A Phase 3, Multicenter, Randomized, Double-Blind, Placebo-Controlled Study to Evaluate Efficacy and Safety of AK002 in Patients With Moderately to Severely Active Eosinophilic Gastritis and/or Eosinophilic Duodenitis (Formerly Referred to as Eosinophilic Gastroenteritis)
Phase: PHASE3
Conditions: Eosinophilic Gastritis, Eosinophilic Duodenitis
Sponsor: Allakos Inc.

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975 Island Drive, Suite 201, Redwood City, CA 94065
Page 1 of 127
Clinical Research Protocol AK002-016
A Phase 3, Multicenter, Randomized, Double-Blind, Placebo-Controlled Study
to Evaluate the Efficacy and Safety of AK002 in Patients with Moderately to
Severely Active Eosinophilic Gastritis and/or Eosinophilic Duodenitis (formerly 
referred to as Eosinophilic Gastroenteritis) Who Have an Inadequate Response 
with, Lost Response to, or Were Intolerant to Standard Therapies
Protocol Number
AK002-016
Version and Date
Original
30 September 2019
Amendment 1
18 March 2020
Amendment 2
07 August 2020
Amendment 3
20 April 2021
Amendment 4
26 October 2021
Investigational Product
AK002 (lirentelimab)
Study Phase
3
Sponsor
Allakos Inc., 975 Island Drive, Suite 201
Redwood City, CA 94065 USA
Medical Monitor
Name:
 MD
Telephone:
Email:
Approval:
MD, MBA
Date
Confidentiality Statement
This confidential information about an investigational product is provided for the exclusive use 
of Investigators of this product and is subject to recall at any time. The information in this 
document may not be disclosed unless federal or state law or regulations require such disclosure. 
Subject to the foregoing, this information may be disclosed only to those persons involved in the 
study who have a need to know, with the obligation not to further disseminate this information. 

	
PPD
PPD
PPD
PPD
PPD
PPD
SIGN

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 2 of 127 
Confidential 
Investigator Protocol Agreement 
I have read the protocol specified below. In my formal capacity as Principal Investigator, my 
duties include ensuring the safety of the study patients enrolled under my supervision and 
providing Allakos Inc. with complete and timely information, as outlined in the protocol. It is 
understood that all information pertaining to the study will be held strictly confidential and that 
this confidentiality requirement applies to all study staff at this site. Furthermore, on behalf of 
the study staff and myself, I agree to maintain the procedures required to carry out the study in 
accordance with accepted Good Clinical Practice (GCP) principles and to abide by the terms of 
this protocol. 
Protocol Number: 
AK002-016 
IND: 
135158 
Protocol Title: 
A Phase 3, Multicenter, Randomized, Double-Blind, Placebo-Controlled 
Study to Evaluate the Efficacy and Safety of AK002 in Patients with 
Moderately to Severely Active Eosinophilic Gastritis and/or Eosinophilic 
Duodenitis (formerly referred to as Eosinophilic Gastroenteritis) Who 
Have an Inadequate Response with, Lost Response to, or Were Intolerant 
to Standard Therapies 
Original Protocol: 
30 September 2019 
Amendment 1:  
18 March 2020 
Amendment 2:  
07 August 2020 
Amendment 3:  
20 April 2021 
Amendment 4:  
26 October 2021 
 
Investigator Printed Name: _____________________________________________ 
 
Investigator Signature: 
_____________________________________________ 
 
Date: 
_____________________________________________ 

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 3 of 127 
Confidential 
Table of Contents 
Clinical Research Protocol AK002-016 ........................................................................................1 
Investigator Protocol Agreement..................................................................................................2 
Table of Contents ...........................................................................................................................3 
List of Tables ..........................................................................................................................9 
List of Abbreviations ............................................................................................................10 
1. 
Protocol Synopsis ................................................................................................................14 
2. 
Background .........................................................................................................................28 
2.1 
Siglec-8 and AK002 .................................................................................................28 
2.2 
Overview of Nonclinical Studies .............................................................................28 
2.3 
Overview of Clinical Studies ...................................................................................29 
2.4 
Eosinophilic Gastrointestinal Disorders ...................................................................31 
3. 
Rationale for Study and Dose Selection ...........................................................................32 
4. 
Study Objectives .................................................................................................................33 
4.1 
Primary Objective ....................................................................................................33 
4.2 
Secondary Objectives ...............................................................................................33 
4.3 
Exploratory Objectives .............................................................................................34 
4.4 
Safety Objectives ......................................................................................................34 
4.5 
Target of Estimation .................................................................................................34 
4.5.1 
Population Targeted by the Scientific Question ........................................35 
4.5.2 
Variables of Interest (or Endpoint) Required to Address the Scientific 
Question .....................................................................................................35 
4.5.3 
Treatment ...................................................................................................35 
4.5.4 
Intercurrent Events .....................................................................................35 
4.5.5 
Strategy for Handling Intercurrent Events .................................................35 
4.5.6 
Summary Measures ....................................................................................36 
5. 
Study Design .......................................................................................................................36 
5.1 
Study Overview ........................................................................................................36 

 
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5.2 
Schedule of Events ...................................................................................................38 
6. 
Criteria for Evaluation ......................................................................................................44 
6.1 
Safety Endpoints ......................................................................................................44 
6.2 
Pharmacokinetic Endpoints ......................................................................................44 
6.3 
Efficacy Endpoints ...................................................................................................44 
6.3.1 
Primary Efficacy Endpoints .......................................................................44 
6.3.2 
Secondary Efficacy Endpoints ...................................................................45 
6.3.3 
Exploratory Efficacy Endpoints .................................................................45 
7. 
Patient Selection .................................................................................................................46 
7.1 
Number of Patients ...................................................................................................46 
7.2 
Study Population ......................................................................................................46 
7.3 
Inclusion Criteria ......................................................................................................46 
7.4 
Exclusion Criteria .....................................................................................................47 
7.5 
Safety Evaluations ....................................................................................................49 
8. 
Prior and Concurrent Medications ..................................................................................49 
8.1 
Prohibited Medications ............................................................................................50 
8.2 
Allowed Medications ...............................................................................................50 
9. 
Study Treatment .................................................................................................................51 
9.1 
Formulation of Test Product and Placebo ................................................................51 
9.2 
Study Drug Packaging and Labeling ........................................................................51 
9.3 
Supply of Study Drug to the Investigational Site .....................................................51 
9.4 
Study Drug Dosage/Dosage Regimen ......................................................................51 
9.5 
Preparation of Study Drug ........................................................................................52 
9.6 
Study Drug Administration ......................................................................................52 
9.7 
Study Drug Storage ..................................................................................................53 
9.8 
Study Drug Accountability .......................................................................................53 
10. 
Patient Numbering, Stratification, Randomization, and Blinding ................................53 
10.1 
Patient Numbering ....................................................................................................53 

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 5  of 1 2 7  
C o nfi d e nti al  
1 0. 2  
Strat ificati o n a n d Ra n d o mizati o n .............................................................................5 4  
1 0. 3  
Bli n di n g  ....................................................................................................................5 5  
1 0. 4  
Brea ki n g t he Bli n d  ...................................................................................................5 6  
1 1.  
St u d y Pr oce d ures a n d G ui deli nes  .....................................................................................5 6  
1 1. 1  
Dietar y a n d Lif est yl e Restricti o ns  ............................................................................5 7  
1 1. 2  
P har mac o d y na mic/ Efficac y -R elate d Pr oce d ures  .....................................................5 7  
1 1. 2. 1  
E G/ E o D P R O Q uesti o n naire ......................................................................5 7  
1 1. 2. 2  
 ..................................................................................5 7  
1 1. 2. 3  
 
1 1. 2. 4  
Es o p ha g o -Gastr o -D u o de n osc o p y wit h Bi o ps y  ..........................................5 8  
1 1. 2. 5  
C o m plete Bl o o d C o u nt wit h Differe ntial  ...................................................5 9  
1 1. 2. 6  
Baseli ne Diet Assess me nt  ..........................................................................5 9  
1 1. 2. 7  
Pre vi o us Treat me nts Re vie w  .....................................................................5 9  
1 1. 3  
Safet y -R elate d Pr oce d ures  .......................................................................................6 0  
1 1. 3. 1  
C o nc o mita nt Me dicati o ns  ..........................................................................6 0  
1 1 . 3. 2 
C o m plete P h ysi cal E x a mi nati o n  ................................................................6 0  
1 1. 3. 3  
B o d y Wei g ht a n d Hei g ht  ...........................................................................6 0  
1 1. 3. 4  
St o ol Sa m ple f or O va a n d Parasite  ............................................................6 0  
1 1. 3. 5  
S y m pt o m -Direct e d P h ysi cal E x a mi nati o n  .................................................6 1  
1 1. 3. 6  
Electr ocar di o gra m  ......................................................................................6 1  
1 1. 3. 7  
Vital Si g ns  ..................................................................................................6 1  
1 1. 4  
Cli nical La b orat or y Meas ure me nts  ..........................................................................6 1  
1 1. 5  
Bl o o d C he mistr y Pr ofile  ...........................................................................................6 2  
1 1. 5. 1  
Pre g n a nc y T est a n d F olli cle -Sti m ulati n g H or m o ne  ...................................6 3  
1 1. 5. 2  
Uri nal ysis  ...................................................................................................6 3  
1 1. 5. 3  
Ser ol o g y  .....................................................................................................6 3  
1 1. 5. 4  
A nti -A K 0 0 2 A nti b o dies  .............................................................................6 4  
1 1. 5. 5  
Bl o o d f or P har m ac o ki netics a n d St ora ge  ...................................................6 4  
1 1. 5. 6  
Bl o o d f or Hista mi ne a n d Tr y pt ase  .............................................................6 4  
C CI
C CI

 
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Amendment 4 
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11.5.7 
Blood for IgE .............................................................................................64 
11.5.8 
Blood for Strongyloides stercoralis ...........................................................64 
11.5.9 
COVID-19 Testing.....................................................................................65 
11.5.10 Concurrent Screening between AK002-014 and AK002-016 ...................65 
11.5.11 Screening Procedures in AK002-014 Used for AK002-016 Eligibility ....65 
12. 
Evaluations and Procedures by Visit ................................................................................66 
12.1 
Screening Period ......................................................................................................66 
12.2 
Prior to Day 1 ...........................................................................................................67 
12.3 
Day 1 – Randomization/Infusion 1 ..........................................................................68 
12.4 
Day 7 (not a Clinic Visit) .........................................................................................69 
12.5 
Day 8 (±2) ................................................................................................................69 
12.6 
Day 15 (±2) ..............................................................................................................69 
12.7 
Day 28 (not a Clinic Visit) .......................................................................................69 
12.8 
Day 29 (±3) – Infusion 2 ..........................................................................................70 
12.9 
Day 57 (±3) –  Infusion 3 .........................................................................................71 
12.10 Day 85 (±3) – Infusion 4 ..........................................................................................72 
12.11 Day 113 (±3) – Infusion 5 ........................................................................................73 
12.12 Day 141 (±3) – Infusion 6 ........................................................................................74 
12.13 Day 169 (±3) or 28 (±3) Days after Last Dose of Study Drug if ET – 
Follow-up EGD ........................................................................................................75 
12.14 Day 176 (±3) or 35 (±3) Days after Last Dose of Study Drug if ET – 
Follow-up Visit 1 .....................................................................................................76 
12.15 Day 197 (±3) or 56 (±3) Days after Last Dose of Study Drug if ET – 
Follow-up Visit 2 .....................................................................................................77 
12.16 Day 225 (±3) or 84 (±3) Days after Last Dose of Study Drug if ET .......................78 
13. 
Adverse Event Reporting and Documentation ................................................................78 
13.1 
Adverse Events .........................................................................................................78 
13.2 
Serious Adverse Events ............................................................................................79 
13.3 
Adverse Events of Special Interest ...........................................................................80 

 
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13.4 
Infusion-Related Reactions ......................................................................................80 
13.5 
Anaphylaxis ..............................................................................................................81 
13.6 
Evaluating Adverse Events and Serious Adverse Events ........................................81 
13.6.1 
Establishing Diagnosis ...............................................................................81 
13.6.2 
Assessment of Intensity .............................................................................82 
13.6.3 
Assessment of Causality to Study Drug.....................................................82 
13.6.4 
Assessment of Causality to Study Procedure.............................................83 
13.6.5 
Action Taken ..............................................................................................84 
13.6.6 
Assessment of Outcome .............................................................................84 
13.7 
Adverse Event Reporting Procedures.......................................................................84 
13.7.1 
All Adverse Events ....................................................................................84 
13.7.2 
Serious Adverse Event Reporting ..............................................................84 
13.7.3 
Pregnancy Reporting ..................................................................................86 
13.7.4 
AESI Reporting ..........................................................................................86 
13.8 
Medical Monitoring ..................................................................................................87 
13.9 
Independent Data Monitoring Committee ................................................................87 
13.10 Study Withdrawal Criteria .......................................................................................87 
13.11 Study Stopping Rules ...............................................................................................87 
14. 
Discontinuation and Replacement of Patients .................................................................88 
14.1 
Definition of Study Completion ...............................................................................88 
14.2 
Early Discontinuation of Study Drug .......................................................................88 
15. 
Statistical Methods and General Considerations ............................................................89 
15.1 
Sample Size ..............................................................................................................89 
15.2 
Analysis Populations ................................................................................................89 
15.3 
Patient Disposition ...................................................................................................90 
15.4 
Demographic and Baseline Characteristics ..............................................................90 
15.5 
Study Drug Exposure ...............................................................................................90 
15.6 
Efficacy Analysis .....................................................................................................90 

 
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15.6.1 
Primary Efficacy Endpoint Analysis .........................................................90 
15.6.2 
Secondary Efficacy Endpoint Analysis .....................................................91 
15.6.3 
Exploratory Analysis .................................................................................92 
15.7 
Safety Analysis .........................................................................................................93 
15.7.1 
Treatment Emergent Adverse Events ........................................................93 
15.7.2 
Anti-Drug Antibodies ................................................................................94 
15.7.3 
Clinical Laboratory Assessments ...............................................................94 
15.7.4 
Vital Signs ..................................................................................................94 
15.7.5 
ECG............................................................................................................94 
15.7.6 
Physical Exam ............................................................................................94 
15.7.7 
Concomitant Medications ..........................................................................94 
15.8 
Patient Confidentiality ..............................................................................................94 
16. 
Data Collection, Retention, and Monitoring ....................................................................95 
16.1 
Data Collection Instruments .....................................................................................95 
16.2 
Data Management Procedures ..................................................................................95 
16.3 
Data Quality Control and Reporting ........................................................................95 
16.4 
Database Lock/Disclosure of Randomization Code .................................................95 
16.5 
Archiving of Data .....................................................................................................96 
16.6 
Availability and Retention of Investigational Records ............................................96 
16.7 
Monitoring ................................................................................................................97 
17. 
Administrative, Ethical, and Regulatory Considerations ...............................................97 
17.1 
Protocol Amendments ..............................................................................................97 
17.2 
Independent Ethics Committees/Institutional Review Boards .................................98 
17.3 
Informed Consent Form ...........................................................................................98 
17.4 
Publications ..............................................................................................................99 
17.5 
Clinical Study Registration ......................................................................................99 
17.6 
Payment to Patients ..................................................................................................99 
17.7 
Investigator Responsibilities ....................................................................................99 

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 9  of 1 2 7  
C o nfi d e nti al  
1 8.  
Refere nces  .........................................................................................................................1 0 1  
1 9.  
A p pe n dices  ........................................................................................................................1 0 3  
1 9. 1  
A p pe n di x 1: P R O Q uesti o n naire  ............................................................................1 0 4  
1 9. 2  
A p pe n di x 2: 
 ...............................................1 0 7  
1 9. 3  
A p pe n di x 3: Baseli ne Di et Assess me nt  .................................................................1 1 3  
1 9. 4  
A p pe n di x 4: C o m m o n Ter mi n ol o g y Criteri a f or A d verse E v e nts v. 5. 0  ...............1 1 4  
1 9. 5  
A p pe n di x 5: E G D Hist ol o g y  ..................................................................................1 1 5  
1 9 . 6 
A p pe n di x 6: Sa m ps o n’s Criteria of A na p h yl a xis  ...................................................1 1 8  
1 9. 7  
A p pe n di x 7: e P R O Teac hi n g T o ol  .........................................................................1 1 9  
1 9. 8  
A p pe n di x 8: 
 
1 9. 9  
A p pe n di x 9: 
 
1 9. 1 0  A p pe n di x 1 0: A d diti o nal Q uesti o ns f or At o pic C o n diti o ns  ...................................1 2 5  
1 9. 1 1  A p pe n di x 1 1: Pre vi o us Treat me nts Re vie w  ...........................................................1 2 6  
1 9. 1 2  A p pe n di x 1 2: He patitis B a n d He patitis C Ser ol o gical Testi n g Details  ................1 2 7  
1 9. 1 2. 1  He patitis B Testi n g  ..................................................................................1 2 7  
1 9. 1 2. 2  He patitis C Testi n g  ..................................................................................1 2 7  
 
 
 
List of T a bles  
Ta ble 1  
Sc he d ule of Assess me nts  ............................................................................................3 9  
Ta ble 2  
A d verse E v e nt Se verit y per C T C A E  ..........................................................................8 2  
Ta ble 3  
A d verse E v e nt Relati o ns hi p t o St u d y Dr u g  ................................................................8 3  
Ta ble 4  
A d verse E v e nt Relati o ns hi p t o St u d y Pr oce d ure  ........................................................8 3  
Ta ble 5  
He patitis B Refle x Testi n g  ........................................................................................1 2 7  
Ta ble 6  
He patitis C Refle x Testi n g  ........................................................................................1 2 7  
C CI
C CI
C CI

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 10 of 127 
Confidential 
List of Abbreviations 
AC 
Allergic conjunctivitis 
ADA 
Anti-drug-antibody 
ADCC 
Antibody-dependent cellular cytotoxicity 
ADL 
Activities of daily living 
AE 
Adverse event(s) 
AESI 
Adverse event(s) of special interest 
ALT 
Alanine aminotransferase 
ANCOVA 
Analysis of covariance 
AST 
Aspartate aminotransferase 
ATC 
Anatomical Therapeutic Chemical Classification System 
BMI 
Body mass index  
CBC 
Complete blood count 
CDC 
Complement-dependent cytotoxicity 
CDF 
Cumulative distribution function 
CFR 
Code of Federal Regulation 
CI 
Confidence interval 
cm 
Centimeter 
CMH 
Cochran-Mantel-Haenszel (test) 
COVID-19 
Coronavirus disease of 2019 
CS 
Clinically significant 
CTCAE 
Common Terminology Criteria for Adverse Events  
CU 
Chronic Urticaria 
eCDF 
empirical Cumulative Distribution Function 
ECG 
Electrocardiogram(s) 
eCRF 
Electronic Case Report Form 
EG 
Eosinophilic gastritis 
EGD 
Esophago-gastro-duodenoscopy 
EGID 
Eosinophilic gastrointestinal disorders 
EGPA 
Eosinophilic granulomatosis with polyangiitis  
ELISA 
Enzyme-linked immunosorbent assay 
EoD 
Eosinophilic duodenitis (formerly referred to as eosinophilic gastroenteritis) 
EoE 
Eosinophilic esophagitis 

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 11 of 127 
Confidential 
EOS 
End of study 
ET 
Early Termination 
FDA 
Food and Drug Administration 
FSH 
Follicle-stimulating hormone 
GCP 
Good Clinical Practice 
GGT 
Gamma-glutamyl transferase 
GI 
Gastrointestinal 
GLP 
Good Laboratory Practice 
hCG 
human Chorionic Gonadotropin 
HEENT 
Head, eyes, ears, nose, and throat 
HES 
Hypereosinophilic Syndrome (HES) 
HIPAA 
Health Insurance Portability and Accountability Act 
hpf 
High power field 
ICE 
Intercurrent events 
ICF 
Informed consent form 
ICH 
International Conference on Harmonisation 
iDMC 
Independent Data Monitoring Committee 
IEC 
Independent Ethics Committee 
IgE 
Immunoglobulin E 
IgG1 
Immunoglobulin G1 
IND 
Investigational New Drug (application) 
IP 
Investigational product 
IRB 
Institutional Review Board 
IRR 
Infusion-Related Reaction 
IRT 
Interactive Response Technology 
ISM 
Indolent systemic mastocytosis 
ITIM 
Immunoreceptor Tyrosine-based inhibitory motif 
ITT 
Intent to treat 
IV 
Intravenous 
kg 
Kilogram 
LLN 
Lower limit of normal 
LSM 
Least squares mean 
MAR 
Missing at random  

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 1 2  of 1 2 7  
C o nfi d e nti al  
M C S  
Me ntal c o m p o ne nt sc ore  
Me d D R A  
Me dical Dicti o nar y f or Re g ul at or y Acti vities  
m g  
Milli gra m  
MI  
M ulti ple i m p utati o n  
MI T T  
M o difie d I nte nti o n -t o-Treat  
m L  
Milliliter  
m M  
Milli m olar  
M M R M  
Mi xe d m o del f or re p eate d me as ures  
M N A R  
Missi n g n ot at ra n d o m  
M T D  
Ma xi m u m t olerate d d ose  
Na Cl  
S o di u m c hl ori de  
N CI  
Nati o nal Ca ncer I nstit ute  
N C S  
N ot cli nicall y si g nifica nt  
N O A E L  
N o -o bser ve d -a d verse -effect le vel  
O & P  
O va a n d P arasite (test)  
O R  
O d ds rati o  
O T C  
O ver T he C o u nter  
P C P  
Pri mar y care p h ysicia n  
P C S  
P h ysical c o m p o ne nt sc ore  
P D  
P har mac o d y na mics  
P D F  
Pr o ba bilit y distri b uti o n f u ncti o n  
P E  
P h ysical e xa mi nati o n  
P E F  
P ea k e x pirat or y fl o w  
 
 
 
  
PI D  
P atie nt i de ntificati o n n u m ber 
P K  
P har mac o ki netic(s)  
P P  
P er Pr ot oc ol  
P PI  
Pr ot o n p u m p i n hi bit or  
P R O  
P atie nt re p orte d o utc o me  
S A E  
Seri o us a d verse e ve nt (s) 
S A P  
Statistical A nal ysis Pla n  
S D  
Sta n dar d De viati o n  
C CI
C CI

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 1 3  of 1 2 7  
C o nfi d e nti al  
S E  
Sta n dar d err or  
 
 
Si glec  
Sialic aci d -bi n di n g, i m m u n o gl o b uli n -li ke lecti n 
S O C  
S yste m or ga n class  
T E A E  
Treat me nt -e mer ge nt a d verse e ve nt (s) 
T E A E SI  
Treat me nt -e mer ge nt a d verse e ve nt (s) of si g nifica nt i nterest  
T N F  
T u m or necr osis fact or  
T S S  
T otal S y m pt o m Sc ore  
U B T  
Urea Breat h T est  
U L N  
U p per li mit of n or mal  
U S P  
U nite d States P har mac o peia  
W H O D D  
W orl d Healt h Or ga nizati o n Dr u g Dicti o nar y  
w/ v  
W ei g ht/ v ol u me  
C CI

 
Protocol AK002-016 
Amendment 4 
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Page 14 of 127 
Confidential 
1. 
Protocol Synopsis 
Study Title 
A Phase 3, Multicenter, Randomized, Double-Blind, Placebo-Controlled Study to 
Evaluate the Efficacy and Safety of AK002 in Patients with Moderately to 
Severely Active Eosinophilic Gastritis and/or Eosinophilic Duodenitis (formerly 
referred to as Eosinophilic Gastroenteritis) Who Have an Inadequate Response 
With, Lost Response to, or Were Intolerant to Standard Therapies 
Sponsor 
Allakos Inc., 975 Island Drive, Suite 201, Redwood City, CA 94065 USA 
Number of Sites 
Approximately 60 clinical centers  
Nonclinical 
Background  
AK002 is a humanized non-fucosylated immunoglobulin G1 (IgG1) monoclonal 
antibody directed against Siglec-8, a member of the CD33-related family of sialic 
acid-binding, immunoglobulin-like lectins (Siglecs).  
Siglec-8 has a restricted tissue distribution, expressed selectively on the surface of 
mature eosinophils and mast cells, but not in early precursors of these cell 
populations. In blood, binding of AK002 to Siglec-8 induces antibody-dependent 
cellular cytotoxicity (ADCC) against eosinophils, leading to rapid and sustained 
depletion of these cells from the circulation. In the tissue, AK002 induces direct 
apoptosis of eosinophils and inhibition of mast cells.  
Clinical 
Background 
AK002, administered as an intravenous infusion, has been previously tested in 
healthy volunteers and in patients with indolent systemic mastocytosis (ISM), 
chronic urticaria (CU), severe allergic conjunctivitis (AC), mast cell gastritis, and 
eosinophilic gastritis (EG) and/or eosinophilic duodenitis (EoD), which was 
referred to as eosinophilic gastroenteritis (EGE) in previous studies. Multiple 
doses of 3 mg/kg have been given to patients with ISM, CU, AC, EG, and/or EoD. 
In these studies, patients reported improvements in disease symptoms, with 
AK002 pharmacodynamic (PD) activity being observed for prolonged periods of 
time and pharmacokinetic (PK) parameters demonstrating a half-life amenable to 
administration every 4 weeks.  
To date, healthy volunteers and patients with ISM, CU, severe AC, EG/EoD, EoE, 
and mast cell gastritis have been enrolled in clinical studies. In general, AK002 has 
been well tolerated. The most common treatment-emergent adverse events (TEAE) 
observed were infusion-related reaction (IRR). Most IRR were mild to moderate 
and resolved on their own, with no treatment required; IRR that were serious 
resolved within approximately 24 hours. Transient lymphopenia was observed 
after infusion of AK002 but was not associated with any clinical consequence, and 
lymphocytes recovered within 24 hours. A sustained depletion of eosinophils was 
observed that is consistent with the mechanism of action of AK002.  
In the randomized, double-blind, placebo-controlled, Phase 2 study of AK002 in 
65 patients with EG and/or EoD, patients were randomized to receive monthly 
doses of placebo, low dose AK002 (0.3, 1, 1, and 1 mg/kg), or high dose AK002 
(0.3, 1, 3, and 3 mg/kg) in a 1:1:1 ratio.  

