatty 
replacement). 
5. History of N meningitidis infection. 
6. Human immunodeficiency virus (HIV) infection (evidenced by HIV Type 1 or Type 2 
antibody titer). 
7. History of unexplained infections. 
8. Active systemic bacterial, viral, or fungal infection within 14 days prior to ravulizumab 
administration. 
9. Presence of fever ≥ 38°C (100.4°F) within 7 days prior to study intervention 
administration on Day 1. 
10. History of hypersensitivity to murine proteins or to 1 of the excipients of ravulizumab. 
11. As per Investigator’s discretion, participants with advanced clinically symptomatic 
interstitial lung disease that would interfere with the participants ability to complete the 
trial. 
12. Any medical condition (such as, cardiac, pulmonary, renal, oncologic, psychiatric 
disease, or with a diagnosis of fibromyalgia) that, in the opinion of the Investigator, 
might interfere with the participant’s participation in the trial, poses any added risk for 
the participant, or confounds the assessment of the participant. This includes participants 
with severe arthritis with limited range of motion or severe diffuse calcinosis or other 
condition which will prevent quantitative muscle strength testing. 
13. History of drug and/or alcohol abuse (according to Diagnostic and Statistical Manual of 
Mental Disorders [DSM] 5) within 1 year of Screening Visit that would limit participant 
participation in the study as determined by the Investigator. 
Prior/Concomitant Therapy 
14. Participants unwilling or unable to complete an appropriate washout period for any of the 
prohibited medications listed in Section 6.5.2 before the Day 1 visit. 
15. Received ≥ 1 mg/kg/day of prednisone or equivalent within 8 weeks before 
randomization or is currently on a prednisone or equivalent maintenance dose that is 
> 20 mg/day. 

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16. Previously or currently treated with a complement inhibitor. 
Prior/Concurrent Clinical Study Experience 
17. Participation in any other investigational drug study or exposure to an investigational 
drug or device within 30 days of Screening or 5 half-lives of the investigational drug, 
whichever is greater. 
Other Exclusions 
18. Participants who begin a new muscle strengthening exercise program for myositis (eg, 
physical therapy) in the last 4 weeks or change their current exercise regimen up to 
4 weeks before the Day 1 visit. Participants should not initiate any new exercise program 
or change their current exercise regimen throughout the randomized phase of the trial. 
19. Pregnant, breastfeeding, or intending to conceive during the course of the study. 
20. Inability or unwillingness to adhere to the protocol requirements. 
5.3. 
Lifestyle Considerations 
5.3.1. 
Meals and Dietary Restrictions 
There will be no dietary restrictions as part of this study. 
5.3.2. 
Activity 
No new exercise program for myositis (including physical therapy) is allowed from 4 weeks 
before Day 1 until the last day of the Randomized Controlled Period. If the participant is already 
involved in an exercise regimen for muscle strengthening, there should be no changes in the 
regimen from 4 weeks before Day 1 to the last day of the Randomized Controlled Period. 
5.4. 
Screen Failures 
Screen failures are defined as participants who consent to participate in the clinical study but are 
not subsequently randomly assigned to study intervention. A minimal set of screen failure 
information is required to ensure transparent reporting of screen failure participants to meet the 
Consolidated Standards of Reporting Trials publishing requirements and to respond to queries 
from regulatory authorities. Minimal information includes demography, screen failure details 
(eg, failed eligibility criteria), and any AEs, including any serious adverse events (SAEs) and any 
related concomitant medication, occurring during the Screening Period. 
Individuals who do not meet the criteria for participation in this study (screen failure) due to a 
reason that is expected to resolve or has resolved, may be rescreened based on discussion and 
agreement between the Investigator and Alexion Medical Monitor or designee. 

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6. 
STUDY INTERVENTION 
Study intervention is defined as any investigational intervention(s), marketed product(s), 
placebo, or medical device(s) intended to be administered to a study participant according to the 
study protocol. 
6.1. 
Study Intervention(s) Administered  
Ravulizumab IV is formulated at 10 mg/mL and 100 mg/mL concentrations with a pH 7.0 and 
7.4, respectively. Both formulations are presented as sterile, preservative-free solutions for IV 
administration and are supplied in single-use vials. 
The placebo comparator product is formulated as a sterile, clear to translucent colorless solution 
(10 mg/mL) or a clear to translucent, colorless to yellow solution (100 mg/mL) with the same 
buffer components, but without active ingredient. 
Details regarding the ravulizumab IV formulation are presented in Table 10. 
Table 10: 
Study Intervention 
Study intervention 
name 
Ravulizumab  
Placebo 
Dose formulation 
Vial 
Vial 
Physical 
description 
Liquid solution practically free from 
particles 
Liquid solution practically free from 
particles 
Dosage Form 
Concentrated sterile, preservative-free 
aqueous solution in single-use 30 mL 
vials (10 mg/mL formulation) or 
single-use 11 mL vials (100 mg/mL 
formulation) 
Sterile, preservative-free aqueous 
solution in single-use 30 mL vials or 
11 mL vials  
 
Unit dose 
strength(s) 
300 mg (10 mg/mL formulation) or 
1100 mg (100 mg/mL formulation) 
Placebo 
Dosage level(s)a  
Weight-based dosing 
Weight-based dosing 
Route of 
administration 
IV infusion 
IV infusion 
Use 
Experimental 
Placebo comparator 
IMP and 
NIMP/AxMP 
IMP 
IMP 
Sourcing 
Provided centrally by Alexion or 
contracted manufacturing organization 
Provided centrally by Alexion or 
contracted manufacturing organization 
Packaging and 
labeling 
Ravulizumab will be provided in glass 
vials and stoppered with a butyl rubber 
stopper with an aluminum overseal and 
a flip-off cap. Study intervention will 
be supplied in kits and labeled as 
required per country requirement. 
Placebo will be provided in glass vials 
and stoppered with a butyl rubber 
stopper with an aluminum overseal 
and a flip-off cap. Placebo will be 
supplied in kits and labeled as required 
per country requirement. 

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Table 10: 
Study Intervention 
a Detailed information of study intervention dose administration is provided Table 11, Table 12, and Table 13. 
Abbreviations: AxMP = auxiliary medicinal product; IMP = investigational medicinal product; IV = intravenous; 
NIMP = non-investigational medicinal product 
6.1.1. 
Study Intervention(s) Administered 
At the scheduled dosing visits (Section 1.3), study intervention infusion should be performed 
after all other tests and procedures have been completed, excluding the post-dose blood sampling 
for PK/PD. 
The ravulizumab or placebo dose for each participant will be based on body weight and will be 
administered as an IV infusion. The dosing regimen consists of an initial loading dose at the 
beginning of the Randomized Controlled Period and the OLE followed by maintenance dosing 
initiated 2 weeks after loading dose. The maintenance dosing will be administered q8w during 
the Randomized Controlled Period and OLE (Table 12 and Table 13).  
Refer to Table 11 for a reference chart for weight-based dosing.  
Table 11: 
Weight-based Doses of Ravulizumab 
Body Weight Range (kg)a 
Loading Dose (mg) 
Maintenance Dose (mg) 
≥ 30 to < 40 
1200 
2700 
≥ 40 to < 60 
2400 
3000 
≥ 60 to < 100 
2700 
3300 
≥ 100 
3000 
3600 
Note: Additional dose preparation instructions are provided in the pharmacy manual. 
a Dose regimen will be based on the last recorded study visit body weight. If the study intervention is prepared the 
night before a visit, the weight from the most recent study visit should be used. 
Abbreviation: aHUS = atypical hemolytic uremic syndrome; gMG = generalized myasthenia gravis; 
PNH = paroxysmal nocturnal hemoglobinuria  

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Table 12: 
Reference Chart for Weight-based Dosing – Study Part A 
Study Period 
Dosing 
Body Weight 
(kg)a  
Ravulizumab 
Dose  
(mg) 
Ravulizumab 
Volume (mL) 
Placebo 
Volume 
(mL) 
Diluent (0.9% 
Sodium Chloride) 
Volume 
(mL) 
Total Volume  
(mL) 
Ravulizumab Group 
Randomized 
Controlled 
(10 mg/mL 
formulation) 
Loading dose 
(Day 1) 
≥ 30 to < 40 
1200 
120 
0 
120 
240 
≥ 40 to < 60 
2400 
240 
0 
240 
480 
≥ 60 to < 100 
2700 
270 
0 
270 
540 
≥ 100 
3000 
300 
0 
300 
600 
Maintenance dose 
(Days 15, 71, 127) 
 
≥ 30 to < 40 
2700 
270 
0 
270 
540 
≥ 40 to < 60 
3000 
300 
0 
300 
600 
≥ 60 to < 100 
3300 
330 
0 
330 
660 
≥ 100 
3600 
360 
0 
360 
720 
Open-Label 
Extension 
(10 mg/mL 
formulation) 
 
Blinded dose 
(Day 183) 
≥ 30 to < 40 
900 
90 
30 
120 
240 
≥ 40 to < 60 
900 
90 
150 
240 
480 
≥ 60 to < 100 
900 
90 
180 
270 
540 
≥ 100 
900 
90 
210 
300 
600 
Open-Label 
Extension 
(100 mg/mL 
formulation) 
Open-label 
maintenance dose 
(Days 197 to 1037, 
q8w) 
≥ 30 to < 40 
2700 
27 
0 
27 
54 
≥ 40 to < 60 
3000 
30 
0 
30 
60 
≥ 60 to < 100 
3300 
33 
0 
33 
66 
≥ 100 
3600 
36 
0 
36 
72 

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Table 12: 
Reference Chart for Weight-based Dosing – Study Part A 
Study Period 
Dosing 
Body Weight 
(kg)a  
Ravulizumab 
Dose  
(mg) 
Ravulizumab 
Volume (mL) 
Placebo 
Volume 
(mL) 
Diluent (0.9% 
Sodium Chloride) 
Volume 
(mL) 
Total Volume  
(mL) 
Placebo Group 
 
Randomized 
Controlled 
(10 mg/mL 
formulation) 
Loading dose 
(Day 1) 
≥ 30 to < 40 
0 
0 
120 
120 
240 
≥ 40 to < 60 
0 
0 
240 
240 
480 
≥ 60 to < 100 
0 
0 
270 
270 
540 
≥ 100 
0 
0 
300 
300 
600 
Maintenance dose 
(Days 15, 71, 127) 
 
≥ 30 to < 40 
0 
0 
270 
270 
540 
≥ 40 to < 60 
0 
0 
300 
300 
600 
≥ 60 to < 100 
0 
0 
330 
330 
660 
≥ 100 
0 
0 
360 
360 
720 
Open-Label 
Extension 
(10 mg/mL 
formulation) 
 
Blinded loading 
dose 
(Day 183) 
 
≥ 30 to < 40 
1200 
120 
0 
120 
240 
≥ 40 to < 60 
2400 
240 
0 
240 
480 
≥ 60 to < 100 
2700 
270 
0 
270 
540 
≥ 100 
3000 
300 
0 
300 
600 
Open-Label 
Extension 
(100 mg/mL 
formulation) 
Open-label 
maintenance dose 
(Days 197 to 1037, 
q8w) 
 
≥ 30 to < 40 
2700 
27 
0 
27 
54 
≥ 40 to < 60 
3000 
30 
0 
30 
60 
≥ 60 to < 100 
3300 
33 
0 
33 
66 
≥ 100 
3600 
36 
0 
36 
72 
a Dose regimen will be based on the participant’s most recently recorded body weight. Contact the Alexion Medical Monitor or designee if a participant’s weight 
drops below 30 kg during the Randomized Controlled Period or Open-Label Extension Period. 
Abbreviation: q8w = every 8 weeks 

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Table 13: 
Reference Chart for Weight-based Dosing – Study Part B 
Study Period 
Dosing 
Body Weight 
(kg)a  
Ravulizumab 
Dose  
(mg) 
Ravulizumab 
Volume (mL) 
Placebo 
Volume 
(mL) 
Diluent (0.9% Sodium 
Chloride) Volume 
(mL) 
Total Volume  
(mL) 
Ravulizumab Group 
Randomized 
Controlled 
(100 mg/mL 
formulation) 
Loading dose 
(Day 1) 
≥ 30 to < 40 
1200 
12 
0 
12 
24 
≥ 40 to < 60 
2400 
24 
0 
24 
48 
≥ 60 to < 100 
2700 
27 
0 
27 
54 
≥ 100 
3000 
30 
0 
30 
60 
Maintenance dose 
(Days 15, 71, 127, 
183, 239, 295) 
≥ 30 to < 40 
2700 
27 
0 
27 
54 
≥ 40 to < 60 
3000 
30 
0 
30 
60 
≥ 60 to < 100 
3300 
33 
0 
33 
66 
≥ 100 
3600 
36 
0 
36 
72 
Open-Label 
Extension 
(100 mg/mL 
formulation) 
Blinded dose 
(Day 351) 
≥ 30 to < 40 
900 
9 
3 
12 
24 
≥ 40 to < 60 
900 
9 
15 
24 
48 
≥ 60 to < 100 
900 
9 
18 
27 
54 
≥ 100 
900 
9 
21 
30 
60 
Open-label 
maintenance dose 
(Days 365 to 813, 
q8w) 
≥ 30 to < 40 
2700 
27 
0 
27 
54 
≥ 40 to < 60 
3000 
30 
0 
30 
60 
≥ 60 to < 100 
3300 
33 
0 
33 
66 
≥ 100 
3600 
36 
0 
36 
72 

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Table 13: 
Reference Chart for Weight-based Dosing – Study Part B 
Study Period 
Dosing 
Body Weight 
(kg)a  
Ravulizumab 
Dose  
(mg) 
Ravulizumab 
Volume (mL) 
Placebo 
Volume 
(mL) 
Diluent (0.9% Sodium 
Chloride) Volume 
(mL) 
Total Volume  
(mL) 
Placebo Group 
 
Randomized 
Controlled 
(100 mg/mL 
formulation) 
Loading dose 
(Day 1) 
≥ 30 to < 40 
0 
0 
12 
12 
24 
≥ 40 to < 60 
0 
0 
24 
24 
48 
≥ 60 to < 100 
0 
0 
27 
27 
54 
≥ 100 
0 
0 
30 
30 
60 
Maintenance dose 
(Days 15, 71, 127, 
183, 239, 295) 
≥ 30 to < 40 
0 
0 
27 
27 
54 
≥ 40 to < 60 
0 
0 
30 
30 
60 
≥ 60 to < 100 
0 
0 
33 
33 
66 
≥ 100 
0 
0 
36 
36 
72 
Open-Label 
Extension 
(100 mg/mL 
formulation) 
Blinded loading 
dose 
(Day 351) 
≥ 30 to < 40 
1200 
12 
0 
12 
24 
≥ 40 to < 60 
2400 
24 
0 
24 
48 
≥ 60 to < 100 
2700 
27 
0 
27 
54 
≥ 100 
3000 
30 
0 
30 
60 
Open-label 
maintenance dose 
(Days 365 to 813, 
q8w) 
≥ 30 to < 40 
2700 
27 
0 
27 
54 
≥ 40 to < 60 
3000 
30 
0 
30 
60 
≥ 60 to < 100 
3300 
33 
0 
33 
66 
≥ 100 
3600 
36 
0 
36 
72 
a Dose regimen will be based on the participant’s most recently recorded body weight. Contact the Alexion Medical Monitor or designee if a participant’s weight 
drops below 30 kg during the Randomized Controlled Period or Open-Label Extension Period. 
Abbreviation: q8w = every 8 weeks 

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6.1.1.1. 
Part A 
For each participant in Part A, the entire duration is up to 156 weeks, consisting of a 
Randomized Controlled Period (26 weeks), and an OLE Period (up to 130 weeks, last scheduled 
dosing at OLE Week 148). 
Randomized Controlled Period 
Randomized Controlled Period is a double-blind, randomized, placebo-controlled period. 
Eligible participants will be randomized 2:1 to receive blinded doses of ravulizumab or placebo 
starting on Day 1 and ending after assessments on Week 26. 
• Participants in the ravulizumab group will receive a blinded loading dose of 
ravulizumab (10 mg/mL formulation) via IV infusion on Day 1, followed by a 
blinded maintenance dose at Week 2, Week 10, and Week 18 (Table 12). 
• Participants in the placebo group will receive a blinded placebo via IV infusion on 
Day 1, followed by a blinded placebo at Week 2, Week 10, and Week 18. 
• Participants who discontinue study intervention will be followed for key efficacy 
(Section 8.1) and safety assessments (Section 8.2) until the end of the Randomized 
Controlled Period, withdrawal of consent, or lost to follow-up, whichever is earlier. 
Participants who will not enter the OLE Period will complete the assessments for Week 26 but 
will not receive an infusion at Week 26. 
Open-Label Extension Period 
The Randomized Controlled Period will end after all predose assessments have been completed 
at the Week 26 visit. The OLE Period will begin when participants, that elect to continue 
treatment, receive the Week 26 study intervention infusion. To maintain the treatment 
randomization blind of the Randomized Controlled Period, participants in both the placebo group 
and the ravulizumab group will receive blinded doses of ravulizumab as follows: 
• Participants in the placebo group will switch to receive a blinded loading dose of 
ravulizumab (10 mg/mL formulation) at Week 26 (Table 12). 
• Participants in the ravulizumab group will receive a blinded ravulizumab dose 
(10 mg/mL formulation) of 900 mg at Week 26. The 900 mg dose at Week 26 is 
chosen to maintain complete C5 inhibition over the 2-week period until the next 
scheduled maintenance dose.  
Starting at Week 28, all participants will receive open-label ravulizumab maintenance doses 
(100 mg/mL formulation) q8w until the last scheduled dose at Week 148 (Table 12). 
6.1.1.2. 
Part B 
For each participant in Part B, the entire duration is up to 124 weeks, consisting of a Randomized 
Controlled Period (50 weeks), and an OLE Period (up to 74 weeks). 

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Randomized Controlled Period 
Randomized Controlled Period is a double-blind, randomized, placebo-controlled period. 
Eligible participants will be randomized 2:1 to receive blinded doses of ravulizumab or placebo 
starting on Day 1 and ending after assessments on Week 50. 
• Participants in the ravulizumab group will receive a blinded loading dose of 
ravulizumab (100 mg/mL formulation) via IV infusion on Day 1, followed by a 
blinded maintenance dose at Week 2, then q8w through Week 42 (Table 13). 
• Participants in the placebo group will receive a blinded placebo via IV infusion on 
Day 1, followed by a blinded placebo at Week 2, then q8w through Week 42 
(Table 13). 
• Participants who discontinue study intervention will be followed for key efficacy 
(Section 8.1) and safety assessments (Section 8.2) until the end of the Randomized 
Controlled Period, withdrawal of consent, or lost to follow-up, whichever is earlier. 
Participants who will not enter the OLE Period will complete the assessments for Week 50 but 
not receive an infusion at Week 50. 
Open-Label Extension Period 
The Randomized Controlled Period will end after all predose assessments have been completed 
at the Week 50 visit. The OLE Period will begin when participants who are permitted to enter 
and elect to continue treatment receive the Week 50 study intervention infusion. To maintain the 
treatment randomization blind of the Randomized Controlled Period, participants in both the 
placebo group and the ravulizumab group will receive blinded doses of ravulizumab as follows: 
• Participants in the placebo group will receive a blinded loading dose of ravulizumab 
(100 mg/mL formulation) at Week 50 (Table 13). 
• Participants in the ravulizumab group will receive a blinded ravulizumab dose 
(100 mg/mL formulation) of 900 mg at Week 50. The 900 mg dose at Week 50 is 
chosen to maintain complete C5 inhibition over the 2-week period until the next 
scheduled maintenance dose. This dosing maintains the treatment randomization 
blind of the Randomized Controlled Period. 
Starting at Week 52, all participants will receive open-label ravulizumab maintenance doses 
(100 mg/mL formulation) q8w (Table 13) until the last scheduled dose at Week 116. 
6.2. 
Preparation/Handling/Storage/Accountability  
Upon arrival of the study intervention at the study site, the study intervention kits should be 
removed from the shipping container and stored in their original cartons under refrigerated 
conditions at 2°C to 8°C (35°F to 47°F) and protected from light. Study interventions should not 
be frozen. 
Study interventions must be stored in a secure, limited-access storage area with temperature 
monitored daily. 