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 15 of 127 
Confidential 
Clinical 
Background cont. 
All primary and secondary endpoints were met in the study. There was a 97% and 
92% mean reduction in eosinophils in the stomach/duodenum at the high and low 
doses, respectively, versus 10% increase for patients on placebo (p<0.0001).  
The reduction of eosinophils was associated with a statistically significant 
reduction in total symptom score on 8 items (TSS8) of 58% in the high dose group 
and 49% in the low dose group versus 24% reduction in placebo (p=0.0012 and 
p=0.015, respectively). Improvement in symptoms was observed within 24 hours 
of the first dose of study drug. In addition, 70% of high dose treated patients and 
68% of low dose treated patients were treatment responders (defined as >30% 
improvement in TSS and >75% reduction from baseline in tissue eosinophils) 
versus 5% for placebo treated patients (p<0.0001).  
Approximately 40% of patients had concomitant eosinophilic esophagitis (EoE). 
In those patients, a mean reduction of 95% of eosinophils/high powered field (hpf) 
in esophageal biopsies for AK002 was observed versus no change for placebo. 
Also, 13 of 14 AK002-treated patients (93%) were histologic responders as 
defined by ≤6 eosinophils/hpf versus 1 of 9 placebo-treated patients (11%). 
Dysphagia improved by 53% in AK002-treated patients versus 17% in 
placebo-treated patients.  
More than 90% of patients in the Phase 2 study elected to continue into a 
long-term extension study (AK002-003X). In that study, a starting dose of 1 mg/kg 
was followed by doses of 3 mg/kg. Premedication of 80 mg oral prednisone was 
administered the day before the first and second doses. Using this premedication 
regimen, no IRR were reported on the first infusion of AK002 in the extension 
study. 
Target Disease 
Background and 
Rationale  
EG and/or EoD (previously referred to as EGE) represent what are traditionally 
believed to be rare types of eosinophilic gastrointestinal disorders (EGID) that are 
characterized by chronic, often severe inflammation due to patchy or diffuse 
infiltration of eosinophils into layers of the stomach, small intestine, or both 
(Prussin, 2014; Reed, 2015; Zhang, 2017).  
The diagnosis is based on clinical presentation (gastrointestinal symptoms) 
combined with increased tissue eosinophils in biopsy specimens from the stomach 
and/or duodenum without any other cause for the eosinophilia. Involvement of the 
small intestine is typically assessed by performing duodenal biopsies using an 
esophago-gastro-duodenoscopy (EGD) and has been referred to as eosinophilic 
gastroenteritis or eosinophilic enteritis though eosinophilic duodenitis (EoD) is 
more appropriate.  
The gastrointestinal symptoms are believed to be due to the release of 
inflammatory mediators from activated eosinophils, and likely mast cells. 
Symptoms that are often severe and debilitating commonly include abdominal 
pain, nausea, bloating, early satiety, fullness before finishing a meal, abdominal  

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 1 6  of 1 2 7  
C o nfi d e nti al  
T ar get Dise ase 
B ac k gr o u n d a n d 
R ati o n ale c o nt.  
cra m pi n g, v o miti n g, diarr hea, a n d wei g ht l oss ( Al h m o u d, 2 0 1 6 ; L o pez -Me di na, 
2 0 1 5 ; Ma ns o or, 2 0 1 7 ; Ree d, 2 0 1 5 ). J e nse n (2 0 1 6 ) esti mate d t he pre vale nce of E G 
a n d E o D t o be 6. 3/ 1 0 0, 0 0 0 a n d 8. 4/ 1 0 0, 0 0 0, res pecti vel y (f or patie nts fr o m 1  t o 
6 4  years of a ge). Ma ns o or ( 2 0 1 7 ) esti mate d t he o verall pre vale nce of E G t o be 
5. 1/ 1 0 0, 0 0 0  pers o ns.  
Patie nts ma y als o ha ve c o nc o mita nt at o pic diseases li ke f o o d aller g y, ast h ma 
a n d at o pic der matitis, w hic h f urt her i m pacts q ualit y of life a n d c o ntri b utes t o 
healt h care c osts. A d diti o nall y, 8 % t o 1 0 % of patie nts ha ve c o nc o mita nt E o E 
(J e nse n, 2 0 1 6).  
T here are n o F D A -a p pr o ve d treat me nts f or E G or E o D. C urre nt t hera pies a n d 
disease ma na ge me nt i ncl u des dietar y restricti o n/eli mi nati o n, pr ot o n p u m p 
i n hi bit ors ( P PI), a nti hista mines, s yste mic or s wall o we d c ortic oster oi ds, a n d 
occasi o nal off -la bel use of i m m u n o m o d ulat or y bi ol o gics (Pr ussi n, 2 0 1 4 ; 
Ree d,  2 0 1 5 ; Z ha n g,  2 0 1 7 ).  
Pr ot o n p u m p i n hi bit ors ha ve little t o n o be nefit i n patie nts wit h E G a n d/ or E o D 
des pite re p orts of pr o vi di n g partial be nefit i n s o me patie nts wit h E o E ( Katz,  2 0 1 3 ). 
Restricte d/ele me ntal diets are n ot effecti ve l o n g -ter m treat me nt as t he y re q uire 
strict c o m plia nce a n d, i n t he case of ele me ntal diets, are e x pe nsi ve a n d are ofte n 
n ot rei m b urse d b y i ns ura nce. I n a d diti o n, c o m plia nce is ver y p o or a n d patie nt 
q ualit y of life is greatl y i m pacte d ( Be dell, 2 0 1 8 ; Peters o n, 2 0 1 3 ; Wec hsler, 2 0 1 4 ). 
C ortic oster oi ds, s yste mic or t o pical, ha ve bee n s h o w n t o pr o vi de s y m pt o m relief 
b ut are n ot a p pr o priate f or l o n g -ter m treat me nt d ue t o n u mer o us si de effects a n d 
ass ociate d ris ks i ncl u di n g a dre nal i ns uffici e nc y, b o ne de mi neralizati o n, i ncrease d 
c ha nce of i nfecti o n, oste o p or osis, be ha vi oral iss ues, a n d wei g ht gai n.  
B y mar ke dl y re d uci n g t he n u m ber of bl o o d a n d tiss ue e osi n o p hils a n d i n hi biti n g 
t he acti vati o n of mast cells, A K 0 0 2 ma y be usef ul i n t he treat me nt of patie nts wit h 
E G a n d/ or E o D. T his pre mise is s u p p orte d b y t he P hase 2 data wit h A K 0 0 2 t hat 
s h o ws si g nifica nt i m pr o ve me nts i n hist ol o g y a n d s y m pt o ms i n t hese patie nts.  
Gi ve n t here are n o a p pr o ve d t hera pies f or t hese c hr o nic a n d de bilitati n g diseases, 
bet ter treat me nt o pti o ns are clearl y nee de d t o ma na ge E G a n d E o D. 
R ati o n ale f or 
D ose  Selecti o n  
Base d o n e x perie nce wit h A K 0 0 2 i n healt h y v ol u nteers a n d i n patie nts wit h I S M, 
C U, se vere A C, a n d E G/ E o D, t he pr o p ose d A K 0 0 2 d ose re gi me n of 6 t otal d oses 
is 1 m g/k g f or t he first i nf usi o n, f oll o we d b y 5 d oses of 3 m g/ k g A K 0 0 2, 
a d mi nistere d e ver y 4 wee ks.  
C CI

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 1 7  of 1 2 7  
C o nfi d e nti al  
R ati o n ale f or 
D ose  Selecti o n 
c o nt. 
N u m ber of P atie nts  A p pr o xi matel y  1 6 0 patie nts wit h s y m pt o matic E G a n d/ or E o D will be ra n d o mize d 
1: 1 t o recei ve 1 of 2 d ose re gi me ns i n a d o u ble -bli n d fas hi o n:  
 
6 d oses of place b o  
 
A K 0 0 2 at 1 m g/ k g f or t he first d ose f oll o we d b y 3 m g/ k g a d mi nistere d e ver y 
4  wee ks f or 5 s u bse q ue nt d oses.  
T he  rati o nale f or t he n u m ber of patie nts is descri be d u n der Statistical A nal ysis. 
A p pr o xi matel y  9 0 patie nts wit h E G ± E o D will be e nr olle d, a n d a p pr o xi matel y 
7 0  patie nts wit h E o D wit h o ut E G will be e nr olle d.  
St u d y Desi g n  
T his is a P hase 3, m ultice nter, ra n d o mize d, d o u ble-bli n d, place b o -c o ntr olle d st u d y 
t o e val uate t he efficac y a n d safet y of A K 0 0 2 i n patie nts wit h E G a n d/ or E o D w h o 
ha ve a n i na de q uate res p o nse wit h, l ost res p o nse t o, or were i nt olera nt t o sta n dar d 
t hera pies. 
Patie nts e nr olle d i n t he st u d y will recei ve 6 i nf usi o ns of place b o or A K 0 0 2 
a d mi nistere d e ver y 4 wee ks a n d will be f oll o we d f or 1 2 wee ks after t he last d ose 
u nless patie nts elect t o e nter t he o pti o nal l o n g -ter m e xte nsi o n st u d y 
( A K 0 0 2-0 1 6 X).  
Patie nts will be c o nse nte d a n d t he n scree ne d f or u p t o 4 5 da ys pri or t o Da y 1. 
Patie nts w h o meet all eli gi bilit y criteria ca n be e nr olle d i nt o t he st u d y. Patie nts 
w h o d o n ot meet all eli gi bilit y criteria at scree ni n g, or w h o q ualif y at scree ni n g b ut 
are n ot e nr olle d, ma y be assi g ne d a ne w patie nt i de ntificati o n n u m ber a n d 
rescree ne d o nce. Patie nts rescree ne d wit hi n 3 0 da ys of si g ni n g t he i nitial c o nse nt 
will n ot nee d t o si g n a ne w i nf or me d c o nse nt f or m (I C F) if n o c ha n ges ha ve bee n 
ma de t o t he I C F.  
T he st u d y is desi g ne d as f oll o ws:  
 
A n 1 8 t o 4 5 -da y scr ee ni n g peri o d wit h baseli ne e val uati o ns f or st u d y 
eli gi bilit y, i ncl u di n g acti ve s y m pt o ms of disease ( gat here d b y t he patie nt 
re p orte d o utc o me [ P R O] q uesti o n naire c o m plete d d uri n g scree ni n g) a n d E G D 
wit h bi o ps y.  
C CI

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Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 2 0  of 1 2 7  
C o nfi d e nti al  
Sec o n d ar y 
O bjecti ves c o nt.  
 
Pr o p orti o n of treat me nt res p o n ders at Wee k 2 4. A res p o n der is defi ne d as 
> 3 0 % i m pr o ve me nt i n T S S a n d  mea n e osi n o p hil c o u nt ≤4 cells/ h pf i n 
5  hi g hest gastric h pf a n d/ or mea n e osi n o p hil c o u nt ≤1 5 cells/ h pf i n 3 hi g hest 
d u o de nal h pf.  
 
Pr o p orti o n of patie nts w h o ac hie ve ≥5 0 % re d ucti o n i n T S S fr o m Baseli ne t o 
Wee ks 2 3 – 2 4.  
 
Pr o p orti o n of patie nts w h o ac hie ve ≥7 0 % re d ucti o n i n T S S fr o m Baseli ne t o 
Wee k s 2 3– 2 4.  
 
C ha n ge i n wee kl y T S S o ver ti me.  
E x pl or at or y 
O bjecti ves  
T o e val uate t he effect of A K 0 0 2 b y c o m pari n g A K 0 0 2 t o place b o treat me nt f or t he 
f oll o wi n g para meters:  
 
C ha n ge fr o m Baseli ne i n 
 o ver ti me. 
 
C ha n ge fr o m Baseli ne i n 
 o ver ti me. 
 
F or patie nts wit h 
 
): Pr o p orti o n of patie nts 
ac hie vi n g a 
 at 
Wee k 2 4.  
 
C ha n ge fr o m Baseli ne i n 
 o ver ti me. 
St u d y P o p ul ati o n  
A d ult male a n d fe male patie nts wit h m o derate t o se vere E G a n d/ or E o D wit h 
i na de q uate or l oss of res p o nse t o, or i nt olera nce t o sta n dar d t hera pies. 
P atie nt Selecti o n 
Criteri a  
I ncl usi o n Criteri a 
Patie nts are eli gi ble t o e nr oll i n t he st u d y if all of t he f oll o wi n g criteria are met:  
1)  
Pr o vi de writte n i nf or me d c o nse nt.  
2)  
Male or fe male a ge d ≥1 8 a n d ≤8 0 years at t he ti me of si g ni n g t he i nf or me d 
c o nse nt f or e ntr y.  
3)  
Baseli ne e n d osc o pic bi o ps y wit h ≥3 0 e osi n o p hils/ h pf i n 5 h pf i n t he st o mac h 
a n d/ or ≥3 0 e osi n o p hils/ h pf i n 3 h pf i n t he d u o de n u m, as deter mi ne d b y 
ce ntral hist ol o g y assess me nt of bi o psies c ollecte d d uri n g t he scree ni n g E G D, 
wit h o ut a n y ot her si g nifica nt ca use f or t he e osi n o p hilia.  
 
Pri or E G D ma y be use d f or eli gi bilit y as l o n g as t he E G D occ urre d wit hi n 
3 0  da ys of t he first scree ni n g visit f or t he A K 0 0 2 -0 1 6 st u d y a n d was 
perf or me d a n d ce ntrall y assesse d as f or t he A K 0 0 2 -0 1 6 st u d y.  
4)  
C o m pleti o n of at least 4 dail y P R O q uesti o n naires per we e k f or a mi ni m u m of 
3 wee ks d uri n g scree ni n g.  
 
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Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 21 of 127 
Confidential 
Patient Selection 
Criteria cont. 
Inclusion Criteria cont. 
5) 
A weekly average score of abdominal pain, nausea, or diarrhea ≥3 on the 
PRO questionnaire (score from 0–10) and a weekly average TSS of ≥10 for at 
least 2 weeks of screening. 
6) 
Patients with inadequate or loss of response to, or who were intolerant to 
standard therapies for EG/EoD symptoms, which could include PPI, 
antihistamines, systemic or topical corticosteroids, and/or diet, among others. 
7) 
If patient is on pre-existing dietary restrictions, willingness to maintain 
dietary restrictions throughout the study. 
8) 
Willing and able to comply with all study procedures and visit schedule 
including follow-up visits. 
9) 
Female patients must be either post-menopausal for at least 1 year with FSH 
level >30 mIU/mL at screening or surgically sterile (tubal ligation, 
hysterectomy, or bilateral oophorectomy) for at least 3 months, or if of 
childbearing potential, have a negative pregnancy test and agree to use dual 
methods of contraception, or abstain from sexual activity from screening until 
the end of the study, or for 120 days following the last dose of study drug, 
whichever is longer. 
 
Male patients with female partners of childbearing potential must agree to use 
a highly effective method of contraception from screening until the end of the 
study or for 120 days following the last dose of study drug, whichever is 
longer. All fertile men with female partners of childbearing potential should 
be instructed to contact the Investigator immediately if they suspect their 
partner might be pregnant (e.g., missed or later menstrual period) at any time 
during study participation. 
Exclusion Criteria 
Patients will be excluded from the study if they meet any of the following criteria: 
1) 
Use of systemic or topical corticosteroids exceeding the equivalent of 
10 mg/day of prednisone within 4 weeks prior to the screening visit. 
2) 
Change in the dose of corticosteroids (systemic or topical), PPI, leukotrienes, 
or diet therapy within 4 weeks prior to the screening visit. 
3) 
Treatment with any immunosuppressive or immunomodulatory drugs that 
may interfere with the study within 12 weeks prior to the screening visit. 
4) 
Prior exposure to AK002 or known hypersensitivity to any constituent of the 
study drug. 
5) 
Active Helicobacter pylori infection, unless treated and confirmed to be 
negative prior to randomization and histology per repeat EGD and symptoms 
still qualify for enrollment after treatment.  

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 22 of 127 
Confidential 
Patient Selection 
Criteria cont. 
Exclusion Criteria cont. 
6) 
History of inflammatory bowel disease, celiac disease, achalasia, or 
esophageal surgery. 
7) 
History of bleeding disorders and/or esophageal varices considered to be 
clinically significant by the Investigator. 
8) 
Other significant causes of gastric and/or duodenal eosinophilia or 
eosinophilic granulomatosis with polyangiitis (EGPA). 
9) 
Confirmed diagnosis of hypereosinophilic syndrome (HES). 
10) Women who are pregnant, breastfeeding, or planning to become pregnant 
while participating in the study. 
11) Presence of an abnormal laboratory value considered to be clinically 
significant by the Investigator. 
12) Any disease, condition (medical or surgical), or cardiac abnormality, which, 
in the opinion of the Investigator, would place the patient at increased risk. 
13) History of malignancy, except carcinoma in situ, early stage prostate cancer, 
or non-melanoma skin cancers. However, patients with cancers that have been 
in remission for more than 5 years and are considered cured, can be enrolled. 
14) Treatment for a clinically significant helminthic parasitic infection within 
6 months of screening. 
15) Positive helminthic infection on Ova and Parasite (O&P) test.  
16) Seropositive for Strongyloides stercoralis at screening, except for patients 
with past but resolved infection. 
17) Seropositive for HIV or hepatitis at screening, except for vaccinated patients 
or patients with past but resolved hepatitis, at screening. 
18) Vaccination with live attenuated vaccines within 30 days prior to initiation of 
treatment in the study, during the treatment period, or vaccination expected 
within 5 half-lives (4 months) of study drug administration. All types and 
formulations of vaccines (including live attenuated vaccines) authorized by 
FDA or other regulatory authority for the prevention of COVID-19 may be 
administered before, during, or after this study. The vaccine should not be 
administered within 7 days prior to and within 7 days after the administration 
of AK002 so that any side effects caused by either of the 2 medications can 
be more easily determined. 
19) Participation in a concurrent interventional study with the last intervention 
occurring within 30 days prior to study drug administration (or 90 days or 
5 half-lives, whichever is longer, for biologic products). 
 

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 2 3  of 1 2 7  
C o nfi d e nti al  
P atie nt Selecti o n 
Criteri a c o nt.  
E xcl usi o n Criteri a c o nt.  
2 0)  K n o w n hist or y of alc o h ol, dr u g, or ot her s u bsta nce a b use or de pe n de nce t hat 
is c o nsi dere d b y t he I n vesti gat or t o be o n g oi n g a n d cli nicall y si g nifica nt.  
2 1)  A n y ot her reas o n t hat i n t he o pi ni o n of t he I n vesti gat or or t he Me dical 
M o nit or ma kes t he patie nt u ns uita ble f or e nr oll me nt.  
Test P r o d uct,  
D ose, a n d 
A d mi nistr ati o n  
A K 0 0 2 ( 
) a n d place b o are s u p plie d as sterile li q ui ds a n d will be dil ute d 
wit h 0. 9 % Na Cl f or i ntra ve n o us (I V) i njecti o n. T he i njecti o n will be a d mi nistere d 
b y I V i nf usi o n, as s pecifie d i n t he P har mac y Ma n ual.  
A K 0 0 2 a n d place b o are f or m ulate d i n 
 
 p H 6. 0, i n Water f or I nj ecti o n 
( W FI). 
A K 0 0 2 at a d ose of 1  m g/ k g or place b o will be pre pare d acc or di n g t o t he patie nt’s 
b o d y wei g ht a n d a d mi nistere d o n Da y 1. S u bse q ue nt  i nf usi o ns of A K 0 0 2 at a d ose 
of 3 m g/ k g or place b o acc or di n g t o t he patie nt’s b o d y wei g ht will be a d mi nistere d 
o n Da y  2 9 ( ± 3), Da y 5 7 ( ± 3), Da y 8 5 ( ± 3), Da y 1 1 3 ( ± 3), a n d Da y 1 4 1 ( ± 3).  
Pri or t o t he first i nf usi o n of A K 0 0 2 or place b o , patie nts will self -a d mi nister 6 0 m g 
oral pre d nis o ne 1 2 – 2 4 h o urs bef ore  t he pre dicte d start of i nf usi o n. A ster oi d 
pre me dicati o n pri or t o t he start of t he sec o n d t hr o u g h si xt h i nf usi o ns ma y o nl y be 
a d mi nistere d wit h t he writte n a p pr o val of t he Me dical M o nit or.  
T he i nitial i nf usi o n s h o ul d be gi ve n o ver at least a 4-h o ur peri o d, a n d t he sec o n d 
i nf usi o n s h o ul d be gi ve n o ver at least a 3-h o ur peri o d. T he t hir d a n d all s u bse q ue nt 
i nf usi o ns s h o ul d be gi ve n o ver at least a 2-h o ur peri o d, de pe n di n g o n t he patie nt’s 
t olera nce of t he pre vi o us i nf usi o ns a n d at t he I n vesti gat or’s discreti o n.  
A n y c ha n ges i n t he i nf usi o n rate sc he d ule d ue t o t olera bilit y will n ot be c o nsi dere d 
de viati o ns fr o m t he pr ot oc ol, as l o n g as t he ma xi m u m i nf usi o n s pee d is n ot 
e xcee de d or i ncrease d be y o n d t he pr ot oc ol s pecifie d li mits.  
All i nf usi o ns m ust be c o m plete d wit hi n 8 h o urs of t he st u d y dr u g bei n g mi xe d 
wit h Na Cl.  
D ur ati o n of 
S u bject 
P artici p ati o n  
T he t otal st u d y d urati o n f or eac h patie nt will be a p pr o xi matel y 8 m o nt hs. T his 
i ncl u des: 
 
A scree ni n g peri o d of  1 8 – 4 5 da ys pri or t o st u d y dr u g a d mi nistrati o n.  
 
A treat me nt peri o d of 2 0 wee ks.  
 
A f oll o w -u p peri o d of 8 4 da ys ( 3) f oll o wi n g  t he last d ose of st u d y dr u g. 
 
Patie nts w h o e nr oll i n t he A K 0 0 2 -0 1 6 X e xte nsi o n st u d y will partici pate i n t he 
A K 0 0 2 -0 1 6 st u d y f or 2 6 – 3 2 wee ks a n d will c o m plete t he st u d y at least 
t hr o u g h t he Da y 1 7 6 visit.  
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Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 2 4  of 1 2 7  
C o nfi d e nti al  
D ur ati o n of 
S u bject 
P artici p ati o n  c o nt. 
 
Patie nts w h o e nr oll i n A K 0 0 2 -0 1 6 X pri or t o Da y 1 9 7 will n ot c o m plete t he 
Da y 1 9 7 or Da y 2 2 5 pr oce d ures u n der Pr ot oc ol A K 0 0 2 -0 1 6.  
 
Patie nts w h o  e nr oll i n A K 0 0 2 -0 1 6 X after Da y 1 9 7 b ut pri or t o Da y 2 2 5 will 
n ot c o m plete t he Da y 2 2 5 pr oce d ures u n der Pr ot oc ol A K 0 0 2 -0 1 6.  
S af et y E v al u ati o ns  Safet y a n d t olera bilit y will be assesse d t hr o u g h o ut t he st u d y b y m o nit ori n g a n d 
e val uati n g A E i ncl u di n g a n y c o m plicati o ns res ulti n g fr o m t he I V i nf usi o n. All 
T E A E will be c ollecte d fr o m t he start of st u d y dr u g a d mi nistrati o n i n A K 0 0 2 -0 1 6 
t hr o u g h t he start of st u d y dr u g a d mi nistrati o n i n A K 0 0 2-0 1 6 X if e nr olli n g i n t he 
A K 0 0 2 -0 1 6 X e xte nsi o n st u d y, Da y 2 2 5 if n ot e n r olli n g i n t he A K 0 0 2-0 1 6 X st u d y, 
or Earl y Ter mi nati o n ( E T).  
Se verit y will be assesse d usi n g t he Nati o nal Ca ncer I nstit ute ( N CI) C o m m o n 
T er mi n ol o g y Criteria f or A d verse E ve nts ( C T C A E) Versi o n 5. 0 ( or m ost c urre nt 
versi o n). All A E will be assi g ne d a se verit y gra de a n d will be assesse d f or cli nical 
si g nifica nce a n d relati o ns hi p t o st u d y dr u g. 
A d diti o nal safet y e val uati o ns i ncl u de cli nical la b orat or y tests, c o m prisi n g 
a nti -dr u g a nti b o d y ( A D A) t o A K 0 0 2, c o m plete bl o o d c o u nts, c he mistries a n d 
uri nal yses, p h ysica l e xa ms ( P E), a n d vital si g ns meas ure me nts. 
T he Me dical M o nit or will re vie w bli n de d safet y data t hr o u g h o ut t he st u d y. Certai n 
safet y data ( p ost-treat me nt cell differe ntials as well as tiss ue e osi n o p hil a n d  
 
) will n ot be pr o vi de d t o st u d y sites or t o t he S p o ns or as it ma y ca use 
bias. T he desi g nate d Safet y M o nit or will re vie w bli n de d safet y data as well as 
p ost -treat me nt cell c o u nts a n d will escalate t o t he Me dical M o nit or as nee de d i n a 
ma n ner t hat d oes n ot ca use bias.  
A n i n de pe n de nt Data M o n it ori n g C o m mittee (i D M C) has bee n c o n ve ne d a n d will 
meet at re g ularl y sc he d ule d i nter vals i n acc or da nce wit h t he i D M C c harter.  
Effic ac y a n d 
P h ar m ac o d y n a mic 
E v al u ati o ns  
Dail y self -a d mi nistrati o n of a disease -s pecific patie nt q uesti o n naire, t he 
E osi n o p hilic  Gastritis/ D u o de nitis P R O will be use d t o e val uate si g ns a n d 
s y m pt o ms ass ociate d wit h E G a n d/ or E o D. Patie nt T S S will be e val uate d, 
ca pt uri n g t he 6 c o m m o n s y m pt o ms of E G/ E o D (a b d o mi nal pai n, na usea, 
a b d o mi nal cra m pi n g, l oss of a p petite, f ull ness bef ore fi n is hi n g a meal [earl y 
satiet y], a n d bl oati n g). V o miti n g a n d diarr hea will als o be ca pt ure d b ut will n ot be 
i ncl u de d i n t he T S S. 
Bi o psies of gastric a n d d u o de nal m uc osa c ollecte d d uri n g pre -treat me nt a n d 
p ost -treat me nt E G D will be e val uate d f or n u m ber of e osi n o p hils. I n a d diti o n, t he 
 will be e val uate d i n patie nts wit h 
. T he 
 will be e val uate d 
pri or t o eac h i nf usi o n a n d 1 h o ur ( ± 1 5 mi n utes) after t he e n d of eac h i nf u si o n. 
 
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Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 2 5  of 1 2 7  
C o nfi d e nti al  
Effic ac y a n d 
P h ar m ac o d y n a mic 
E v al u ati o ns c o nt.  
F or patie nts wit h c o nc o mita nt aller gic ast h ma or at o pic der matitis, e val uati o n will 
i ncl u de a q uesti o n f or eac h a b o ut t he se verit y of s y m pt o ms o ver t he past 2 4 h o urs. 
F or all patie nts d uri n g t he scree ni n g peri o d, dail y e val uati o n will i ncl u de a 
q uesti o n a b o ut t he se verit y of d ys p ha gia o ver t he past 2 4 h o urs. After 
ra n d o mizati o n, t his d ys p ha gia q uesti o n will c o nti n ue f or patie nts sc ori n g > 3 o n 
a n y 2 wee ks of scree ni n g d ys p ha gia c o m pleti o n.  
Patie nts will rate t heir q ualit y of life usi n g t he n o n -disease -s pecific 
 at 
vari o us st u d y visits.  
Patie nts  will rate t heir i m pressi o n of disease se verit y  
 a n d disease 
i m pr o ve me nt  
 at s pecifie d ti me p oi nts d uri n g t he st u d y. 
P h ar m ac o ki netic 
E v al u ati o ns  
Bl o o d (ser u m) will be c ollecte d f or assess me nt of A K 0 0 2  c o nce ntrati o ns usi n g a 
vali date d e nz y me -li n ke d i m m u n os or be nt assa y ( E LI S A) met h o d.  
P har mac o ki netic ( P K) bl o o d sa m ples will be o btai ne d o n Da ys 1, 8, 1 5, 2 9, 5 7, 8 5, 
1 1 3, 1 4 1, 1 6 9, 1 7 6, 1 9 7, a n d 2 2 5 or 2 8, 3 5, 5 6, a n d 8 4 ( ± 3) da ys after last d ose of 
st u d y dr u g, if E T. O n d osi n g da ys ( Da ys 1, 2 9, 5 7, 8 5, 1 1 3, a n d 1 4 1), bl o o d f or P K 
will be c ollecte d pre d ose.  
Bl o o d (ser u m) will be c ollecte d f or assess me nt of A K 0 0 2 A D A usi n g a vali date d 
assa y met h o d. A D A bl o o d sa m ples will be o btai ne d pre d ose o n Da ys 1, 2 9, 5 7, 8 5, 
1 1 3, a n d 1 4 1, as well as o n Da ys 8, 1 5, 1 6 9, 1 7 6, 1 9 7, a n d 2 2 5 or 2 8, 3 5, 5 6, a n d 
8 4 ( ± 3) da ys after last d ose of st u d y dr u g, if E T, a n d i n t he e ve nt of a s us pecte d 
i m m u n o ge nicit y-relate d A E .  
S a m ple Size 
C alc ul ati o n  
First C o -P ri m ar y E n d p oi nt:  A s a m ple size of 8 0 patie nts per treat me nt gr o u p 
will ha ve > 9 9 % p o wer t o de m o nstrate a greater pr o p orti o n of res p o n ders at 
Wee k  2 4 i n A K 0 0 2 patie nts w he n c o m pare d t o place b o patie nts, ass u mi n g t he 
pr o p orti o ns of res p o n ders are 0. 6 a n d 0. 1 i n A K 0 0 2 a n d place b o gr o u ps, 
res pecti vel y.  
Sec o n d C o -Pri m ar y E n d p oi nt:  A sa m ple size of 8 0 patie nts per gr o u p will 
pr o vi de 9 6 % p o wer t o detect a statisticall y si g nifica nt differe nce of 7. 4 p oi nts 
bet wee n A K 0 0 2 a n d place b o i n t he mea n re d ucti o n fr o m baseli ne  i n T S S at 
Wee ks  2 3 – 2 4, ass u mi n g a c o m m o n sta n dar d de viati o n of 1 2. 5 p oi nts a n d a 
p o p ulati o n mea n Baseli ne T S S of 3 0 p oi nts ( A K 0 0 2 -0 0 3 data o n file).  
St atistic al A n al ysis  T he pri mar y efficac y a nal ysis p o p ulati o n is  t he M o difie d I nte nt -t o-Treat ( MI T T) 
p o p ulati o n, defi ne d as all ra n d o mize d patie nts w h o ha ve recei ve d at leas t 
1  i nf usi o n of st u d y dr u g. T he sec o n dar y efficac y a nal ysis p o p ulati o n is t he 
Per  Pr ot oc ol ( P P) p o p ulati o n, defi ne d as MI T T patie nts w h o ha ve recei ve d at least 
1  i nf usi o n of st u d y dr u g a n d di d n ot ha ve si g nifica nt pr ot oc ol vi olati o ns p ossi bl y 
i nterferi n g wit h assess me nt of efficac y. T he safet y p o p ulati o n is defi ne d as all 
patie nts w h o are ra n d o mize d a n d ha ve recei ve d at least 1 i nf usi o n of st u d y dr u g.  
 
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Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 26 of 127 
Confidential 
Statistical Analysis 
cont. 
The MITT population will be used for all efficacy analysis. The Per Protocol 
population will be used for the primary endpoints and select secondary endpoints 
analyses. The Safety population will be used for all safety analysis.  
Patient disposition and reason for early discontinuation will be tabulated. Patient 
demographics, baseline characteristics, and treatment exposure will be 
summarized. 
Efficacy Analysis: To evaluate the clinical benefit of AK002 in adult patients with 
active EG and/or EoD when compared with placebo, efficacy endpoints will be 
co-primary.  
The first co-primary endpoint will be analyzed using the Fisher’s exact test 
comparing AK002 with placebo for the proportion of treatment responders. 
Patients who experience an intercurrent event (i.e., exit the study prematurely or 
initiate prohibited or restricted medications) prior to the end of Week 24 will be 
treated as non-responders. Proportion of responders and the associated 95% 
confidence interval (CI) will be presented for each treatment group. Additionally, 
the between group difference and the associated 95% CI will be computed and 
presented.  
Sensitivity analysis will be carried out using the Cochran-Mantel-Haenszel (CMH) 
test stratified by the randomization stratification factors (Baseline TSS<28 vs ≥28 
and EG ± EoD [i.e., EG with or without EoD] versus EoD-only).  
The second co-primary endpoint will be analyzed by analysis of covariance 
(ANCOVA). The least square (LS) mean, standard error (SE), and 95% 
Confidence Interval for each treatment group and for the between group difference 
will be derived from ANCOVA with treatment as a factor, Baseline PRO TSS 
(continuous) and EoD without EG (categorical) as covariates. Data on patients 
who experience an intercurrent event (i.e., exit the study prematurely or initiate 
prohibited or restricted medications) prior to the end of Week 24 will be set to 
missing.  
Detailed specifications for the missing data imputation will be provided in the 
Statistical Analysis Plan (SAP).  
Analysis of binary secondary endpoints will be based on the methods outlined 
above for the first co-primary efficacy analysis. 
Change from baseline in continuous secondary outcomes measured at multiple 
post-baseline time points will be analyzed longitudinally using a mixed model. 
The model will include fixed effects for baseline value, treatment, week, and the 
treatment by week interaction and allow for random subject effects and assume an 
unstructured covariance structure. The Kenward-Rogers approach for computing 
denominator degrees of freedom will be used to account appropriately for pooling 
of within and between-subject variance estimates. Least square means and the 
95% CI for the between group difference will be estimated for each week. 

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Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 28 of 127 
Confidential 
2. 
Background  
2.1 
Siglec-8 and AK002 
Siglec-8, a member of the CD33-related family of sialic acid-binding, immunoglobulin-like 
lectins (Siglecs), is a transmembrane cell surface protein with restricted tissue distribution, 
expressed selectively on the surface of mature eosinophils and mast cells, but not in early 
precursors of these cell populations. Siglec-8 contains 3 extracellular immunoglobulin-like 
domains, a transmembrane region, and a cytoplasmic tail containing 2 tyrosine-based signaling 
motifs including an immunoreceptor tyrosine-based inhibitory motif (ITIM) with inhibitory 
function. Engagement of Siglec-8 in mast cells can result in inhibition of mediator release, and in 
eosinophils can induce apoptosis (Bochner, 2009). AK002 also shows potent antibody-dependent 
cellular cytotoxicity (ADCC) against eosinophils in vivo and in vitro. 
2.2 
Overview of Nonclinical Studies 
AK002 is a humanized non-fucosylated immunoglobulin G1 (IgG1) monoclonal antibody 
directed against the inhibitory receptor Siglec-8, a member of the CD33-related family of 
Siglecs. 
Siglec-8 has a restricted tissue distribution, expressed selectively on the surface of mature 
eosinophils and mast cells, but not in early precursors of these cell populations. In blood, binding 
of AK002 to Siglec-8 induces ADCC against eosinophils, leading to rapid and sustained 
depletion of these cells from circulation. In the tissue, AK002 induces direct apoptosis of 
eosinophils and inhibition of mast cells. This profile of activity may provide clinical benefit in 
diseases in which these cell types play a role, such as eosinophilic gastritis and eosinophilic 
duodenitis.  
Siglec-8 is not expressed in species other than humans and therefore 2 novel mouse models have 
been developed for in vivo testing of AK002. AK002 has been studied in Siglec-8 humanized 
and transgenic mouse models and with human blood and tissue cells. The first model uses 
immunodeficient mice capable of generating human immune cells including mast cells and 
eosinophils when engrafted with human hematopoietic stem cells. The ability of anti-Siglec-8 
antibodies to inhibit mast cell-mediated reactions has been evaluated in this model. The second 
rodent model is a transgenic mouse line that expresses human Siglec-8. The expression of 
Siglec-8 on the cell surface in these mice is restricted to eosinophils, mast cells, and basophils, a 
pattern of surface expression equivalent to that in humans. Anti-Siglec-8 antibodies can prevent 
IgE-mediated anaphylaxis in this transgenic mouse line, indicating that Siglec-8 is 
pharmacologically active in the model. The ability of AK002 to effect mast cells and eosinophils 
has been evaluated in this model. 

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 29 of 127 
Confidential 
AK002 inhibits IgE-mediated mast cell degranulation and release of the newly formed mediator 
prostaglandin D2 in vitro without affecting mast cell viability. In peripheral blood preparations 
from normal human donors, AK002 shows selective depletion of eosinophils. Importantly, in a 
whole-blood cytokine-release assay using immobilized AK002 to enhance the potential for 
antibody crosslinking, AK002 did not lead to dose-dependent release of pro-inflammatory 
cytokines.  
To evaluate the in vivo activity of anti-Siglec-8 antibodies in an immunocompetent rodent 
model, a transgenic mouse strain has been developed that selectively expresses human Siglec-8 
on the surface of mouse mast cells, eosinophils and basophils. In single- and repeat-dose studies 
in Siglec-8 transgenic mice, AK002 demonstrated selective depletion of peritoneal mast cells and 
circulating and tissue (spleen) eosinophils and basophils.  
In 2 Good Laboratory Practice (GLP) toxicity and toxicokinetic studies, AK002 was well 
tolerated at doses of 50 mg/kg and 100 mg/kg, 5-fold and 10-fold, respectively, the level of the 
highest dose proposed to be studied in the humans. AK002 showed sustained systemic exposure 
in Siglec-8 transgenic mice with an extended terminal half-life estimated as 272 hours or 
337 hours following single IV administration of 50 mg/kg or 100 mg/kg, respectively. There 
was no evidence of anti-drug antibodies (ADA) in either study. Decreases in eosinophil counts 
in both sexes were observed, which reflect the expected pharmacology of AK002. The no-
observed-adverse-effect-level (NOAEL) following IV administration of AK002 to transgenic 
mice was 100 mg/kg, which supports the Phase 1 studies in humans.  
2.3 
Overview of Clinical Studies 
AK002, administered as an intravenous infusion has been previously tested in healthy volunteers 
and in patients with indolent systemic mastocytosis (ISM), chronic urticaria (CU), severe allergic 
conjunctivitis (AC), mast cell gastritis, and eosinophilic gastritis (EG) and/or eosinophilic 
duodenitis (EoD), which was previously referred to as eosinophilic gastroenteritis (EGE).  
Multiple doses of 3 mg/kg have been given to patients with ISM, CU, severe AC, mast cell 
gastritis, and EG and/or EoD. In these studies, patients reported improvements in disease 
symptoms with AK002 pharmacodynamic (PD) activity being observed for prolonged periods of 
time and AK002 pharmacokinetic (PK) parameters demonstrating a half-life amenable to 
administration every 4 weeks. 
To date, healthy volunteers and patients with ISM, CU, severe AC, EG/EoD, EoE, and mast cell 
gastritis have been enrolled in clinical studies. In general, AK002 has been well tolerated. The 
most common treatment-emergent adverse event (TEAE) observed was infusion-related reaction 
(IRR). Most IRR were mild to moderate and resolved on their own, with no treatment required. 

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 30 of 127 
Confidential 
Infusion-related reactions that were serious resolved within approximately 24 hours. Common 
symptoms of IRR were headache, nausea, sweating, flushing, and redness. Most IRR that 
occurred during the infusion could be managed by slowing or temporary interruption of the 
infusion, with minimal intervention. In 6 healthy volunteers who received 2 doses of 0.3 mg/kg, 
4 weeks apart, the second dose was better tolerated than the first dose. This is also the case in 
patients with ISM, CU, AC, and EG/EoD with fewer adverse events (AE) reported during the 
second and subsequent infusions, when compared to the first infusion.  
In all studies there was a transient decrease in lymphocyte count after the AK002 infusion 
(usually resolving within 1 day) that was not associated with any clinical consequence and a 
sustained suppression in eosinophils that was consistent with the mechanism of action of AK002. 
No significant trends were observed for changes in vital signs, electrocardiograms (ECG), 
clinical laboratory parameters, or physical examinations. 
In the randomized, double-blind, placebo-controlled, Phase 2 study of AK002 in 65 patients with 
EG and/or EoD, patients were randomized to receive monthly doses of placebo, low dose AK002 
(0.3, 1, 1, and 1 mg/kg), or high dose AK002 (0.3, 1, 3, and 3 mg/kg) in a 1:1:1 ratio. All 
primary and secondary endpoints were met in the study. There was a 97% and 92% mean 
reduction in eosinophils in the stomach/duodenum for the high dose and low dose AK002-treated 
patients, respectively, versus a 10% increase for placebo-treated patients (p<0.0001). The 
reduction of eosinophils was associated with a statistically significant reduction in total symptom 
score (TSS) of 58% in the high dose AK002 group and 49% reduction in the low dose AK002 
group versus a 24% reduction in the placebo group (p=0.0012 and p=0.015, respectively). 
Improvement in symptoms were observed within 24 hours of the first dose of study drug. In 
addition, 70% of high dose treated patients and 68% of low dose treated patients were treatment 
responders (defined as >30% improvement in TSS and >75% reduction from baseline in tissue 
eosinophils) versus 5% for placebo-treated patients (p<0.0001).  
Approximately 40% of patients had concomitant eosinophilic esophagitis (EoE). In those 
patients, a mean reduction of 95% of eosinophils/hpf in esophageal biopsies for AK002-treated 
patients was observed versus no change for placebo-treated patients. Also, 13 of 14 AK002-
treated patients (93%) were histologic responders as defined by ≤6 eosinophils/hpf versus 1 of 
9 placebo-treated patients (11%). Dysphagia improved by 53% in AK002-treated patients versus 
17% in placebo-treated patients.  
More than 90% of patients in the Phase 2 study elected to continue into a long-term continuation 
study. In that study, a starting dose of 1 mg/kg was used, followed by subsequent doses of 
3 mg/kg. Premedication of 80 mg prednisone was administered the day before the first and 

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 31 of 127 
Confidential 
second dose for 20 of the 58 patients dosed. Using this premedication regimen, no IRR were 
observed on the first infusion of the extension study.  
2.4 
Eosinophilic Gastrointestinal Disorders  
Eosinophilic gastrointestinal disorders (EGID) are chronic inflammatory disorders characterized 
by infiltration of eosinophils along different segments of the gastrointestinal (GI) tract, in the 
absence of any cause of the eosinophilia (Caldwell, 2014). 
Eosinophilic gastritis and/or eosinophilic duodenitis (previously referred to as eosinophilic 
gastroenteritis) represent what are traditionally believed to be rare types of EGID that are 
characterized by chronic, often severe inflammation due to patchy or diffuse infiltration of 
eosinophils into layers of the stomach, small intestine, or both the stomach and small intestine 
(Prussin, 2014; Reed, 2015; Zhang, 2017). The diagnosis is based on clinical presentation 
(gastrointestinal symptoms) combined with increased tissue eosinophils in biopsy specimens 
from the stomach and/or duodenum without any other cause for the eosinophilia. Involvement of 
the small intestine is typically assessed by performing duodenal biopsies using an esophago-
gastro-duodenoscopy (EGD) and has been referred to as eosinophilic gastroenteritis or 
eosinophilic enteritis, though eosinophilic duodenitis (EoD) is more appropriate. The 
gastrointestinal symptoms are believed to be due to the release of inflammatory mediators from 
activated eosinophils, and likely mast cells. Symptoms that are often severe and debilitating 
commonly include abdominal pain, nausea, bloating, early satiety, fullness before finishing a 
meal, abdominal cramping, vomiting, diarrhea, and weight loss (Alhmoud, 2016; Lopez-Medina, 
2015; Mansoor, 2017; Reed, 2015). 
Jensen et al. (2016) estimated the prevalence of EG and EoD to be 6.3/100,000 and 8.4/100,000 
respectively (for patients ages 1–64 years old). Mansoor et al. (2017) estimated the overall 
prevalence of EG to be 5.1/100,000 persons.  
Patients may also have concomitant atopic diseases like food allergy, asthma, and atopic 
dermatitis, which further impact qualify of life and contribute to health care costs. Additionally, 
8% to 10% of patients have concomitant EoE (Jensen, 2016).  
There are no FDA-approved treatments for EG and/or EoD. Current therapies and disease 
management include dietary restriction/elimination, PPI, antihistamines, systemic or topical 
corticosteroids, and occasional off-label use of immunomodulatory biologics (Prussin, 2014; 
Reed, 2015; Zhang, 2017). Proton pump inhibitors have little to no benefit in patients with EG 
and/or EoD, despite reports of providing partial benefit in some patients with EoE (Katz, 2013). 
Restricted/elemental diets are not effective long-term treatment as they require strict compliance 
and, in the case of elemental diets, are expensive and are often not reimbursed by insurance. In 

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 3 2  of 1 2 7  
C o nfi d e nti al  
a d diti o n, c o m plia nce is ver y p o or, a n d p atie nt q ualit y of life is greatl y i m pacte d ( Be dell, 2 0 1 8 ; 
Peters o n,  2 0 1 3 ; Wec hsler, 2 0 1 4 ). C ortic oster oi ds, s yste mic or t o pical (s wall o we d) ha ve b ee n 
s h o w n t o pr o vi de s y m pt o m relief b ut are n ot a p pr o priate f or l o n g-t er m treat me nt d ue t o 
n u mer o us si de effects a n d ass ociate d ris ks i ncl u di n g a dre nal i ns ufficie nc y, b o ne 
de mi neralizati o n, i ncreas e d c ha n ce of i nfecti o n, oste o p or osis, be ha vi oral iss ues, a n d wei g ht gai n.  
B y mar k e dl y re d uci n g t h e n u m ber of bl o o d a n d tis s ue e osi n o p hils a n d i n hi biti n g t he acti vati o n of 
mast cells, A K 0 0 2 ma y b e usef ul i n t he treat me nt of patie nts wit h E G a n d/ or E o D. T his pre mise 
is s u p p orte d b y t he P has e 2 data wit h A K 0 0 2 t hat s h o ws si g nifica nt i m pr o v e me nt i n hist ol o g y 
a n d s y m pt o ms i n t hese  p atie nts.  
Gi ve n t here are n o a p pr o ve d t hera pies f or t hese c hr o nic a n d de bilitati n g dis eases, better 
treat me nt o pti o ns are cle arl y n ee d e d t o ma na ge E G a n d E o D. 
3.  
R ati o n ale f or St u d y a n d D ose Selecti o n  
Base d o n e x perie nce wit h A K 0 0 2 i n healt h y v ol u nteers a n d  i n patie nts wit h I S M, C U, se vere 
A C, a n d E G/ E o D, t he pr o p ose d A K 0 0 2 d ose re gi me n of 6 t otal d oses is 1  m g/ k g f or t he first 
i nf usi o n, f oll o we d b y 5 d oses of 3 m g/ k g a d mi nistere d e v er y 4  wee ks.  
 
 
 
T he i nf usi o ns were ge nerall y w ell t olerate d at all d oses wit h m ost I R R bei n g mil d t o m o derate 
a n d ver y fe w A E  o utsi de t he i nf usi o n wi n d o w. Patie nts wit h I S M, C U, se vere A C, mast cell 
gastritis, a n d E G/ E o D h a ve recei ve d m o nt hl y d os es of 1 m g/ k g a n d 3 m g / k g A K 0 0 2. 
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4.
Study Objectives 
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Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 3 4  of 1 2 7  
C o nfi d e nti al  
 
Pr o p orti o n of treat me nt r es p o n ders at Wee k 2 4. A res p o n der is defi ne d as > 3 0 % 
i m pr o ve me nt i n T S S a n d  mea n e osi n o p hil c o u nt ≤4 cells /h pf i n 5 hi g hest gastric h pf a n d/ or 
mea n e osi n o p hil c o u nt ≤1 5 cells /h pf i n 3 hi g hest d u o de nal h pf.  
 
Pr o p orti o n of patie nts w h o ac hie ve ≥5 0 % re d u cti o n i n T S S fr o m B aseli ne t o Wee ks 23 – 2 4.  
 
Pr o p orti o n of patie nts w h o ac hie ve ≥7 0 % re d u cti o n i n T S S fr o m B aseli ne t o Wee ks 23 – 2 4.  
 
C ha n ge i n wee kl y T S S o ver ti me.  
4. 3  
E x pl or at or y O bjecti ves  
T he e x pl orat or y o bj ecti v es are t o e val uate t he effect of A K 0 0 2 b y c o m p ari n g A K 0 0 2 t o place b o 
treat me nt f or t he f oll o wi n g parameters:  
 
C ha n ge  fr o m Baseli ne i n 
 o ver ti me.  
 
C ha n ge fr o m Baseli ne i n 
 o ver ti me . 
 
F or patie nts wit h 
 
: Pr o p orti o n of patie nts ac hie vi n g a 
 
 at W ee k 2 4. 
 
C ha n ge fr o m Baseli ne i n 
 o ver ti me . 
4. 4  
S afet y O bjecti ves  
T o e val uate t he s afet y a n d t olera bilit y of A K 0 0 2 b y det er mi ni n g i nci d e nce a n d se verit y of 
a d verse e ve n ts, st u d y wit h dra wals d ue t o a d verse e ve nts, c ha n ges i n vital si g ns a n d la b orat or y 
tests i ncl u di n g i m m u n o ge nicit y, c ha n ges i n c o n c o mita nt me dicati o n use d ue t o a d verse e ve nts, 
a n d ot her safet y para met ers.  
4. 5  
T ar get of Esti m ati o n  
T he esti ma n d (tar get of esti ma ti o n) f or Pr ot oc ol A K 0 0 2-0 1 6 is : 
 
I n p atie nts wit h E G a n d/ or E o D, w h at is bet wee n gr o u p ( A K 0 0 2 vs. Pl a ce b o) 
differe nce i n t he pr o p orti o n of tiss ue e osi n o p hil res p o n ders at Week 2 4, a n d gr o u p 
differe nce i n T S S fr o m b aseli ne  t o Weeks 2 3– 2 4 as me as ure d by t he  p atie nt -re p orte d 
o utc o me ( P R O) q uesti o n n aire.  
T he s ecti o ns bel o w des cri be t he attri b utes of t he esti ma n d c o nsiste nt wit h t he I C H E 9 A d de n d u m  
(F D A, 2 0 2 1 ). 
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Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 3 9  of 1 2 7  
C o nfi d e nti al  
T a ble 1  
Sc he d ule of Assess me nts  
 
Scree ni n g  
( 1 8– 4 5 da ys)  
Tre at me nt Peri o d  
( 2 0 wee ks) 
F oll o w -U p Peri o d
3 0 
( 1 2 wee ks) 
B aseli ne 1 
Pri or 
t o 
D a y 1  
D ose 1  
D a y 1  
 
 
D a y 8  
( ± 2 da ys) 
 
D a y 1 5  
( ± 2 da ys)  
 
D ose 2  
D a y 2 9  
( ± 3 da ys) 
D ose 3  
D a y 5 7  
( ± 3 da ys) 
D ose 4  
D a y 8 5  
( ± 3 da ys) 
D ose 5  
D a y 1 1 3  
( ± 3 da ys) 
D ose 6  
D a y 1 4 1  
( ± 3 da ys) 
D a y 1 6 9  
( ± 3 da ys) or 
2 8 da ys 
after last 
d ose  
D a y 1 7 6  
( ± 3 da ys) or 
3 5 da ys 
after last 
d ose if E T 2 9 
D a y 1 9 7  
( ± 3 da ys) or 
5 6  da ys 
after last 
d ose if E T 2 9 
D a y 2 2 5  
( ± 3 da ys) or 
8 4  da ys 
after last 
d ose if E T 2 9 
I nf or me d c o nse nt 
X  
 
 
 
 
 
 
 
 
 
 
 
 
 
De m o gr a p hics  
X  
 
X  
 
 
 
 
 
 
 
 
 
 
 
Me dical Hist or y  
X  
 
X  
 
 
 
 
 
 
 
 
 
 
 
Pri or/ C o nc o mita nt Me dicati o ns  
X  
 
X  
 
 
X  
X  
X  
X  
X  
X  
X  
X  
X  
B o d y wei g ht a n d hei g ht 2 
X  
 
X  
 
 
X  
X  
X  
X  
X  
 
X  
X  
X  
Vital Si g ns 3 
X  
 
X  
 
 
X  
X  
X  
X  
X  
 
X  
X  
X  
1 0 or 1 2 -lea d E C G4 
X  
 
 
 
 
 
 
 
 
 
 
 
 
 
C o m plete P h ysical E xa m 5 
X  
 
 
 
 
 
 
 
 
 
 
 
 
 
S y m pt o m -Directe d P h ysical 
E xa m 6 
 
 
X  
 
 
X  
X  
X  
X  
X  
 
X  
X  
X  
Baseli n e Diet Assess me nt 7 
X  
 
 
 
 
 
 
 
 
 
 
 
 
 
Baseli n e Diet C o m plia nce 8 
 
 
X  
 
 
X  
X  
X  
X  
X  
 
X  
X  
X  
St o ol f or O va a n d Parasite 9 
X  
 
 
 
 
 
 
 
 
 
 
 
 
 
e P R O Acti vati o n a n d Trai ni n g 1 0 
X  
 
 
 
 
 
 
 
 
 
 
 
 
 
e P R O Q u esti o n naire ( ma y 
i ncl u de A d diti o nal Q u esti o ns)1 1 
< ------------------------------------------------------------------C o m plete electr o nicall y o ne ti me d ail y -------------------------------------------------------------->  
 
 
X  
 
X  
 
 
X  
X  
X  
X  
X  
 
X  
X  
 
 
< ----------------------------------------C o m plete electr o nicall y o n Scree ni n g Da y 1 9 , St u d y Da y 7, a n d St u d y Da y 2 8 ---------------------------------------->  
 
< ---------------------------------------------------C o m plete electr o nicall y o n  St u d y Da y 7 a n d St u d y Da y 2 8 ----------------------------------------------------->  
E G D wit h Bi o ps y 1 2, 1 4 
X  
 
 
 
 
 
 
 
 
 
X  
 
 
 
Bl o o d f or Scree ni n g C he mistr y 
(i ncl u des h C G a n d F S H)1 2, 1 5 
X  
 
 
 
 
 
 
 
 
 
 
 
 
 
C CI
C CI
C CI

Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 40 of 127 
Confidential 
Table 1 
Schedule of Assessments cont. 
 