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Infusions of study intervention should be prepared using aseptic technique. Ravulizumab and 
placebo will be further diluted in a 1:1 ratio with compatible diluent. Ravulizumab and placebo 
will be filtered with a 0.2 micron filter during infusion. 
1. The Investigator or designee must confirm appropriate temperature conditions have been 
maintained during transit for all study intervention received and that any discrepancies 
are reported and resolved before use of the study intervention. 
2. Only participants enrolled in the study may receive the study intervention and only 
authorized site staff may supply or administer the study intervention. All study 
intervention must be stored in a secure, environmentally controlled, and monitored 
(manual or automated) area in accordance with the labeled storage conditions with access 
limited to the Investigator and authorized site staff. 
3. The Investigator, institution, or the head of the medical institution (where applicable) is 
responsible for study intervention accountability, reconciliation, and record maintenance 
(ie, receipt, reconciliation, and final disposition records). 
a. This responsibility includes the reporting of any temperature excursions and product 
complaints to AlexionIMPTE@alexion.com and productcomplaints@alexion.com 
within 1 business day of awareness. A product complaint is defined as any written, 
electronic, or oral communication that alleges deficiencies related to the identity, 
quality, durability, reliability, usability, safety, effectiveness, or performance of a 
product or clinical study material and/or its packaging components after it is has been 
released for distribution to an end customer that affects the performance of such 
product. 
b. The pharmacist or other designated individual will maintain records of study 
intervention delivered to the study site, the inventory at the study site, the distribution 
to and use by each participant, and the return of materials to the sponsor for storage or 
disposal/destruction of materials at the study site. These records may include 
information such as dates, quantities, batch/serial numbers, expiration dates, in-clinic 
temperature log, and unique code numbers assigned to the study intervention and 
study participants. 
c. The Investigator will maintain records that adequately document that the participants 
were administered the correct study treatment kits and reconcile the products received 
from the drug dispensing center. Investigational product will not be returned to the 
sponsor or disposed of until accountability has been fully monitored. 
 
4. Further guidance regarding preparation, handling, storage, and accountability and 
information for the final disposition of unused study intervention is provided in the 
Pharmacy Manual. 
6.3. 
Measures to Minimize Bias: Randomization and Blinding 
6.3.1. 
Randomization 
Participants in Parts A and B will be randomly allocated on Day 1 to one of two treatment groups 
after the Investigator and Alexion Medical Monitor or designee have verified that they are 
eligible. Participants will be randomized 2:1 in Part A. For Part B, participants will be stratified 

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by CDASI Activity Score: ≤ 14 and > 14) and randomized 2:1 to either ravulizumab IV infusion 
or placebo IV infusion within each stratum. Participants will be centrally randomized using 
interactive response technology (IRT). 
6.3.2. 
Blinding 
Participants, all investigative site personnel, Alexion staff, Alexion designees, and any staff 
directly associated with the conduct of the study will be blinded to participant treatment 
assignments. To protect the blind, study Part B requires an unblinded pharmacist and potentially 
an unblinded study nurse. The blinding will be maintained by using identical study intervention 
kits and labels for ravulizumab and placebo. The randomization code will be maintained by the 
IRT provider. Participants who elect to continue treatment after completion of the Randomized 
Controlled Period enter the OLE Period at the end of the Week 26 (Part A) or Week 50 (Part B) 
visit after completing all scheduled assessments and before receiving ravulizumab. To maintain 
blinding to the participant’s treatment assignment during the Randomized Controlled Period, 
participants in the placebo group will receive a blinded loading dose of ravulizumab, and 
participants in the ravulizumab group will receive a blinded dose of 900 mg. For participants in 
the ravulizumab group, a blinded ravulizumab dose of 900 mg was chosen to ensure maintenance 
of complete C5 inhibition until the next scheduled maintenance dose at Week 28 (Part A) or 
Week 52 (Part B). Blind to previous assignment will be maintained for participants, all 
investigative site personnel, Alexion staff, Alexion designees, and any staff directly associated 
with the conduct of the study during the OLE Period until after data from the Randomized 
Controlled Period of the study have been cleaned, locked, and unblinded. Starting at Week 28 
(Part A) or Week 52 (Part B), all participants will begin open-label weight-based ravulizumab 
maintenance doses q8w. Investigators should avoid unscheduled laboratory tests which could 
potentially break the blind (eg, complement activity assays such as CH50). Access to exploratory 
biomarker data should be restricted to the Biomarker Development group and all exploratory 
biomarker data will be received as masked data for exploratory assessment of matrix and assay 
performance. All exploratory biomarker data that may potentially unblind patients’ randomized 
treatment assignment will not be reported to blinded study personnel until the study blind is 
broken. 
In case of an emergency, the Investigator has the sole responsibility for determining if 
unblinding of a participant’s intervention assignment is warranted. Participant safety must 
always be the first consideration in making such a determination. If the Investigator decides that 
unblinding is warranted, the Investigator should make every effort to contact the Sponsor before 
unblinding a participant’s intervention assignment unless this could delay emergency treatment 
of the participant. If a participant’s intervention assignment is unblinded, Alexion must be 
notified within 24 hours after breaking the blind. The date and reason that the blind was broken 
must be recorded in the source documentation. 
When unblinding is the result of an AE which is unexpected or related and serious, the blind will 
be broken for that specific participant only. The blind with regard to treatment allocation for that 
specific participant will be maintained for all study personnel and those responsible for data 
analysis and interpretation of results at the conclusion of the study, such as biometrics personnel. 

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Unblinded information will be accessible to those who need to be involved in the safety 
reporting to Health Authorities, Independent Ethics Committees (IECs), Institutional Review 
Boards (IRBs), and/or IDMC.  
There may be additional analyses in Part A, which may be generated and reviewed by an 
unblinded team (independent of the study team). 
Participants will remain blinded to the treatment received in the Randomized Controlled Period 
through the OLE Period and may only be unblinded after the study has been completed. 
Any participant whose treatment is unblinded during the Randomized Controlled Period will be 
discontinued from the study. 
6.4. 
Study Intervention Compliance 
The infusion of study intervention into participants will be under the supervision of the 
Investigator or their designee to ensure that participants receive the appropriate dose at the 
appropriate time points during the study. 
The date and time of each dose administered in the clinic will be recorded in the source 
documents and case report form (CRF). 
The volume (mL) of study intervention and study participant identification will be confirmed at 
the time of dosing by a member of the study site staff other than the person administering the 
study intervention. 
For additional information on study intervention and management, refer to the Pharmacy 
Manual. 
6.5. 
Concomitant Therapy 
Any medication (including over the counter or prescription medicines, vitamins, and/or herbal 
supplements), vaccine, or other specific categories of interest that the participant is receiving at 
the time of enrollment or receives during the study must be recorded along with: 
• Reason for use 
• Dates of administration, including start and end dates 
• Dosage information including dose and frequency 
The Alexion Medical Monitor or designee should be contacted if there are any questions 
regarding concomitant or prior therapy. 
6.5.1. 
Allowed Medicine and Therapy 
6.5.1.1. 
Dermatomyositis Treatment 
Participants should not discontinue an effective therapy solely for the purpose of entering the 
clinical study. 
Participants who continue allowed DM treatments as concomitant therapy will be required to 
have received those treatments for at least the amount of time described in Table 14 before the 
Day 1 Visit and will be required to remain on the same stable dose during the Randomized 

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Controlled Period. Maximally allowed stable doses are described in Table 14. In some cases, 
stable doses of allowed DM treatments may be decreased due to safety and/or tolerability issues. 
Investigators must contact the Alexion Medical Monitor or designee to discuss possible dose 
changes before adjusting the participant’s allowed DM treatment dose. 
During the OLE Period, doses of allowed DM treatments may be changed or discontinued. New 
allowed DM treatments may be started in the OLE Period. Medications listed in Section 6.5.2 are 
prohibited during the OLE Period. Any change in medication will be properly documented in the 
CRF. 
Table 14: 
Allowed Concomitant DM Treatments 
Medication 
Duration 
of Stable 
Dose 
Before 
Day 1 Visit 
Treatment 
Duration 
Required 
Before Day 1 
Visit 
Maximally 
Allowed Stable 
Dose as 
Concomitant 
therapy 
Dose Modifications 
Permitted During 
Randomized 
Controlled Perioda 
Azathioprine 
4 weeks 
12 weeks 
2.5 mg/kg daily 
None 
Cyclosporine 
4 weeks 
12 weeks 
5 mg/kg daily 
None 
Glucocorticoid 
4 weeks 
4 weeks  
20 mg daily 
Prednisone 
equivalentb 
None 
Hydroxychloroquine 
4 weeks 
12 weeks 
400 mg daily 
None 
Intramuscular 
glucocorticoidsb,c 
NA 
NA 
80 mg per dose 
Only 2 injections 
allowed (must be 
separate days) 
Leflunomide 
4 weeks 
12 weeks 
20 mg daily 
None 
Methotrexate 
4 weeks 
12 weeks 
25 mg/week 
None 
Mycophenolate 
mofetil/mycophenolic 
acid 
4 weeks 
12 weeks 
3000 mg daily 
None 
Sulfasalazine 
4 weeks 
12 weeks 
3 g daily 
None 
Tacrolimus 
4 weeks 
12 weeks 
0.2 mg/kg daily 
None 
a Unless medically necessary or due to participant safety reasons. 
b Prednisone equivalent medications and doses are described in the Study Manual. 
c Do not administer within 72 hours prior to a study visit. 
Abbreviations: DM = dermatomyositis; NA = not applicable 
Alternatively, participants may choose to discontinue previous DM treatments before the Day 1 
Visit but will be required to complete an appropriate washout period, as described in Table 15. 
Table 15: 
Washout Periods Required Before Day 1 Visit 
Medication a 
Washout 
Azathioprine 
4 weeks 

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Table 15: 
Washout Periods Required Before Day 1 Visit 
Medication a 
Washout 
Cyclosporine 
4 weeks 
Glucocorticoid b 
4 weeks 
Hydroxychloroquine 
8 weeks 
Intramuscular glucocorticoids 
4 weeks 
Leflunomide 
12 weeks 
Methotrexate 
4 weeks 
Mycophenolate mofetil/mycophenolic acid 
4 weeks 
Sulfasalazine 
4 weeks 
Tacrolimus 
4 weeks 
a For questions regarding a washout period for previous dermatomyositis treatments not listed please consult the 
Alexion Medical Monitor or designee. 
b 8-week washout before randomization if received ≥ 1 mg/kg/day or on a maintenance dose > 20 mg/day 
6.5.1.2. 
Other Allowed Therapies 
• Medications listed below may be taken as needed but should not be administered within 
72 hours prior to the study visit.  
o Antihistamines  
o  Non-steroidal anti-inflammatory drugs (NSAIDs) 
o Acetaminophen 
o Antipruritics  
However, participants taking the medications listed above at a stable dose for at least 4 
weeks before Screening are allowed to continue these medications. 
• Topical steroid hydrocortisone (1%) may be taken as needed but should not be 
administered within 72 hours prior to the study visit. 
• Vitamin B12, vitamin E, creatine, coenzyme Q10, and biotin supplements are permitted 
in this study. Participants who take any or all of these supplements should be on a stable 
dose beginning 14 days prior to the first dose of study intervention and remain on the 
same stable dose for the duration of the Randomized Controlled Period unless alteration 
in dose is deemed medically necessary or reviewed with the Alexion Medical Monitor or 
designee. 
• All other vitamins and supplements are permitted in this study. Participants are 
encouraged to remain on stable dosing for the duration of the Randomized Controlled 
Period of the study.  

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6.5.2. 
Disallowed Medicine and Therapy 
The following medications and therapies are prohibited during the study: 
• Treatments listed in Table 16. Participants must complete the appropriate washout 
period for these treatments as listed in Table 13 before the Day 1 Visit. 
• Eculizumab or other complement inhibitory agent. 
• Any investigational therapy or off-label usage of an approved product other than the 
allowed medication in this protocol for the treatment of DM during the study 
(Table 14). 
Table 16: 
Washout Periods Required Before Day 1 for Prohibited Medications 
Medication a  
Washout 
Abatacept 
12 weeks 
Adalimumab 
12 weeks 
Anakinra 
1 week 
Corticotropin injection 
8 weeks 
Cyclophosphamide 
12 weeks 
Etanercept 
4 weeks 
Infliximab 
8 weeks 
IVIg/SCIg 
12 weeks 
IV glucocorticoids 
4 weeks 
Ocrelizumab 
20 weeks 
Rituximab 
24 weeks 
Tocilizumab 
10 weeks 
Tofacitinib or other JAK inhibitors 
4 weeks 
a For questions regarding a washout period for previous prohibited dermatomyositis treatments and monoclonal 
antibodies not listed please consult the Alexion Medical Monitor or designee.  
Abbreviations: IVIg = intravenous immunoglobulin; JAK = Janus kinase; SCIg = subcutaneous immunoglobulin 
Participants who require prohibited medications at any point during the study will be 
discontinued from the study intervention. 
6.5.3. 
Acute Therapy with Standard DM Treatment 
To allow for sufficient time for the study drug to become effective, it is recommended that 
participants not receive any acute therapy with standard DM treatment during the first 10 weeks 
of receiving the study intervention during the Randomized Controlled Period.  
Acute therapy with standard DM treatment includes an increased dose of a medication that is 
currently being taken for DM or the initiation of a new DM treatment (glucocorticoid and/or 
ISTs).  

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Participants in the Randomized Controlled Period (Part A and Part B) who receive acute therapy 
with standard DM treatment with protocol allowed medication (see Section 6.5.1) upon 
confirmation of Clinical Worsening (see Section 4.1.3) will discontinue study intervention, 
complete the Randomized Controlled Period, and will be permitted to enter the OLE Period. 
Participants in the Randomized Controlled Period who receive acute therapy with standard DM 
treatment for other reasons will discontinue study intervention, complete the Randomized 
Controlled Period visit assessments, but will not be permitted to enter the OLE Period.  
All participants who received acute therapy with standard DM treatment during the Randomized 
Controlled Period and are permitted to enter the OLE will require a weight-based blinded loading 
dose at Week 26 (Part A) or Week 50 (Part B) as described in Table 12, Table 13, and 
Section 6.1.1.  
Participants randomized to ravulizumab: 
Participants in Part A who discontinue therapy before Week 18 will resume treatment in 
Week 26 with the weight-based blinded loading dose described in the Placebo Group section of 
Table 12 (no dose adjustments needed).  
Participants in Part A who discontinue therapy after Week 18 will resume treatment in Week 26 
with the weight-based blinded dose described in the Ravulizumab Group section of Table 12 (no 
dose adjustments needed).  
Participants in Part B who discontinue therapy before Week 42 will resume treatment in 
Week 50 with the weight-based blinded loading dose described in the Placebo Group section of 
Table 13 (no dose adjustments needed).  
Participants in Part B who discontinue therapy after Week 42 will resume treatment in Week 50 
with the weight-based blinded dose described in the Ravulizumab Group section of Table 13 (no 
dose adjustments needed).  
Participants randomized to placebo: 
Participants will resume treatment in Week 26 (Part A) or Week 50 (Part B) with the weight-
based blinded loading dose described in the Placebo Group section of Table 12 and Table 13 (no 
dose adjustments needed).  
All participants will then continue to receive the weight based open-label maintenance dose. 
OLE Period 
Adjustments of protocol allowed DM medications will be permitted throughout the OLE Period. 
6.6. 
Dose Modification  
Dose modification is not permitted for this study. However, in the event of a missed or 
incomplete dose, and with the guidance of the Sponsor, unscheduled doses may be administered 
in order to limit the risk of losing complete terminal complement inhibition. 
In the event of treatment discontinuation during the Randomized Controlled Period 
modifications to the first dose of the OLE may be required (see Section 6.5.3). 

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6.7. 
Intervention After the End of the Study 
Participants will receive ravulizumab until ravulizumab is registered or approved (in accordance 
with country-specific regulations) or for up to 130 weeks (approximately 2.5 years) (Part A) or 
up to 74 weeks (approximately 1.5 years) (Part B) in the OLE Period, whichever occurs first. 
Ravulizumab will not be provided to participants after the last scheduled dose (Section 1.3). 
Participants in the Randomized Controlled Period who discontinue study intervention early and 
do not agree to continue in the study, will be expected to complete the study visit (if at the site 
for a scheduled visit) or return for an Unscheduled Visit as soon as possible within a week and an 
ET Visit 8 weeks after the participant’s last dose of study intervention. Participants will be 
followed via a phone call for an additional 21 weeks (± 1 week) after the last dose of study 
intervention. 

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7. 
DISCONTINUATION OF STUDY INTERVENTION AND 
PARTICIPANT DISCONTINUATION/WITHDRAWAL 
7.1. 
Discontinuation of Study Intervention 
In rare instances, it may be necessary for a participant to discontinue study intervention.  
Participants in the Randomized Controlled Period who discontinue study intervention but do not 
withdraw consent will remain in the study and will continue to complete study visits as described 
in the SoA (Section 1.3).  
If the decision to discontinue study intervention for any reason falls outside of a study visit, 
participants are expected to return for an Unscheduled Visit as soon as possible within a week 
and complete the remaining scheduled visits for the Randomized Controlled Period.  
All participants completing the Randomized Controlled Period and not entering the OLE Period 
will have a follow-up phone call 21 weeks (± 1 week) after the participant’s last dose of study 
intervention to collect information on concomitant medications, non-pharmacologic therapies 
and procedures, and AEs. 
See the SoA (Section 1.3) for data to be collected at the time of discontinuation of study 
intervention and for any further evaluations that need to be completed. 
Participants should be considered for discontinuation of study intervention if any of the 
following occur: 
• Severe uncontrolled infection. 
• Serious infusion or hypersensitivity reaction (such as bronchospasm with wheezing or 
requiring ventilator support or symptomatic hypotension, refer to Section 10.1) or 
serum sickness-like reactions manifesting 1 to 14 days after drug administration and 
assessed as related to study drug. 
• Grade 3 rash or pruritus unresponsive to appropriate treatment according to local or 
institutional guidelines and assessed as related to study drug. 
• Newly diagnosed cardiac arrythmias refractory to treatment as per local or 
Institutional guidelines and assessed as related to study intervention. 
• Severe unintended weight loss (greater or equal to 20% from baseline) during a 
6-month period.  
• Pregnancy or planned pregnancy. 
• Participant is treated with prohibited medications (Section 6.5.2) or acute therapy 
with standard DM treatment (Section 6.5.3). 
• Alexion or the Investigator deem it necessary for the participant based on a 
documented safety concern or AE or lack of improvement. 
• Clinical Worsening as outlined in Section 4.1.3. 