Screening 
(18–45 days) 
Treatment Period 
(20 weeks) 
Follow-Up Period30 
(12 weeks) 
Baseline1 
Prior 
to 
Day 1 
Dose 1 
Day 1 
 
 
Day 8 
(±2 days) 
 
Day 15  
(±2 days) 
 
Dose 2 
Day 29 
(±3 days) 
Dose 3 
Day 57 
(±3 days) 
Dose 4 
Day 85 
(±3 days) 
Dose 5 
Day 113 
(±3 days) 
Dose 6 
Day 141 
(±3 days) 
Day 169 
(±3 days) or 
28 days 
after last 
dose 
Day 176 
(±3 days) or 
35 days 
after last 
dose if ET29 
Day 197 
(±3 days) or 
56 days 
after last 
dose if ET29 
Day 225 
(±3 days) or 
84 days 
after last 
dose if ET29 
Blood for Serology and 
Strongyloides stercoralis 12,16 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
Blood for Total Serum IgE12,17 
X 
 
 
 
 
 
 
 
 
 
 
X 
 
 
Previous Treatments Review 
X 
 
 
 
 
 
 
 
 
 
 
 
 
 
Eligibility Assessment 
X 
X 
X 
 
 
 
 
 
 
 
 
 
 
 
Access IRT: Stratification and 
Randomization18 
 
 
X 
 
 
 
 
 
 
 
 
 
 
 
Access IRT: IP Kit Assignment 
 
 
X 
 
 
X 
X 
X 
X 
X 
 
 
 
 
Premedication: Prednisone19 
 
X 
 
 
 
 
 
 
 
 
 
 
 
 
Study Drug Administration20 
 
 
X 
 
 
X 
X 
X 
X 
X 
 
 
 
 
Blood for CBC with 
differential12,21 
X 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Blood for Chemistry12,22 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Blood for PK12,23 
X 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Blood for ADA12,24 
X 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Urine for Urinalysis12,25 
X 
 
X 
 
 
X 
X 
X 
X 
X 
 
X 
X 
 
Dipstick Pregnancy Test26 
 
 
X 
 
 
X 
X 
X 
X 
X 
 
X 
X 
 
Non-serious Adverse Events27 
 
 
X 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Serious Adverse Events28 
 
 
X 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Begin AK002-016X extension 
study at least 1 day after 
Day 176 Visit (if applicable)31 
 
 
 
 
 
 
 
 
 
 
 
X33 
X33 
X33 
Blood for histamine/tryptase32 
 
 
X 
 
 
X 
X 
X 
X 
X 
 
 
 
 

Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 4 1  of 1 2 7  
C o nfi d e nti al  
T a ble 1 N otes  
A D A:  A nti -A K 0 0 2 a nti b o d y  
E T:  
Earl y T er mi nati o n  
I R T: 
I nteracti ve Res p o nse T ec h n ol o g y 
C B C:  C o m plete bl o o d c o u nt  
F S H:  F ollicle -sti m ulati n g h or m o ne 
  
E C G:  Electr ocar di o gra m  
h C G:  H u ma n C h ori o nic G o na d otr o pi n  
 
 
e P R O: electr o nic P at ie nt Re p orte d O utc o me 
I P: 
I n vesti gati o nal Pr o d uct 
P K:  
P har mac o ki netics  
1)  
Baseli ne scree ni n g visit ca n o cc ur o ver se veral da ys wit hi n t he scree ni n g peri o d. Da y 1 ca n be gi n as s o o n as eli gi bilit y crit eria are met  a n d at least 4 diar y e ntries ha ve bee n 
c o m p lete d d uri n g t he t hir d we e k of scree ni n g.  
2)  
At scree ni n g, hei g ht (i n c m) a n d wei g ht (i n k g) will be rec or de d. B o d y wei g ht will als o be meas ure d o n Da ys 1, 2 9, 5 7, 8 5, 1 1 3, 1 4 1 a n d o n f oll o w -u p Da y 1 7 6 , Da y 1 9 7  a n d 
Da y 2 2 5  or 2 8 , 5 6 , a n d 8 4 da ys after las t d ose, if E T. C urre nt b o d y wei g ht or b o d y wei g ht fr o m 1 da y pri or will be use d t o calc ulate t he a m o u nt of A K 0 0 2/ place b o t o be 
mi xe d wit h Na Cl f or t he a p pr o priate d ose t o be a d mi nistere d o n eac h i nf usi o n da y.  
3)  
Vital si g ns will be meas ure d at scree ni n g, D a ys 1 7 6, 1 9 7 , a n d 2 2 5  or 2 8 , 5 6, a n d 8 4  da ys after last d ose if E T a n d o n all d osi n g da ys: wit hi n 3 0 mi n utes pre d ose, 1 5 mi n utes 
( ± 5 mi n utes) after t he start of st u d y dr u g i nf usi o n, wit hi n 1 5 mi n utes f oll o wi n g t he e n d of i nf usi o n a n d j ust pri or t o disc har g e. A d diti o nal vital si g ns meas ure me nts ma y be 
c ollecte d at t he I n vesti gat or’s discreti o n if a n I R R occ urs. Vital si g ns i ncl u di n g s yst olic a n d diast olic bl o o d press ure, p ul se, b o d y te m perat ure, a n d res pirat or y rate will be 
meas ure d after t he patie nt has bee n at rest f or ≥5 mi n utes a n d bef ore a n y bl o o d dra ws ha ve bee n o btai ne d ( u nless c ollect e d f or a n I R R).  
4)  
A 1 0 -lea d or 1 2-lea d E C G will b e o btai ne d at scree ni n g bef ore a n y bl o o d is dra w n a n d after t he patie nt has bee n i n t he a p pr o priate p ositi o n for ≥5 mi n u tes. 
5)  
A c o m plete p h ysical e xa mi nati o n will be perf or me d b y eit her t he I n vesti gat or or desi g nee a n d i ncl u de t he f oll o wi n g b o d y s yste m or or ga n assess me nts: s ki n; hea d, e yes, ears, 
n ose a n d t hr oat; t h yr oi d; l u n gs; car di o vasc ular; a b d o me n; e xtre mities; l y m p h n o des; a n d a brief ne ur ol o gical e xa mi nati o n.  
6)  
A s y m pt o m -directe d P E (i ncl u di n g assess me nt of p ossi ble i nf usi o n site reacti o ns) will be perf or me d b y t he I n vesti gat or or desi g nee, as nee de d if a n y s y m pt o ms are re p orte d.  
7)  
A baseli ne diet assess me nt ( A p pe n di x 3 ) will be perf or me d usi n g sta n dar dize d q uesti o ns. Eati n g patter ns, f o o d a v oi da nce be ha vi ors, a n d c o nfir me d all er gies will be ca pt ure d.  
8)  
A baseli ne diet c o m plia nce c h ec k will be perf or me d at e ver y st u d y visit, e xce pt as  n ote d a b o ve, a n d a n y varia nces fr o m t he baseli ne diet d oc u me nte d. P atie nts s h o ul d 
mai ntai n t he baseli ne diet t hr o u g h o ut t he st u d y.  
9)  
Fecal c ollecti o n kits f or O va a n d P arasite test will be pr o vi de d t o patie nts at scree ni n g. C ollecti o n kits s h o ul d be ret u r ne d t o t he cli nical site wit hi n 1 da y of c ollecti o n. 
Ne gati ve res ults m ust b e a vail a ble pri or t o ra n d o mizati o n.  
1 0)  Acti vate P R O q uesti o n naire a n d pr o vi de patie nt wit h u ni q ue user na me a n d pass w or d. P R O q uesti o n naire s h o ul d be acti vate d f or a ll patie nts o n scree ni n g Da y 1. P atie nts wit h 
c o nc o mita nt hist or y of ast h ma or at o pic der matitis will recei ve a n e xtra q uesti o n, a b o ut eac h, as a p pr o priate. All patie nts w ill recei ve d ys p ha gia q uesti o n d uri n g scree ni n g a n d 
will c o nti n ue t o recei ve t he q uesti o n after e nr oll me nt if wee kl y a vera ge d ys p ha gia is ≥3 d uri n g a n y 2 wee ks of scree ni n g.  
1 1)  P R O s h o ul d be c o m plete d ar o u n d t he sa me ti me eac h da y. Pri or t o e nr oll me nt, t he P R O wee kl y a vera ges of a b d o mi nal pai n, na usea , a n d diarr hea o ver t he scree ni n g peri o d 
will b e ca lc ulate d a n d use d t o assess eli gi bilit y. Wee kl y a ver a ge T otal S y m pt o m Sc ore ( T S S 6) will be calc ulate d f or eli gi bilit y a n d stratificati o n. P R O wee kl y a vera ge f or 
d ys p ha gia will als o be assesse d pri or t o e nr oll me nt t o deter mi ne if t he patie nt s h o ul d c o nti n ue  recei vi n g t he 1-q uesti o n dail y d ys p ha gia q uesti o n.  
1 2)  S peci me n pr ocesse d b y ce ntral la b orat or y. See ce ntral la b orat or y ma n ual f or c ollecti o n a n d pr ocessi n g details.  
C CI
C CI

Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 42 of 127 
Confidential 
Table 1 Notes cont. 
13) To be completed electronically by patient, in clinic, prior to any blood draw, physical exam, or vital sign measurements. 
14) See Appendix 5 for biopsy assessments. The post-treatment endoscopy (EGD) and biopsy assessments will be performed on Day 169 (±3) or 28 (±3) days after last dose of 
study drug if ET. If the Day 141 infusion occurs out of window, the EGD should occur 28 (±3) days from the date of Day 141. Post-treatment EGD biopsy results will be 
blinded to the site.  
15) Blood for baseline Chemistry, including hCG and FSH, will be collected during the screening period. Only patients of childbearing potential and post-menopausal women are 
required to have hCG and FSH testing completed.  
16) Blood for Serology testing will be collected during screening and will include HBsAg, hepatitis C antibody, anti-HBc, and HIV, as well as Strongyloides stercoralis.  
17) Blood samples for Total Serum IgE will be collected during screening and on Day 176 or 35 (±3) days after last dose of study drug, if ET. 
18) Stratification based on TSS of <28 or ≥28 and whether patient is EoD-only will occur. Randomization and stratification will be conducted through the IRT system. 
19) Premedication with 60 mg oral prednisone or approved alternative is required 12–24 hours prior to first infusion. Premedication may be administered prior to subsequent 
infusions at the Investigator’s discretion, but only with written Medical Monitor approval. 
20) Study drug will be administered as a single peripheral IV infusion over at least 4 hours for Dose 1 and at least 3 hours for Dose 2. Doses 3–6 should occur over at least 
2 hours, depending on prior infusion tolerability. Please refer to the Pharmacy Manual. 
21) Blood for CBC with differential, including absolute blood eosinophil count, will be obtained just prior to each infusion, 1 hour (±15 minutes) after the end of each infusion as 
well as during the screening period, and on Days (±3) 8, 15, 169, 176, 197, and 225 or 35, 56, and 84 (±3) days after last dose if ET. All differential blood counts from Day 1 
(post-dose) through the end of the patient’s participation will be blinded to the Sponsor and the site. An unscheduled CBC may be collected at the request of the Safety 
Monitor.  
22) Blood for chemistry will be obtained predose on dosing Days 1, 29, 57, 85, 113, and 141, as well as on Days 8, 15, 169, 176, 197, and 225 or 28 (±3), 35 (±3), 56 (±3), and 
84 (±3) days after last dose of study drug if ET. 
23) Blood for PK will be obtained predose on dosing Days 29, 57, 85, 113, and 141, as well as during screening and on Days 8, 15, 169, 176, 197, and 225 or 28 (±3), 35 (±3), 
56 (±3), and 84 (±3) days after last dose of study drug if ET. 
24) Blood for ADA will be collected predose on dosing Days 29, 57, 85, 113, and 141, as well as during screening and on Days 8, 15, 169, 176, 197, and 225 or 28 (±3), 35 (±3), 
56 (±3), and 84 (±3) days after last dose of study drug if ET. ADA sample will also be collected any time an immunogenicity-related AE occurs. 
25) Urine for standard urinalysis will be obtained predose on dosing Days 1, 29, 57, 85, 113, and 141 as well as during the screening period and on Day 176 and Day 197 or 
35 (±3) days and 56 (±3) days after last dose of study drug if ET. 
26) A small amount of urine collected for urinalysis will be used for dipstick pregnancy test on all infusion days and on Day 176 and 197 or 35 and 56 (±3) days after last dose of 
study drug, for all patients of childbearing potential. Test kits will be supplied by the central laboratory. Tests will be completed on site and evaluated prior to each infusion. 
27) The capture of non-serious AE and adverse events of special interest will begin after the first dose of study drug has occurred. 

Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 43 of 127 
Confidential 
Table 1 Notes cont. 
28) The reporting of SAE occurring after signing Informed consent and prior to the first infusion will be limited to those that relate to screening procedures. The capture of all 
SAE and AE that are not related to screening procedures will begin at the time of first infusion of study drug. 
29) Patients who sign the informed consent for the AK002-016X extension study will complete the procedures for Day 176 and may begin open-label dosing in the extension 
study, if eligible, one day after the completion of Day 176 visit. In this case, patients will not complete the Day 197 or Day 225 procedures under Protocol AK002-016. 
Open-label dosing and follow-up will occur under the AK002-016X extension study. Patients who choose to enter the AK002-016X extension study after Day 197 but before 
Day 225 will not complete Day 225 procedures.  
30) The ET visits should be conducted 28 (±3), 35 (±3), 56 (±3), and 84 (±3) days after the last dose of study drug or prior to this, if necessary, to ensure compliance with the 
visit. If only 1 ET visit is possible, EGD and end-of-study blood work may occur on the same day (28 days after last dose and 35 days after last dose visit procedures). If the 
end-of-study visit occurs more than 35 days after the last dose of study drug, then perform the visit as soon as possible. The procedures listed under the 28-day and 35-day 
post-study drug visit will be conducted unless otherwise directed by the Medical Monitor. 
31) The final hematology assessment for AK002-016 must be collected prior to the subject taking prednisone premedication for AK002-016X. Therefore, dosing in 
AK002-016X must take place at least 1 day after completion of the Day 176 visit for AK002-016. Subjects may start AK002-016X dosing 1 day after completion of the 
Day 176 Visit. 
32)  Blood samples for histamine and tryptase to be collected within 1–2 hours of start of symptoms if there is any suspicion of anaphylaxis. 
33)  For patients who do not start the extension study before Day 197 or Day 225, visit procedures will occur according to the AK002-016 study. 
 
 

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Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 4 6  of 1 2 7  
C o nfi d e nti al  
 
C ha n ge fr o m Baseli ne i n 
 o ver ti me . 
 
C ha n ge fr o m Baseli ne i n 
 o ver ti me . 
 
F or patie nts wit h 
 
): Pr o p orti o n of patie nts ac hie vi n g  a 
 
 at W ee k 2 4. 
 
C ha n ge fr o m Baseli ne i n 
 o ver ti me . 
7.  
P ati e nt Selecti o n  
7. 1  
N u m ber of P atie nts  
A t otal of a p pr o xi matel y 1 6 0 patie nts will be d ose d i n t he st u d y i n w hic h 8 0 patie nts will recei ve 
A K 0 0 2 at a d ose  of 1  m g/ k g f or t h e first d ose f oll o we d b y 3  m g/ k g f or 5 s u bse q ue nt d oses a n d 
8 0  patie nts will recei ve place b o, i n a ra n d o mize d, d o u ble -bli n d ma n ner. T h e st u d y will ai m t o 
e nr oll a p pr o xi matel y 9 0 patie nts wit h E G  ± E o D a n d a p pr o xi matel y 7 0  patie nts  wit h E o D o nl y.  
7. 2  
St u d y P o p ul ati o n  
Male a n d fe male E G a n d/ or E o D patie nts, a ge d ≥1 8 a n d ≤8 0 years w h o f ulfill t he eli gi bilit y 
criteria s pecifie d bel o w.  
7. 3  
I ncl usi o n Criteri a 
Patie nts wit h E G a n d/ or E o D are eli gi ble f or e nr oll me nt i nt o t he st u d y if all of t he f oll o wi n g 
criteria are met:  
1)  
Pr o vi de writte n i nf or me d c o nse nt.  
2)  
Male or fe m ale a ge d ≥1 8 a n d ≤8 0 years at t he ti me of si g ni n g t he i nf or me d c o nse nt f or 
e ntr y.  
3)  
Baseli ne e n d osc o pic bi o ps y wit h > 3 0 e osi n o p hils/ h pf i n 5 h pf i n t he st o mac h a n d/ or 
> 3 0  e osi n o p hils/ h pf i n 3 h pf i n t he d u o de n u m, as deter mi ne d b y ce ntral hist ol o g y 
assess me nt of bi o psies c ollecte d d uri n g t he scree ni n g E G D, wit h o ut a n y si g nifica nt ca use 
f or t he e osi n o p hilia.  
 
Pri or E G D ma y be use d f or eli gi bilit y as l o n g as t he E G D occ urre d wit hi n 3 0 da y s of t he 
first scree ni n g visit f or t h e A K 0 0 2-0 1 6 st u d y a n d was perf or me d a n d ce ntr all y ass esse d as 
f or t he A K 0 0 2-0 1 6 st u d y.  
4)  
C o m pleti o n of at least 4 dail y P R O q uesti o n naires per wee k f or a mi ni m u m of 3 wee ks 
d uri n g scree ni n g.  
C CI
C CI
C CI
C CI
C CI

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 47 of 127 
Confidential 
5) 
A weekly average score of abdominal pain, nausea, and/or diarrhea ≥3 on the PRO 
questionnaire (score from 0–10) and a weekly average TSS of ≥10 for at least 2 weeks of 
screening. 
6) 
Patients with inadequate or loss of response to, or who were intolerant to standard therapies 
for EG/EoD symptoms which could include PPI, antihistamines, systemic or topical 
corticosteroids, and/or diet, among others. 
7) 
If patient is on pre-existing dietary restrictions, willingness to maintain dietary restrictions 
throughout the study. 
8) 
Willing and able to comply with all study procedures and visit schedule including 
follow-up visits. 
9) 
Female patients must be either post-menopausal for at least 1 year with FSH level 
>30 mIU/mL at screening or surgically sterile (tubal ligation, hysterectomy, or bilateral 
oophorectomy) for at least 3 months, or if of childbearing potential, have a negative 
pregnancy test and agree to use dual methods of contraception, or abstain from sexual 
activity from screening until the end of the study, or for 120 days following the last dose of 
study drug, whichever is longer. 
 
Male patients with female partners of childbearing potential must agree to use a highly 
effective method of contraception from screening until the end of the study or for 120 days 
following the last dose of study drug, whichever is longer. All fertile men with female 
partners of childbearing potential should be instructed to contact the Investigator 
immediately if they suspect their partner might be pregnant (e.g., missed or late menstrual 
period) at any time during study participation. 
7.4 
Exclusion Criteria 
Patients will be excluded from the study if they meet any of the following criteria: 
1) 
Use of systemic or topical corticosteroids exceeding the equivalent of 10 mg/day of 
prednisone within 4 weeks prior to the screening visit. 
2) 
Change in the dose of corticosteroids (systemic or topical), PPI, leukotrienes, or diet 
therapy within 4 weeks prior to screening. 
3) 
Treatment with any immunosuppressive or immunomodulatory drugs that may interfere 
with the study within 12 weeks prior to the screening visit. 
4) 
Prior exposure to AK002 or known hypersensitivity to any constituent of the study drug. 
5) 
Active Helicobacter pylori infection, unless treated and confirmed to be negative prior to 
randomization and histology per repeat EGD and symptoms still qualify for enrollment 
after treatment. 

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 48 of 127 
Confidential 
6) 
Confirmed history of inflammatory bowel disease, celiac disease, achalasia, or esophageal 
surgery. 
7) 
History of bleeding disorders and/or esophageal varices considered to be clinically 
significant by the Investigator. 
8) 
Other significant causes of gastric and/or duodenal eosinophilia or eosinophilic 
granulomatosis with polyangiitis (EGPA). 
9) 
Confirmed diagnosis of Hypereosinophilic Syndrome (HES). 
10) Women who are pregnant, breastfeeding, or planning to become pregnant while 
participating in the study. 
11) Presence of an abnormal laboratory value considered to be clinically significant by the 
Investigator. 
12) Any disease, condition (medical or surgical), or cardiac abnormality, which, in the opinion 
of the Investigator, would place the patient at increased risk. 
13) History of malignancy, except carcinoma in situ, early stage prostate cancer, or 
non-melanoma skin cancers. However, patients with cancers that have been in remission for 
more than 5 years and are considered cured, can be enrolled. 
14) Treatment for a clinically significant helminthic parasitic infection within 6 months of 
screening. 
15) Positive helminthic infection on Ova and Parasite (O&P) test. 
16) Seropositive for Strongyloides stercoralis at screening, except for patients with past but 
resolved disease. 
17) Seropositive for HIV or hepatitis at screening, except for vaccinated patients or patients 
with past but resolved disease. 
18) Vaccination with live attenuated vaccines within 30 days prior to initiation of treatment in 
the study, during the treatment period, or vaccination expected within 5 half-lives 
(4 months) of study drug administration. All types and formulations of vaccines (including 
live attenuated vaccines) authorized by FDA or other regulatory authority for the prevention 
of COVID-19 may be administered before, during, or after this study. The vaccine should 
not be administered within 7 days prior to and within 7 days after the administration of 
AK002 so that any side effects caused by either of the 2 medications can be more easily 
determined. 