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7.2. 
Participant Discontinuation/Withdrawal from the Study 
• All efforts should be made to ensure participants are willing to comply with study 
participation prior to conducting the screening procedures. 
• The study staff should notify Alexion and their site monitor of all study withdrawals 
as soon as possible. The reason for participant discontinuation must be recorded in the 
source documents and electronic case report form (eCRF). 
• A participant may withdraw from the study at any time at the participant’s own 
request. 
• Participants who discontinue/withdraw from the study during the Randomized 
Controlled Period should complete the study visit (if at the site for a scheduled visit) 
or return for an Unscheduled Visit as soon as possible within a week and complete 
the ET Visit 8 weeks after the participant’s last dose of study intervention. In 
addition, a follow-up phone call 21 weeks (± 1 week) after the participant’s last dose 
of study intervention will be performed to collect information on concomitant 
medications, non-pharmacologic therapies and procedures, and AEs.  
• Participants who discontinue/withdraw from study during the Randomized Controlled 
Period will not be permitted to enter the OLE Period.  
• Participants who discontinue/withdraw from the study during the OLE Period should 
complete the ET Visit 8 weeks after the participant’s last dose of study intervention. 
In addition, a follow-up phone call 21 weeks (± 1 week) after the participant’s last 
dose of study intervention will be performed to collect information on concomitant 
medications, non-pharmacologic therapies and procedures, and AEs.  
• Refer to the SoA for data to be collected at the time of study discontinuation and 
follow-up and for any further evaluations that need to be completed. 
• If the participant withdraws consent for disclosure of future information, Alexion may 
retain and continue to use any data collected before such a withdrawal of consent. 
• If a participant withdraws from the study, the participant may request destruction of 
any samples taken and not tested, and the Investigator must document this in the site 
study records and communicate to the Sponsor. 
7.3. 
Lost to Follow-up 
A participant will be considered lost to follow-up if the participant repeatedly fails to return for 
scheduled visits and is unable to be contacted by the study site. 
The following actions must be taken if a participant fails to return to the clinic for a required 
study visit: 
• The site must attempt to contact the participant to reschedule the missed visit as soon 
as possible, counsel the participant on the importance of maintaining the assigned 
visit schedule and ascertain whether or not the participant wishes to and/or should 
continue in the study. 

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• Before a participant is deemed lost to follow-up, the Investigator or designee must 
make every effort to regain contact with the participant (where possible, 3 telephone 
calls and, if necessary, a certified letter to the participant’s last known mailing 
address or local equivalent methods). These contact attempts should be documented 
in the participant’s medical record. 
• Should the participant continue to be unreachable, he/she will be considered lost to 
follow-up. 
Discontinuation of specific sites or of the study as a whole are handled as part of Section 10.2.9. 

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8. 
STUDY ASSESSMENTS AND PROCEDURES 
• Study procedures and their timing are summarized in the SoA (Section 1.3). Protocol 
waivers or exemptions are not allowed. 
• Immediate safety concerns should be discussed with Alexion immediately upon 
occurrence or awareness to determine if the participant should continue or 
discontinue study intervention. 
• Adherence to the study design requirements, including those specified in the SoA 
(Section 1.3), is essential and required for study conduct. 
• All screening evaluations must be completed and reviewed to confirm that potential 
participants meet all eligibility criteria. The Investigator will maintain a screening log 
to record details of all participants screened and to confirm eligibility or record 
reasons for screening failure, as applicable. 
• Procedures conducted as part of the participant’s routine clinical management (eg, 
blood count) and obtained before signing of the ICF may be utilized for screening or 
baseline purposes provided the procedures met the protocol-specified criteria and 
were performed within the time frame defined in the SoA (Section 1.3). 
• See Section 10.3 for the list of clinical laboratory tests. 
8.1. 
Efficacy Assessments  
All efficacy assessments, not completed by the participants themselves, should preferably be 
performed by the same study staff member throughout the study. 
8.1.1. 
International Myositis Assessment and Clinical Studies (IMACS) Core Set 
Measures (CSM) 
The IMACS group developed a consensus on outcome measures and definitions of improvement 
that should be used in clinical trials for DM (Aggarwal, 2017). The CSM are described in the 
following subsections. 
8.1.1.1. 
Myositis Disease Activity Assessment Tool (MDAAT) 
The MDAAT assesses disease activity of extramuscular organ systems and muscle in patients 
with DM (Section 10.8.1). It is a combined tool that includes the Myositis Disease Activity 
Assessment VAS (MYOACT) and the Myositis Intention to Treat Activities Index (MITAX). 
The MITAX assesses specific manifestations in 7 organs/systems: constitutional, cutaneous, 
skeletal, gastrointestinal, pulmonary, cardiac, and muscle. The MYOACT consist of a 10-cm 
VAS for each organ system and overall. The MDAAT is administered in-person and completed 
by the clinician (Rider, 2011b). MDAAT will be completed at the timepoints listed in the SoA 
(Section 1.3) and should be the first clinician assessed IMACS CSM to be completed. 
8.1.1.2. 
Physician Global Activity Assessment 
The physician global activity assessment provides an overall rating of disease activity related to 
myositis Section 10.8.2). Disease activity is judged by the physician based on all information 
available at the time of evaluation, including the participant’s appearance, medical history, 

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physical examination, laboratory testing, and prescribed medical therapy. The global disease 
activity score is recorded on a 10-cm VAS anchored at the end points and the middle  
(Rider, 2011b). The form also includes a 5-point Likert scale to assess the global disease activity. 
The physician global activity assessment will be completed at timepoints listed in the SoA 
(Section 1.3). 
8.1.1.3. 
Patient Global Activity Assessment 
The patient global activity assessment provides an overall rating of disease activity related to 
myositis from the participant’s perspective (Section 10.8.3). Participants are asked to consider all 
of the active inflammation in their own muscles, skin, joints, intestines, heart, lungs, or other 
parts of the body that can improve with treatment. The patient global disease activity score is 
recorded on a 10-cm VAS that contains a smiley face at the 0-cm anchor and a sad face at the 
10-cm anchor to help participants understand the scale (Rider, 2011b). The patient global activity 
assessment will be completed at timepoints listed in the SoA (Section 1.3). 
8.1.1.4. 
Manual Muscle Testing 8 Muscles Group (MMT-8) 
The purpose of the MMT-8 is to measure muscle strength as part of the physical examination. It 
includes a subset of 8 muscle groups: neck flexors, deltoids, biceps, wrist, extensors, gluteus 
maximus and medius, quadriceps, and ankle dorsiflexors (Rider, 2011b). MMT-8 will be 
administered at timepoints listed in the SoA (Section 1.3). 
8.1.1.5. 
Health Assessment Questionnaire (HAQ) 
The HAQ is a brief self-report questionnaire that assesses physical function pertaining to 
activities of daily living in a variety of domains (Rider, 2011b). In this study, the HAQ Disability 
Index (Section 10.8.5) will be completed at timepoints listed in the SoA (Section 1.3). 
8.1.1.6. 
Muscle Enzymes 
As part of the IMACS CSM, laboratory tests to measure serum activities of muscle-associated 
enzymes including CK, ALT and AST, LDH, and aldolase will be performed. The most 
abnormal serum muscle enzyme value at baseline will be used for calculation of the TIS 
(Aggarwal, 2017). Muscle enzymes will be assessed at the timepoints listed in the SoA 
(Section 1.3). 
8.1.2. 
Cutaneous Dermatomyositis Disease Area and Severity Index (CDASI) 
The CDASI is an instrument that separately measures activity and damage in the skin of DM 
patients (Section 10.8.6). It is a 1-page instrument that contains 3 activity measures (erythema, 
scale, and erosion/ulceration) and 2 damage measures (poikiloderma and calcinosis). CDASI is 
completed by the Clinician or Clinician-Investigator while examining the participant  
(Rider, 2011b). CDASI will be completed at the timepoints listed in the SoA (Section 1.3). 
8.1.3. 
Cutaneous Dermatomyositis Activity Physician’s Global Assessment (CDA-IGA) 
The Cutaneous Dermatomyositis Activity Physician’s Global Assessment (CDA-IGA) is a scale 
that was created to measure disease severity in patients with skin disease. It is a 5-point scale 
(0 = clear; 1 = almost clear; 2 = mild; 3 = moderate; 4 = severe) with morphologic descriptors for 

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each score (Section 10.8.7). The CDA-IGA is completed by the Investigator and is used to 
describe the overall appearance of lesions at a given time point. The CDA-IGA will be 
completed at the timepoints listed in the SoA (Section 1.3). 
8.1.4. 
EuroQoL 5 Dimensions (EQ-5D-5L) 
The European Quality of Life Health 5-item questionnaire dimensions 5 level (EQ-5D-5L) 
(Section 10.8.8) is a self-assessed, standardized instrument to measure health-related quality of 
life and has been used in a wide range of health conditions (Schrag, 2000). The EQ-5D-5L 
consists of 2 pages: the EQ-5D-5L descriptive system and the EQ VAS. The EQ-5D-5L will be 
completed at time points specified in the SoA (Section 1.3), or if a participant is not able to 
attend the scheduled onsite visit, EQ-5D-5L can be assessed via a phone call. 
8.1.4.1. 
EQ-5D-5L Descriptive System 
The descriptive system is a 5-component scale including mobility, self-care, usual activities, 
pain/discomfort, and anxiety/depression (Section 10.8.8). Each level is rated on a scale that 
describes the degree of problems in that area. 
8.1.4.2. 
EQ Visual Analog Scale 
The EQ VAS is an overall health state scale where the participant selects a number between 0 
and 100 to describe the condition of their health, with 100 being ‘The best health state you can 
imagine’ and 0 being ‘The worst health state you can imagine’ (Section 10.8.8). 
This information can be used as a quantitative measure of health outcome as judged by the 
individual respondents. Previously published studies by EuroQol Group members showed 
preliminary evidence of the instrument’s feasibility, reliability, and validity. 
8.1.5. 
5D-Itch Scale 
The 5D-itch scale is a multidimensional questionnaire, which includes the following 5 
dimensions: degree, duration, direction, disability, and distribution (Section 10.8.9). The 5D-itch 
scale will be completed by the participant at the timepoints described in the SoA (Section 1.3). 
8.1.6. 
Patient-Reported Outcomes Measurement Information System (PROMIS) 29 
v2.1 Tool 
The Patient-Reported Outcomes Measurement Information System (PROMIS)-29 v2.1 
(Section 10.8.10) profile assesses pain intensity using a single 0-10 numeric rating item and 7 
health domains (physical function, fatigue, pain interference, depressive symptoms, anxiety, 
ability to participate in social roles and activities, and sleep disturbance) using 4 items per 
domain. PROMIS-29 v2.1 will be completed by the participant at the timepoints described in the 
SoA (Section 1.3). 
8.1.7. 
Short Form Health Survey (36 Questions Version) (SF-36) 
The Short Form Health Survey (36 Questions Version) (SF-36) (Version 2.0) is a 36-item self-
report of health-related quality of life (Stewart, 1988; Ware, 1992). It contains 8 subscales 
measuring different domains of health-related quality of life: physical functioning, role 
limitations due to physical problems, bodily pain, general health perceptions, vitality, social 

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functioning, role limitations due to emotional problems, and mental health (Section 10.8.11). The 
SF-36 will be conducted at Screening and at timepoints specified per SoA (Section 1.3). The 2 
summary scores are the physical component summary and the mental component summary. 
There is no single overall score for the SF-36. 
8.1.8. 
Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue) 
The Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue) Scale (Version 
4) is a short, 13-item, self-reported, easy to administer tool that measures an individual’s level of 
fatigue during their usual daily activities over the past week (Section 10.8.12). The level of 
fatigue is measured on a five-point Likert-type scale (0 = not at all fatigued; 1 = a little bit 
fatigued, 2 = somewhat fatigued, 3 = quite a bit fatigued, and 4 = very much fatigued). All items 
contribute to the sum score with equal weight. FACIT-Fatigue will be completed at timepoints 
specified in the SoA (Section 1.3). 
8.1.9. 
Dermatomyositis Disease Symptoms Questionnaire (DM-DSQ) 
The Dermatomyositis Disease Symptom Questionnaire (DM-DSQ) is a PRO instrument 
designed to assess symptoms relevant to the experience of patients with DM in the past 24 hours 
(Part A, RCP) or in the past 7 days (Part A, OLE Period and Part B RCP and OLE Period) 
(Section 10.8.13). Each item was generated based on a corresponding concept extracted from 
published qualitative literature (interviews or focus groups with patients) or from direct patient 
input (minutes from meeting with patients describing their disease and video testimonials of 
patients from the Myositis Association). There are symptom questions that are rated according to 
their severity on a 5-point response scale (None, Mild, Moderate, Severe, and Very severe) and 
questions about disease activity rated on a 5-point response scale (Not at all active, Mildly 
active, Moderately active, Very active, Extremely active). While DM-DSQ version 1.1 will be 
used in the Part A RCP and OLE Period, DM-DSQ version 5.0 will be used in the Part B RCP 
and OLE Period. The DM-DSQ will be completed at the timepoints specified in the SoA 
(Section 1.3). 
8.1.10. 
30-Second Chair Stand Test (30s CST) 
The 30s CST is a procedure that assesses proximal muscle function (Agarwal, 2006; Rider, 
2018) (Section 10.8.14). During the test a participant is asked to rise from a standard-height chair 
and to sit down as many times as possible in 30 seconds. The 30s CST will be assessed at the 
timepoints specified in the SoA (Section 1.3). 
8.1.11. 
Handheld Dynamometry 
Handheld dynamometry (Rider, 2018) is a procedure for quantitative strength testing. This 
testing will be conducted by the Investigator or any designee who has been properly trained for 
the quantitative muscle strength evaluation. When possible, it is highly recommended that all 
assessments be performed by the same assessor. Muscle strength testing will be performed on 
prespecified muscles in the upper and lower extremities bilaterally and the force measurements 
recorded. Handheld dynamometry will be assessed at timepoints specified in the SoA 
(Section 1.3). 

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8.1.12. 
 Home Electronic Patient-Reported Outcomes 
For Part A, participants will be asked to complete the following PROs at the frequencies 
described in Table 1. 
• DM-DSQ  
The PRO will be completed using an electronic device (eg, iPad). Further details of the selected 
PROs and the process associated with completing the PROs will be included in a separate 
electronic PRO (ePRO) Manual. 
8.2. 
Safety Assessments  
Planned time points for all safety assessments are provided in the SoA (Section 1.3). 
8.2.1. 
Vaccine and Antibiotic Prophylaxis 
As with any complement C5 inhibition, the use of ravulizumab increases the participant’s 
susceptibility to meningococcal infection (N meningitidis). To reduce the risk of meningococcal 
infection, all participants must be vaccinated against meningococcal infection within the 3 years 
before initiating study intervention. 
• Participants must receive a vaccination at least 2 weeks before first study 
intervention. Participants must be vaccinated or revaccinated according to current 
national vaccination guidelines or local practice for vaccination use with complement 
inhibitors (eg, eculizumab, ravulizumab). 
• Vaccines against serotypes A, C, Y, W135, and B, where available, are recommended 
to prevent common pathogenic meningococcal serotypes. 
• Vaccination may not be sufficient to prevent meningococcal infection. Consideration 
should be given according to official guidance and local practice on the appropriate 
use of antibacterial agents. 
• All participants should be monitored for early signs of meningococcal infection, 
evaluated immediately if infection is suspected, and treated with appropriate 
antibiotics, if necessary. 
8.2.2. 
Physical Examinations 
• A complete physical examination will include, at a minimum, assessments of the 
following organs/body systems: skin, head, ears, eyes, nose, throat, neck, lymph 
nodes, chest, heart, abdomen, extremities, and musculoskeletal. 
• An abbreviated physical examination will include, at minimum, a body-system 
relevant examination based upon Investigator judgment and participant symptoms. 
• Examiners should pay special attention to clinical signs related to previous serious 
illnesses. 
• For consistency, all efforts should be made to have the physical examination 
performed by the same qualified study staff at each study visit. 

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• Additional physical examinations can be performed as medically indicated during the 
study at the Investigator’s discretion. 
8.2.3. 
Height and Weight 
Body weight will be measured in pounds or kilograms. Height will be measured in inches or 
centimeters (Section 1.3). 
8.2.4. 
Vital Signs  
• Temperature (°C or °F), pulse rate, respiratory rate, and systolic and diastolic blood 
pressure (mm Hg), and pulse oximetry will be assessed (Section 1.3). 
• Blood pressure and pulse measurements will be assessed seated with a completely 
automated device. Manual techniques will be used only if an automated device is not 
available. 
• Blood pressure and pulse measurements should be preceded by at least 5 minutes of 
rest for the participant in a quiet setting without distractions (eg, television, cell 
phones). Ideally, the same arm for each participant should be used for measurements. 
• O2 saturation (%) will be collected using pulse oximetry. 
8.2.5. 
Electrocardiograms 
• Single 12-lead electrocardiogram (ECG) will be performed at protocol specified visits 
in the SoA (Section 1.3) using an ECG machine to obtain heart rate and measures of 
PR, QRS, QT, and RR intervals. 
• Participants must be supine for approximately 5 to 10 minutes before ECG collection 
and remain supine but awake during ECG collection. 
• The Investigator, Co-Investigator, or Sub-Investigator will be responsible for 
reviewing the ECG to assess whether the ECG is within normal limits and determine 
the clinical significance of the results. These assessments will be recorded in the 
source documents and the eCRF. 
8.2.6. 
Clinical Safety Laboratory Assessments 
• See Section 10.3 for the list of clinical laboratory tests to be performed and to the 
SoA (Section 1.3) for the timing and frequency. 
• The Investigator must review the laboratory report, document this review, and record 
any clinically relevant changes occurring during the study in the AE section of the 
eCRF. The laboratory reports must be filed with the source documents. Clinically 
significant abnormal laboratory findings are those which are not associated with the 
underlying disease, unless judged by the Investigator to be more severe than expected 
for the participant’s condition. 
• All laboratory tests with values considered clinically significantly abnormal during 
participation in the study or within 8 weeks after the final dose of study intervention 
should be repeated until the values return to normal or baseline or are no longer 

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considered clinically significant by the Investigator or Alexion Medical Monitor or 
designee. 
− If such values do not return to normal/baseline within a period of time judged 
reasonable by the Investigator, the etiology should be identified, and Alexion 
notified. 
− All protocol-required laboratory assessments, as defined in Section 10.3, must be 
collected in accordance with the laboratory manual and the SoA. 
− Laboratory assessments performed at the institution’s local laboratory that require 
a change in participant management or are considered clinically significant by the 
Investigator must be recorded in the AE/SAE eCRF. 
8.2.7. 
Pregnancy 
Pregnancy testing must be performed on all women of childbearing potential (WOCBP) at the 
time points specified in the SoA (Section 1.3). Pregnancy tests (local urine testing will be 
standard unless serum testing is required by local regulation or ethic committees may also be 
performed at any time during the study at the Investigator’s discretion. 
WOCBP must have a negative pregnancy test (serum if required per country regulations) before 
study intervention administration. 
• Details of all pregnancies in female participants and, if indicated, female partners of 
male participants will be collected after the start of study intervention and until 
termination of the pregnancy. 
• If a pregnancy is reported, the Investigator should inform Alexion within 24 hours of 
learning of the pregnancy and should follow the procedure outlined in Section 10.5. 
• Abnormal pregnancy outcomes (eg, spontaneous abortion, fetal death, stillbirth, 
congenital anomalies, ectopic pregnancy) are considered SAEs. Pregnancy alone is 
not considered an AE. 
• If a participant becomes pregnant, the study intervention must be immediately 
discontinued, and Alexion must be notified as per Section 10.5. Each pregnancy will 
be followed to term and Alexion should be notified regarding the outcome 
(Section 10.5.3). 
8.2.8. 
Participant Safety Card  
Before the first dose of the study intervention, a Participant Safety Card will be provided to 
participants to carry with them at all times until 5.5 terminal half-lives (8 months) after the final 
dose of ravulizumab. The card is provided to increase participant awareness of the risk of 
meningococcal infection and promote quick recognition and disclosure of any potential signs or 
symptoms of meningococcal infection experienced during the course of the study and to inform 
participants on what actions must be taken if they are experiencing signs or symptoms of 
infection. 
At each visit throughout the study, the study staff will ensure that the participant has the 
Participant Safety Card (Section 1.3). 