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 4 9  of 1 2 7  
C o nfi d e nti al  
1 9)  Partici pati o n i n a c o nc urre nt i nter ve nti o nal st u d y wit h t he last i nter ve nti o n occ urri n g wit hi n 
3 0 da ys pri or t o s t u d y dr u g a d mi nistrati o n or 9 0 d a ys or 5 half-li ves, w hic h e ver is l o n ger, 
f or bi ol o gic pr o d ucts. 
2 0)  K n o w n hist or y of alc o h ol, dr u g, or ot h er s u bsta nce a b use or de pe n d e nce t h at is c o nsi dere d 
b y t he I n vesti gat or t o be o n g oi n g a n d cli nicall y si g nifica nt.  
2 1)  A n y ot her reas o n t hat i n t he o pi ni o n of t he I n vesti gat or or t he Me dical M o nit or ma kes t he 
patie nt u ns uita ble f or e nr oll me nt.  
7. 5  
S afet y E v al u ati o ns  
Safet y a n d t olera bilit y will be assesse d t hr o u g h o ut t he st u d y b y m o nit ori n g a n d e val uati n g A E  
i ncl u di n g a n y c o mplicati o ns res ulti n g fr o m t he I V i nf usi o n. All T E A E will be c ollecte d fr o m t he 
start of st u d y dr u g a d mi nistrati o n i n A K 0 0 2-0 1 6 t hr o u g h t h e start of st u d y dr u g a d mi nistrati o n i n 
A K 0 0 2 -0 1 6 X (Da y 1 7 6 if e nr olli n g i n t he A K 0 0 2 -0 1 6 X e xte nsi o n st u d y ), Da y 2 2 5 if n ot 
e nr olli n g i n t he A K 0 0 2 -0 1 6 X st u d y, or E arl y Ter mi nati o n ( E T) . 
Se verit y will be assesse d usi n g t he Nati o nal Ca ncer I nstit ute ( N CI) C o m m o n Ter mi n ol o g y 
Criteria f or A d v erse E v e nts ( C T C A E) Versi o n 5. 0 ( or m ost c urre nt versi o n). All A E  will be 
assi g ne d a se v erit y gra de a n d will be assesse d f or cli nical si g nifica nce a n d relati o ns hi p t o st u d y 
dr u g.  
A d diti o nal safet y e val u ati o ns i ncl u de cli nical la b orat or y tests c o m prisi n g A D A t o A K 0 0 2, C B C, 
c he mistries a n d uri nal yses, p h ysical e x a ms, a n d  vital si g ns meas ure me nts.  
T he Me dical M o nit or will re vie w bli n de d safet y d ata t hr o u g h o ut t he st u d y. Certai n safet y d ata 
( p ost-treat me nt c ell differe ntials, as well as tiss ue e osi n o p hil a n d 
) will n ot be 
pr o vi de d t o st u d y sites or t o t he S p o ns or as it ma y ca use bias . T h e desi g nate d S afet y M o nit or 
will re vie w bli n de d safet y dat a as well as p ost -tr eat me nt cell c o u nts a n d will escalate t o t he 
Me dical M o nit or , as nee de d , i n a ma n ner t h at d oes n ot ca use bias.  
A n i n de pe n de nt D ata M o nit ori n g C o m mi ttee (i D M C) has bee n c o n v e ne d a n d will meet at 
re g ularl y sc h e d ule d i nter vals i n acc or da nce wit h t he i D M C c harter.  
8.  
Pri or a n d C o nc urre nt Me dic ati o ns  
Pri or a n d c o nc o mita nt m e dicati o ns i ncl u de b ot h prescri be d a n d o ver -t he-c o u nter me dicati o ns a n d 
will be rec or d e d i n t he el ectr o nic Case R e p ort F or ms (e C R F) f or 3 0 d a ys pri or t o t he scree ni n g 
visit. Pri or me dicati o ns use d f or t he tr eat me nt of E G a n d/ or E o D s y m pt o ms, e ve n if t he y are 
> 3 0  da ys bef ore t he s cree ni n g visit will be d oc u me nte d i n t he e C R F.  
C CI

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 50 of 127 
Confidential 
Any medication must have been stopped as required in the exclusion criteria. Patients should be 
advised against taking any new medication, both prescribed and over the counter, without 
consulting the Investigator, unless the new medication is required for emergency use. 
Immediately prior to the first infusion, study site personnel should ensure that the patient 
continues to meet the inclusion criteria and none of the exclusion criteria (including no receipt or 
use of prohibited medications). 
All medications taken for the 30 days before screening and during participation in this study 
must be documented on the eCRF. All medications used to treat IRR or AE must be documented. 
All medications given during the conduct of EGD must also be documented.  
8.1 
Prohibited Medications  
Any biologics or other medications that may interfere with the study, such as 
immunosuppressive or immunomodulatory drugs (i.e., azathioprine, JAK inhibitors, 6-
mercaptopurine, methotrexate, cyclosporine, tacrolimus, anti-TNF, anti-IL-5, anti-IL-5 receptor, 
dupilumab, anti-IgE antibodies, omalizumab) are prohibited medications. The use of systemic or 
topical corticosteroids with a dose of >10 mg/day of prednisone or equivalent is prohibited 
unless it is due to unforeseen circumstances when it is deemed to be medically necessary to treat 
an unrelated medical condition or when given as a premedication prior to infusion or to treat an 
IRR that occurs during infusion. 
If a prohibited medication other than corticosteroids as described above is started during the 
course of the study, the patient may be withdrawn from study treatment and followed for the 
12-week follow-up period. The follow-up EGD may not be performed.  
8.2 
Allowed Medications  
Medications, other than those that are prohibited (Section 8.1) such as antihistamines, 
leukotriene antagonists, and sodium cromolyn, are allowed during the study and, unless required 
due to unforeseen medical necessity, doses are to remain stable. All medication use during the 
screening period and throughout the study will be documented in the CRF. Any medications 
used for the treatment of IRR are not considered deviations from the protocol.  
Systemic or swallowed corticosteroids with a dose of ≤10 mg/day of prednisone or equivalent 
are acceptable, as long as the dose remains stable throughout screening and during the study.  
The use of systemic or topical corticosteroids with a dose of >10 mg/day of prednisone or 
equivalent is permitted if it is deemed to be medically necessary to treat an unrelated medical 
condition or when given as a premedication prior to infusion or to treat an IRR that occurs during 
infusion. 

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 5 1  of 1 2 7  
C o nfi d e nti al  
9.  
St u d y Tre at me nt  
9. 1  
F or m ul ati o n of Test Pr o d uct a n d Pl ace b o  
A K 0 0 2 is a h u ma nize d n o n -f uc os ylate d I g G 1 m o n ocl o nal a nti b o d y dir ecte d a gai nst Si glec-8. 
A K 0 0 2 dr u g pr o d uct is s u p plie d as a sterile li q ui d i n a si n gle -us e 1 0 R gl ass vial wit h a fill 
v ol u me of n ot less t ha n 1 0 m L. T he pr o d uct is st ore d at 2° C t o 8° C. T he A K 0 0 2 f or m ulati o n is 
 
 p H 6. 0, i n steril e Water f or I njecti o n.  
P lace b o is s u p plie d as a sterile li q ui d i n a si n gle-us e 1 0 R glass vial wit h a fill v ol u me of 
a p pr o xi matel y 1 0. 6 m L. Place b o c o ntai ns 
 
, p H 6. 0, i n sterile Water for I njecti o n.  
N ote : A K 0 0 2 a n d place b o will be referre d t o as “st u d y dr u g. ”  
9. 2  
St u d y Dr u g P ac k a gi n g a n d L a beli n g  
St u d y dr u g is s u p plie d as a sterile li q ui d i n a si n gl e -use 1 0 R glass vial wit h a fill v ol u me of 
a p pr o xi matel y 1 0. 6 m L. Glass vials are pl u g ge d wit h Tefl o n -c oat e d r u b ber st o p pers a n d seale d 
wit h al u mi n u m seals.  
Eac h vial will be la bel e d wit h t he re q uire d i n vesti gati o nal use st ate me nt, l ot n u m ber, kit n u m ber, 
S p o ns or na me, a n d directi o ns f or st ora ge. E ac h vial will als o c o ntai n a tear -off la bel wit h kit 
n u m ber a n d s pace t o d oc u me nt Patie nt I D a n d pre parati o n date. T his tear -off la bel s h o ul d be 
a p plie d t o t he I P D os e Calc ulati o n a n d Pre parati o n W or ks heet a n d mai ntai ne d wit h t he s o urce 
d oc u me nts.  
9. 3  
S u p pl y of St u d y Dr u g t o t he I n vesti g ati o n al Site  
T he S p o ns or ( or desi g nee) will s hi p st u d y dr u g t o t he i n vesti gati o nal sites. T he i nitial st u d y dr u g 
s hi p me nt will be s hi p pe d after all re q uire d re g ulat or y d o c u me ntati o n a n d a p pr o vals ha ve b ee n 
recei v e d b y t he S p o ns or, c o ntract has b ee n e x ec ute d, a n d t he first scree n e d patie nt is e ntere d i nt o 
t he I R T. S u bse q u e nt st u d y dr u g s hi p me nts will be tri g gere d a ut o maticall y b ase d o n 
pre deter mi ne d s u p pl y le v els a n d e nr oll me nt acti vit y at t he site.  
9. 4  
St u d y Dr u g D os a ge/ D os a ge Re gi me n  
Patie nts will be ra n d o ml y assi g ne d t hr o u g h t he I R T s yste m t o a n acti ve d ose gr o u p of 1 m g/ k g 
A K 0 0 2 f oll o we d b y 5 d oses of 3 m g/ k g or pl ace b o. T he e x act d ose will be calc ulate d pri or t o 
eac h i nf usi o n a n d b ase d o n c urre nt p atie nt wei g ht. St u d y dr u g will be a d mi nistere d as a si n gle 
peri p heral I V i nf usi o n usi n g a n i nf usi o n p u m p as i n dicate d i n t he st u d y P har mac y Ma n u al o n 
Da ys 1, 2 9 ( ± 3), 5 7 ( ± 3), 8 5 ( ± 3), 1 1 3 ( ± 3), a n d 1 4 1 ( ± 3).  
C CI
C CI

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 52 of 127 
Confidential 
9.5 
Preparation of Study Drug 
A study pharmacist or designee will prepare the study drug for each infusion. Based on patient 
weight obtained the day of dosing, the designated study pharmacist will prepare the appropriate 
dilution of AK002 or placebo for IV administration.  
Appropriate aseptic technique will be used, and the drug will be prepared according to the 
pharmacy manual for AK002. Please refer to the Pharmacy Manual for additional details and 
step-by-step instructions regarding study drug preparation. 
Based on current USP 2019 guidelines, AK002 is not considered to be a hazardous drug and 
therefore special precautions do not need to be taken when handling or preparing the study drug.  
The infusion must be completed within 8 hours of preparation. Preparation is when the 
AK002/placebo is first mixed with NaCl. 
9.6 
Study Drug Administration 
Specific instructions on administration and supplies required for administration are detailed in 
the Pharmacy Manual. In general, study drug will be infused through a peripheral vein IV set. 
The IV line will be kept open before and after the infusion with sufficient quantities of 0.9% 
NaCl to assure patency.  
A volume of 100 mL* of the calculated dose of study drug will be infused over at least 4 hours 
on Study Day 1, over at least 3 hours on Study Day 29 (±3), and over at least 2 hours on Study 
Days 57 (±3), 85 (±3), 113 (±3), and 141 (±3). If the infusion is slowed or interrupted, the time 
may be extended longer than 4 hours, as long as it does not exceed 8 hours. 
* 
Due to rounding of the total infusion volume by some programmable infusion pumps, an 
infusion of 99 to 101 mL will be considered a complete infusion and will not be recorded as 
a deviation from the study. 
For the first infusion of study drug, patients will be premedicated with 60 mg oral prednisone (or 
approved equivalent) 12–24 hours prior to the start of the study drug infusion. For subsequent 
infusions, premedication may be used at the discretion of the Investigator and with written 
approval from the Medical Monitor.  
The IV infusion may be interrupted, and/or the rate may be reduced if a patient has an IRR. 
The time the infusion is initiated/concluded (including any interruptions) will be documented in 
the eCRF. If the infusion is restarted after an interruption, the infusion must be completed within 
8 hours of preparation. Administration will be discontinued if, in the opinion of the Investigator, 
an interrupted infusion cannot be restarted for safety reasons or if the infusion cannot be 

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 53 of 127 
Confidential 
completed within 8 hours of preparation. Administration will also be discontinued in any patient 
experiencing a SAE during the course of the infusion.  
The patient will be observed for at least 1 hour after the end of each infusion, as per Investigator 
discretion.  
9.7 
Study Drug Storage 
Study drug will be stored by the study sites at 2°C to 8ºC under lock at the designated pharmacy 
location. Access will be restricted to designated pharmacy staff. The NaCl 0.9% will be stored at 
ambient temperature, per manufacturer’s requirements. All study drug and NaCl will be stored in 
an area that is temperature controlled and monitored. If the temperature of study drug storage in 
the clinic/pharmacy exceeds or falls below this range, it will be reported to the Sponsor or 
designee and captured as a deviation. The Sponsor will notify the site if the study drug is to be 
quarantined or if it can be used. 
9.8 
Study Drug Accountability 
The site’s study pharmacist/designee is responsible for maintaining accurate and current records 
accounting for the receipt, dispensing, preparation, use, return (or destruction), and final 
disposition of all investigational product (IP).  
All dosage calculations will be documented on the source documents. The Master IP 
Accountability Log should be used to capture receipt, dispensing, and return (or destruction). 
Electronic IP accountability systems may be used, depending on site preference, as long as the 
same information is captured. The study monitor will verify entries on these documents 
throughout the course of the study.  
Study drug will be labeled with kit numbers but will not reveal whether the kit is an active kit or 
a placebo kit. 
10. Patient Numbering, Stratification, Randomization, and Blinding 
10.1 
Patient Numbering  
Each patient who provides informed consent will be assigned a patient identification number 
(PID) that uniquely identifies them as a patient in the study. The PID will consist of a 9-digit 
number: 

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Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 5 6  of 1 2 7  
C o nfi d e nti al  
 
After t he i nitial i nf usi o n of st u d y dr u g a n d pri or t o e nr olli n g i n t he A K 0 0 2 -0 1 6 X e xte nsi o n  
st u d y (if a p plica ble), res ults of t he assess me nts n ote d bel o w will n ot be pr o vi de d t o t he 
I n v esti gat or a n d S p o ns or u ntil after data bas e l oc k s o as t o n ot i ntr o d uce bias. T he res ults 
will be re vie we d o n a n o n g oi n g basis b y t he Safet y M o nit or a n d escalat e d as a p pr o priat e.  
–  Differe ntial cell c o u nts i ncl u di n g ne utr o p hils, e osi n o p hils, bas o p hils, m o n oc yt es, a n d 
l y m p h oc ytes.  
–  E n u merati o n of e osi n o p hils a n d  
 fr o m D a y 1 6 9 E G D bi o psies.  
Ot her t ha n u n der t he c o n diti o ns descri be d a b o ve, t he st u d y bli n d will be re v eale d o n c o m pleti o n 
of t he st u d y as n ote d i n Secti o n 1 6. 4 . 
1 0. 4  
Bre a ki n g t he Bli n d  
Brea ki n g t he  bli n d i n a cli nical trial o n a n e mer ge n c y b asis b y t h e site s h o ul d o nl y occ ur w h e n 
k n o wle d ge of t he tr eat me nt t o w hic h a s u bject was all ocate d w o ul d ha ve i m plicati o ns f or t he 
e mer ge n c y me dical ma n a ge m e nt of t he s u bject or if re q uire d f or re g ulat or y re p ort i n g, or if t here 
is a pre g na n c y d uri n g t he pre g na nc y re p orti n g peri o d. If necessar y, e mer ge nc y brea ki n g of t he 
bli n d ca n be c o n d u cte d t hr o u g h t h e I R T b y re gist ere d site users a n d/ or t he Me dical M o nit or. 
W he ne ver p ossi ble, t he I n vesti gat or s h o ul d c o nt act t h e Me dical M o nit or bef ore a n e mer ge nc y 
brea ki n g of t he bli n d. Reas o n f or u n bli n di n g, p ers o n c o n d ucti n g t h e u n bli n di n g, pers o n nel w h o 
k n o w t he u n bli n de d treat me nt, a n d date/ti me of u n bli n di n g will be rec or de d.  
1 1.  St u d y Pr oce d ures a n d G ui deli nes  
Ta ble 1  pr o vi des t he s c he d ule of e ve nts de pi cti n g t he re q uir e d testi n g pr oce d ures t o be 
perf or me d f or t he d urati o n of t he st u d y.  
W he n m ulti ple e val uati o ns are sc h e d ul e d at t he s a me ti me p oi nt, t he pri orit y f or eac h will be as 
f oll o ws:  
 
(self-a d mi nistere d f or mat) s h o ul d be c o m pl ete d at t he be gi n ni n g of t he st u d y visit 
bef ore a n y ot her assess m e nts or pr oce d ures.  
 
P R O q uesti o n naire s h o ul d be c o m plete d b y eac h s u bjec t dail y (at a p pr o xi matel y t h e sa me 
ti me eac h da y) d uri n g t he scree ni n g, tr eat me nt, a n d f oll o w-u p peri o ds.  
 
Vital si g ns will be o btai n e d after t he s u bject has b ee n at r est f or ≥5 mi n utes.  
 
P h ysical e x a mi nati o ns ca n be perf or me d a n d uri ne sa m ples ca n be c olle cte d eit her bef ore or 
after ot her e val u ati o ns, u nless ot her wise s pecifie d.  
C CI
C CI

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 5 7  of 1 2 7  
C o nfi d e nti al  
1 1. 1  
Diet ar y a n d Lif est yle Restricti o ns  
Patie nts s h o ul d mai ntai n t he sa me diet a n d f o o d restricti o ns fr o m t he scree ni n g visit t hr o u g h t he 
E n d -of -St u d y visit. C o m plia nce wit h pre vi o us di etar y a n d lifest yle restricti o ns will be ca pt ure d 
i n t he e C R F at eac h st u d y visit. 
1 1. 2  
P h ar m a c o d y n a mi c/ Effic ac y -Rel ate d Pr o ce d ures  
1 1. 2. 1  
E G/ E o D P R O Q uesti o n n aire  
A n electr o nic v ersi o n of t he E G/ E o D P R O Q uesti o n naire ( A p pe n di x 1 ) will be  c o m plete d dail y 
at a p pr o xi matel y t he sa m e ti me of da y, b y t he pati e nt, t hr o u g h o ut t he st u d y.  
Patie nts will n ot be a ble t o c o m plete a q uesti o n naire m ore t ha n 2 4 h o urs aft er it is d ue a n d will 
o nl y be a ble t o g o bac k a n d ma ke c orrecti o ns or c ha n ges t o t he data ori gi n all y e nt ere d wit h t he 
a p pr o val of t he I n vesti gat or a n d E D C ve n d or. T h e P R O i nf or mati o n will be a ut o maticall y 
ca pt ure d a n d mai ntai ne d i n t he e P R O s yste m of t h e E D C.  
A pa per versi o n of t he P R O Q uesti o n naire is a vaila ble t o patie nts i n case t he y a re n ot a ble t o 
c o m plete t he ele ctr o nic v ersi o n f or a s h ort peri o d of ti me. O nl y 1 P R O s h o ul d be c o m plete d per 
da y a n d t he recall peri o d s h o ul d n ot be a n y m or e t ha n a p pr o xi matel y 2 4 h o urs l o n g. T his 
i nf or mati o n will be ma n uall y ca pt ure d a n d e ntere d  t he E D C b y t he st u d y sit e.  
If patie nts ha ve a hist or y of c o nc o mita nt at o pic der matitis or ast h ma, a n e xtra q uesti o n will be 
p o p ulate d f or eac h rele va nt c o n diti o n o n t he e P R O we bsite f or t he patie nt t o c o m plete dail y. 
All  patie nts will recei ve a n e xtra q u esti o n a b o ut d ys p ha gia d uri n g scree ni n g, a n d p atie nts wit h a 
wee kl y a v era ge > 3 o n at least 2 wee ks d uri n g s cree ni n g will c o nti n ue recei vi n g t his q uesti o n 
after e nr oll me nt i nt o t he st u d y. A pa p er versi o n of t hese q uesti o ns ( A p p e n di x 1 0 ) is a vaila ble, 
s h o ul d t he we bsite n ot be accessi ble, or t he patie nt n ot ha ve inter net access.  
1 1. 2. 2  
 
A n electr o nic v ersi o n of t he 
 (A p pe n di x 2 ) will be c o m plete d b y t h e patie nt 
at t he scree ni n g visit, pre d ose o n i nf usi o n Da ys 1, 2 9, 5 7, 8 5, 1 1 3, a n d 1 4 1 a n d o n f oll o w-u p 
Da y  1 7 6 a n d D a y  1 9 7 or 3 5 ( ± 3) da ys a n d 5 6 ( ±) 3 da ys after l ast d ose of st u d y dr u g if E T. 
A  pa per versi o n of t his q uesti o n naire will als o be a vaila ble f or c o m pleti o n i n case t he el ectr o nic 
q uesti o n naire is n ot a vail a ble t o t he patie nt. T his i nf or mati o n will be e ntere d i nt o t he E D C b y t he 
st u d y site.  
1 1. 2. 3  
 
A n electr o nic v ersi o n of t he 
 (A p pe n di x 9 ) will be 
c o m plete d b y t he patie nt o n St u d y Da y 7 a n d Da y 2 8. A n electr o nic v ersi o n of t he 
 
C CI
C CI
C CI
C CI
C CI

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 5 8  of 1 2 7  
C o nfi d e nti al  
 (A p pe n di x 8 ) will be c o m plete d b y t he patie nt o n Scree ni n g 
Da y  1 8  as w ell as o n S t u d y D a y 7 a n d Da y 2 8. A pa per versi o n of t hese q u esti o n naires will als o 
be a vaila ble f or c o m pleti o n i n case t he el ectr o nic q uesti o n naire is n ot a vail a ble t o t he patie nt. 
T his i nf or mati o n will be e ntere d i nt o t he E D C b y t he st u d y site.  
1 1. 2. 4  
Es o p h a g o -G astr o -D u o de n osc o p y wit h Bi o ps y  
A n E G D wit h bi o ps y will be perf or m e d d uri n g t he scree ni n g p eri o d a n d o n Da y 1 6 9 ( ± 3 da ys) or 
2 8 ( ± 3) da ys after t he last d ose of st u d y dr u g if E T. If t he last i nf usi o n o n Da y 1 4 1 occ urs o utsi de 
t he pr ot oc ol-s pecifie d wi n d o w, t he E G D dat e s h o ul d be m o ve d s o t hat it occ urs 2 8  ( ± 3) da ys 
fr o m t he date of t h e last d ose, e ve n if t his d oes  n ot  fall o n Da y 1 6 9  ( ± 3 da ys). Bi o ps y sa m ples 
will be c ollecte d acc or di n g t o sta n dar dize d i nstr ucti o ns a n d will be se nt t o t he ce ntral la b orat or y 
( or desi gnee) f or fi xi n g a n d stai ni n g. A bli n de d ce ntral rea d er will re p ort, a m o n g ot her t hi n gs, 
ma xi m u m n u m ber of e osi n o p hils per h pf  a n d ma xi m u m n u m ber of tr y ptas e -p ositi ve mast cells 
per h pf, a n d gastric bi o psies will be gra de d usi n g t he S y d ne y S yste m o n i nfla m mati o n, 
meta plasia, atr o p h y, a n d reacti ve gastr o pat h y. T h e Mars h Scale Classificati o n will be use d t o 
gra de d u o de n al sa m ples.  
P os t-treat me nt E G D res ults will n ot be pr o vi de d t o t he I n v esti gat or a n d S p o ns or u ntil after 
data base l oc k. T he Safet y M o nit or will re vie w t h e E G D res ults a n d re p ort a n y iss ues f or 
escalati o n t o t he Me dic al M o nit or a n d t he cli nical site, as a p pr o priat e, w hile mai ntai ni n g t he 
bli n d.  
T he scree ni n g E G D will be use d t o deter mi ne t h e f oll o wi n g i ncl usi o n/e xcl usi o n criteria, a n d t he 
res ults m ust be a vaila ble fr o m t he ce ntr al rea der bef ore t h e patie nt’s eli gi bilit y ca n b e verifie d.  
 
I n cl usi o n Criteri o n  # 3: Baseli ne e n d o sc o pi c bi o ps y wit h > 3 0 e osi n o p hils/ h pf i n 5 h pf i n t he 
st o mac h a n d/ or > 3 0 e osi n o p hils/ h pf i n 3 h pf i n t he d u o de n u m.  
 
E x cl usi o n  Criteri o n  # 5: Acti ve Helic o b a cter pyl ori  i nfecti o n, u nless treate d a n d c o nfir me d 
t o be ne gati ve pri or t o r a n d o mizati o n a n d hist ol og y per re p eat E G D a n d s y m pt o ms still 
q ualif y f or e nr oll me nt aft er treat me nt.  
N ote : A dia g n osis of acti ve H.  pyl ori at scree ni n g ma y b e treate d wit h sta n dar d t h era pies 
a n d a re p eat E G D c o m pl ete d pri or t o e nr oll me nt  t o verif y t hat hist ol o g y criteria are 
still met a n d s y m pt o ms r e mai n c o nsiste nt . If H.  p yl ori  is still prese nt o n re peat E G D 
b ut U B T a n d ot her cli nic al assess me nts of acti ve i nfecti o n are ne gati ve,  t he patie nt 
ma y b e ra n d o mize d i nt o t he st u d y.  
C CI

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 59 of 127 
Confidential 
11.2.5 
Complete Blood Count with Differential 
Blood will be obtained for complete blood count (CBC) with differential at the screening visit, as 
well as predose and 1 hour (±15 minutes) postdose on Days 1, 29, 57, 85, 113, and 141 and on 
Days 8, 15, 169, 176, 197, and 225 or 28, 35, 56, and 84 (±3) days after last dose of study drug 
if ET. The blood sample will be processed and shipped in accordance with laboratory manual 
and lab kit instructions. A central laboratory will analyze the blood sample and provide results 
for CBC with differential including hemoglobin, hematocrit, platelet count, red blood cell count, 
white blood cell count, and absolute differential count (neutrophils, lymphocytes, monocytes, 
eosinophils, and basophils).  
The blood differential test results (neutrophils, eosinophils, basophils, monocytes, and 
lymphocytes) will be blinded from the Investigator and Sponsor from postdose Day 1 through 
Day 225 or ET and until database lock has occurred. As described in the Investigator’s Brochure, 
these are part of the expected effects of AK002 and could potentially serve to introduce bias in 
blinded members of the study. The Safety Monitor will have real-time access to these laboratory 
results and will review and escalate any concerns/issues to the Medical Monitor and/or the site as 
appropriate. An unscheduled CBC with differential may be collected if requested by the Safety 
Monitor. All panic alerts for blinded values will be sent to the Safety Monitor and evaluated in 
real time. 
11.2.6 
Baseline Diet Assessment  
During the screening visit the Investigator or designee will ask the patient a standardized series 
of dietary assessment questions (Appendix 3). This baseline diet assessment involves questions 
regarding food behavior and patterns, as well as types of foods generally avoided, and will serve 
to establish the baseline diet. Answers will be documented in the source documents and recorded 
in the eCRF. This baseline diet should be maintained, as much as possible, throughout the course 
of the study, even if symptoms improve. Compliance with the baseline diet will be assessed at 
study visits on Days 1, 29, 57, 85, 113, 141, 176, 197, and 225 or 35, 56, and 84 (±3) days past 
last dose of study drug if ET. Whether or not the patient has maintained the baseline diet and 
what deviations were made, if applicable, should be documented in the source documents and 
the eCRF.  
11.2.7 
Previous Treatments Review 
During the screening visit the Investigator or designee will ask the patient about the various 
treatments or methods of symptom control that they have tried in relation to their EG/EoD 
symptoms. These may be under the supervision of a doctor or self-attempted by the patient. 
These may include medications (prescription or OTC), food type/eating avoidance or adaptive 
behaviors, as well as alternative medicine (i.e., acupuncture or hypnotic therapy). 