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8.3. 
Adverse Events and Serious Adverse Events 
The definitions of AEs and SAEs can be found in Section 10.4. 
AEs will be reported to the Investigator by the participant (or, when appropriate, by a caregiver, 
surrogate, or the participant’s legally authorized representative). 
The Investigator and any qualified designees are responsible for detecting, documenting, and 
recording events that meet the definition of an AE or SAE and remain responsible for following 
up AEs that are serious, considered related to the study intervention or study procedures, or that 
caused the participant to discontinue the study intervention (Section 7). 
Procedures for recording, evaluating, follow-up, and reporting AEs and SAEs are outlined in 
Section 10.4. 
8.3.1. 
Time Period and Frequency for Collecting AE and SAE Information 
All AEs and SAEs will be collected from the signing of the ICF until the last visit specified in 
the SoA (Section 1.3). 
All SAEs will be recorded and reported to Alexion or the designee immediately and under no 
circumstance should this exceed 24 hours, as indicated in Section 10.4. The Investigator will 
submit any updated SAE data to Alexion within 24 hours of it being available. 
Investigators are not obligated to actively seek AE or SAE data after conclusion of the study 
participation. However, if the Investigator learns of any SAE, including a death, at any time after 
a participant has been discharged from the study, and he/she considers the event to be reasonably 
related to the study intervention or study participation, the Investigator must promptly notify 
Alexion. 
8.3.2. 
Method of Detecting AEs and SAEs 
The method of recording, evaluating, and assessing causality of AE and SAE and the procedures 
for completing and transmitting SAE reports are provided in Section 10.4. 
Care will be taken not to introduce bias when detecting AEs and/or SAEs. Open-ended and 
non-leading verbal questioning of the participant is the preferred method to inquire about AE 
occurrences. 
8.3.3. 
Follow-up of AEs and SAEs 
After the initial AE/SAE report, the Investigator is required to proactively follow-up on each 
participant at subsequent visits/contacts. All SAEs and adverse events of special interest (AESIs; 
as defined in Section 8.3.5) will be followed up until resolution, stabilization, the event is 
otherwise explained, or the participant is lost to follow-up (as defined in Section 7.3). Further 
information on follow-up procedures is provided in Section Section 10.4. 
8.3.4. 
Regulatory Reporting Requirements for SAEs  
• Prompt notification of an SAE by the Investigator to Alexion is essential so that legal 
obligations and ethical responsibilities towards the safety of participants and the 
safety of a study intervention under clinical investigation are met. 

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• Alexion has a legal responsibility to notify both the local regulatory authority and 
other regulatory agencies about the safety of a study intervention under clinical 
investigation. Alexion will comply with country-specific regulatory requirements 
relating to safety reporting to the regulatory authority, IRBs/IECs, and Investigators. 
• Suspected unexpected serious adverse reactions (SUSARs) must be reported 
according to local regulatory requirements and Alexion policy and forwarded to 
Investigators as necessary. 
• An Investigator who receives an Investigator safety report describing an SAE or other 
specific safety information (eg, summary or listing of SAEs) from Alexion will 
review and then file it along with the IB and will notify the Institutional Review 
Board/Independent Ethics Committee (IRBs/IECs), if appropriate according to local 
requirements. 
− Under the EU CTR 536/2014, events other than SAEs (eg, unexpected events) 
that may impact the benefit-risk balance should be reported. See definitions in 
Section 10.4.5. 
8.3.5. 
Medication Error, Drug Abuse, and Drug Misuse 
8.3.5.1. 
Timelines 
If an event of medication error, drug abuse, or drug misuse occurs during the study, then the 
Investigator or other site personnel will report to Alexion or designee immediately but no later 
than 24 hours of when they become aware of it.  
The full definitions and examples of medication error, drug abuse, and drug misuse can be found 
in Section 10.5. 
8.3.5.2. 
Medication Error 
For the purposes of this clinical study, a medication error is an unintended failure or mistake in 
the treatment process for a study intervention that either causes harm to the participant or has the 
potential to cause harm to the participant. 
8.3.5.3. 
Drug Abuse 
Drug abuse is the persistent or sporadic intentional, non-therapeutic excessive use of study 
intervention for a perceived reward or desired non-therapeutic effect. 
8.3.5.4. 
Drug Misuse 
Drug misuse is the intentional and inappropriate use (by a study participant) of study intervention 
for medicinal purposes outside of the authorized product information, or for unauthorized study 
intervention, outside the intended use as specified in the protocol, including deliberate 
administration of the product by the wrong route. 
8.3.6. 
Adverse Events of Special Interest 
Meningococcal infections will be recorded as AESIs. 

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8.4. 
Treatment of Overdose 
For this study, any dose of ravulizumab greater than that specified in the protocol will be 
considered an overdose. If dose cannot be established during the Randomized Controlled Period 
due to blinding, suspected overdose should be defined by the volume administered. 
Overdoses are medication errors that are not considered AEs unless there is an untoward medical 
occurrence resulting from the overdose. 
Alexion does not recommend specific treatment for an overdose. 
In the event of an overdose or suspected overdose, the Investigator or treating physician should: 
• Capture and forward the event, with or without associated AEs, to Alexion Global 
Patient Safety via email or facsimile (clinicalsae@alexion.com or + 1.203.439.9347) 
using the Alexion Clinical Study Overdose Report Form within 24 hours of 
awareness. 
• Contact the Alexion Medical Monitor or designee immediately. 
• Closely monitor the participant for any AE/SAE.  
• Obtain a plasma sample for PK analysis if requested by the Alexion Medical Monitor 
or designee (determined on a case-by-case basis). 
• For unblinded participants, document the quantity of the excess dose as well as the 
duration of the overdose in the eCRF. 
Decisions regarding dose interruptions or modifications will be made by the Investigator in 
consultation with the Alexion Medical Monitor or designee based on the clinical evaluation of 
the participant. 
8.5. 
Pharmacokinetics and Pharmacodynamics 
• Blood samples for determination of serum drug concentrations and serum free and 
total C5 will be collected before and after administration of study intervention at the 
time points specified in the SoA (Section 1.3) according to applicable regulations. 
• Instructions for the collection and handling of biological samples will be provided by 
Alexion. The actual date and time (24-hour clock time) of each sample will be 
recorded on the eCRF and the central laboratory requisition form. 
• Samples collected for analyses of ravulizumab serum concentration may also be used 
to evaluate safety or efficacy aspects related to concerns arising during or after the 
study. 
• Baseline and trough PK/PD blood samples will be collected at predose, within 
90 minutes before administering study intervention at visits specified in the SoA 
(Section 1.3). The predose blood sample may be drawn through the venous access 
created for the dose infusion, prior to administration of the dose. 
• Post-dose PK/PD blood samples will be collected post-dose, within 60 minutes after 
completing study intervention infusion. The post-dose blood samples will be drawn 
from the participant’s opposite, non-infused arm. 

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• PK/PD blood samples collected at the ET/EOS visit and at Unscheduled Visits will be 
collected at any time. 
• In the event of an Unscheduled Visit, a PK/PD blood sample will be collected 
anytime. 
• Additional information on sample collection, including blood volume requirements, is 
provided in the Laboratory Manual. 
Study intervention concentration information that may unblind the study will not be reported to 
investigative sites or blinded personnel. 
8.6. 
Genetics 
Genetics are not evaluated in this study. 
8.7. 
Biomarkers  
Please refer to the Laboratory Study Manual for details on sample collection, including blood 
volume requirements. Biomarker samples may be analyzed after study completion by the 
absolute value and change from baseline. 
8.7.1. 
Blood Exploratory Biomarkers  
Blood (serum and plasma) samples for biomarker research will be collected from all participants 
at the time points specified in the SoA (Section 1.3) according to applicable regulations. 
Biomarkers to be measured may include, but are not limited to, assessments of the following: 
• Complement pathway dysregulation (eg, soluble C5b-9 etc) 
• Myositis-specific autoantibodies (eg, antimelanoma differentiation-associated 
protein 5 [anti‑MDA5], antinuclear matrix protein 2 (anti-NXP2/MJ), 
anti-synthetase/Jo-1, etc) 
• Soluble biomarkers including inflammatory and prognostic markers (eg, IL6, KL6, 
etc) 
8.7.2. 
Additional Biomarker Research 
Remaining samples from PK, PD, immunogenicity, and biomarker testing will be stored for 
additional method developments of assays (eg, prognostics and/or companion diagnostics related 
to the study intervention target, disease process, pathways associated with disease state, other 
complement related diseases, and/or mechanism of action of ravulizumab). 
Samples will be retained for up to 25 years after termination of the study or other period as per 
local requirements. 
8.8. 
Immunogenicity Assessments  
Antibodies to ravulizumab (ie, ADAs) will be evaluated in serum samples collected predose (90 
minutes prior to the start of infusion of study intervention) from all participants according to the 
SoA (Section 1.3) according to applicable regulations. Additionally, serum samples should also 

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be collected at the final visit from participants who discontinued the study intervention or were 
withdrawn from the study. These samples will be tested by Alexion or Alexion’s designee. 
Serum samples will be screened for antibodies binding to ravulizumab and the titer of confirmed 
positive samples will be reported. Other analyses may be performed to further characterize the 
immunogenicity of ravulizumab. 
The detection and characterization of antibodies to ravulizumab will be performed using a 
validated assay method by or under the supervision of Alexion. Antibodies may be further 
characterized and/or evaluated for their ability to neutralize the activity of the study 
intervention(s). Samples may be stored for a maximum duration according to local regulations 
following the last participant’s last visit for the study at a facility selected by Alexion to enable 
further analysis of immune responses to ravulizumab. 
8.9. 
Health Economics Data and/or Medical Resource Utilization 
Information regarding outpatient medical visits and hospitalization will be collected in the eCRF 
by the Investigator and study-site personnel for all participants throughout the study.  
This data may be used to conduct exploratory economic analyses. 
8.10. 
Other Assessments and Procedures 
8.10.1. 
Medical History and DM History and Diagnosis 
The Principal Investigator or Sub-Investigator will review the participant’s medical history 
including DM history and diagnosis. 
The following will be evaluated and documented at the Screening Visit and/or other visits as 
specified in the SoA (Section 1.3). 
• Date of first diagnosis with DM. 

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9. 
STATISTICAL CONSIDERATIONS  
9.1. 
Statistical Hypotheses 
The null hypothesis associated with the primary endpoint is that there is no difference in TIS40 
response rates between ravulizumab and placebo at Week 26 (Part A) or Week 50 (Part B). The 
alternative hypothesis is that the response rates are different.  
9.2. 
Sample Size Determination 
9.2.1. 
Part A 
A total number of 36 participants will be randomized into the study with a 2:1 
(ravulizumab:placebo) allocation ratio to ensure approximately 80% power to detect a difference 
(ravulizumab−placebo) of 45% in TIS40 response rates with a 2-sided Type 1 error of 0.2, 
assuming the placebo response rate of 23% and approximately 20% dropout rate. 
The sample size was calculated in PASS2022 using the 2-sample test for the difference of 
proportions with a pooled estimate of variance for the primary endpoint (TIS40). 
9.2.2. 
Part B 
A total number of 114 participants will be randomized into the study with a 2:1 
(ravulizumab:placebo) allocation ratio to ensure approximately 90% power to detect a difference 
(ravulizumab−placebo) of 35% in TIS40 response rate with a 2-sided Type 1 error of 0.05, 
assuming the placebo TIS40 response rate of 23% and approximately 20% dropout rate. The 
sample size was calculated in PASS2022 using the 2-sample test for the difference of proportions 
with a pooled estimate of variance for the primary endpoint (TIS40). 
An unblinded sample size re-estimation is planned to possibly increase the sample size to a 
maximum of 150 participants in Part B. The maximum sample size may be updated once the 
primary analysis of Part A is completed (Section 9.5). 
9.3. 
Populations for Analyses 
The analysis sets are defined in Table 17. Unless otherwise specified, the same definitions will 
be used for the statistical analyses of Part A and Part B where applicable. 
Table 17: 
Study ALXN1210-DM-310 Analysis Populations  
Population 
Description 
Randomized Set  
All randomized participants grouped by randomized treatment group 
(for reporting disposition, demographics, baseline characteristics and 
efficacy). 
PK Analysis Set (PKAS) 
All participants who receive at least 1 dose of study intervention and 
have at least 1 post-dose PK sample 
PD Analysis Set (PDAS) 
All participants who receive at least 1 dose of study intervention and 
who have evaluable free or total C5 data 

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Table 17: 
Study ALXN1210-DM-310 Analysis Populations  
Population 
Description 
Per Protocol Set (PPS) 
(applicable for Part B only) 
All randomized participants without any major protocol deviationsa 
that could impact the interpretation of efficacy. 
The PPS will be used for supplemental analyses of the primary and 
secondary efficacy endpoints. 
Safety Set (SS) 
All participants who receive at least 1 dose of study intervention. 
Participants will be analyzed according to the study intervention they 
actually received. 
The SS will be used for the analysis of safety data. 
OLE Set 
All randomized participants who received at least 1 dose of 
ravulizumab starting from Week 26 (Part A and Part B) onward. 
Immunogenicity Analysis 
Set (IAS) 
All participants who receive at least 1 dose of study intervention and 
have at least one reportable result in the ADA assay. Participants will 
be analyzed according to the study intervention they actually received 
a Determination of applicable major protocol deviations for this purpose will be made prior to database lock and 
study unblinding. 
Abbreviations: ADA = antidrug antibody; C5 = complement component 5; OLE = Open-Label Extension; 
PD = pharmacodynamics; PK = pharmacokinetics 
9.4. 
Statistical Analyses 
Statistical methods described in this section will be further detailed in separate SAPs for Part A 
and Part B for both RCP and OLE Periods. The SAPs will be developed and finalized prior to the 
database lock of the Randomized Controlled Period for each part. Statistical analyses will 
include tabulations of summary data, inferential analyses, by-participant listings, and figures. 
The summary statistics for continuous variables will include, but not be limited to, the number of 
participants, mean, standard deviation, minimum, median, and maximum. For categorical 
variables, frequencies and percentages will be presented. 
All efficacy analyses will be based on the randomized set. Supplemental per-protocol analyses 
for primary and key secondary efficacy endpoints will be performed based on the Per Protocol 
Set (PPS) in the same manner as for the randomized set. Safety analyses will be performed on 
the Safety Set (SS).  
The baseline value for analysis and reporting will be based on the last non-missing measurement 
on or prior to the first dose of study intervention unless stated otherwise. 
All data collected during the first 26-week Randomized Controlled Period in Part A will be 
analyzed independently of Part B and not be included in Part B's formal hypothesis testing.  
Analyses will be performed using the SAS® software Version 9.4 or higher. 
9.4.1. 
Efficacy Analyses  
This section describes the planned analyses for the primary and key secondary endpoints during 
the Randomized Controlled Periods for Part A and B. Further details will be provided in the 
separate SAPs for each part. 

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9.4.1.1. 
Efficacy Analysis of Part A  
The statistical testing in Part A will be performed with a 2-sided Type 1 error of 0.2 unless stated 
otherwise. 
The estimated treatment effect, 2-sided p-value, and the 2-sided 80% confidence interval (CI) of 
the treatment effect will be presented. 
9.4.1.1.1. Analyses of Primary Efficacy Endpoint for Part A 
The primary efficacy analysis will be based on the Randomized Set.  
The primary endpoint is TIS≥40 response at Week 26. For the binary composite estimand 
described in Section 3.1.1, participants experiencing an intercurrent event will be considered 
non-responders at Week 26, regardless of available TIS data. For all other participants without an 
intercurrent event, TIS values at Week 26 will be dichotomized into a binary endpoint.  
The differences in proportions, along with 2-sided 80% confidence intervals (CIs) using Chan 
and Zhang method (Chan, 1999), will be presented between the ravulizumab group and the 
placebo group. Barnard’s unconditional exact method will be applied to test whether there is a 
difference in the proportions of responders between the 2 treatment groups.  
Further details, including but not limited to additional sensitivity analyses will be provided in the 
SAP for Part A. 
9.4.1.1.2. Analyses of Secondary Efficacy Endpoints for Part A 
A mixed effect repeated measures model will be used to analyze continuous efficacy endpoints. 
The analysis as stated for the primary endpoint will be used to analyze binary efficacy endpoints 
and the Cox proportional hazard model will be used for the survival (time-to-event) efficacy 
endpoints. 
Further details will be provided in the SAP for Part A. 
9.4.1.2. 
Efficacy Analysis of Part B 
All data collected during the 50-week Randomized Controlled Period in Part B will be analyzed 
independently of Part A. 
The formal statistical hypothesis testing in Part B will be performed with 2-sided Type 1 error of 
0.05. 
9.4.1.2.1. Analyses of Primary Efficacy Estimand and/or Endpoint for Part B 
The primary efficacy analysis will be based on the Randomized Set.  
The primary endpoint is defined as TIS≥40 response at Week 50. For the binary composite 
estimand described in Section 3.1.1, participants will be considered non-responders after 
experiencing the intercurrent event, regardless of available TIS data. Missing TIS values from 
participants without intercurrent events will be handled via multiple imputation (MI) assuming 
missing at random (MAR).   
Cochran-Mantel-Haenszel weighting will be used in the estimation of the difference in 
proportions between treatment and placebo and its variance where the weights account for the 

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randomization strata (CDASI Activity Score [≤ 14, >14]). If MI is used, Rubin's rule will be used 
to combine estimates of the difference in proportions and the standard error across the 
imputations and used to compute the p-value and 95% confidence interval. A 2-sided Type I 
error of 0.05 and the computed p-value will be used to determine whether the study is considered 
positive. 
The study will be considered positive if the estimated treatment effect favors ravulizumab and 
the 2-sided p-value is < 0.05. 
Further details, including but not limited to the additional sensitivity analyses and subgroup 
analyses, will be provided in the SAP for Part B. 
The planned interim analysis for the sample size re-estimation may also be conducted as 
described in Section 9.5. 
9.4.1.2.2. Sensitivity Analyses for the Primary Estimand for Part B 
The following sensitivity analyses will be performed for the primary efficacy endpoint to explore 
the robustness of the primary efficacy analysis. Additional details will be provided in the SAP 
for Part B. 
Control-Based Multiple Imputation 
This sensitivity analysis will assess the robustness of the primary endpoint results due to possible 
violation of the MAR assumption. Missing TIS40 data will be handled in the same fashion as 
described in Section 9.4.1.2.1 except that missing TIS data for patients in the ravulizumab group 
who do not experience intercurrent events will be multiply imputed assuming a trajectory similar 
to the placebo group.  
The same analysis method as described in Section 9.4.1.2.1 will be used. 
Tipping Point Analysis: 
In this analysis, TIS40 data will be handled in the same fashion as described in Section 9.4.1.2.1 
except that missing data from participants in the ravulizumab group who do not experience the 
intercurrent events will be multiply imputed with an adjustment to the imputed values. The size 
of the adjustment can be varied and the adjustment which results in a non-significant p-value will 
be considered the “tipping point”. 
9.4.1.2.3. Supplemental Analysis of Primary Endpoint Using Treatment-Policy Estimand 
Under the treatment-policy estimand, all available TIS40 data will be used for analysis regardless 
of whether patients experience intercurrent events. For example, suppose a participant becomes a 
TIS40 responder after initiation of acute therapy with standard DM treatment. In that case, the 
observed response will be used, unlike treating the participant as a non-responder described in 
the primary estimand. Other conventions described in Section 9.4.1.2.1 will remain the same. 
9.4.1.2.4. Analyses of Key Secondary Efficacy Endpoint(s) for Part B 
The comparison of the treatment groups for the mean IMACS-TIS at Week 50 of the 
Randomized Controlled Period will be based on the randomized set. 

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Consistent with the primary composite estimand strategy, for participants who experience the 
intercurrent events, TIS scores will be assumed to be zero (no improvement) from the point of 
intercurrent event occurrence. Missing data for other participants will be considered missing at 
random. 
A mixed model for repeated measures will be used for the statistical analysis of the TIS data. The 
MMRM model will include the observed TIS values at post-baseline visits as the dependent 
variable. The model will include categorical effects of treatment, study visit, treatment-by-study 
visit interaction, and the randomization strata. An unstructured covariance matrix will be used to 
model the correlations among repeated measurements within each participant. The Kenward-
Roger method will be used to estimate the denominator degrees of freedom. The least square 
means, the associated SEs, the p-value and 95% CIs of the mean IMACS-TIS at week 50 for 
each treatment and difference between ravulizumab and placebo will be calculated.  
A control-based imputation and tipping point analysis will also be performed on the mean 
IMACS-TIS as sensitivity analysis. 
A supplemental analysis will also be performed using the Treatment Policy Estimand strategy. 
All other continuous key secondary endpoints will be analyzed similarly. Further details will be 
provided in the SAP for Part B. 
9.4.1.2.5. Multiplicity Adjustment for Part B 
The primary hypothesis for the primary endpoint will be tested at a 2-sided Type 1 error of 0.05 
with statistical inference taking into account the planned sample size re-estimation (details will 
be provided in the SAP for Part B) to control the overall Type I error for Part B. 
Hypothesis testing associated with the key secondary endpoints will proceed only if the null 
hypothesis associated with the primary endpoint is rejected. 
Holm’s method will be used for multiplicity adjustment of the key Part B secondary endpoints. 
9.4.2. 
Safety Analyses  
The safety and tolerability of ravulizumab will be assessed based on AE incidence, clinical 
laboratory findings, ECGs, and vital signs findings. Safety analyses will be performed on the SS 
population. 
9.4.2.1. 
Analysis of Adverse Events 
Analysis and reporting for AEs will be based on treatment-emergent adverse events (TEAEs), 
including treatment-emergent serious adverse events (TESAEs) and TEAE leading to drug 
discontinuation, defined as an AE with onset on or after the first dose of study intervention in the 
Randomized Controlled Period. AEs will be summarized by Medical Dictionary for Regulatory 
Activities (MedDRA) System Organ Class (SOC) and Preferred Term, by severity, and 
relationship to the study intervention. Participant-years adjusted event rates will be generated to 
characterize the long-term safety profile. 

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9.4.2.2. 
Analysis of Clinical Laboratory Parameters, Vital Sign Measurements, and ECG 
Parameters 
Laboratory measurements as well as their changes from baseline at each visit and shift from 
baseline, if applicable, will be summarized descriptively. Significant findings related to ECG and 
vital signs will also be summarized using descriptive analyses. 
9.4.3. 
Other Analyses  
The following sections describe the general analysis approach to the other endpoints. Further 
details will be provided in the SAPs for Part A and Part B, respectively.  
9.4.3.1. 
Pharmacokinetic/Pharmacodynamic Analysis 
Individual serum concentration data for all participants in the PKAS will be used to derive PK 
parameters for ravulizumab. 
Graphs of mean serum concentration-time profiles will be constructed. Graphs of serum 
concentration-time profiles for individual participants may also be provided. 
Descriptive statistics will be calculated for serum concentration data at each sampling time, as 
appropriate. Assessment of population-PK may be considered using data from this study or in 
combination with data from other studies. 
Descriptive statistics will be presented for all PD endpoints at each sampling time (see 
Section 1.3). The PD effects of ravulizumab administered IV will be evaluated by assessing the 
absolute values and changes and percent changes from baseline in free and total C5 serum 
concentrations over time, as appropriate. Boxplots of absolute values of free and total C5 serum 
concentrations by study visit will be constructed. Assessments of ravulizumab PK/PD 
relationships may be explored using data from this study or in combination with data from other 
studies. 
9.4.3.2. 
Analysis of Immunogenicity  
Analysis of immunogenicity will be based on the IAS. 
The presence of ADAs to ravulizumab in serum will be assessed throughout the duration of the 
study. Further characterization of antibody responses may be conducted as appropriate, including 
neutralizing antibodies and the titer of confirmed positive samples. Immunogenicity results will 
be analyzed by summarizing the number and percentage of participants according to their ADA 
response status. The association of ADAs with ravulizumab concentration, PD parameters, 
efficacy, and TEAEs may be explored as appropriate. 
9.4.3.3. 
Analysis of Biomarkers 
Analyses of exploratory biomarkers will be described in a separate analysis plan. 
9.4.3.4. 
Analyses of Exploratory Endpoint(s)  
Analyses of exploratory endpoints will be discussed in the SAP. 

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9.5. 
Interim Analyses 
9.5.1. 
Part A Interim Analysis 
An unblinded interim analysis may be conducted for futility when approximately 24 (67%) 
participants complete the Week 26 visit or have discontinued prematurely. The comparative 
primary and safety data would be assessed in this interim analysis. There is no plan to alter the 
Part A study design; therefore, no Type 1 error adjustment is needed for the final statistical 
analysis. 
The interim analysis would be conducted by an IDMC to maintain study integrity and blinding. 
Details of futility criterion, statistical analysis methods, maintenance of study blinding, decision-
making and communication plan would be provided in the DMC Charter and the Interim 
Analysis Plan for Part A. 
If the futility criterion is met the Sponsor may stop further enrollment following the IDMC 
recommendation.  
Part B will not be initiated if Part A results in futility or is terminated due to safety concerns. 
At the time of the interim analysis there may be additional Part A analyses which may be 
generated and reviewed by an unblinded team (independent of the study team). 
9.5.2. 
Part B Interim Analysis 
An unblinded interim analysis may be conducted for sample size re-estimation using all available 
TIS data when approximately 30 % of the participants have completed the Week 50 visit or have 
discontinued prematurely in Part B. The sample size may increase to a maximum of 150 
participants in Part B based on the conditional power (Mehta, 2011). Complete details will be 
included in the SAP. The maximum sample size may be updated once the primary analysis of 
Part A is completed.  
The interim analysis would be performed by an IDMC to maintain study integrity and blinding. 
Further details of the interim analysis would be provided in the DMC Charter and the Interim 
Analysis Plan for Part B. 
9.6. 
Data Monitoring Committee 
An IDMC, comprising experts in relevant fields with no direct relationship to the study, will be 
appointed by Alexion. The IDMC will be used for: 
• Conduct of interim analyses in Part A and Part B and providing recommendations to the 
Sponsor (Section 4.1.1, Section 4.1.2, and Section 9.5).  
• Monitoring of safety data. 
The specific responsibilities of the IDMC and a schedule of meetings will be described in the 
DMC Charter. 

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10. 
SUPPORTING DOCUMENTATION AND OPERATIONAL 
CONSIDERATIONS 
10.1. 
Management of Potential Infusion-Associated Adverse Events 
During Study Intervention Administration 
IV and infusion-associated reactions are a potential risk with the use of mAbs; these reactions 
can be nonimmune or immune-mediated (eg, hypersensitivity reactions). Signs and symptoms 
may include headache, fever, facial flushing, pruritus, myalgia, nausea, chest tightness, dyspnea, 
vomiting, erythema, abdominal discomfort, diaphoresis, shivers, hypertension, lightheadedness, 
hypotension, palpitations, and somnolence. Signs and symptoms of hypersensitivity or allergic 
reactions may include hives, swollen face, eyelids, lips, or tongue, or trouble with breathing. 
All administration-, IV-, and infusion-associated reactions will be reported to the Investigator 
and qualified designee. The Investigator and qualified designee are responsible for detecting, 
documenting, and recording events that meet the definition of AE or SAE and remain 
responsible for following up events that are serious, considered related to the study intervention, 
or study procedures; or that caused the participant to discontinue the study intervention 
(Section 7). 
Definitions and procedures for recording, evaluating, follow-up, and reporting AEs and SAEs are 
outlined in Section 10.4. 
Participants who experience a reaction during the administration of study intervention should be 
treated according to institutional guidelines. 
Participants who experience a severe reaction during administration of study intervention 
resulting in discontinuation of study intervention should undergo all scheduled safety, PK, and 
PD evaluations required by the protocol. Alexion must be notified within 24 hours of any 
infusion reaction requiring interruption or discontinuation of study intervention. All AEs that 
may indicate an infusion-related response will be graded according to the Common Terminology 
Criteria for Adverse Events (CTCAE) V5.0 or higher. 
If anaphylaxis occurs according to the criteria listed in Table 15, then administration of 
subcutaneous (SC) epinephrine (1/1000, 0.3 mL to 0.5 mL, or equivalent) should be considered. 
In the case of bronchospasm, treatment with an inhaled beta agonist also should be considered. 
Participants administered an antihistamine for the treatment or prevention of an infusion reaction 
should be given appropriate warnings about drowsiness and impairment of driving ability before 
being discharged from the center. 
Table 18: 
Clinical Criteria for Diagnosing Anaphylaxis 
Anaphylaxis is highly likely when any 1 of the following 3 criteria is fulfilled: 
• Acute onset of an illness (minutes to several hours) with involvement of the skin, mucosal 
tissue, or both (eg, generalized hives, pruritus or flushing, swollen lips-tongue-uvula), and 
at least 1 of the following: 
o Respiratory compromise (eg, dyspnea, wheeze-bronchospasm, stridor, reduced PEF, 
hypoxemia) 

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Table 18: 
Clinical Criteria for Diagnosing Anaphylaxis 
Anaphylaxis is highly likely when any 1 of the following 3 criteria is fulfilled: 
o Reduced BP or associated symptoms of end-organ dysfunction (eg, hypotonia 
[collapse], syncope, incontinence) 
• Two or more of the following that occur rapidly after exposure to a likely allergen for that 
participant (minutes to several hours): 
o Involvement of the skin-mucosal tissue (eg, generalized hives, itch-flush, swollen 
lips/tongue/uvula) 
o Respiratory compromise (eg, dyspnea, wheeze/bronchospasm, stridor, reduced PEF, 
hypoxemia) 
o Reduced BP or associated symptoms (eg, hypotonia [collapse], syncope, 
incontinence) 
o Persistent gastrointestinal symptoms (eg, crampy abdominal pain, vomiting) 
• Reduced BP after exposure to known allergen for that participant (minutes to several 
hours): 
o Systolic BP of less than 90 mmHg or greater than 30% decrease from that 
participant’s baseline 
Abbreviations: BP = blood pressure; PEF = peak expiratory flow 
Source: (Sampson, 2006) 
 

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10.2. 
Regulatory, Ethical, and Study Oversight Considerations 
10.2.1. 
Regulatory and Ethical Considerations 
• This study will be conducted in accordance with the protocol and the following: 
− Consensus ethical principles derived from international guidelines including the 
Declaration of Helsinki and Council for International Organizations of Medical 
Sciences (CIOMS) International Ethical Guidelines 
− Applicable International Council for Harmonisation of Technical Requirements 
for Pharmaceuticals for Human Use (ICH) Good Clinical Practice (GCP) 
Guidelines 
− Applicable laws and regulations 
 
The protocol, protocol amendments, ICF, IB, and other relevant documents (eg, 
advertisements) must be submitted to an IRB/IEC by the Investigator/Alexion and 
reviewed and approved by the IRB/IEC before the study is initiated. 
− If any of these documents require regulatory/health authority approval per local 
regulations, Alexion will also obtain such approval before the study is initiated. 
• Any substantial amendments to the protocol will require IRB/IEC and 
regulatory/health authority approval before implementation of changes made to the 
study design, except for changes necessary to eliminate an immediate hazard to study 
participants. 
• The Investigator will be responsible for the following: 
− Providing written summaries of the status of the study to the IRB/IEC annually or 
more frequently in accordance with the requirements, policies, and procedures 
established by the IRB/IEC 
− Notifying the IRB/IEC of SAEs or other significant safety findings as required by 
IRB/IEC procedures 
- 
Providing oversight of the conduct of the study at the site and adherence to 
requirements of 21 CFR, ICH guidelines, the IRB/IEC EU CTR 536/2014 for 
clinical studies and all other applicable local regulations 
− Promptly notifying Alexion of any (potential) serious breach of the protocol or 
regulations (including if a data breach compromises the integrity, confidentiality, 
or availability of the personal data of participants) so that legal and ethical 
obligations are met. A ‘serious breach’ means a breach likely to affect to a 
significant degree the safety and rights of a participant or the reliability and 
robustness of the data generated in the clinical study. 
• In certain regions/countries, Alexion has a legal responsibility to notify both the local 
regulatory authority and other regulatory agencies about serious breaches. Alexion 
will comply with country-specific regulatory requirements relating to serious breach 
reporting to the regulatory authority (including data protection authorities and, if 

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applicable, affected participants in case of a personal data breach), IRB/IEC, and 
Investigators.  
• The Investigator should have a process in place to ensure that: 
− The site staff or service providers delegated by the Investigator/institution are able 
to identify the occurrence of a (potential) serious breach, including personal data 
breaches 
− A (potential) serious breach is promptly reported to Alexion or delegated party, 
through the contacts (email address or telephone number) provided by Alexion. 
• The Sponsor and the site have taken all necessary steps to avoid personal data 
breaches and have undertaken measures to prevent such breaches from occurring in 
the first place and to mitigate the impact of occurred data breaches (eg, applying 
encryption, maintaining, and keeping systems and information technology security 
measures up-to-date, regular reviews and testing, regular training of employees, and 
developed security policies and standards). 
• Both the Sponsor and the site have developed an internal data breach reporting and 
investigation process and internal protocols with guidance on how to respond swiftly 
and diligently to the occurrence of a personal data breach. 
• In compliance with applicable laws, the data controller for the processing activity 
where the personal data breach occurred (the Sponsor or respectively the site) will 
notify the data protection authorities without undue delay within the legal terms 
provided for such notification and within the prescribed form and content. 
• If the personal data breach needs to be notified to participants, the notification to 
participants is done by the site for the data breaches that occurred within the 
processing activities for which the site is the data controller and for data breaches 
occurred within the processing activities of the Sponsor as the data controller, the 
notification is done in collaboration with the site and is performed by the site and/or 
Investigator, acting on behalf of the Sponsor, so that the Sponsor has no access to the 
identifying personal information of the participants. The site and/or Investigator shall 
conduct the notification by contacting the participants using the information that they 
gave for communication purposes in clinical research.  
• If a personal data breach occurs in a processor’s systems, engaged by the Sponsor, the 
processor under contractual obligations with the Sponsor promptly and in due course 
after discovering the breach notifies the Sponsor and provides full cooperation with 
the investigation. In these cases, to the extent the Sponsor is the data controller for the 
processing activity where the breach occurred, it will be responsible for the 
notification to data protection authorities and, if applicable, to participants. If the 
personal data breach needs to be notified to the participants, the notification to 
participants is done in collaboration with the site and is performed by the site and/or 
Investigator, acting on behalf of the Sponsor, so that the Sponsor has no access to the 
identifying personal information of the participants.  
• Where a personal data breach is suffered by the Study Monitor, the latter will provide 
the Sponsor with all of the information needed for notification of the breach, without 

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disclosing data that allows the Sponsor directly or indirectly to identify the 
participants. The notification will be done by the Sponsor solely with the information 
provided by the Study Monitor and in no event with access to information that could 
entail a risk of reidentification of the participants. If the data breach must be notified 
to the data participants, the notification will be done directly by the Study Monitor in 
collaboration with the site and/or Investigator, acting on behalf of the Sponsor, so that 
the Sponsor has no access to the identifying personal information of the participants. 
The contract between the Sponsor and the Study Monitor shall expressly specify these 
conditions.  
• The contract between the site and the Sponsor for performing the clinical research 
includes the provisions and rules regarding who is responsible for coordinating and 
directing the actions in relation to the breaches and performing the mandatory 
notifications to authorities and participants, where applicable. 
10.2.2. 
Financial Disclosure 
Investigators and Sub-Investigators will provide Alexion with sufficient, accurate financial 
information as requested to allow Alexion to submit complete and accurate financial certification 
or disclosure statements to the appropriate regulatory authorities. Investigators are responsible 
for providing information on financial interests during the course of the study and for 1 year after 
completion of the study. 
10.2.3. 
Informed Consent Process 
• It is the responsibility of the Investigator or designee to obtain signed (written or 
electronic signature) informed consent from all study participants, or the participant’s 
legally authorized representative, prior to performing any study-related procedures 
including screening assessments. 
• The Investigator or designee will explain the nature of the study (including but not 
limited to the objectives, potential benefits and risks, inconveniences, and the 
participant’s rights and responsibilities) to the participant or his/her legally authorized 
representative, defined according to local and country regulations where the study is 
taking place, and answer all questions regarding the study. 
• Participants must be informed that their participation is voluntary. Participants or 
their legally authorized representative will be required to sign a statement of informed 
consent or a certified translation, if applicable, that meets the requirements of 
21 CFR 50, local regulations, EU General Data Protection Regulation (GDPR), ICH 
GCP guidelines, Health Insurance Portability and Accountability Act (HIPAA) 
requirements, where applicable, and the IRB/IEC or study center. 
• The participant’s medical record must include a statement that signed (written or 
electronic) informed consent was obtained before any screening procedures were 
performed with a participant, and the date the written consent was obtained. The 
authorized person obtaining the informed consent must also sign the ICF(s). 
• Participants must be reconsented to the most current version of the ICF(s) during their 
participation in the study, as applicable. 

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• A copy of the signed (written or electronic) informed consent documentation (ie, a 
complete set of participant information sheets and fully executed signature pages) 
must be provided to the participant or the participant’s legally authorized 
representative, as applicable. This document may require translation into the local 
language. Original signed (written or electronic) consent forms must remain in each 
participant’s study file and must be available for verification at any time. 
Participants who are rescreened outside of the Screening window (Section 1.3) are required to 
sign a new ICF (Section 5.4). 
10.2.4. 
Recruitment Strategy 
Participants will be identified by qualified research staff. This may be done through a review of 
medical records, external referrals or using databases. Recruitment strategies may include study 
posters, referral letters, recruitment brochures, advertisements, social media posts, and websites, 
where permitted by local regulations. All recruitment materials will be submitted to local 
IRB/EC as required, for review and approval for use. 
10.2.5. 
Data Protection 
• Participants will be assigned a unique identifier by a Trusted Third Party contracted 
by Alexion or by a Principal Investigator. Any participant records or datasets that are 
transferred to Alexion will contain the identifier only; participant names, initials, or 
any information which would make the participant identifiable will not be transferred. 
• Participants must be informed that their personal study-related and coded 
(pseudonymized) data will be used in accordance with applicable data protection law, 
and participants must also be informed of any individuals rights they may have with 
regard to their personal data. Participants will be informed about how their personal 
study-related data will be disclosed, and will be required to agree to the information 
contained in the informed consent and provide consent to the processing of their 
personal data, if required by applicable data protection law. 
• Participants must be informed that their medical records may be examined by Clinical 
Quality Assurance auditors or other authorized personnel appointed by Alexion, 
appropriate IRB/IEC members, and inspectors from regulatory authorities. 
• Alexion as a data controller has implemented privacy and security controls designed 
to help protect participant personal data; including information security controls, 
firewalls, incident detection, and secure transfer measures. 
• The contract between Alexion and study sites specifies responsibilities of the parties 
related to data protection, including handling of data security breaches and respective 
communication and cooperation of the parties. 
• Information technology systems used to collect, process, and store study-related data 
are secured by technical and organizational security measures designed to protect 
such data against accidental or unlawful, loss, alteration, or unauthorized disclosure 
or access. 