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 60 of 127 
Confidential 
11.3 
Safety-Related Procedures 
11.3.1 
Concomitant Medications 
All concomitant medication and concurrent therapies will be documented at screening and at 
study visits if changes are made. Dose, route, unit, frequency of administration, indication for 
administration, and dates of medication will be captured. Any prior medication received within 
30 days before screening and during the study through Day 225 (±3) or 84 (±3) days after last 
dose of study drug, if ET, will be recorded, or through the first dose of study drug in 
AK002-016X if patient enters the AK002-016X extension study.  
11.3.2 
Complete Physical Examination 
A complete physical exam will be performed by either the Investigator or a qualified designee 
during the screening visit. A complete physical exam will include the following body system or 
organ assessments: skin; head, eyes, ears, nose, and throat (HEENT); thyroid; lungs; 
cardiovascular; abdomen; extremities; lymph nodes; and a brief neurological examination.  
11.3.3 
Body Weight and Height 
At screening, height in cm and weight in kg will be measured and body mass index (BMI) will 
be calculated. On Days 1, 29, 57, 85, 113, and 141, weight will be calculated predose and used to 
determine the amount of study drug to be administered. Body weight will be entered into the IRT 
for each dosing visit and will also be recorded on the IP Dose Calculation and Preparation 
Worksheet that the pharmacist will maintain and document for each patient’s dose calculations. 
Body weight should be collected on site on the day of each study drug infusion or the day prior 
to each infusion. Body weight will also be captured on Day 176 (±3), Day 197, and Day 225 (±3) 
or 35, 56, and 84 (±3) days after last dose of study drug if ET. 
11.3.4 
Stool Sample for Ova and Parasite 
At screening, fecal collection kits will be provided to patients for the ova and parasite test. 
Patients will return the sample to the site during the screening period, within 1 day of collection. 
The site will ship samples to a central laboratory where they will be tested for the presence of 
ova and/or parasites. A negative result for helminthic parasites must be obtained from the central 
laboratory prior to randomization into the study (Day 1).  
A sample collected and analyzed by the central laboratory within 30 days prior to screening may 
be used to satisfy eligibility for the AK002-016 study and a duplicate sample will not be 
collected.  

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 61 of 127 
Confidential 
11.3.5 
Symptom-Directed Physical Examination 
A symptom-directed physical exam, an examination of reported or observed subject symptoms 
warranting examination (in the opinion of the Investigator), including assessments of possible 
infusion site reactions and IRR, will be performed by either the Investigator or a qualified 
designee at all study visits during the treatment period and follow-up period. New, abnormal 
physical exam findings must be documented and will be followed by the Investigator or 
Subinvestigator at the next scheduled visit or sooner if clinically indicated or referred to a non-
study Physician.  
11.3.6 
Electrocardiogram 
An ECG will be obtained during screening after the patient has been in the required position for 
≥5 minutes and before any blood draw. The Investigator or Subinvestigator will review and 
assess any abnormalities on the ECG in terms of clinical significance. The ECG (without 
intensive QT analysis) will be used to identify diseases or conditions that would put the patient at 
increased risk if participating in a clinical trial, so this should be taken into consideration when 
evaluating eligibility for entry into the study. 
11.3.7 
Vital Signs 
Vital signs including systolic and diastolic blood pressure, pulse, body temperature, and 
respiratory rate will be taken after the patient has been at rest for ≥5 minutes and before any 
blood draw (except for post-infusion when vital signs will be obtained as described below).  
On dosing days, vital signs will be measured within 30 minutes predose, 15 (±5) minutes after 
the start of infusion, immediately following the end of infusion (+15 minutes), and just prior to 
discharge. Please refer to the schedule of events in Table 1. 
11.4 
Clinical Laboratory Measurements  
Blood and urine samples for clinical safety laboratory tests will be collected at the time points 
described below and in Table 1. Investigators may have additional laboratory tests performed for 
the purpose of planning treatment administration or following AE or abnormal lab values. 
The site will process and ship blood and urine samples per central laboratory instructions. A 
central laboratory or designee will analyze blood and urine samples and provide results for the 
following clinical safety laboratory tests.  
Clinical laboratory testing may be performed locally if the site thinks the central laboratory may 
not be able to provide results in a timely fashion due to staff reductions, shipping issues, or other 
factors associated with the COVID-19 pandemic. The site will strive to use the central laboratory 
whenever possible. 

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Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 63 of 127 
Confidential 
11.5.1 
Pregnancy Test and Follicle-Stimulating Hormone 
A serum pregnancy (hCG) test will be completed for all patients of childbearing potential. 
Women who are surgically sterile (tubal ligation, hysterectomy, or bilateral oophorectomy) for at 
least 3 months or those who are postmenopausal for at least 1 year with FSH level >30 mIU/mL 
are not considered to be of childbearing potential. At screening, FSH levels will be tested for 
female patients to confirm post-menopausal vs. childbearing status. Both FSH and hCG samples 
will be processed by the central laboratory. 
Patients with FSH levels ≤30 mIU/mL are considered to be of childbearing potential. For 
patients of childbearing potential, the site will perform a urine dipstick pregnancy test prior to 
each study drug dosing and at Day 176 and Day 197 (±3) or 35 and 56 (±3) days after last dose 
of study drug if ET. This test is to be assessed by the study staff prior to the start of each study 
drug infusion. If a patient has a positive pregnancy test, dosing will immediately be discontinued. 
To ensure patient safety, each pregnancy in a patient that received study drug must be reported 
within 24 hours of learning of its occurrence. If the patient received AK002, the pregnancy 
should be followed up to determine outcome, including spontaneous or voluntary termination, 
details of the birth, and the presence of absence of any birth defects, congenital abnormalities, or 
maternal and/or newborn complications. If the patient received AK002, any serious adverse 
event (SAE) experienced during pregnancy must be reported on the SAE Report Form.  
11.5.2 
Urinalysis 
Urine will be obtained for urinalysis at screening and on Days 1, 29, 57, 85, 113, 141, 176, and 
197 or 35 and 56 (±3) days after last dose of study drug if ET. The urine sample will be 
processed and shipped in accordance with the laboratory manual and laboratory kit instructions. 
A central laboratory will analyze the urine sample for specific gravity, pH, protein, glucose, 
ketones, blood, and leukocyte esterase.  
11.5.3 
Serology 
Blood will be obtained at screening for serology tests including hepatitis B surface antigen 
(HbsAG), hepatitis C antibody, hepatitis B core antibody (anti-HBc), and human 
immunodeficiency virus (HIV). The blood sample will be processed and shipped to the central 
laboratory in accordance with the laboratory manual and lab kit instructions. A positive result 
will be verified by appropriate reflex testing. A positive result, if clinically significant (and not 
due to previous vaccination or resolved disease or exposure) will exclude the patient from 
enrollment. 

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 64 of 127 
Confidential 
11.5.4 
Anti-AK002 Antibodies 
Blood will be collected for determination of ADA at screening, on Days 8, 15, 29, 57, 85, 113, 
and 141, and on Days 169, 176, 197, and 225 or 28, 35, 56, and 84 (±3) days after last dose of 
study drug if ET. An unscheduled blood sample for ADA may also be obtained if a related AE 
suspected of being associated with immunogenicity occurs. The serum sample will be collected 
predose and processed and shipped in accordance with the laboratory manual and lab kit 
instructions. A central laboratory will analyze the sample for anti-AK002 antibodies using a 
validated assay method. 
11.5.5 
Blood for Pharmacokinetics and Storage 
Blood samples for serum PK assessments will be collected during the screening period as well as 
pre-dose on dosing Days 29, 57, 85,113, and 141 and on Days 8, 15, 169, 176, 197, and 225 or 
28, 35, 56, and 84 (±3) days after last dose of study drug, if ET. The serum samples will be 
collected pre-dose and processed and shipped frozen in accordance with the study laboratory 
manual and lab kit instructions.  
AK002 concentrations will be determined by the central laboratory or designee using a validated 
ELISA method. Specific information on PK sample collection, processing, storage, and shipment 
will be provided in the laboratory manual.  
11.5.6 
Blood for Histamine and Tryptase 
If anaphylaxis is suspected, a blood sample should be obtained for plasma histamine level and 
tryptase within 1–2 hours of the onset of symptoms. The sample will be sent to the central 
laboratory for processing. Refer to Appendix 6 for more details.  
11.5.7 
Blood for IgE 
Blood will be collected for determination of serum IgE levels and sent to the central laboratory 
for processing. Blood will be collected during screening and on follow-up Day 176 (±3) or 
35 (±3) days after last dose of study drug if ET. 
11.5.8 
Blood for Strongyloides stercoralis 
Blood collected for the screening serology sample will be tested for Strongyloides stercoralis. 
The sample will be processed by the central laboratory. A negative result must be available prior 
to the first dose of study drug. A positive result could indicate past/resolved infection, and a 
patient may be enrolled into the study with a positive Strongyloides stercoralis results as long as 
their ova and parasite test is negative for current infection and the Investigator has no clinical 
indication to believe active infection is present.  

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Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 6 6  of 1 2 7  
C o nfi d e nti al  
 
A n E G D wit h bi o ps y d o es n ot nee d t o be c o m plete d f or A K 0 0 2 -0 1 6 s cree ni n g  i n 
acc or da nce wit h  I ncl usi o n Criteri o n 3: “ Pri or E G D ma y b e use d f or eli gi bilit y as l o n g as t he 
E G D occ urre d wit hi n 3 0 da ys of t he first scree ni n g visit f or t he A K 0 0 2 -0 1 6 st u d y a n d was 
perf or me d a n d ce ntrall y assesse d as f or t he A K 0 0 2 -0 1 6 st u d y. ” 
A n y testi n g re q uire d f or t he A K 0 0 2 -0 1 6 st u d y a n d n ot c o m plete d d uri n g t h e A K 0 0 2 -0 1 4 st u d y 
scree ni n g m ust be c o m pl ete d pri or t o e nr oll me nt i n t he A K 0 0 2 -0 1 6  st u d y.  
T he A K 0 0 2 -0 1 6 
 s h o ul d be c o m plete d b y t he p atie nt pre d ose o n Da y 1.  
St o ol testi n g s h o ul d be re peate d f or t he A K 0 0 2 -0 1 6  st u d y i n t he e ve nt of cli nical s us pici o n of 
hel mi nt hic/ parasitic i nfecti o n or if t he patie nt has tra vele d t o areas w here parasitic i nfecti o ns are 
e n de mic si nce t he A K 0 0 2 -0 1 4 st o ol testi n g  was d o ne .  
1 2.  E v al u ati o ns a n d Pr oce d ures b y Visit  
E val uati o ns a n d pr oce d ures b y visit are s h o w n i n Ta ble 1 . 
Ge neral I nf or m ati o n:  
 
All rec or de d cl oc k ti mes s h o ul d utilize a 2 4-h o ur cl oc k.  
 
Da y 1 is t he da y of t he first i nf usi o n.  
 
Pr oce d ures f or scree ni n g ma y b e perf or me d o ver t he c o urse of m ulti ple visits pri or t o t he 
first i nf usi o n. 
1 2. 1  
Scree ni n g Peri o d  
1)  
O btai n writte n i nf or me d c o nse nt.  
2)  
Assi g n t he partici pa nt a PI D.  
3)  
Be gi n t he c ollecti o n of S A E  relate d t o a n y scree ni n g acti vities. 
4)  
C ollect de m o gra p hics a n d me dical hist or y.  
5)  
Rec or d pri or a n d c o nc o mita nt me dicati o ns.  
6)  
Deter mi ne b o d y w ei g ht a n d hei g ht.  
7)  
Acti vate patie nt a ccess t o e P R O q uesti o n naire p ort al a n d i nstr uct patie nt o n use of t he 
we bsite t o c o m plete t he q uesti o n naire(s). Use t he e P R O Teac hi n g T o ol t o i nstr uct t he 
patie nt o n use of t he el ectr o nic platf or m ( A p pe n di x 7 ). 
8)  
 t o b e c o m pleted b y t he patie nt.  
C CI
C CI

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 6 7  of 1 2 7  
C o nfi d e nti al  
9)  
Perf or m baseli ne di et ass ess me nt . 
1 0)  C o m plete pre vi o us treat me nts re vie w . 
1 1)  O btai n vital si g ns bef ore bl o o d dra ws a n d after patie nt at rest ≥5 mi n utes.  
1 2)  Perf or m a c o m plet e p h ysical e x a mi nati o n.  
1 3)  O btai n a 1 0 -lea d or 1 2-le a d E C G bef ore bl o o d dra w.  
1 4)  C ollect t he f oll o wi n g sa m ples f or t he ce ntral la b orat or y:  
a)  C B C wit h differe ntial  
b)  C he mistr y ( sa m ple t o be teste d f or F S H a n d h C G if patie nt is of c hil d beari n g p ote ntial)  
c)  Uri nal ysis  
d)  Bl o o d f or ser ol o g y testi n g (i ncl u d es Str o n g yl oi des sterc oralis)  
e)  Bl o o d f or P K  
f) Bl o o d f or A D A  
g)  Bl o o d f or t otal ser u m I g E  
1 5)  Pr o vi de patie nt a st o ol c ollecti o n kit a n d as k patie nt t o pr o vi de a st o ol sa m ple w hile o n site 
or ret ur n it t o t he site wit hi n 1 da y of c ollecti o n.  
1 6)  Perf or m a scree ni n g E G D wit h bi o ps y f oll o wi n g pr oce d ures pr o vi de d b y Alla k os a n y ti me 
d uri n g t he s cree ni n g p eri o d.  
1 7)  
 t o be self-c o m plete d b y patie nt o n scree ni n g Da y 1 8  ( n ot a cli nic visit).  
1 8)  Usi n g res ults fr o m t he Ce ntral Hist ol o g y Rea der, c o nfir m t he e o si n o p hil c o u nt fr o m t he 
gastri c a n d/ or d u o de n al bi o psies q ualif y t he patie nt f or t he st u d y a n d n o e x cl usi o nar y 
criteria are f o u n d o n t he E G D.  
1 2. 2  
Pri o r t o D a y 1  
T he f oll o wi n g pr oce d ures will be perf or me d pri or t o Da y 1:  
 
Patie nt s h o ul d self -a d mi nister 6 0 m g or al pre d nis o ne ( or alter nati ve pre me dicati o n 
a p pr o ve d b y t he M e dical M o nit or) 1 2 – 2 4 h o urs pri or t o i nf usi o n start. Patie nt s h o ul d 
re me m ber w hat ti me t he y t o o k t he pre me dicati o n.  
C CI

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 6 8  of 1 2 7  
C o nfi d e nti al  
1 2. 3  
D a y 1 –  R a n d o miz ati o n/I nf usi o n 1  
1)  
Pri or t o t he i nf usi o n:  
a)  Assess t he patie nt f or S A Es relate d t o scree ni n g pr oce d ures.  
b)  C o nfir m c o nti n ui n g eli gi bilit y.  
c)  D oc u me nt a n y c h a n ges t o healt h stat us.  
d)  D oc u me nt a n y c h a n ges t o c o nc o mita nt me dicati o ns.  
e)  D oc u me nt a n y c h a n ges t o baseli ne diet.  
f) 
. 
g)  C o nfir m 
 was c o m plete d electr o ni call y o n scree ni n g Da y 1 8. If it was n ot 
c o m plete d ha ve p atie nt c o m plete a pa per versi o n of t he q uesti o n naire.  
h)  D eter mi ne b o d y w ei g ht.  
i) Uri ne f or uri nal ysis.  
j) Perf or m uri ne pre g na n c y test (if patie nt is of c hil d beari n g p o te ntial). 
k ) C ollect vital si g ns wit hi n 3 0 mi n utes of t he start of t he i nf usi o n. 
l) Perf or m s y m pt o m -dir ect e d p h ysic al e xa m, if nee d e d.  
m ) Bl o o d f or C B C wit h differe ntial.  
n ) Bl o o d f or C he mistr y.  
2)  
Pri or t o ra n d o mizi n g t he patie nt i n t he I R T s yste m, t he site will i de ntif y t he hi g hest w ee kl y 
T S S of disease acti vit y rec or de d d uri n g t he s cree ni n g peri o d i n or der t o stratif y patie nts t o 
T S S ≥2 8 or T S S < 2 8 a n d w het her t he patie nt has a n E o D -o nl y di a g n osis , as i de ntifie d b y 
t he scree ni n g E G D. T he st u d y c o or di n at or or desi g nee will e nter t he hi g h est wee kl y T S S 
i nt o t he I R T o n St u d y Da y 1 t o stratif y t he patie nt, as well as b o d y wei g ht a n d PI D t o assi g n 
kit(s).  
3)  
T he I R T s yst e m will t he n ra n d o ml y assi g n t he p atie nt t o A K 0 0 2 at a d ose of 1  m g/ k g (first 
d ose) or place b o i n a d o u ble -bli n d ma n ner a n d will se n d a n e mail t o t he p har macist a n d/ or 
desi g nee detaili n g t he kit n u m ber(s) t o use t o pr e p are t he i nf usi o n, t he d os e t o pre pare 
( 1 m g/ k g), a n d t he patie nt’s b o d y wei g ht.  
4)  
T he st u d y p h ar macist will pre pare st u d y dr u g usi n g t he wei g ht o btai ne d at t he visit. T he 
fi nal c o m bi ne d v ol u me of t he I V ba g of st u d y dr u g + 0. 9 % Na Cl will be 1 2 0  m L.  
N ote : 1 0 0  m L  of t h e calc ul ate d d ose of st u d y dr u g will be a d mi nistere d t o t he pati e nt. 
T he  e xtra 2 0 m L is t o be use d t o pri me t he I V i nf usi o n li ne d uri n g t he pre parati o n of 
t he I V li ne at t he be dsi d e or t o be left o ver i n t he i nf usi o n ba g. 
C CI
C CI

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 6 9  of 1 2 7  
C o nfi d e nti al  
5)  
I nf usi o n of St u d y Dr u g: 
a)  I nf use 1 0 0 m L of st u d y dr u g o v er at least 4 h o urs usi n g a n i nf usi o n p u m p. See t he 
P har mac y Ma n u al f or i nf usi o n rates. Rec or d t he st art a n d st o p ti mes of t he i nf usi o n 
i ncl u di n g a n y ti mes t he i nf usi o n is i nterr u pte d. 
b)  C ollect vital si g ns 1 5 ( ± 5) mi n utes af ter t he start of i nf usi o n. 
c)  If a na p h yl a xis is s us pecte d, a sa m ple of bl o o d s h o ul d be o btai ne d f or plas m a hista mi ne 
le vel a n d tr y ptase wit hi n 1– 2 h o urs of t he o nset of s y m pt o ms. Als o, a n u nsc he d ule d 
A D A bl o o d sa m ple ma y be o btai ne d if a n i m m u n o ge ni cit y -relate d A E  is s us pecte d. 
6)  
P ost -i nf usi o n: 
a)  C ollect vital si g ns wit hi n 1 5 mi n utes of t he e n d of t he i nf usi o n.  
b)  C ollect C B C wit h differe ntial 1 h o ur ( ± 1 5 mi n utes) after t h e e n d of t h e i nf usi o n.  
c)  O bser ve t he p atie nt f or at least 1 h o ur after t he e n d of i nf usi o n. C ollect vital si g ns j ust 
pri or t o disc har ge.  
1 2. 4  
D a y 7 ( n ot a Cli nic Visit)  
1)  
 (A p p e n di x 8 ) 
2)  
 (A p p e n di x 9 ) 
1 2. 5  
D a y 8 ( ± 2)  
1)  
C B C wit h differe ntial  
2)  
C he mistr y  
3)  
Bl o o d f or A D A  
4)  
Bl o o d f or P K  
1 2. 6  
D a y 1 5 ( ± 2)  
1)  
C B C wit h differe ntial  
2 ) 
C he mistr y  
3 ) 
Bl o o d f or A D A  
4 ) 
Bl o o d f or P K  
1 2. 7  
D a y 2 8 ( n ot a Cli nic Visit)  
1)  
 (A p p e n di x 8 ) 
2)  
 (A p p e n di x 9 ) 
C CI
C CI
C CI
C CI

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 7 0  of 1 2 7  
C o nfi d e nti al  
1 2. 8  
D a y 2 9 ( ± 3) –  I nf usi o n 2 
1)  
Pri or t o t he i nf usi o n:  
a)  Assess t he patie nt f or A E  a n d S A E . 
b)  D oc u me nt a n y c h a n ges t o c o nc o mita nt me dicati o ns.  
c)  Assess baseli ne diet c o m plia nce.  
d)  Assess dail y diar y c o m plia nce (i ncl u di n g a n y a d diti o nal q uesti o ns).  
e)  
 
f) Deter mi ne b o d y w ei g ht.  
g)  Uri nal ysis  
h)  Perf or m uri ne pre g na n c y test (if patie nt is of c hil d beari n g p ote ntial).  
i) C ollect vital si g ns wit hi n 3 0 mi n utes of  t he start of t he i nf usi o n. 
j) Perf or m s y m pt o m -dir ect e d p h ysic al e xa m, as nee de d.  
k)  C B C wit h differe ntial  
l) C he mistr y  
m)  Bl o o d f or P K  
n)  Bl o o d f or A D A  
o)  T he I R T will be ac cesse d, a n d t he patie nt’s PI D a n d b o d y wei g ht will be e ntere d.  
2)  
T he st u d y p h ar macist will pre pare st u d y dr u g usi n g t he c urre nt b o d y wei g ht o btai ne d a n d 
t he d osa ge ( 3 m g/ k g) a n d kit n u m ber(s) pr o vi de d b y t he I R T.  
3)  
I nf usi o n of St u d y Dr u g: 
a)  I nf use 1 0 0 m L of st u d y dr u g o v er at least 3 h o urs usi n g a n i nf usi o n p u m p. See t he 
P har mac y Ma n u al f or i nf usi o n rates. Rec or d t he st art a n d st o p ti mes of t he i nf usi o n 
i ncl u di n g a n y ti mes t he i nf usi o n is i nterr u pte d. 
b)  C ollect vital si g ns 1 5 ( ± 5) mi n utes after t he sta rt of i nf usi o n. 
c)  If a na p h yl a xis is s us pecte d, a sa m ple of bl o o d s h o ul d be o btai ne d f or plas m a hista mi ne 
le vel a n d tr y ptase wit hi n 1– 2 h o urs of t he o nset of t he s y m pt o ms. Als o, a n u nsc he d ule d 
A D A bl o o d sa m ple ma y be o btai ne d if a n i m m u n o ge ni cit y -relate d A E  is s us pecte d. 
4)  
P ost -i nf usi o n: 
a)  C ollect vital si g ns wit hi n 1 5 mi n utes of t he e n d of t he i nf usi o n.  
b)  C ollect C B C wit h differe ntial 1 h o ur ( ± 1 5 mi n utes) after t h e e n d of t h e i nf usi o n.  
C CI

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 7 1  of 1 2 7  
C o nfi d e nti al  
c)  O bser ve t he p atie nt f or at least 1 h o ur after t he e n d of t he i nf u si o n. C ollect vital si g ns 
j ust pri or t o disc har ge. 
1 2. 9  
D a y 5 7 ( ± 3) –   I nf usi o n 3 
1)  
Pri or t o t he i nf usi o n:  
a)  Assess t he patie nt f or A E  a n d S A E . 
b)  D oc u me nt a n y c h a n ges t o c o nc o mita nt me dicati o ns.  
c)  Assess baseli ne diet c o m plia nce.  
d)  Assess dail y diar y c o m pl ia nce (i ncl u di n g a n y a d diti o nal q uesti o ns). 
e)  
 
f) Deter mi ne b o d y w ei g ht.  
g)  Perf or m uri ne pre g na n c y test (if patie nt is of c hil d beari n g p ote ntial).  
h)  C ollect vital si g ns wit hi n 3 0  mi n utes of  t he start of t he i nf usi o n. 
i) Perf or m s y m pt o m-dir ect e d p h ysic al e xa m, as nee de d.  
j) C B C wit h differe ntial  
k)  C he mistr y  
l) Uri nal ysis  
m)  Bl o o d f or P K  
n)  Bl o o d f or A D A  
2)  
T he I R T will be accesse d, a n d t he patie nt’s PI D a n d wei g ht will be e ntere d.  
3)  
T he st u d y p h ar macist or desi g nee will pre p are  st u d y dr u g usi n g t he wei g ht o btai ne d at t he 
visit a n d t he d osa ge ( 3 m g/ k g) a n d kit n u m ber(s) pr o vi de d b y t he I R T.  
4)  
I nf usi o n of St u d y Dr u g: 
a)  I nf use 1 0 0 m L of st u d y dr u g o v er at least 2 h o urs usi n g a n i nf usi o n p u m p. See t he 
P har mac y Ma n u al f or i nf usi o n rates. Rec or d t he st art a n d st o p ti mes of t he i nf usi o n 
i ncl u di n g a n y ti mes t he i nf usi o n is i nterr u pte d. 
b)  C ollect vital si g ns 1 5 ( ± 5) mi n utes after t he start of i nf usi o n.  
c)  If a na p h yl a xis is s us pecte d, a sa m ple of bl o o d s h o ul d be o btai ne d f or plas m a hista mi ne 
le vel a n d tr y ptase wit hi n 1– 2 h o urs of t he o nset of s y m pt o ms. Als o, a n u nsc he d ule d 
A D A bl o o d sa m ple ma y be o btai ne d if a n i m m u n o ge ni cit y -relate d A E  is s us pecte d. 
C CI