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• The General Data Protection Regulation defines pseudonymization as the processing 
of personal data in such a way that the personal data can no longer be attributed to a 
specific individual without the use of additional information, provided that such 
additional information is kept separately and protected by technical and 
organizational measures to ensure that the personal data are not attributed to an 
identified or identifiable natural person. 
• Appropriate safeguards will be implemented to protect coded data during and after 
the study that include: 
− 
Access to the coded data will be limited to specific individuals subject to 
confidentiality obligations (including the obligation to not attempt to re-identify 
individuals/decode the clinical data). 
− 
The coded data will be protected with security measures to avoid data alteration, 
loss, and unauthorized accesses and further de-identification techniques may be 
applied. 
− 
A data protection impact assessment, where required, will apply to identify and 
mitigate privacy risks, if any, associated with each scientific research. 
− 
The coded data will not be shared for direct marketing purposes or other 
purposes that are not legal duties or are not considered scientific research 
according to the applicable data protection legislation. In particular, it will not be 
used to make decisions about future services available to the participant, such as 
insurance. 
• In addition to having the participants’ data and biosamples coded, the data are also 
protected by high-standard technical security means, such as strong access control 
and encryption. 
• Participants are also protected legally by the following means if the level of 
disclosure of the coded data includes sharing of the latter with other third parties, as 
the participants will be explained in the ICF: 
− The participants’ coded data are protected by contractual arrangements, Codes of 
Conduct, or certifications that set the rules for personal information protection to 
those available in European countries or other alternatives set forth in the law, as 
well as any supplementary technical and organizational measures that may results 
out of conducted transfer impact assessments. 
 
10.2.6. 
Dissemination of Clinical Study Data 
Study-related information and study results may be posted on publicly accessible clinical study 
databases (eg, the US website www.clinicaltrials.gov or the EU website 
www.clinicaltrialsregister.eu), as appropriate, and in accordance with national, regional, and 
local regulations. However, posting of study results per local regulations may be deferred to a 
later date for one of the following reasons: 
• Study is still ongoing in other countries or regions 

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• Study is part of an ongoing review for approval by Health Authorities; study result data 
deferral request can be submitted. 
10.2.7. 
Data Quality Assurance 
• All participant data relating to the study will be recorded on paper or eCRFs unless 
transmitted to Alexion or designee electronically (eg, laboratory data). The 
Investigator is responsible for verifying that data entries are accurate and correct by 
physically or electronically signing the CRF. 
• The Investigator must maintain accurate documentation (source data) that supports 
the information entered in the eCRF. 
• The Investigator must permit study-related monitoring, audits, IRB/IEC review, and 
regulatory agency inspections and provide direct access to source data documents. 
• Alexion or designee is responsible for the data management of this study including 
quality checking of the data. 
• Study monitors will perform ongoing source data verification to confirm that data 
entered into the eCRF by authorized site personnel are accurate, complete, and 
verifiable from source documents; that the safety and rights of participants are being 
protected; and that the study is being conducted in accordance with the currently 
approved protocol and any other study agreements, ICH GCP, and all applicable 
regulatory requirements. 
− Remote source data verification may be employed where permitted by local 
regulations. 
− The scope of the source data verification will be described in detail in the Clinical 
Monitoring Plan. 
• Records and documents, including signed ICFs, pertaining to the conduct of this 
study must be retained by the Investigator for at least 30 years after study completion 
or longer as per local regulations or institutional policies. No records may be 
destroyed without the written approval of Alexion. No records may be transferred to 
another location or party without written notification to Alexion. Clinical study 
documents and records required as part of the TMF are archived and stored by 
Alexion for at least 30 years. 
• Quality tolerance limits (QTLs) will be predefined in the study-specific risk 
register to identify systematic issues that can impact participant safety and/or 
reliability of study results. These predefined parameters will be monitored during the 
study, and important deviations from the QTLs and remedial actions taken will be 
summarized in the clinical study report. 
10.2.8. 
Source Documents 
Source documents provide evidence for the existence of the participant and substantiate the 
integrity of the data collected. The Investigator or designee will prepare and maintain adequate 
and accurate source documents (eg, medical records, ECGs, AE and concomitant medication 

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reporting, raw data collection forms) designed to record all observations and other pertinent data 
for each participant. 
Data reported on the eCRF that are transcribed from source documents must be consistent with 
the source documents or the discrepancies must be explained. eCRFs must be completed by the 
Investigator or designee as indicated in the site delegation log. The Investigator may need to 
request previous medical records or transfer records, depending on the study. Also, current 
medical records must be available to Alexion, Alexion delegates, and health authorities, as 
requested. Source documents are filed at the investigational site. 
Per ICH E6 (R2) guidelines and good documentation practice requirements, source documents 
and study records in all media (eg, paper, electronic) must be Attributable, Legible, 
Contemporaneous, Original, Accurate, and Complete. 
10.2.9. 
Study and Site Start and Closure 
The study start date is the date on which the clinical study will be open for recruitment of 
participants (ie, first site activation). 
Alexion reserves the right to close the study site or terminate the study at any time for any reason 
at its sole discretion. Study sites will be closed after the study is completed or following the 
decision to close or terminate the study. A study site is considered closed when all participants 
have completed the EOS or ET Visit, all data have been collected and entered into the electronic 
data capture (EDC) system, all required documents and study supplies have been collected and 
reconciled, and a study-site closure visit has been performed. 
The Investigator may initiate study-site closure at any time, provided there is reasonable cause 
and sufficient notice is given in advance of the intended termination. 
Reasons for the early closure of a study site by Alexion or Investigator may include but are not 
limited to: 
• Failure of the Investigator to comply with the protocol, the requirements of the 
IRB/IEC or local health authorities, Alexion’s procedures, or ICH GCP guidelines 
• Inadequate recruitment of participants by the Investigator 
• Discovery of an unexpected, serious, or unacceptable risk of the study drug to 
participants enrolled or continuing in the study 
• Discontinuation of further study intervention development 
If futility criteria are met or if the benefit/risk is not considered favorable, the Sponsor may stop 
further enrollment in the study, under guidance from an IDMC.  
Part B will not be initiated if Part A results in futility or is terminated due to safety concerns. If 
the study is prematurely terminated or suspended, Alexion shall promptly inform the 
Investigators, the IECs/IRBs, the regulatory authorities, and any contract research 
organization(s) used in the study of the reason for termination or suspension, as specified by the 
applicable regulatory requirements. The Investigator shall promptly inform the participant and 
should assure appropriate participant therapy and/or follow-up. 

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10.2.10. 
Publication Policy 
• Where possible, primary manuscripts reporting results of the primary efficacy 
endpoint or the final results will be submitted for publication within 12 to 18 months 
of the primary evaluation date or end of study, whichever is earlier. 
• Investigators who participate as authors in manuscripts derived from Alexion 
sponsored studies will agree to the prerequisites as outlined in the Alexion author 
engagement agreement prior to engaging in manuscript development. 
• The Investigator agrees to submit proposals for new manuscripts (whether or not the 
proposed analyses are derived from protocol specified endpoints) to Alexion for 
review and consideration. All manuscripts or abstracts emanating from approved 
proposals are to be submitted to Alexion for review before submission to the 
journal/society. This allows Alexion to protect proprietary information and provide 
comments. 
− The proprietary nature of some development work may preclude publication. In 
some cases, it may be necessary to delay a publication to allow Alexion to ensure 
protection of intellectual property. 
• Primary publications, including congress and journal publications, containing the 
protocol-specified results of a study should occur prior to the publication of 
individual study site results or case reports. Alexion’s policy prohibits duplicate 
publication, whereby the same results must not be published in multiple 
peer-reviewed journal manuscripts. 
− Encore congress publications may be appropriate to allow communication of 
research findings to relevant audience and geographical regions. 
• Alexion will comply with the requirements for publication of study results as defined 
by the Pharmaceutical Research and Manufacturers of America and the International 
Committee of Medical Journal Editors and per the Alexion Publication Policy. In 
accordance with standard editorial and ethical practice, Alexion will generally 
support publication of multicenter studies only in their entirety and not as individual 
site data. In this case, a Coordinating Investigator will be designated by mutual 
agreement. 
• Authorship will be determined by mutual agreement and in line with International 
Committee of Medical Journal Editors authorship requirements and per the Alexion 
Publication Policy. 
• Alexion will Publish Patient Lay Summaries and include participants and/or 
caregivers as reviewers for readability and understanding of lay person language. 
10.2.11. 
Good Clinical Practice Compliance 
Alexion and any third party to whom aspects of the study management or monitoring have been 
delegated will undertake their assigned roles for this study in compliance with all applicable 
industry regulations, ICH GCP Guideline E6 R2, EU Directive 2001/20/EC, as well as all 
applicable national and local laws and regulations. 

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Visits to sites are conducted by representatives of Alexion and/or the company 
organizing/managing the research on behalf of Alexion to inspect study data, participants’ 
medical records, and eCRFs in accordance with current GCP and respective local and 
(inter)national government regulations and guidelines. Records and data may additionally be 
reviewed by auditors or by regulatory authorities. 
Alexion ensures that local regulatory authority requirements are met before the start of the study. 
Alexion (or designee) is responsible for the preparation, submission, and confirmation of receipt 
of any regulatory authority approvals required prior to release of ravulizumab for shipment to the 
site. 

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10.3. 
Clinical Laboratory Tests 
• The tests detailed in Table 19 will be performed by the central laboratory. 
• Local laboratory results are only required in the event that the central laboratory 
results are not available in time for either study intervention administration and/or 
response evaluation. If a local sample is required, it is important that the sample for 
central analysis is obtained at the same time. Additionally, if the local laboratory 
results are used to make either a study intervention decision or response evaluation, 
the results must be available in the participant’s source documents. 
• Protocol-specific requirements for inclusion or exclusion of participants are detailed 
in Section 5. 
• Additional tests may be performed at any time during the study as determined 
necessary by the Investigator or required by local regulations. 
• Pregnancy testing: women of childbearing potential should only be enrolled after a 
negative serum or urine pregnancy test. Urine pregnancy testing will be standard for 
the protocol unless serum testing is required by local regulation or ethics committees 
and should be performed at the time points specified in the SoA (Section 1.3). 
Table 19: 
Laboratory Assessments 
Laboratory 
Assessments 
Parameters 
Hematology 
Platelet count  
RBC count 
Hemoglobin 
Hematocrit 
RBC indices: 
Distribution width 
Mean corpuscular volume 
Mean corpuscular 
Hemoglobin 
%Reticulocytes 
WBC count with 
differential: 
Neutrophils 
Lymphocytes 
Monocytes 
Eosinophils 
Basophils 
Clinical 
Chemistry 
BUN 
C-reactive protein 
Creatinine 
Chloride  
Potassium 
Bicarbonate  
Sodium  
Glucose (non-fasting) 
Calcium 
Magnesium 
Creatine kinase 
Aldolase 
LDH 
AST 
ALT 
Alkaline phosphatase 
Gamma 
glutamyltransferase 
Total and direct bilirubin 
Total protein 
Albumin 
Uric acid 
Coagulation 
International normalized ratio, partial thromboplastin time, prothrombin time 

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Table 19: 
Laboratory Assessments 
Laboratory 
Assessments 
Parameters 
Urinalysis 
Appearance, color, specific gravity, pH, glucose, protein, leukocyte esterase, blood, 
ketones, bilirubin, urobilinogen, nitrite, microscopic examination (if blood or protein 
is abnormal)  
Other screening 
tests 
Serum/urine β-HCG pregnancy test (as needed for participants of childbearing 
potential)a 
Serum follicle-stimulating hormone test to be performed at Screening in selected 
female participants to confirm postmenopausal status 
HIV-1 and HIV-2 antibodies 
Complement 
activity 
Free C5 
Total C5 
Other 
Antidrug antibodies 
a Local urine testing will be standard for the protocol unless serum testing is required by local regulation or ethics 
committees. 
Abbreviations: ALT = alanine aminotransferase; AST = aspartate aminotransferase; BUN = blood urea nitrogen; 
C5 = complement component 5; HCG = human chorionic gonadotropin; HIV = human immunodeficiency virus; 
LDH = lactate dehydrogenase; RBC = red blood cells; WBC = white blood cells 

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10.4. 
Adverse Events: Definitions and Procedures for Recording, 
Evaluating, Follow-up, and Reporting 
10.4.1. 
Definition of AE 
AE Definition 
• 
An AE is any untoward medical occurrence in a participant or clinical investigation participant 
administered a pharmaceutical product and which does not necessarily have to have a causal 
relationship with this treatment (ICH E2A). 
• 
Note: An AE can therefore be any unfavorable and unintended sign (including an abnormal 
laboratory finding), symptom, or disease [new or exacerbated] temporally associated with the use 
of the study intervention, whether or not considered related to the study intervention. 
 
Events Meeting the AE Definition 
• 
Any abnormal laboratory test results (hematology, clinical chemistry, or urinalysis) or other safety 
assessments (eg, ECG, radiological scans, vital signs measurements), including those that worsen 
from baseline, considered clinically significant in the medical and scientific judgment of the 
Investigator (ie, not related to progression of underlying disease).  
• 
Exacerbation of a chronic or intermittent pre-existing condition including either an increase in 
frequency and/or intensity of the condition. 
• 
New conditions detected or diagnosed after study intervention administration even though it may 
have been present before the start of the study. 
• 
Signs, symptoms, or the clinical sequelae of a suspected drug-drug interaction. 
• 
Signs, symptoms, or the clinical sequelae of a suspected overdose of either study intervention or a 
concomitant medication. Overdose per se will not be reported as an AE/SAE unless it is an 
intentional overdose taken with possible suicidal/self-harming intent. Such overdoses should be 
reported regardless of sequelae.  
 
Events Not Meeting the AE Definition 
• 
Medical or surgical procedure (eg, endoscopy, appendectomy): The condition that leads to the 
procedure is the AE. Situations in which an untoward medical occurrence did not occur (eg, 
hospitalization for elective surgery if planned before the signing the ICF, admissions for social 
reasons or for convenience).  
• 
Anticipated day-to-day fluctuations of pre-existing disease(s) or condition(s) present or detected at 
the start of the study that do not worsen. 
• 
A medication error (including intentional misuse, abuse, and overdose of the product) or use other 
than what is defined in the protocol is not considered an AE unless there is an untoward medical 
occurrence as a result of a medication error. 
• 
Cases of pregnancy that occur during maternal or paternal exposure to study intervention are to be 
reported within 24 hours of Investigator/site awareness. Data on fetal outcome and breastfeeding 
will be collected for regulatory reporting and safety evaluation. 

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Events Not Meeting the AE Definition 
• 
Any clinically significant abnormal laboratory findings or other abnormal safety assessments 
which are associated with the underlying disease, unless judged by the Investigator to be more 
severe than expected for the participant’s condition. 
• 
The disease/disorder being studied or expected progression, signs, or symptoms of the 
disease/disorder being studied, unless more severe than expected for the participant’s condition. 
• 
Situations in which an untoward medical occurrence did not occur (social and/or convenience 
admission to a hospital). 
• 
“Lack of efficacy” or “failure of expected pharmacological action” per se will not be reported as 
an AE or SAE. Such instances will be captured in the efficacy assessments. However, the signs, 
symptoms, and/or clinical sequelae resulting from lack of efficacy will be reported as AE or SAE 
if they fulfil the definition of an AE or SAE. 
10.4.2. 
Definition of SAE 
If an event is not an AE per definition above, then it cannot be an SAE even if serious conditions 
are met (eg, hospitalization for signs/symptoms of the disease under study, death due to 
progression of disease). 
An SAE is defined as any untoward medical occurrence that, at any dose: 
1. Results in death 
2. Is life-threatening 
The term “life-threatening” in the definition of “serious” refers to an event in which the participant was 
at risk of death at the time of the event. It does not refer to an event, which hypothetically might have 
caused death, if it was more severe. 
3. Requires inpatient hospitalization or prolongation of existing hospitalization 
In general, hospitalization signifies that the participant has been detained (usually involving at least an 
overnight stay) at the hospital or emergency ward for observation and/or treatment that would not have 
been appropriate in the physician’s office or outpatient setting. Complications that occur during 
hospitalization are AEs. If a complication prolongs hospitalization or fulfills any other serious criteria, 
the event is serious. When in doubt as to whether “hospitalization” occurred or was necessary, the AE 
should be considered serious. 
Hospitalization for elective treatment of a pre-existing condition that did not worsen from baseline is 
not considered an AE. 
4. Results in persistent disability/incapacity 
• 
The term disability means a substantial disruption of a person’s ability to conduct normal life 
functions. 
• 
This definition is not intended to include experiences of relatively minor medical significance such 
as uncomplicated headache, nausea, vomiting, diarrhea, influenza, and accidental trauma (eg, 
sprained ankle) which may interfere with or prevent everyday life functions but do not constitute a 
substantial disruption. 
5. Is a congenital anomaly/birth defect 
6. Other situations: 
• 
Medical or scientific judgment should be exercised in deciding whether SAE reporting is 
appropriate in other situations such as important medical events that may not be immediately life-

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An SAE is defined as any untoward medical occurrence that, at any dose: 
threatening or result in death or hospitalization but may jeopardize the participant or may require 
medical or surgical intervention to prevent one of the other outcomes listed in the above 
definition. These events should usually be considered serious. 
• 
Examples of such events include invasive or malignant cancers, intensive treatment in an 
emergency room or at home for allergic bronchospasm, blood dyscrasias or convulsions that do 
not result in hospitalization, or development of drug dependency or drug abuse. 
 
A suspected unexpected serious adverse reaction (SUSAR) is defined as: 
An event that is assessed as serious by the Investigator and/or Alexion that is not listed in the 
appropriate Reference Safety Information (IB) and has been assessed that there is at least a reasonable 
possibility that the event is related to the investigational medicinal product by the Investigator and/or 
Alexion. 
Alexion has procedures that will be followed for the recording, medical assessment, and expedited 
reporting of SUSARs that are consistent with global regulations, legislation, and guidance documents. 
Suspected unexpected serious adverse reactions will undergo expedited reporting to the national 
regulatory authorities, IRBs/IECs, and Investigators following local regulatory reporting requirements 
where applicable. 
10.4.3. 
Recording and Follow-Up of AE and/or SAE 
Recording of AE and/or SAE 
• 
When an AE/SAE occurs, it is the responsibility of the Investigator to review all documentation 
(eg, hospital progress notes, laboratory reports, and diagnostics reports) related to the event. 
• 
The Investigator will then record all relevant AE/SAE information in the eCRF. 
• 
It is not acceptable for the Investigator to send photocopies of the participant’s medical records to 
Alexion in lieu of completion of the Alexion AE/SAE eCRF page. 
• 
There may be instances when copies of medical records for certain cases are requested by 
Alexion. In this case, all participant identifiers, with the exception of the participant number, will 
be redacted on the copies of the medical records before submission to Alexion. 
• 
The Investigator will attempt to establish a diagnosis of the event based on signs, symptoms, 
and/or other clinical information. Whenever possible, the diagnosis (not the individual 
signs/symptoms) will be documented as the AE/SAE. 
Assessment of Intensity 
The Investigator will make an assessment of intensity for each AE and SAE reported during the study 
and assign it to one of the following categories from National Cancer Institute CTCAE v5.0, published 
27 Nov 2017:  
• 
Grade 1: Mild (awareness of sign or symptom, but easily tolerated) 
• 
Grade 2: Moderate (discomfort sufficient to cause interference with normal activities) 
• 
Grade 3: Severe (incapacitating, with inability to perform normal activities) 
• 
Grade 4: Life-threatening 
• 
Grade 5: Fatal 
 

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Recording of AE and/or SAE 
An event is defined as “serious” when it meets at least one of the predefined outcomes as described in 
the definition of an SAE, not when it is rated as severe. 
 
Assessment of Causality 
• 
The Investigator is obligated to assess the relationship between the study intervention and each 
occurrence of each AE or SAE. An Investigator causality assessment must be provided for all AEs 
(both nonserious and serious). This assessment must be recorded in the eCRF and on any 
additional forms, as appropriate. The definitions for the causality assessments are as follows: 
− 
Not related: There is no reasonable possibility the study intervention caused the AE.  
(a) The AE has a more likely alternative etiology; it may be due to underlying or concurrent 
 illness, complications, concurrent treatments, or effects of another concurrent drug.  
(b) The event does not follow a reasonable temporal relationship to administration of the study 
 intervention. 
− 
Related: There is a reasonable possibility the study intervention caused the AE. 
(c) The AE has a temporal relationship to the administration of the study intervention. 
(d) The event does not have a likely alternative etiology.  
(e) The event corresponds with the known pharmaceutical profile of the study intervention. 
(f) There is improvement on discontinuation and/or reappearance on rechallenge. 
• 
The Investigator will use clinical judgment to determine the relationship. 
• 
Alternative causes, such as underlying disease(s), concomitant therapy, and other risk factors, as 
well as the temporal relationship of the event to study intervention administration will be 
considered and investigated. 
• 
The Investigator will also consult the IB and/or Product Information, for marketed products, in 
his/her assessment. 
• 
For each AE/SAE, the Investigator must document in the medical notes that he/she has reviewed 
the AE/SAE and has provided an assessment of causality. 
• 
There may be situations in which an SAE has occurred, and the Investigator has minimal 
information to include in the initial report to Alexion. However, it is very important that the 
Investigator always make an assessment of causality for every event before the initial transmission 
of the SAE data to Alexion. 
• 
The Investigator may change his/her opinion of causality in light of follow-up information and 
send an SAE follow-up report with the updated causality assessment. 
• 
The causality assessment is one of the criteria used when determining regulatory reporting 
requirements. 
 
Follow-up of AEs and SAEs 
• 
The Investigator is obligated to perform or arrange for the conduct of supplemental measurements 
and/or evaluations as medically indicated or as requested by Alexion to elucidate the nature and/or 
causality of the AE or SAE as fully as possible. This may include additional laboratory tests or 
investigations, histopathological examinations, or consultation with other health care 
professionals. 

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Follow-up of AEs and SAEs 
• 
If a participant dies during participation in the study or during a recognized follow-up period, the 
Investigator will provide Alexion with a copy of any postmortem findings including 
histopathology. 
• 
New or updated information will be recorded in the originally completed eCRF. 
• 
The Investigator will submit any updated SAE data to Alexion within 24 hours of receipt of the 
information. 
10.4.4. 
Reporting of SAEs  
SAE Reporting to Alexion via an Electronic Data Collection Tool 
• 
All SAEs will be recorded and reported to Alexion immediately and within 24 hours of awareness. 
• 
The primary mechanism for reporting an SAE to Alexion will be the EDC system. 
• 
If the electronic system is unavailable or site staff is unable to process the SAE via the EDC 
system at the time that the Investigator or site becomes aware of an SAE, the site will use the 
paper Contingency Form for SAE Reporting via facsimile or email. Facsimile transmission or 
email may also be used in the event of electronic submission failure. 
− 
Email: clinicalsae@alexion.com or Fax: + 1.203.439.9347 
• 
The site will enter the SAE data into the EDC system as soon as it becomes available. 
• 
When further information becomes available, the EDC should be updated immediately with the 
new information and an updated SAE report should be submitted to Alexion Global Patient Safety 
(GPS) within 24 hours of Investigator/site awareness.  
• 
After the participant has completed the study, no new data or changes to existing data are expected 
to be entered in the EDC system. 
o If a site receives a report of a new SAE from a study participant which the Investigator 
considers to be related to the study intervention, or the site receives updated data on a 
previously reported SAE after the EDC system has been taken offline, then the site can report 
this information on a paper Contingency Form for SAE Reporting via facsimile or email. 
10.4.5. 
Unexpected Events 
Apart from the reporting of SUSARs, there may be other events which are relevant in terms of 
benefit-risk balance and which should be reported in a timely manner according to regional and 
national requirements. It is important for participant safety that, in addition to SAEs and 
reactions, all unexpected events that might materially influence the benefit-risk assessment of the 
study intervention or that would lead to changes in the administration of the study intervention or 
in overall conduct of a clinical study should be reported. Examples of such unexpected events 
include an increase in the rate of occurrence of expected serious adverse reactions which may be 
clinically important, a significant hazard to the patient population, such as lack of efficacy of a 
medicinal product, or a major safety finding from a newly completed animal study (such as, 
carcinogenicity). 
Under the EU CTR 536/2014 (49), where unexpected events require an urgent modification of a 
clinical study, Alexion and the Investigator may need to take urgent safety measures without 
awaiting prior authorization. If such measures constitute a temporary halt of the clinical study, 
Alexion will apply for a substantial modification before restarting the clinical study. 

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10.5. 
Medication Error, Drug Abuse, and Drug Misuse 
Medication Error 
For the purposes of this clinical study, a medication error is an unintended failure or mistake in 
the treatment process for study intervention that either causes harm to the participant or has the 
potential to cause harm to the participant.  
Any events of medication error, with or without associated AEs, are to be captured and 
forwarded to Alexion Global Patient Safety via email or facsimile (clinicalsae@alexion.com or + 
1.203.439.9347) using the Alexion Clinical Study Medication Error Report Form. 
A medication error is not lack of efficacy of the drug, but rather a human or process related 
failure while the drug is in control of the study site staff or participant. 
Medication error includes situations where an error:  
• Occurred 
• Was identified and intercepted before the participant received the drug 
• Did not occur, but circumstances were recognized that could have led to an error 
Examples of events to be reported in clinical studies as medication errors:  
• Drug name confusion 
• Dispensing error, eg, medication prepared incorrectly, even if it was not actually 
given to the participant 
• Drug not administered as indicated, eg, wrong route, wrong device, or wrong site of 
administration 
• Drug not stored as instructed, eg, kept at room temperature when it should be stored 
in the refrigerator  
• Wrong participant received the medication (excluding IRT errors) 
• Wrong drug administered to participant (excluding IRT errors) 
Examples of events that do not require reporting as medication errors in clinical studies: 
• Errors related to or resulting from IRT - including those which led to one of the above 
listed events that would otherwise have been a medication error  
• Participant accidentally missed drug dose(s), eg, forgot to take medication 
• Accidental overdose (will be captured as an overdose) 
• Participant failed to return unused medication or empty packaging  
Medication errors are not regarded as AEs but AEs may occur as a consequence of the 
medication error. 
Drug Abuse 

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For the purpose of this clinical study, drug abuse is defined as the persistent or sporadic 
intentional, nontherapeutic excessive use of study intervention for a perceived reward or desired 
nontherapeutic effect. 
Any events of drug abuse, with or without associated AEs, are to be captured and forwarded to 
Alexion Global Patient Safety via email or facsimile (clinicalsae@alexion.com or + 
1.203.439.9347) using the Alexion Clinical Study Drug Misuse or Drug Abuse Report Form. 
This form should be used both if the drug abuse happened in a study participant or if the drug 
abuse involves a person not enrolled in the study (such as a relative of the study participant). 
Drug Misuse 
Drug misuse is the intentional and inappropriate use (by a study participant) of study intervention 
for medicinal purposes outside of the authorized product information, or for unauthorized study 
intervention, outside the intended use as specified in the protocol, including deliberate 
administration of the product by the wrong route. 
Events of drug misuse, with or without associated AEs, are to be captured and forwarded to 
Alexion Global Patient Safety via email or facsimile (clinicalsae@alexion.com or + 
1.203.439.9347) using the Alexion Clinical Study Drug Misuse or Drug Abuse Report Form. 
This form should be used both if the drug misuse happened in a study participant or if the drug 
misuse involves a person not enrolled in the study (such as a relative of the study participant). 
Examples of drug misuse include but are not limited to: 
• The drug is used with the intention to cause an effect in another person 
• The drug is sold to other people for recreational purposes  
• The drug is used to facilitate assault on another person 
• The drug is deliberately administered by the wrong route 
• Only half the dose is taken because the study participant feels that he/she is feeling 
better when not taking the whole dose 
• Someone who is not enrolled in the study intentionally takes the drug 

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10.6. 
Contraceptive Guidance and Collection of Pregnancy Information  
10.6.1. 
Definitions 
Woman of Childbearing Potential (WOCBP) 
A woman is considered fertile following menarche and until becoming postmenopausal unless 
permanently sterile (see below). 
If fertility is unclear (eg, amenorrhea in adolescents or athletes) and a menstrual cycle cannot be 
confirmed before first dose of study intervention, additional evaluation should be considered. 
Women in the Following Categories Are Not Considered WOCBP 
1. Premenarchal 
2. Premenopausal female with one of the following: 
• Documented hysterectomy 
• Documented bilateral tubal ligation or bilateral salpingectomy 
• Documented bilateral oophorectomy 
For individuals with permanent infertility due to an alternate medical cause other than the 
above, (eg, Mullerian agenesis, androgen insensitivity), Investigator discretion should be 
applied to determining study entry. 
Note: Documentation can come from the site personnel’s review of the participant’s 
medical records, medical examination, or medical history interview. 
3. Postmenopausal female 
• A postmenopausal state is defined as no menses for 12 months without an alternative 
medical cause prior to the Day 1 Visit. 
− A high follicle-stimulating hormone (FSH) level in the postmenopausal range 
may be used to confirm a postmenopausal state in women not using hormonal 
contraception or hormone replacement therapy (HRT). However, in the absence 
of 12 months of amenorrhea, confirmation with more than 1 FSH measurement 
may be required. In the absence of 12 months of amenorrhea the reason for not 
obtaining FSH levels should be documented by the Investigator at the time of 
Screening. 
• Females on HRT and whose menopausal status is in doubt will be required to use one 
of the non-estrogen hormonal highly effective contraception methods if they wish to 
continue their HRT during the study. Otherwise, they must discontinue HRT to allow 
confirmation of postmenopausal status before study enrollment. 
4. Permanent sterilization at least 6 weeks prior to the Day 1 Visit. 
10.6.2. 
Contraception Guidance 
Contraceptive use by male or female participants should be consistent with local regulations 
regarding the methods of contraception utilized for those participating in clinical studies. If 

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teratogenic effects are suspected to be transferred to a fetus/embryo from a female spouse/partner 
of a male participant, pregnancy follow-up information will be obtained for the partner who 
becomes pregnant (refer to Section 10.5.3.1). In these cases, follow-up will be conducted on the 
pregnant partner in the same manner as a female participant who becomes pregnant during the 
study. 
10.6.2.1. Guidance for Female Participants 
Female participants of childbearing potential must use a highly effective or acceptable method of 
contraception, including at least 1 of the following until at least 8 months after the final dose of 
study intervention. 
1. Intrauterine device in place for at least 6 weeks prior to first dose of study intervention. 
2. Progestogen-only hormonal contraception associated with inhibition of ovulation (either 
oral, injectable, or implantable) for at least 6 weeks prior to first dose of study 
intervention. 
3. Intrauterine progestogen releasing system for at least 6 weeks prior to first dose of study 
intervention. 
4. Bilateral tubal occlusion for at least 6 weeks prior to first dose of study intervention. 
5. Combined (estrogen- and progestogen-containing) hormonal contraception (either oral, 
intravaginal, or transdermal) for at least 6 weeks prior to first dose of study intervention. 
6. Surgical sterilization of the male partner (medical assessment of azoospermia is required 
if vasectomy was performed within 6 months prior to first dose of study intervention). 
Male partner is still required to use condom during sexual intercourse. 
7. Sexual abstinence for female participants: 
a. Sexual abstinence is considered a highly effective method only if defined as 
refraining from heterosexual intercourse. In this study, abstinence is only acceptable 
if consistent with the participant’s preferred and usual lifestyle. Abstinent female 
participants must refrain from heterosexual intercourse for at least 8 months after the 
final dose of study intervention. 
Other methods of contraception that are not considered as highly effective for female 
participants, but are acceptable birth control methods (that result in a failure rate of more than 
1% per year) include: 
8. Progestogen-only oral hormonal contraception, where inhibition of ovulation is not the 
primary mode of action; 
9. Male or female condom with or without spermicide 
10. Cap, diaphragm, or sponge with spermicide 
11. A combination of male condom with cap, diaphragm, or sponge with spermicide 
(double-barrier methods) 
Female participants must not donate ova from the Day 1 Visit at least until 8 months after their 
final dose of study intervention. 

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The following methods of contraception are considered unacceptable in this study: 
−
Periodic abstinence (calendar, symptothermal, or post-ovulation methods
−
Withdrawal (coitus interruptus)
−
Spermicides only
−
Lactational amenorrhea method
−
Female condom and male condom should not be used together
10.6.2.2. Guidance for Male Participants 
Contraception is the responsibility of the heterosexually active male participants in the study, 
regardless of his female partner’s method of contraception. 
Male participants who have had a vasectomy > 6 months prior to the first dose of study 
intervention must use a condom during heterosexual intercourse. Male participants who have had 
a vasectomy < 6 months prior to the first dose study intervention and those who have not had a 
vasectomy must use a condom and spermicide during heterosexual intercourse for at least 
8 months after their final dose of study intervention. 
Participants with a spouse/partner of childbearing potential or a pregnant or breastfeeding spouse 
or partner must agree to use double barrier contraception (male condom plus appropriate barrier 
method for the female partner) while on treatment and for at least 8 months after the last dose of 
study intervention. Double barrier contraception is required even with documented medical 
assessment of surgical success of a vasectomy. 
Male participants must not donate sperm from the Day 1 Visit until 8 months after their final 
dose of study intervention. 
10.6.2.2.1. Sexual Abstinence for Male Participants 
Sexual abstinence is considered a highly effective method only if defined as refraining from 
heterosexual intercourse. In this study, abstinence is only acceptable if consistent with the 
participant’s preferred and usual lifestyle. Abstinent male participants who become 
heterosexually active must use a condom and spermicide during intercourse. 
Periodic abstinence (eg, calendar, symptothermal, or post-ovulation methods for a female 
partner) is not considered a highly effective method of contraception for male participants. 
10.6.3. 
Collection of Pregnancy Information 
Pregnancy data will be collected during this study for all female participants and female 
spouses/partners of male participants from the first dose of study intervention until the EOS 
Visit. 
Any female participant who becomes pregnant during the study should be discontinued from the 
study intervention.  
Exposure during pregnancy (also referred to as exposure in utero) can be the result of either 
maternal exposure or transmission of study intervention via semen following paternal exposure. 
If a female participant or a male participant’s female spouse/partner becomes pregnant during the 

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conduct of this study, the Investigator must submit the “Pregnancy/Breastfeeding Reporting and 
Outcome Form” to Alexion GPS via facsimile or email. When the outcome of the pregnancy 
becomes known, the form should be updated and submitted to Alexion GPS. If additional follow-
up is required, the Investigator will be requested to provide the information. 
Exposure of an infant to study intervention during breastfeeding must also be reported (via the 
“Pregnancy/Breastfeeding Reporting and Outcome Form”) and any AEs experienced by the 
infant must be reported to Alexion GPS via email or facsimile. 
Pregnancy is not regarded as an AE unless there is a suspicion that the study intervention may 
have interfered with the effectiveness of a contraceptive medication. However, complications of 
pregnancy and abnormal outcomes of pregnancy are AEs and may meet the criteria for an SAE 
(eg, ectopic pregnancy, spontaneous abortion, intrauterine fetal demise, neonatal death, or 
congenital anomaly). Elective abortions without complications should not be reported as AEs. 
10.6.3.1. Male Participants with Partners Who Become Pregnant 
• The Investigator will attempt to collect pregnancy information on any male 
participant’s female partner who becomes pregnant while the male participant is in 
this study. This applies only to male participants who receive study intervention. 
• After obtaining the necessary signed informed consent from the pregnant female 
partner directly, the Investigator will record pregnancy information on the appropriate 
“Pregnancy/Breastfeeding Reporting and Outcome Form” and submit it to Alexion 
within 24 hours of learning of the partner’s pregnancy. The female partner will also 
be followed to determine the outcome of the pregnancy. Information on the status of 
the mother and child will be forwarded to Alexion. Generally, the follow-up will be 
no longer than 3 months following the delivery date. Any termination of the 
pregnancy will be reported regardless of fetal status (presence or absence of 
anomalies) or indication for the procedure. 
10.6.3.2. Female Participants Who Become Pregnant 
• The Investigator will collect pregnancy information on any female participant who 
becomes pregnant while participating in this study. The information will be recorded 
on the “Pregnancy/Breastfeeding Reporting and Outcome Form” and submitted to 
Alexion within 24 hours of learning of a participant’s pregnancy. 
• For all Alexion products, both in development or post-approval, exposure during 
pregnancy must be recorded and the pregnancy followed, until the outcome of the 
pregnancy is known (ie, spontaneous miscarriage, elective termination, normal birth, 
or congenital abnormality), even if the participant discontinues the study intervention 
or withdraws from the study. The Investigator will collect follow-up information on 
the participant and the neonate and the information will be forwarded to Alexion. 
Generally, follow-up will not be required for longer than 3 months beyond the 
estimated delivery date. Any termination of pregnancy will be reported, regardless of 
fetal status (presence or absence of anomalies) or indication for the procedure. 
• While pregnancy itself is not considered to be an AE or SAE, any pregnancy 
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reported as an AE or SAE. A spontaneous abortion (occurring at < 22 weeks 
gestational age) or still birth (occurring at > 22 weeks gestational age) is always 
considered to be an SAE and will be reported as such. Any post-study 
pregnancy-related SAE considered reasonably related to the study intervention by the 
Investigator will be reported to Alexion. While the Investigator is not obligated to 
actively seek this information in former study participants, he or she may learn of an 
SAE through spontaneous reporting. 

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10.7. 
Biomarkers 
• Blood will be collected in all the study sites. All biomarker analyses and the data will 
be used for research (eg, exploratory) related to ravulizumab or DM and related 
diseases. The samples may also be used to develop tests/assays including diagnostic 
tests related to ravulizumab and/or other C5 inhibitors and DM. 
• The samples may be analyzed as part of a multistudy assessment of biomarkers in the 
response to ravulizumab or C5 inhibitors to understand study disease or related 
disease. 
• The results of biomarker analyses may be reported in the Clinical Study Report or in 
a separate study summary. 
• Alexion or designee will store the samples obtained for biomarker analyses in a 
secure storage space with adequate measures to protect confidentiality. 
• The samples will be retained while research on ravulizumab or C5 inhibitors 
continues but no longer than 5 years after all data have been collected for the study or 
other period/time point per local requirements. 
 