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 7 2  of 1 2 7  
C o nfi d e nti al  
5)  
P ost -i nf usi o n: 
a)  C ollect vital si g ns wit hi n 1 5 mi n utes of t he e n d of t he i nf usi o n.  
b)  C ollect C B C wit h differe ntial 1 h o ur ( ± 1 5 mi n utes) after t h e e n d of t h e i nf usi o n.  
c)  O bser ve t he p atie nt f or at least 1 h o ur after t he e n d of t he i nf usi o n. C ollect vital si g ns 
j ust pri or t o disc har ge. 
1 2. 1 0  D a y 8 5 ( ± 3) –  I nf usi o n 4 
1)  
Pri or t o t he i nf usi o n:  
a) Assess t he patie nt f or A E  a n d S A E . 
b)  D oc u me nt a n y c h a n ges t o c o nc o mita nt me dicati o ns.  
c)  Assess baseli ne diet c o m plia nce.  
d)  Assess dail y diar y c o m plia nce (i ncl u di n g a n y a d diti o nal q uesti o ns)  
e)  
. 
f) Deter mi ne b o d y w ei g ht.  
g)  Uri nal ys is 
h)  Perf or m uri ne pre g na n c y test (if patie nt is of c hil d beari n g p ote ntial).  
i) C ollect vital si g ns wit hi n 3 0 mi n utes of  t he start of t he i nf usi o n. 
j) Perf or m s y m pt o m -dir ect e d p h ysic al e xa m, as nee de d.  
k)  C B C wit h differe ntial  
l) C he mistr y  
m)  Bl o o d f or P K  
n)  Bl o o d f or A D A  
2)  
T he I R T will be accesse d, a n d t he patie nt’s PI D a n d b o d y wei g ht will be e ntere d.  
3)  
T he st u d y p h ar macist will pre pare st u d y dr u g usi n g t he wei g ht  o btai ne d at t he visit  a n d t he 
d osa ge ( 3 m g/ k g) a n d kit n u m ber(s) pr o vi d e d b y t he I R T.  
4)  
I nf usi o n of St u d y Dr u g: 
a)  I nf use 1 0 0 m L of st u d y dr u g o v er at least 2 h o urs usi n g a n i nf usi o n p u m p. See t he 
P har mac y Ma n u al f or i nf usi o n rates. Rec or d t he st art a n d st o p ti mes of t he i nf usi o n 
i ncl u di n g a n y ti mes t he i nf usi o n is i nterr u pte d. 
b)  C ollect vital si g ns 1 5 ( ± 5) mi n utes after t he start of i nf usi o n.  
C CI

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 7 3  of 1 2 7  
C o nfi d e nti al  
c)  If a na p h yl a xis is s us pecte d, a sa m ple of bl o o d s h o ul d be o btai ne d f or plas m a hista mi ne 
le vel a n d tr y ptase wit hi n 1– 2 h o urs of t he o nset of s y m pt o ms. Als o, a n u nsc he d ule d 
A D A bl o o d sa m ple ma y be o b tai ne d if a n i m m u n o ge ni cit y-relate d A E  is s us pecte d. 
5)  
P ost -i nf usi o n: 
a)  C ollect vital si g ns wit hi n 1 5 mi n utes of t he e n d of t he i nf usi o n.  
b)  C ollect C B C wit h differe ntial 1 h o ur ( ± 1 5 mi n utes) after t h e e n d of t h e i nf usi o n.  
c)  O bser ve t he p atie nt f or at l east 1 h o ur after t he e n d of t he i nf usi o n. C ollect vital si g ns 
j ust pri or t o disc har ge. 
1 2. 1 1  D a y 1 1 3 ( ± 3) –  I nf usi o n 5 
1)  
Pri or t o t he i nf usi o n:  
a)  Assess t he patie nt f or A E  a n d S A E . 
b)  D oc u me nt a n y c h a n ges t o c o nc o mita nt me dicati o ns.  
c)  Assess baseli ne diet c o m plia nce.  
d)  Assess dail y diar y c o m plia nce (i ncl u di n g a n y a d diti o nal q uesti o ns).  
e)  
. 
f) Deter mi ne b o d y w ei g ht.  
g)  Uri nal ysis  
h)  Perf or m uri ne pre g na n c y test (if patie nt is of c hil d beari n g p ote ntial).  
i) C ollect vital si g ns wit hi n 3 0 mi n utes of  t he start of t he i nf usi o n. 
j) Perf or m s y m pt o m -dir ect e d p h ysic al e xa m, as nee de d.  
k)  C B C wit h differe ntial  
l) C he mistr y  
m)  Bl o o d f or P K  
n)  Bl o o d f or A D A  
2)  
T he I R T will be accesse d, a n d t he patie nt’s PI D a n d b o d y wei g ht will be e ntere d.  
3)  
T he st u d y  p h ar macist will pre pare st u d y dr u g usi n g t he wei g ht  o btai ne d at t he visit  a n d t he 
d osa ge ( 3 m g/ k g) a n d kit n u m ber(s) pr o vi d e d b y t he I R T.  
C CI

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 7 4  of 1 2 7  
C o nfi d e nti al  
4)  
I nf usi o n of St u d y Dr u g: 
a)  I nf use 1 0 0 m L of st u d y dr u g o v er at least 2 h o urs usi n g a n i nf usi o n p u m p. See t he 
P har mac y Ma n u al f or i nf usi o n rates. Rec or d t he st art a n d st o p ti mes of t he i nf usi o n 
i ncl u di n g a n y ti mes t he i nf usi o n is i nterr u pte d. 
b)  C ollect vital si g ns 1 5 ( ± 5) mi n utes after t he start of t he i nf usi o n.  
c)  If a na p h yl a xis is s us pecte d, a sa m ple of bl o o d sh o ul d be o btai ne d f or plas m a hista mi ne 
le vel a n d tr y ptase wit hi n 1– 2 h o urs of t he o nset of s y m pt o ms. Als o, a n u nsc he d ule d 
A D A bl o o d sa m ple ma y be o btai ne d if a n i m m u n o ge ni cit y -relate d A E  is s us pecte d. 
5)  
P ost -i nf usi o n: 
a)  C ollect vital si g ns wit hi n 1 5 mi n u tes of t he e n d of t he i nf usi o n. 
b)  C ollect C B C wit h differe ntial 1 h o ur ( ± 1 5 mi n utes) after t h e e n d of t h e i nf usi o n.  
c)  O bser ve t he p atie nt f or at least 1 h o ur after t he e n d of t he i nf usi o n. C ollect vital si g ns 
j ust pri or t o disc har ge. 
1 2. 1 2  D a y 1 4 1 ( ± 3) –  I nf usi o n 6 
1)  
Pri or t o t he i nf usi o n:  
a)  Assess t he patie nt f or A E  a n d S A E . 
b)  D oc u me nt a n y c h a n ges t o c o nc o mita nt me dicati o ns.  
c)  Assess baseli ne diet c o m plia nce.  
d)  Assess dail y diar y c o m plia nce (i ncl u di n g a n y a d diti o nal q uesti o ns)  
e)  
. 
f) Deter mi ne b o d y w ei g ht.  
g)  Uri nal ysis  
h)  Perf or m uri ne pre g na n c y test (if patie nt is of c hil d beari n g p ote ntial).  
i) C ollect vital si g ns wit hi n 3 0  mi n utes of  t he start of t he i nf usi o n. 
j) Perf or m s y m pt o m -dir ect e d p h ysic al e xa m, as nee de d.  
k)  C B C wit h differe ntial  
l) C he mistr y  
m)  Bl o o d f or P K  
n)  Bl o o d f or A D A  
C CI

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 75 of 127 
Confidential 
2) 
The IRT will be accessed, and the patient’s PID and body weight will be entered. 
3) 
The study pharmacist will prepare study drug using the weight obtained at the visit and the 
dosage (3 mg/kg) and kit number(s) provided by the IRT. 
4) 
Infusion of Study Drug: 
a) Infuse 100 mL of study drug over at least 2 hours using an infusion pump. See the 
Pharmacy Manual for infusion rates. Record the start and stop times of the infusion 
including any times the infusion is interrupted. 
b) Collect vital signs 15 (±5) minutes after the start of the infusion. 
c) If anaphylaxis is suspected, a sample of blood should be obtained for plasma histamine 
level and tryptase within 1–2 hours of the onset of symptoms. Also, an unscheduled 
ADA blood sample may be obtained if an immunogenicity-related AE is suspected. 
5) 
Post-infusion: 
a) Collect vital signs within 15 minutes of the end of the infusion. 
b) Collect CBC with differential 1 hour (±15 minutes) after the end of the infusion. 
c) Observe the patient for at least 1 hour after the end of the infusion. Collect vital signs 
just prior to discharge. 
12.13 Day 169 (±3) or 28 (±3) Days after Last Dose of Study Drug if ET – Follow-up EGD 
1) 
Patient should arrive fasting for the EGD procedure as specified by instructions from the 
EGD provider. 
2) 
Blood Draws: 
a) Blood for CBC with differential 
b) Blood for Chemistry 
c) Blood for PK 
d) Blood for ADA 
3) 
Collect AE, SAE, and changes in baseline diet. Collect all concomitant medications 
provided to the patient during the EGD. 
4) 
Perform EGD with biopsy following procedures provided by Allakos and all EGD facility 
standard operating procedures.  

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 7 6  of 1 2 7  
C o nfi d e nti al  
F or E a rl y Ter mi n ati o n:  Perf or m t he E G D 2 8 ( ± 3) da ys after t he last d ose of st u d y dr u g or pri or 
t o t his, if necessar y, t o e ns ure c o m plia nce wit h t he visit. If patie nt disc o nti n ues t he st u d y m or e 
t ha n 2 8 da ys after t he last d ose of st u d y dr u g, p erf or m t he E G D as s o o n as p ossi ble.  
If D a y 1 4 1 (I nf usi o n 6) occ urs o utsi de t he pr ot oc ol wi n d o w: D o n ot c o n d uct E G D o n Da y  1 6 9 
b ut rat her o n a d a y t hat is 2 8 ( ± 3) d a ys after t he Da y 1 4 1 i nf usi o n . 
1 2. 1 4  D a y 1 7 6 ( ± 3) or 3 5 ( ± 3) D a ys after L ast D ose of St u d y Dr u g if E T –  
F oll o w -u p  Visit  1  
1)  
Assess t he patie nt f or A E  a n d S A E . 
2)  
D oc u me nt a n y c h a n ges t o c o nc o mita nt me dicati o n s. 
3)  
Assess baseli ne diet c o m plia nce.  
4)  
Assess dail y diar y c o m plia nce (i ncl u di n g a n y a d diti o nal q uesti o ns).  
5)  
. 
6)  
Deter mi ne b o d y w ei g ht.  
7)  
C ollect vital si g ns.  
8)  
Perf or m s y m pt o m -dir ect e d p h ysic al e xa m, as nee de d.  
9)  
Bl o o d Dra ws:  
a)  Bl o o d f or C B C wit h differe ntial  
b)  Bl o o d f or C he mistr y  
c)  Bl o o d f or P K  
d)  Bl o o d f or A D A  
e)  Bl o o d f or I g E  
1 0)  Uri nal ysis a n d uri ne pre g na nc y test (if patie nt is of c hil d beari n g p ote ntial) 
1 1 ) Patie nts w h o e nr oll i n t he A K 0 0 2 -0 1 6 X e xte nsi o n st u d y will be gi n  e xte nsi o n st u d y d osi n g 
1  d ay after  c o m pleti n g th e Da y 1 7 6 pr oce d ures f or Pr ot oc ol A K 0 0 2 -0 1 6. Patie nt s ma y si g n 
c o nse nt f or t he A K 0 0 2-0 1 6 X st u d y d uri n g partici pati o n i n t he A K 0 0 2 -0 1 6 st u d y a n d ma y 
recei v e t he pre me dicati o n f or t he first A K 0 0 2 -0 1 6 X d ose as s o o n as all Da y 1 7 6 pr oce d ures 
ha ve bee n c o m plete d i n t he mai n st u d y. If patie nts ca n n ot start t he e xte nsi o n st u d y 1  da y 
after t he Da y 1 7 6 visit, t he y will c o nti n ue partici pati o n i n t he mai n st u d y. If patie nts ca n n ot 
start t he e xte nsi o n st u d y wit hi n 2 8 da ys of t he Da y 1 7 6 visit i n t he mai n st u d y, t he Da y 1 9 7 
visit will occ ur.  
C CI

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 7 7  of 1 2 7  
C o nfi d e nti al  
F or E a rl y Ter mi n ati o n:  Perf or m t he visit 3 5 ( ± 3) da ys after t h e last d ose of st u d y dr u g or pri or 
t o t his, if necessar y, t o e ns ure c o m plia nce wit h t he visit. If patie nt disc o nti n ues t he st u d y m or e 
t ha n 3 5 da ys after t he last d ose of st u d y dr u g, p erf or m t he visit as s o o n as p ossi ble. If o nl y o n e 
E T visit is p ossi ble, E G D a n d F oll o w -u p Visit  1 ma y o cc ur o n t h e sa me da y. Bl o o d dra ws s h o ul d 
occ ur pri or t o E G D me di cati o ns, if p ossi bl e.  
1 2. 1 5  D a y 1 9 7 ( ± 3) or 5 6 ( ± 3) D a ys after L ast D ose of St u d y Dr u g if E T –  
F oll o w -u p  Visit  2  
1)  
Assess t he patie nt f or A E  a n d S A E .  
2)  
D oc u me nt a n y c h a n ges t o c o nc o mita nt me dicati o ns.  
3)  
Assess baseli ne diet c o m plia nce.  
4)  
. 
5)  
Deter mi ne b o d y w ei g ht.  
6)  
C ollect vital si g ns.  
7)  
Perf or m s y m pt o m -dir ect e d p h ysic al e xa m, as nee de d.  
8)  
Uri nal ysis a n d uri ne pre g na nc y test (if patie nt is of c hil d beari n g p ote ntial) 
9)  
Bl o o d Dra ws:  
a)  Bl o o d f or C B C wit h differe ntial  
b)  Bl o o d f or C he mistr y  
c)  Bl o o d f or P K 
d)  Bl o o d f or A D A  
1 0)  Patie nts o pti n g t o e nr oll i n t he A K 0 0 2 -0 1 6 X e xte nsi o n st u d y after t he Da y 1 9 7 visit will 
be gi n e xte nsi o n st u d y d osi n g wit hi n 2 8 da y s of  c o m pleti n g t he Da y 1 9 7 pr oce d ures f or 
Pr ot oc ol A K 0 0 2 -0 1 6. If patie nts ca n n ot start t he e xte nsi o n st u d y wit hi n 2 8 da ys of t he 
Da y  1 9 7 visit, t he y will c o nti n ue partici pati o n i n  t he mai n st u d y. If patie nts ca n n ot start t he 
e xte nsi o n st u d y wit hi n 2 8 da ys of t he Da y 1 9 7 visit i n t he mai n st u d y, t he Da y 2 2 5 visit 
will occ ur  
F or E a rl y Ter mi n ati o n:  Perf or m t he visit 5 6 ( ± 3) da ys after t h e last d ose of st u d y dr u g or pri or 
t o t his, if necessar y, t o e ns ure c o m plia nce wit h t he visit. If patie nt disc o nti n ues t he st u d y m or e 
t ha n 5 6 da ys after t he last d ose of st u d y dr u g, p erf or m t he visit as s o o n as p ossi ble.  
C CI

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Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 82 of 127 
Confidential 
AE eCRF as separate AE. The Investigator (or qualified Subinvestigator) must assign the 
following AE attributes listed below and is responsible for ensuring this information is recorded 
in the source documentation. 
13.6.2 
Assessment of Intensity 
The Investigator will use their clinical judgment as well as the guidelines laid out in the NCI 
CTCAE Version 5.0 (or most current version) tables (Table 2 and Appendix 4) to assess the 
intensity of each AE and SAE. 
Table 2 
Adverse Event Severity per CTCAE 
Grade 
CTCAE Description* 
1 
Mild; asymptomatic or mild symptoms; clinical or diagnostic observations only; intervention 
not indicated. 
2 
Moderate; minimal, local or noninvasive intervention indicated; limiting age appropriate 
instrumental activities of daily living (ADL). 
3 
Severe or medically significant but not immediately life-threatening, hospitalization or 
prolongation of hospitalization indicated; disabling; limiting self-care ADL. 
4 
Life-threatening consequences, urgent intervention indicated. 
5 
Death related to adverse event. 
* CTCAE v. 5.0: Grade refers to the severity of the AE. The CTCAE displays Grades 1–5 with unique clinical 
descriptions of severity for each AE based on this general guideline. 
The term “severe” is a measure of intensity, and a severe AE is not necessarily a SAE.  
When the intensity of an AE changes more than once a day, the maximum severity for the event 
should be entered into the AE eCRF. If the intensity changes over a number of days, these 
changes should be recorded separately (i.e., as having distinct onset dates). 
13.6.3 
Assessment of Causality to Study Drug 
The Investigator should use their clinical judgment as well as the guidelines in Table 3 to assess 
the relationship between study drug and AE. 

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 83 of 127 
Confidential 
Table 3 
Adverse Event Relationship to Study Drug  
Relationship to 
Study Drug 
Comment 
Related 
There is clear evidence that the event is related to the use of study drug (e.g., confirmation by 
positive re-challenge test, if possible). Another etiology is considerably less likely. 
Possible 
The event cannot be explained by the subject’s medical condition, concomitant therapy, or 
other causes, and there is a plausible temporal relationship between the event and study drug 
administration.  
Unlikely/Remote 
An event for which an alternative explanation is more likely (e.g., concomitant medications 
or ongoing medical conditions) or the temporal relationship to study drug administration 
and/or exposure suggests that a causal relationship is unlikely. (For reporting purposes, 
Unlikely/Remote will be grouped together with Not Related.)  
Not Related 
The event can be readily explained by the subject’s underlying medical condition, 
concomitant therapy, or other causes, and therefore, the Investigator believes no relationship 
exists between the event and study drug.  
13.6.4 
Assessment of Causality to Study Procedure 
The Investigator should use their clinical judgment as well as the guidelines in Table 4 to assess 
the relationship between study procedure and AE. Assessment of causality to study procedure 
should include causality to such items as EGD with biopsy or blood draw (as appropriate), or 
other.  
Table 4 
Adverse Event Relationship to Study Procedure 
Relationship to 
Study Procedure 
Comment 
Related 
There is clear evidence that the event is related to a study procedure. 
Possible 
The event cannot be explained by the subject’s medical condition, concomitant therapy, or 
other causes, and there is a plausible temporal relationship between the event and a study 
procedure.  
Unlikely/Remote 
An event for which an alternative explanation is more likely (e.g., concomitant medications 
or ongoing medical conditions) or the temporal relationship to any study procedure suggests 
that a causal relationship is unlikely (For reporting purposes, Unlikely/Remote will be 
grouped together with Not Related).  
Not Related 
The event can be readily explained by the subject’s underlying medical condition, 
concomitant therapy, or other causes, and therefore, the Investigator believes no relationship 
exists between the event and a study procedure.  

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 84 of 127 
Confidential 
13.6.5 
Action Taken 
Action taken with respect to study drug will be categorized as none, study drug permanently 
discontinued, study drug temporarily withdrawn, or other (specify). 
Action taken with respect to study participation will be categorized as none, withdrawal from 
study participation, or other (specify).  
Action taken with respect to treatment of an AE will be categorized as none, concomitant 
medication, concomitant procedure, or other (specify).  
13.6.6 
Assessment of Outcome 
Event outcome at resolution or time of last follow-up will be recorded as: recovered, recovering, 
not recovered, recovered with sequelae, fatal, or unknown.  
13.7 
Adverse Event Reporting Procedures  
13.7.1 
All Adverse Events  
Any clinically significant AE that is ongoing at the time of study completion or early termination 
will be followed by the Investigator until event resolution, the AE is otherwise explained, not 
considered clinically significant by the Investigator, or the subject is lost to follow-up. 
All AE identified, whether serious or non-serious, will be recorded in the AE eCRF beginning 
after the first administration of study drug and ending on Day 225 (±3) or 84 (±3) days after last 
dose if patient is not enrolling in the AK002-016X extension study, or until the start of the first 
dose on Day 1 of the extension study, if enrolling in AK002-016X, unless otherwise directed by 
Allakos. 
Whenever appropriate, the CTCAE (v. 5.0 or most current version) should be utilized for naming 
common AE (Appendix 4). 
13.7.2 
Serious Adverse Event Reporting  
In the event of any SAE reported or observed during the study, whether or not attributable to the 
study drug, site personnel must report it immediately (within 24 hours of becoming aware of 
the SAE) by telephone or email to the Sponsor, Allakos Inc.  
SAE report forms will be provided to the investigational site to assist in collecting, organizing, 
and reporting SAE, and forms must be completed with as much information as is available and 
should be submitted to the Sponsor within 24 hours of becoming aware of the event. Serious 
adverse events must also be recorded on the AE eCRF and designated as “serious.”  

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Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 86 of 127 
Confidential 
Serious adverse events must be reported within 24 hours to: 
 
SAE Reporting 
 
Fax: 
+1-888-237-7475 
 
Email: 
SAE@allakos.com 
13.7.3 
Pregnancy Reporting 
Pregnancies are captured if they occur in female patients or in the sexual partners of male 
patients from the time the patient is first exposed to the investigational product through Day 225 
(±3) or 84 (±3) days after the last dose if patient is not enrolling in the AK002-016X extension 
study, or until the start of the first dose on Day 1 of extension study, if enrolling in 
AK002-016X, unless otherwise directed by Allakos. 
Female patients must be instructed to discontinue all study drugs and inform the Investigator 
immediately if they become pregnant during the study. Male patients must be instructed to 
inform the Investigator immediately if their partner becomes pregnant during the study. 
The Investigator must report any pregnancy to Allakos within 24 hours of becoming aware of it 
using the provided pregnancy reporting forms. The patient must be immediately discontinued 
from study drug. An uncomplicated pregnancy will not be considered an AE or SAE, but all 
pregnancies in patients who received AK002 will be followed through term.  
Any congenital abnormalities noted at birth in the offspring of a patient who received AK002 
will be reported as an SAE. If the patient received AK002, the outcome of any pregnancy and the 
presence or absence of any congenital abnormality will be recorded in the source documentation 
and reported to the Medical Monitor and Sponsor.  
13.7.4 
AESI Reporting 
Beginning from the time of first study drug infusion and ending on Day 225 (±3) or 84 (±3) days 
after last dose if patient is not enrolling in the AK002-016X extension study, or until the start of 
the first dose on Day 1 of the extension study, if enrolling in AK002-016X, unless otherwise 
directed by Allakos any new AESI (or new information related to a previously reported AESI) 
must be recorded in the AE eCRF and designated as an “adverse event of special interest.”  
An AESI that also qualifies as a SAE (per Section 13.2) must also be reported as a SAE in 
accordance with Section 13.7.2. Adverse events of special interest that are also SAE must be 
recorded in the AE eCRF and designated as both “serious” and as an “adverse event of special 
interest.” These will be reported on the Sponsor-provided SAE forms and should be reported to 
the Sponsor within 24 hours of site awareness. 

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 8 7  of 1 2 7  
C o nfi d e nti al  
1 3. 8  
Me dic al M o nit ori n g  
Dr. 
 s h o ul d be c o ntacte d directl y usi n g t he p h o ne n u m ber a n d/ or e mail a d dress 
bel o w t o re p ort me dic al c o ncer ns or f or q uesti o ns re gar di n g safet y.  
 
Alla k os Me dical M o nit or  
 
 M D 
 
P h o ne:  
 
 
E mail:  
 
1 3. 9  
I n de pe n de nt D at a M o nit ori n g C o m mittee 
A n I n de pe n d e nt Data M o nit ori n g C o m mittee (i D M C) has bee n c o n v e ne d f or t his st u d y. T he 
i D M C will meet at esta blis he d i nter vals t hr o u g h o ut t he st u d y a n d will als o c o n ve ne as 
necessitate d b y d ata a n d/ or safet y re vie ws.  
1 3. 1 0  St u d y Wit h dr a w al Criteri a  
Partici pati o n  of a patie nt will be disc o nti n ue d i n t he e ve nt t hat:  
 
Occ urre nce of a n e x cl usi o n criteri o n, w hic h is cli nicall y rele va nt a n d affects t he patie nt’s 
safet y, if disc o nti n uati o n is c o nsi dere d necessar y b y t he I n v esti gat or a n d/ or S p o ns or.  
 
Re b o u n di n g of e osi n o p h il c o u nts t o > 1 5 0 0/L i n patie nts w h o e ntere d t he st u d y wit h 
e osi n o p hil le vels > 1 5 0 0/ L, a n d w h os e e osi n o p hil c o u nts were i nitiall y s u p presse d after 
st u d y dr u g will be wit h dr a w n fr o m t he st u d y at t he i nstr ucti o n of t he Safet y M o nit or.  
 
Ser u m tra nsa mi nases ( A L T a n d/ or A S T) > 3 × U L N a n d t otal bilir u bi n > 2 × U L N 
(c o nfir me d b y s u bs e q ue nt re peat) wit h o ut a n alter nati ve e x pla nati o n.  
 
Ele vati o n of A L T or A S T > 3 × U L N (c o nfir me d b y re peat) wit h t he a p peara nce or 
w orse ni n g of s y m pt o ms felt b y t he I n v esti gat or t o be p ote ntiall y relate d t o h e patic 
i nfla m mati o n, s uc h as fati g ue, n a usea, v o miti n g, ri g ht u p per q ua dra nt pai n or te n der ness, 
fe ver, ras h. 
1 3. 1 1  St u d y St o p pi n g R ules  
T he st u d y ma y b e disc o nti n ue d pre mat urel y i n t he e ve nt of a n y of t he f oll o wi n g:  
 
A life -t hreate ni n g A E  t hat is p ossi bl y or pr o ba bl y relate d t o treat me nt.  
 
A fatal A E  t hat is p ossi bl y or pr o ba bl y relate d t o treat me nt.  
 
Ne w i nf or mati o n le a di n g t o u nfa v ora ble ris k -be nefit j u d g me nt of t he st u d y dr u g.  
 
S p o ns or’s decisi o n t hat c o nti n uati o n of t he trial is u nj ustifia ble f or me dical or et hical 
reas o ns.  
 