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10.8. 
Clinical Outcome Assessments  
10.8.1. 
Myositis Disease Activity Assessment Tool (MDAAT) 
 

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MDAAT (Continued) 
 

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MDAAT (Continued) 
 

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MDAAT (Continued) 
 

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10.8.2. 
Physician Global Activity Assessment 
 

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10.8.3. 
Patient Global Activity Assessment  
 
 

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10.8.4. 
Manual Muscle Test (MMT-8) 
 
 

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10.8.5. 
Health Assessment Questionnaire (HAQ) 
 

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Health Assessment Questionnaire (HAQ) - Continued 
 

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10.8.6. 
Cutaneous Dermatomyositis Disease Area and Severity Index (CDASI) 
 
 

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10.8.7. 
Cutaneous Dermatomyositis Activity Physician’s Global Assessment (CDA-IGA)  
 

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10.8.8. 
EuroQoL 5 Dimensions (EQ-5D-5L) 
10.8.8.1. EQ-5D-5L Version for In-Clinic Use 
 
 
 

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EQ-5D-5L Version for In-Clinic Use (Continued) 
 

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EQ-5D-5L Version for In-Clinic Use (Continued) 
 

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10.8.9. 
5D-Itch Scale 

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10.8.10. 
PROMIS-29 v2.1 Tool 
 

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10.8.11. 
Short Form Health Survey (36 Questions Version) (SF-36) 
 

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SF-36 (Continued) 
 
 

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SF-36 (Continued) 
 

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SF-36 (Continued) 
 
 

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SF-36 (Continued) 
 
 

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SF-36 (Continued) 
 

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10.8.12. 
Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue) 
 

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10.8.13. 
Dermatomyositis Disease Symptoms Questionnaire (DM-DSQ) v1.1 and v5.0 
 

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10.8.14. 
30-Second Chair Stand 
 
 

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10.9. 
COVID-19 Risk Assessment 
DM can cause irreversible morbidity and even mortality, if untreated. As such, and due to the 
limited number of available treatment options, the benefit a participant may receive from joining 
an investigational study with a therapeutic treatment is potentially significant. Given that 
treatment for DM does involve immunosuppression, there is a theoretical concern that the risk 
for infection may be higher than in participants not receiving immunosuppressants. However, 
there is no specific data to further inform this risk. The site Investigator will therefore balance 
the risk/benefit considerations in the study participant taking these factors into account.  
The potential risks identified and mitigation measures put in place in light of the COVID-19 
pandemic are provided in Table 20. 
Table 20: 
Potential Risks and Mitigation Measures Due to COVID-19 
Risks Category 
Summary of Data/ 
Rationale for Risk 
Mitigation Strategy 
Potential risks 
Healthcare institution 
availability for 
non-COVID-19-related 
activities  
COVID-19 pandemic may impact the 
workload of healthcare institutions 
globally and may reduce staff 
availability to perform non-urgent 
activities and non-COVID-19-related 
activities. 
During the time that the 
COVID19 pandemic is active, 
Alexion will only open study sites 
that report enough personnel 
capacity to sufficiently conduct 
clinical study related activities. 
Data quality and 
integrity 
Lack of availability of site personnel to 
perform study assessments and capture 
study specific data in a timely manner 
and to maintain adequate quality 
standards. 
Lack of availability of site personnel to 
ensure adequate and continuous chain of 
custody, storage conditions, and 
monitoring for investigational product 
and biological samples. 
Inability of study monitors and quality 
personnel to conduct in-person visits to 
exercise adequate oversight of study 
execution at investigational sites. 
Missing data (COVID19 pandemic may 
impact study visit schedules and 
increase missed visits and/or participant 
study discontinuations inadvertently 
resulting in missing data [eg, for 
protocol-specified procedures]). 
During the time that the 
COVID19 pandemic is active, 
Alexion will only open study sites 
that report enough personnel 
capacity to sufficiently conduct 
clinical study related activities.  
During this timeframe, 
participants eligibility as well as 
site capacity will be reviewed by 
the site Investigator and the 
Alexion Medical Monitor or 
designee prior to Screening. Each 
site is also evaluated for the 
capacity to perform remote 
monitoring visits and remote 
source data verification. 
During the time that the 
COVID-19 pandemic is active, it 
will be important to capture 
specific information in the eCRF 
that explains the reason the data 

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Table 20: 
Potential Risks and Mitigation Measures Due to COVID-19 
Risks Category 
Summary of Data/ 
Rationale for Risk 
Mitigation Strategy 
are missing (eg, missed study 
visits or participant study 
discontinuations due to 
COVID-19). 
Abbreviations: COVID-19 = coronavirus disease 2019; eCRF = electronic case report form 

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10.10. 
COVID-19 Vaccine Risk Assessment 
Following a review of the available COVID-19 vaccine data (eg, Pfizer/BioNTech, Moderna, 
AstraZeneca, Johnson & Johnson), it is unlikely that the immune response to a COVID-19 
vaccine (and therefore the efficacy of the vaccination) would be diminished with concomitant 
ravulizumab administration, based on ravulizumab’s mechanism of action. There is currently no 
information available evaluating the safety and efficacy of COVID-19 vaccines in participants 
treated with ravulizumab. 
Vaccination may further activate complement. As a result, participants with 
complement-mediated diseases may experience increased signs and symptoms of their 
underlying disease. Therefore, participants should be closely monitored for disease symptoms 
after recommended vaccination. 
Because vaccines may activate complement, if possible, consider vaccination when the 
underlying complement-mediated disease is clinically controlled and when systemic C5 inhibitor 
concentration (and subsequent complement blockade) is relatively high, shortly after 
administration. 
Local and national guidelines should be consulted for recommendations related to COVID-19 
vaccination. 
The potential risks identified and mitigation measures put in place in light of the COVID-19 
vaccination rollout are provided in Table 21. 
Table 21: 
Potential Risks and Mitigation Measures Due to COVID-19 Vaccine 
Risks Category 
Summary of Data/Rationale for Risk 
Mitigation Strategy 
Potential risks 
Data quality and 
integrity 
Missing data due to appointments for 
COVID-19 vaccination or side effects of 
COVID-19 vaccine may impact study visit 
schedules and increase missed visits and/or 
participant study discontinuations, 
inadvertently resulting in missing data (eg, 
for protocol-specified procedures). 
Capture specific information in 
the eCRF that explains the 
reason the data is missing (eg, 
missed study visits due to 
appointments for COVID-19 
vaccination or side effects of 
COVID-19 vaccine). 
Abbreviations: COVID-19 = coronavirus disease 2019; eCRF = electronic case report form 
 

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10.11. 
Abbreviations 
The following abbreviations and terms are used in this study protocol. 
Table 22: 
Abbreviations and Specialist Terms 
Abbreviation or Specialist Term 
Explanation 
30s CST 
30-second Chair Stand Test 
ACR 
American College of Rheumatology 
ADA 
antidrug antibody 
AE 
adverse event 
AESI 
adverse events of special interest  
aHUS 
atypical hemolytic uremic syndrome 
ALT 
alanine aminotransferase 
anti‑MDA5 
antimelanoma differentiation-associated protein 5 
anti-NXP2/MJ 
antinuclear matrix protein 2 
AST 
aspartate aminotransferase 
C3 
complement component 3 
C5 
complement component 5 
C5a 
complement component 5a 
C5b 
complement component 5b 
C5b-9 
terminal complement complex 
CDA-IGA 
Cutaneous Dermatomyositis Activity Physician’s Global 
Assessment 
CDASI 
Cutaneous Dermatomyositis Disease Area and Severity Index 
CI 
confidence interval 
CIOMS 
Council for International Organizations of Medical Sciences 
CK 
creatine kinase 
COVID-19 
coronavirus disease 2019 
CRF 
case report form 
CSM 
core set measure 
CTCAE 
Common Terminology Criteria for Adverse Events 
DM 
dermatomyositis 
DMC 
Data Monitoring Committee 
DM-DSQ 
Dermatomyositis Disease Symptoms Questionnaire 

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Table 22: 
Abbreviations and Specialist Terms 
Abbreviation or Specialist Term 
Explanation 
DSM 
Diagnostic and Statistical Manual of Mental Disorders 
ECG 
electrocardiogram 
eCRF 
electronic case report form 
EDC 
electronic data capture 
EOS 
End of Study 
ePRO 
electronic patient-reported outcome 
EQ-5D-5L 
European Quality of Life Health 5-item questionnaire 
dimensions 5 level 
ET 
Early Termination 
EULAR 
European League Against Rheumatism 
FACIT 
Functional Assessment of Chronic Illness Therapy 
FDA 
Food and Drug Administration 
FSH 
follicle-stimulating hormone 
GCP 
Good Clinical Practice 
GDPR 
General Data Protection Regulation 
GPS 
Global Patient Safety 
gMG 
generalized myasthenia gravis 
HAQ 
Health Assessment Questionnaire 
HIPAA 
Health Insurance Portability and Accountability Act 
HIV 
human immunodeficiency virus 
HRT 
hormone replacement therapy 
IB 
Investigator’s Brochure 
ICF 
informed consent form 
ICH 
International Council for Harmonisation of Technical 
Requirements for Pharmaceuticals for Human Use 
IDMC 
Independent Data Monitoring Committee 
IEC 
Independent Ethics Committee 
IMACS 
International Myositis Assessment and Clinical Studies 
IMACS-TIS 
International Myositis Assessment and Clinical Studies Total 
Improvement Score 
IRB 
Institutional Review Board 
IRT 
interactive response technology 

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Table 22: 
Abbreviations and Specialist Terms 
Abbreviation or Specialist Term 
Explanation 
IST 
immunosuppressive/immunomodulatory therapy 
IV 
intravenous(ly) 
IVIg 
intravenous immunoglobulin 
LDH 
lactate dehydrogenase 
mAb 
monoclonal antibody 
MAC 
membrane attack complex 
MDAAT 
Myositis Disease Activity Assessment Tool 
MedDRA 
Medical Dictionary for Regulatory Activities 
MITAX 
Myositis Intention to Treat Activities Index 
MMT-8 
manual muscle testing subset of 8 muscles 
MRI 
magnetic resonance imaging 
MYOACT 
Myositis Disease Activity Assessment VAS 
NMOSD 
neuromyelitis optica spectrum disorder 
NSAID 
non-steroidal anti-inflammatory drug 
OLE 
Open-Label Extension 
PD 
pharmacodynamic(s) 
PK 
pharmacokinetic(s) 
PNH 
paroxysmal nocturnal hemoglobinuria 
PPS 
Per Protocol Set 
PRO 
patient-reported outcome 
PROMIS 
Patient-Reported Outcomes Measurement Information System 
PT 
physical therapy 
q8w 
every 8 weeks 
RCP 
Randomized Controlled Period 
SAE 
serious adverse events 
SAP 
Statistical Analysis Plan 
SC 
subcutaneous 
SF-36 
Short Form Health Survey (36 questions version) 
SLE 
systemic lupus erythematosus 
SoA 
Schedule of Activities 
SOC 
System Organ Class 

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Table 22: 
Abbreviations and Specialist Terms 
Abbreviation or Specialist Term 
Explanation 
SS 
Safety Set 
SUSAR 
suspected unexpected serious adverse reactions 
TEAE 
treatment-emergent adverse event 
TESAE 
treatment-emergent serious adverse event 
TIS 
total improvement score 
TIS20 
≥ 20-point improvement response on IMACS-TIS 
TIS40 
≥ 40-point improvement response on IMACS-TIS 
TIS60 
≥ 60-point improvement response on IMACS-TIS 
ULN 
upper limit of normal 
VAS 
visual analog scale 
wGEE 
weighted generalized estimating equation 
WOCBP 
woman of childbearing potential 

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10.12. 
Protocol Amendment History 
The protocol amendment summary of changes table for the current amendment is located 
directly before the Table of Contents.  
DOCUMENT HISTORY 
Document 
Type of 
Amendment 
(Global or 
Country-specific) 
Date 
Summary of Key Changes in the 
Amendment 
Amendment 
2.0 
Global  
30 Aug 2022 
To broaden the target population, reduce the 
risk of screen failures, improve patient 
experience, and to facilitate recruitment of 
participants.  
Amendment 
1.0 
Global 
27 Aug 2021 
To provide information on the IDMC, a 
clarification on Part A interim analysis, 
individual and study closure criteria. 
Amendment 
0.2 
UK 
10 Aug 2021 
To provide information regarding the IDMC, 
and to clarify interim analysis 
Amendment 
0.1 
Germany 
11 Aug 2021 
To introduce an IDMC and update study 
closure criteria  
Original 
protocol 
Not applicable 
07 May 2021 
Not applicable 
 

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11. 
REFERENCES 
Agarwal S, Kiely PD. Two simple, reliable and valid tests of proximal muscle function, and their 
application to the management of idiopathic inflammatory myositis. Rheumatology (Oxford). 
2006;45(7):874-879. 
Aggarwal R, Rider LG, Ruperto N, et al. 2016 American College of Rheumatology/European 
League Against Rheumatism Criteria for Minimal, Moderate, and Major Clinical Response in 
Adult Dermatomyositis and Polymyositis: An International Myositis Assessment and Clinical 
Studies Group/Paediatric Rheumatology International Trials Organisation Collaborative 
Initiative. Arthritis Rheumatol. 2017;69(5):898-910. 
Bendewald MJ, Wetter DA, Li X, Davis MD. Incidence of dermatomyositis and clinically 
amyopathic dermatomyositis: a population-based study in Olmsted County, Minnesota. Arch 
Dermatol. 2010;146(1):26-30. 
Bohan A, Peter JB. Polymyositis and dermatomyositis (first of two parts). N Engl J Med. 
1975;292(7):344-347. 
Casadevall N, Nataf J, Viron B, et al. Pure red-cell aplasia and antierythropoietin antibodies in 
patients treated with recombinant erythropoietin. N Engl J Med. 2002;346(7):469-475. 
Chan IS, Zhang Z. Test-based exact confidence intervals for the difference of two binomial 
proportions. Biometrics. 1999;55(4):1202-1209. 
Chandra T, Aggarwal R. Clinical trials and novel therapeutics in dermatomyositis. Expert Opin 
Emerg Drugs. 2020:1-16. 
Dalakas MC. Review: An update on inflammatory and autoimmune myopathies. Neuropathol 
Appl Neurobiol. 2011;37(3):226-242. 
Dalakas MC. Inflammatory muscle diseases. N Engl J Med. 2015;372(18):1734-1747. 
Dalakas MC, Hohlfeld R. Polymyositis and dermatomyositis. Lancet. 2003;362(9388):971-982. 
Dalakas MC, Alexopoulos H, Spaeth PJ. Complement in neurological disorders and emerging 
complement-targeted therapeutics. Nat Rev Neurol. 2020;16(11):601-617. 
Ernste FC, Reed AM. Idiopathic inflammatory myopathies: current trends in pathogenesis, 
clinical features, and up-to-date treatment recommendations. Mayo Clin Proc. 2013;88(1):83-
105. 
Howard JF, Jr., Utsugisawa K, Benatar M, et al. Safety and efficacy of eculizumab in anti-
acetylcholine receptor antibody-positive refractory generalised myasthenia gravis (REGAIN): a 
phase 3, randomised, double-blind, placebo-controlled, multicentre study. Lancet Neurol. 
2017;16(12):976-986. 
Isak V, Jorizzo JL. Recent developments on treatment strategies and the prognosis of 
dermatomyositis: a review. J Dermatolog Treat. 2018;29(5):450-459. 

Protocol Amendment 3.0 
ALXN1210-DM-310 
23 Jun 2023 
Page 187 of 188 
Alexion Confidential 
Kissel JT, Mendell JR, Rammohan KW. Microvascular deposition of complement membrane 
attack complex in dermatomyositis. N Engl J Med. 1986;314(6):329-334. 
Kronzer VL, Kimbrough BA, Crowson CS, Davis JM, 3rd, Holmqvist M, Ernste FC. Incidence, 
prevalence, and mortality of dermatomyositis: a population-based cohort study. Arthritis Care 
Res (Hoboken). 2021. 
Lahoria R, Selcen D, Engel AG. Microvascular alterations and the role of complement in 
dermatomyositis. Brain. 2016;139(Pt 7):1891-1903. 
Li J, Yang C, Xia Y, et al. Thrombocytopenia caused by the development of antibodies to 
thrombopoietin. Blood. 2001;98(12):3241-3248. 
Lundberg IE, Tjarnlund A, Bottai M, et al. 2017 European League Against 
Rheumatism/American College of Rheumatology Classification Criteria for Adult and Juvenile 
Idiopathic Inflammatory Myopathies and Their Major Subgroups. Arthritis Rheumatol. 
2017;69(12):2271-2282. 
Magro CM, Crowson AN. The immunofluorescent profile of dermatomyositis: a comparative 
study with lupus erythematosus. J Cutan Pathol. 1997;24(9):543-552. 
Mahil S, Marks D, McCormack M, Rahman A. Dermatomyositis. Br J Hosp Med (Lond). 
2012;73(2):C18-22. 
Marie I, Hachulla E, Hatron PY, et al. Polymyositis and dermatomyositis: short term and 
longterm outcome, and predictive factors of prognosis. J Rheumatol. 2001;28(10):2230-2237. 
Matis LA, Rollins SA. Complement-specific antibodies: designing novel anti-inflammatories. 
Nat Med. 1995;1(8):839-842. 
Mehta CR, Pocock SJ. Adaptive increase in sample size when interim results are promising: a 
practical guide with examples. Stat Med. 2011;30(28):3267-3284. 
Muppidi S, Utsugisawa K, Benatar M, et al. Long-term safety and efficacy of eculizumab in 
generalized myasthenia gravis. Muscle Nerve. 2019;60(1):14-24. 
Pinal-Fernandez I, Casciola-Rosen LA, Christopher-Stine L, Corse AM, Mammen AL. The 
Prevalence of Individual Histopathologic Features Varies according to Autoantibody Status in 
Muscle Biopsies from Patients with Dermatomyositis. J Rheumatol. 2015;42(8):1448-1454. 
Pittock SJ, Berthele A, Fujihara K, et al. Eculizumab in aquaporin-4–positive neuromyelitis 
optica spectrum disorder. N Engl J Med. 2019;381(7):614-625. 
Rider LG, Miller FW. Deciphering the clinical presentations, pathogenesis, and treatment of the 
idiopathic inflammatory myopathies. JAMA. 2011a;305(2):183-190. 
Rider LG, Aggarwal R, Machado PM, et al. Update on outcome assessment in myositis. Nat Rev 
Rheumatol. 2018;14(5):303-318. 

Protocol Amendment 3.0 
ALXN1210-DM-310 
23 Jun 2023 
Page 188 of 188 
Alexion Confidential 
Rider LG, Werth VP, Huber AM, et al. Measures of adult and juvenile dermatomyositis, 
polymyositis, and inclusion body myositis: Physician and Patient/Parent Global Activity, Manual 
Muscle Testing (MMT), Health Assessment Questionnaire (HAQ)/Childhood Health Assessment 
Questionnaire (C-HAQ), Childhood Myositis Assessment Scale (CMAS), Myositis Disease 
Activity Assessment Tool (MDAAT), Disease Activity Score (DAS), Short Form 36 (SF-36), 
Child Health Questionnaire (CHQ), physician global damage, Myositis Damage Index (MDI), 
Quantitative Muscle Testing (QMT), Myositis Functional Index-2 (FI-2), Myositis Activities 
Profile (MAP), Inclusion Body Myositis Functional Rating Scale (IBMFRS), Cutaneous 
Dermatomyositis Disease Area and Severity Index (CDASI), Cutaneous Assessment Tool 
(CAT), Dermatomyositis Skin Severity Index (DSSI), Skindex, and Dermatology Life Quality 
Index (DLQI). Arthritis Care Res (Hoboken). 2011b;63 Suppl 11:S118-157. 
Sallum AM, Kiss MH, Silva CA, et al. Difference in adhesion molecule expression (ICAM-1 and 
VCAM-1) in juvenile and adult dermatomyositis, polymyositis and inclusion body myositis. 
Autoimmun Rev. 2006;5(2):93-100. 
Sampson HA, Munoz-Furlong A, Campbell RL, et al. Second symposium on the definition and 
management of anaphylaxis: summary report--Second National Institute of Allergy and 
Infectious Disease/Food Allergy and Anaphylaxis Network symposium. J Allergy Clin Immunol. 
2006;117(2):391-397. 
Schrag A, Selai C, Jahanshahi M, Quinn NP. The EQ-5D--a generic quality of life measure-is a 
useful instrument to measure quality of life in patients with Parkinson's disease. J Neurol 
Neurosurg Psychiatry. 2000;69(1):67-73. 
Selva-O'Callaghan A, Pinal-Fernandez I, Trallero-Araguas E, Milisenda JC, Grau-Junyent JM, 
Mammen AL. Classification and management of adult inflammatory myopathies. Lancet Neurol. 
2018;17(9):816-828. 
Stewart AL, Hays RD, Ware JE, Jr. The MOS short-form general health survey. Reliability and 
validity in a patient population. Med Care. 1988;26(7):724-735. 
Suarez-Calvet X, Gallardo E, Pinal-Fernandez I, et al. RIG-I expression in perifascicular 
myofibers is a reliable biomarker of dermatomyositis. Arthritis Res Ther. 2017;19(1):174. 
Tegla CA, Cudrici C, Patel S, et al. Membrane attack by complement: the assembly and biology 
of terminal complement complexes. Immunol Res. 2011;51(1):45-60. 
Ware JE, Jr., Sherbourne CD. The MOS 36-item short-form health survey (SF-36). I. Conceptual 
framework and item selection. Med Care. 1992;30(6):473-483.