Disc o nti n uati o n of de vel o p me nt of t he S p o ns or’s st u d y dr u g.  
P P D
P P D
P P D
P P D

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14. Discontinuation and Replacement of Patients 
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Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 89 of 127 
Confidential 
Reasonable attempts will be made by the Investigator to provide reasons for patient withdrawals. 
The reason for the patient’s withdrawal from the study or all attempts to acquire such, will be 
specified in the source documents.  
15. Statistical Methods and General Considerations 
This section outlines the statistical methods to be used for the analysis of the data from the study. 
A separate Statistical Analysis Plan (SAP), which must be documented as completed prior to 
unblinding the study, will describe data handling and statistical techniques in full detail and will 
supersede the statistical methods detailed in the protocol. The SAP will detail any modifications 
to the analysis plan described below.  
Unless specified otherwise, baseline will be defined as the last 3 weeks of observation before the 
first IV infusion of the study drug. All patient data will be listed. When appropriate, summary 
statistics of number of non-missing values, mean, median, standard deviation, minimum, and 
maximum will be computed for continuous variables and summary statistics of number and 
proportion will be computed for categorical variables. Two-sided 95% CI will be provided for 
the mean and proportion. No formal statistical inferences will be made for safety parameters.  
15.1 
Sample Size 
A total of approximately 160 patients will be enrolled.  
First Co-Primary Endpoint: A sample size of 80 patients per treatment group will have 
>99% power to demonstrate a greater proportion of responders in AK002 patients than in 
placebo patients, assuming the proportions of responders are 0.6 and 0.1 in AK002 and placebo 
groups, respectively.  
Second Co-Primary Endpoint: A sample size of 80 patients per group will provide 96% power 
to detect a statistically significant difference between AK002 and placebo in the mean reduction 
from baseline in TSS score, assuming a mean reduction of 16.1 points on AK002 versus 
8.7 points on placebo and a common standard deviation of 12.5 points (AK002-003 data on file). 
Eighty patients per group will provide 96% power to pick up a difference between placebo and 
AK002 of 7.4 in TSS with a mean Baseline TSS of 30 and a standard deviation (change from 
baseline) of 12.5. These assumptions are based on data observed in the Phase 2 AK002-003 
study.  
15.2 
Analysis Populations 
The safety population is defined as all patients who are randomized and have received at least 
1 infusion of the study drug. 

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Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 91 of 127 
Confidential 
factors (Baseline TSS [<28 vs ≥28] and disease strata [EG ± EoD vs EoD]) to assess robustness 
of Fisher’s exact test results. 
The rationale for specifying Fisher’s exact test as the primary analysis as opposed to specifying 
CMH is because when a stratum has 100% response for 1 treatment group and 0% response for 
another treatment group, the CMH test may lose efficiency or not be computable. This is evident 
from the Phase 2 study outcome. 
The second co-primary endpoint will be analyzed by ANCOVA using the imputed data set 
outlined in the SAP. The LSM, SE, and 95% CI for each treatment group and for the between 
group difference will be derived from ANCOVA with treatment as a factor, and Baseline PRO 
TSS (continuous) and EoD without EG (categorical) as covariates. The hypothesis test for the 
treatment effect will be carried out by the F-test. The synthesizing method will be used to 
combine the results from multiple imputations.  
Two sensitivity analyses will be conducted to assess the departures from the missing at random 
(MAR) data assumption. The first sensitivity analysis will be based on the placebo-based pattern 
mixture model for the missing data imputation under the missing not at random (MNAR) 
assumption. In this model, subjects from the active treatment group after the ICE events are 
assumed to behave like the subjects from the placebo group. Their missing data are imputed 
using the response profile from the placebo subjects who have similar baseline covariates and 
prior response trajectory. The second sensitivity analysis will be based on the tipping point 
method. In this method, the missing biweekly TSS will be imputed with different adjustments for 
the active treatment subjects and placebo subjects under the MNAR assumption in search for a 
tipping point that reverses the study conclusion (i.e., p-value no longer <0.05 for the treatment 
effect). Detailed specifications for the analyses outlined above will be provided in the SAP. 
15.6.2 
Secondary Efficacy Endpoint Analysis 
If both tests of the co-primary endpoints are statistically significant, the hypothesis tests for the 
secondary endpoints will proceed sequentially in a prespecified order specified in the synopsis. If 
at any point, the statistical test is not significant at 2-sided α=0.05 level, the hypothesis testing 
procedure will stop. 
For patients who provide gastric or duodenal only biopsy, the calculation will be based on the 
average count of the highest readings from the respective mucosa at baseline and Day 169 
(Week 24). For patients who provide both gastric and duodenal biopsies, the calculation will be 
based on the average count of the highest readings from the Day 169 biopsy that correspond in 
location (gastric or duodenal) to the location with the highest average count at baseline. The 
change in tissue eosinophil count from baseline to Day 169 will be analyzed using ANCOVA 

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 9 2  of 1 2 7  
C o nfi d e nti al  
wit h treat me nt as a fact or, a n d baseli ne e osi n o p hil c o u nts, Bas eli ne  P R O T S S, a n d d isease stat us 
as c o vari ates. T he L S M , S E, a n d 9 5 % CI f or i n di vi d ual treat me nt gr o u ps, a n d L S M, S E, 9 5 % CI, 
a n d p-val ue f or t he bet w ee n treat me nt differe n ce will be prese nte d.  
Pr o p orti o n of patie nts ac hie vi n g gastri c a n d/ or d u o de nal e osi n o p hil c o u nt of ≤1 c ell/ h pf will be 
a nal yze d usi n g Fis her’s e x act test si milar t o t he a nal ysis f or t h e first c o -pri mar y e n d p oi nt.   
Pr o p orti o n of treat me nt r es p o n ders defi ne d b y > 3 0 % i m pr o ve me nt i n T S S a n d  mea n e osi n o p hil 
c o u nt ≤4 cells per h pf i n 5 gastri c h pf a n d/ or m ea n e osi n o p hil c o u nt ≤1 5 cells per h pf i n 
3  d u o de nal h pf will be a n al yze d usi n g Fis her’s e x act test.  
Pr o p orti o n of patie nts wit h ≥5 0 % re d ucti o n a n d ≥7 0 % re d ucti o n i n T S S fr o m baseli ne t o 
Wee ks  2 3 – 2 4 will be a nal yz e d usi n g t he C M H test stratifie d b y t h e ra n d o mi zati o n stratificati o n 
fact ors.  
C ha n ge i n wee kl y T S S will be a nal yze d usi n g t he M M R M m o del . T he m o del will i ncl u de fi x e d 
effects f or bas eli ne val ue, treat me nt, wee k , a n d t h e treat me nt b y wee k i nteracti o n a n d all o w f or 
ra n d o m s u bject effects a n d ass u me a n u nstr uct ur e d c o varia n ce str uct ure. T he Ke n war d -R o gers 
a p pr oac h f or c o m p uti n g de n o mi nat or de grees of free d o m will be use d t o acc o u nt a p pr o priatel y 
f or p o oli n g of wit hi n a n d bet wee n-s u bj ect vari a nce esti mates . T he L S M  a n d t he 9 5 % CI f or t he 
bet wee n gr o u p differe nce will be esti mate d f or eac h wee k.   
T he e C D F a n d P D F pl ots will be prese nte d f or c h a n ge fr o m B aseli ne T S S sc ore at Wee ks 2 3 – 2 4 
stratifie d b y  
 a n d  
 s c ores. 
1 5. 6. 3  
E x pl or at or y A n al ys is 
A nal ysis of patie nts  wit h 
 will be carri e d o ut si milarl y usi n g  
 
 test. C ha n ge fr o m Baseli ne  
 
at W ee k 2 5 will be a nal yze d usi n g t he 
 si milar t o t he a nal ysis o utl i ne d a b o ve. 
C ha n ge fr o m bas eli ne  i n t he 
 will be s u m marize d b y 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
C CI
C CI
C CI
C CI
C CI
C CI
C CI
C CI
C CI
C CI
C CI
C CI
C CI
C CI

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 9 3  of 1 2 7  
C o nfi d e nti al  
 will be a nal yze d usi n g 
 as descri b e d 
a b o ve. T he 
 a n d t he 
 f or t he bet wee n gr o u p c o m paris o n will be 
prese nte d f or t he 
 acr oss Wee k 1 t hr ou g h Wee k  2 4 a n d f or  
 at eac h wee k.  
T he 
 will be s u m me d u p t o deri ve t he  
 
 T he y will t he n be a nal yz e d usi n g t he 
 wit h 
 
 
1 5. 7  
S afet y A n al ysis  
A d vers e E ve nts: All A E  will be c o de d usi n g t h e Me dical Dicti o nar y f or R e g ul at or y Acti vities 
( Me d D R A) a n d will be classifie d b y M e d D R A s yste m or ga n class ( S O C) a n d preferre d t er m. 
Listi n gs will i ncl u de all A E  c ollecte d o n st u d y. T he s u m maries of A E  will be base d o n T E A E, 
defi ne d as a n A E  re p orte d i n t he cli nical data bas e wit h a date of o nset ( or w orse ni n g) o n or after 
t he start date of t he first I V i nf usi o n of t he st u d y me dicati o n.  
1 5. 7. 1  
Tre at me nt E mer g e nt A d verse E ve nts  
Patie nt i nci de nce ( N a n d %) of T E A E will be s u m m arize d as f oll o ws:  
 
O ver vie w of T E A E t o i n cl u de  
–  N u m ber ( %) of patie nts w h o re p orte d at least 1  T E A E o verall, b y se v erit y, a n d b y 
relati o ns hi p 
–  N u m ber ( %) of patie nts w h o re p orte d at least 1  seri o us T E A E  
–  N u m ber ( %) of patie nts w h o re p orte d at least 1  T E A E l ea di n g t o treat me nt 
disc o nti n uati o n  
–  N u m ber ( %) of patie nts w h o re p orte d at least 1  T E A E of s peci al i nterest ( T E A E SI)  
 
T E A E b y preferre d ter m  
 
T E A E b y S O C a n d preferre d ter m  
 
T E A E b y m a xi m u m se verit y, S O C, a n d preferre d t er m  
 
T E A E b y S O C a n d preferre d ter m  a n d rel ati o ns hi p t o st u d y dr u g  
 
T E A E lea di n g t o wit h dra wal b y S O C a n d preferre d ter m  
 
Seri o us T E A E b y S O C a n d preferre d t er m  
 
T E A E SI b y S O C a n d preferre d ter m  
C CI
C CI
C CI
C CI
C CI
C CI
C CI
C CI
C CI
C CI

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 94 of 127 
Confidential 
15.7.2 
Anti-Drug Antibodies 
Samples will be obtained for testing of ADA at times identified in Section 11.5.4. 
15.7.3 
Clinical Laboratory Assessments 
Samples will be obtained for the clinical laboratory tests identified in Section 11.4, and 
laboratory tests to be summarized include chemistry, hematology, urinalysis, and AK002 ADA. 
Descriptive statistics will be used to summarize laboratory results at baseline, each visit, and the 
change from baseline for each visit. In addition, shift tables will summarize the laboratory results 
relative to normal reference ranges at baseline and each post-baseline time point.  
15.7.4 
Vital Signs 
Vital signs will be summarized at baseline, each visit, and change from baseline at each visit.  
15.7.5 
ECG 
Patient incidence of the Investigator’s overall assessment (normal, abnormal – not clinically 
significant, and abnormal – clinically significant) will be summarized. 
15.7.6 
Physical Exam 
New or worsening symptoms in the symptom-directed physical exams will be included in the 
by-patient data listing.  
15.7.7 
Concomitant Medications 
All medications (prior and concomitant) will be coded using the most current World Health 
Organization Drug Dictionary (WHODD). Concomitant medications will be summarized by 
Anatomical Therapeutic Chemical (ATC) Class and preferred term.  
15.8 
Patient Confidentiality 
Patient identity should be confirmed, if possible, by the presentation of a photo identification to 
ensure the correct individual is consented, screened, and enrolled (if eligible).  
Only the PID, patient initials, and demographics will be recorded in the eCRF. If the patient’s 
name appears on any source document collected (A., hospital discharge summary), it must be 
removed from the document if the document will be viewed by the Sponsor or a sponsor-
contracted study vendor not permitted access to patient-identifying information. All study 
findings will be stored in electronic databases. The patients will give explicit written permission 
for representatives of the Sponsor, regulatory authorities, and the IRB to inspect their medical 
records to verify the information collected. Patients will be informed that all personal 
information made available for inspection will be kept confidential to the extent permitted by all 

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17. Administrative, Ethical, and Regulatory Considerations 
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Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 98 of 127 
Confidential 
17.2 
Independent Ethics Committees/Institutional Review Boards 
The protocol and ICF will be reviewed and approved by the IEC/IRB of each participating study 
site prior to study initiation. A Central IRB may be used if permitted by the participating study 
site. All SAE, regardless of causality, will be reported to the IRB in accordance with the standard 
operating procedures and policies of the IRB, and the Investigator will keep the IRB informed as 
to the progress of the study. The Investigator will obtain assurance of IRB compliance with 
regulations.  
Any documents that the IRB may need to fulfill its responsibilities (such as protocol, protocol 
amendments, Investigator’s Brochure, ICF, information concerning patient recruitment, payment 
or compensation procedures, or other pertinent information) will be submitted to the IRB. The 
IRB’s written unconditional approval of the study protocol and the ICF will be in the possession 
of the Investigator before the study is initiated. The IRB’s approval of the investigational site 
must be available to Allakos prior to shipment of study supplies to the site. This approval must 
refer to the study by exact protocol title and number and should identify the documents reviewed 
and the date of review.  
The IRB must be informed of revisions to other documents originally submitted for review; 
serious and/or unexpected adverse experiences occurring during the study in accordance with the 
standard operating procedures and policies of the IRB; new information that may adversely 
affect the safety of subjects or the conduct of the study; an annual update and/or request for 
reapproval; and when the study has been completed.  
17.3 
Informed Consent Form 
Prior to study enrollment, all patients must consent to participate. The process of obtaining the 
informed consent will comply with all federal regulations, ICH requirements, and local laws.  
In accordance with ICH GCP Guideline E6 Section 4.3.3, patients should be asked whether they 
would like their primary care physician (PCP) notified of their study participation. If yes, the 
PCP should be notified in writing. Otherwise, the patient should sign a form stating that he/she 
does not wish to disclose such information.  
The Investigator or designee will review the study and the ICF with each potential patient. The 
review will include the nature, scope, procedures, and possible consequences of participation in 
the study. The consent and review must be in a form understandable to the potential patient. The 
Investigator or designee and the subject must both sign and date the ICF after review and before 
the patient can participate in the study. The patient will receive a copy of the signed and dated 
form, and the original will be retained in the site’s study files. The Investigator or designee must 

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 99 of 127 
Confidential 
emphasize to the patient that study participation is entirely voluntary and that consent regarding 
study participation may be withdrawn at any time without penalty or loss of benefits to which the 
patient is otherwise entitled.  
In addition, prior to undergoing biopsies, patients will provide informed consent in accordance 
with the standard operating procedures and policies of the EGD facility/investigational site.  
17.4 
Publications 
The preparation and submittal for publication of manuscripts containing the study results will be 
in accordance with a process determined by mutual written agreement among the study Sponsor 
and respective site. The publication or presentation of any study results will comply with all 
applicable privacy laws including but not limited to the Health Insurance Portability and 
Accountability Act of 1996.  
17.5 
Clinical Study Registration 
This clinical study is registered on the Clinical Trial Registry Website, www.ClinicalTrials.gov 
as NCT #04322604. 
17.6 
Payment to Patients 
All patients may be compensated for participating in this study, in accordance with the payment 
amounts per study day stated in the patient’s signed ICF approved by the IRB. If the patient is 
discontinued from the study prior to the last study visit, the patient will be compensated for each 
completed study visit on a pro rata basis, as stated in the patient’s ICF. After randomization, 
patients at participating study sites will be compensated for each completed week of daily 
questionnaires as long as at least 4 questionnaires per week are completed. Patients may be 
reimbursed for expenses associated with attending study visits. No additional compensation 
beyond what is stated in the ICF is permitted.  
17.7 
Investigator Responsibilities  
By signing the Investigator Protocol Agreement page, the Investigator agrees to:  
1) 
Conduct the study in accordance with the protocol and only make changes after notifying 
the Sponsor (or designee), except when to protect the safety, rights, or welfare of subjects.  
2) 
Personally conduct or supervise the study. 
3) 
Ensure that the requirements relating to obtaining informed consent and IRB review and 
approval meet federal guidelines.  

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 100 of 127 
Confidential 
4) 
Report to the Sponsor or designee any AE that occur in the course of the study, in 
accordance with 21 CFR Part 312.64 and ICH Guideline E2A.  
5) 
Ensure that all associates, colleagues, and employees assisting in the conduct of the study 
are informed about their obligations in meeting the above commitments.  
6) 
Maintain adequate and accurate records in accordance with 21 CFR Part 312.62 and ICH 
Guideline E6 and to make those records available for inspection with the Sponsor (or 
designee).  
7) 
Ensure that an IRB that complies with the requirements of 21 CFR Part 56 and ICH 
Guideline E6 will be responsible for initial and continuing review and approval of the 
clinical study.  
8) 
Promptly report to the IRB and the Sponsor (or designee) all changes in the research 
activity and all unanticipated problems involving risks to patients or others (to include 
amendments and IND safety reports).  
9) 
Seek IRB approval before any changes are made in the research study except, when 
necessary, to eliminate hazards to the patients. 
10) Comply with all other requirements regarding the obligations of clinical Investigators and 
all other pertinent requirements listed in 21 CFR Part 312.  

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 101 of 127 
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18. References  
Alhmoud T, Hanson J, Parasher G. Eosinophilic gastroenteritis: an underdiagnosed condition. 
Dig Dis Sci, 2016;61:2585–92. 
Bedell A, Taft T, Craven M, Guadagnoli L, Hirano I, Gonsalves N. Impact on health-related 
quality of life in adults with eosinophilic gastritis and gastroenteritis: A qualitative 
assessment. Dig Dis Sci, 2018;63:1148–57. 
Bochner B. Siglec-8 on human eosinophils and mast cells, and Siglec-F on murine eosinophils, 
are functionally related inhibitory receptors. Clin Exp Allergy 2009;39(3):317-24. 
Caldwell J, Collins M, Stucke E, Putnam P, Franciosi J, Kushner J, et al. Histologic eosinophilic 
gastritis is a systemic disorder associated with blood and extragastric eosinophilia, TH2 
immunity, and a unique gastric transcriptome. J Allergy Clin Immunol 2014; 
134:1114-24. 
Food and Drug Administration. Guidance for industry E9 (R1): Statistical Principles for clinical 
trials: addendum: estimands and sensitivity analysis in clinical trials. ICH, May 2021. 
Hudson S, Herrmann H, Du J, Cox P, Haddad E, Butler B, et al. Developmental, malignancy-
related, and cross-species analysis of eosinophil, mast cell, and basophil siglec-8 
expression. J Clin Immunol 2011;31(6):1045-53. 
Jensen E, Martin C, Kappelman M, Dellon E. Prevalence of eosinophilic gastritis, gastroenteritis, 
and colitis: Estimates from a national administrative database. J Pediatr Gastroenterol 
Nutr 2016; 62:36-42. 
Katz P, Gerson L, Vela M. Guidelines for the Diagnosis and Management of Gastroesophageal 
Reflux Disease. The American Journal of Gastroenterology, 2013;108:308–328. 
López-Medina G, Gallo M, Prado A, Vicuna-Honorato I, Díaz de León R. Eosinophilic 
gastroenteritis: case report and review in search for diagnostic key points. Case Rep 
Gastrointest Medicine, 2015; 239506:1–5. 
Mansoor E, Saleh M, Cooper G. Prevalence of eosinophilic gastroenteritis and colitis in a 
population-based study, from 2012-2017. Clin Gastroenterol Hepatol, 2017; 15:1733-41. 
Peterson K, Byrne K, Vinson L, et al. Elemental diet induces histologic response in eosinophilic 
esophagitis. Am J Gastroenterol, 2013;108:759–66. 

 
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Prussin C. Eosinophilic gastroenteritis and related eosinophilic disorders. Gastroenterol Clin 
North Am 2014; 43: 317-27. 
Reed C, Woosley J, Dellon E. Clinical characteristics, treatment outcomes and resource 
utilization in children and adults with eosinophilic gastroenteritis. Dig Liver Dis 2015; 
47: 197-201. 
Sampson H, Munoz-Furlong A, Campbell R, Adkinson Jr N, Bock S, Branum A, 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):391–7. 
Wechsler J, Schwartz S, Amsden K, Kagalwalla A. Elimination diets in the management of 
eosinophilic esophagitis. J Asthma Allergy, 2014;7:85–94. 
Zhang M, Li Y. Eosinophilic gastroenteritis: A state-of-the-art review. J Gastroenterol Hepatol 
2017; 32: 64-72.  

 
Pr ot oc ol A K 0 0 2 -0 1 6  
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1 9.  A p pe n dices  
1 9. 1  
A p pe n di x 1:  P R O Q uesti o n naire  
1 9. 2  
A p pe n di x 2:  
  
1 9. 3  
A p pe n di x 3:  Baseli ne Di et Assess me nt  
1 9. 4  
A p pe n di x 4:  C o m m o n Ter mi n ol o g y Criteria f or A d verse E ve nts v. 5. 0  
1 9. 5  
A p pe n di x 5:  E G D Hist ol o g y  
1 9. 6  
A p pe n di x 6:  Sa m ps o n’s Criteria of A na p h yl a xis  
1 9. 7  
A p pe n di x 7:  e P R O Teac hi n g T o ol   
1 9. 8  
A p pe n di x 8:  
  
1 9. 9  
A p pe n di x 9:  
  
1 9. 1 0  A p pe n di x 1 0:  A d diti o nal Q uesti o ns f or At o pic C o n diti o ns   
1 9. 1 1  A p pe n di x 1 1:  Pre vi o us Treat me nts Re vie w   
1 9. 1 2  A p pe n di x 1 2:  He patitis B a n d He patitis C Ser ol o gical T esti n g Details   
 
 
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Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
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19.1 
Appendix 1: PRO Questionnaire 
 

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 105 of 127 
Confidential 
19.1 
Appendix 1: PRO Questionnaire cont. 
 

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 106 of 127 
Confidential 
19.1 
Appendix 1: PRO Questionnaire cont. 
 
 

 
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Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 1 1 2  of 1 2 7  
C o nfi d e nti al  
 
 
C CI
C CI

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 113 of 127 
Confidential 
19.3 
Appendix 3: Baseline Diet Assessment  
Instructions: To be completed by Study Personnel, through direct interview with Study Participant. Please ask 
questions to Study Participants, much as they appear below. This Assessment should be conducted on Day 1 of 
Screening. This Assessment asks about symptoms of eosinophilic gastritis (EG) and eosinophilic duodenitis (EoD). 
1. 
Are you on Specific, Doctor-Prescribed Diet? 
Yes ☐ 
No ☐ 
 
If Yes, what is the diet? 
 
☐ Elemental 
[If ticked, enteral/tube feeding?]  
Yes ☐  
No ☐ 
 
☐ 6-food or 3 Food Elimination Diet 
 
☐ Supplemental Protein Shake/drink  
specify:  
 
 
☐ Other; describe:  
 
2. 
Do you have any confirmed food allergies  
Yes ☐ 
No ☐ 
(i.e., confirmed by skin-prick testing or blood tests)? 
 
If Yes, what are they?  
 
 
 
 
3. 
Does eating certain foods seem to make your EG/EoD symptoms worse?  
Yes ☐ 
No ☐ 
 
If Yes, what are the 3 specific foods/types of foods that make the effects worse? 
Food or Type of Food 
Effect 
 
 
 
 
 
 
4. 
Do you avoid eating any specific foods or types of foods  
Yes ☐ 
No ☐ 
due to your EG/EoD symptoms?  
 
If Yes, which foods are always avoided?  
 
 
 
 
5. 
Do you avoid? (tick all that are appropriate) 
 
☐ Milk 
☐ Egg 
☐ Wheat  
☐ Soy  
 
What are the main foods that YOU DO eat? 
 
If a full diet is eaten do not list all types of foods, just write “All foods.” 
 
 
 
6. 
Do you avoid eating at certain times of the day to avoid symptoms of EG/EoD? 
Yes ☐ 
No ☐ 
 
If Yes, please describe:  
 
 
 
 
v. 14Mar2020 
Page 1 of 1 

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 114 of 127 
Confidential 
19.4 
Appendix 4: Common Terminology Criteria for Adverse Events v. 5.0 
Common Terminology Criteria for Adverse Events (CTCAE) Version 5 for download can be 
found at:  
 
https://ctep.cancer.gov/protocolDevelopment/electronic_applications/docs/CTCAE_v5_ 
Quick_Reference_5x7.pdf 
Example of Grading for Infusion-Related Reactions 
Adverse 
Event 
General Disorders and Administration Site Conditions 
Grade 1 
Grade 2 
Grade 3 
Grade 4 
Grade 5 
Infusion 
related 
reaction 
Mild transient 
reaction; infusion 
interruption not 
indicated; 
intervention not 
indicated 
Therapy or infusion 
interruption indicated but 
responds promptly to 
symptomatic treatment 
(e.g., antihistamines, 
NSAIDS, narcotics, IV 
fluids); prophylactic 
medications indicated for 
≤24 hours 
Prolonged (e.g., not 
rapidly responsive to 
symptomatic medication 
and/or brief interruption 
of infusion); recurrence 
of symptoms following 
initial improvement; 
hospitalization indicated 
for clinical sequelae 
Life-threatening 
consequences; urgent 
intervention 
indicated 
Death 
Definition: A disorder characterized by adverse reaction to the infusion of pharmacological or biological substances. 
Example of Grading for Laboratory Abnormalities 
Adverse Event 
Grade 
1 
2 
3 
4 
5 
Growth hormone 
abnormal 
Asymptomatic; 
clinical or diagnostic 
observations only; 
intervention not 
indicated  
Symptomatic; 
medical 
intervention 
indicated; limiting 
instrumental ADL 
– 
– 
– 
Definition: A finding based on laboratory test results that indicate abnormal levels of growth hormone in biological specimen. 
Haptoglobin decreased 
<LLN  
– 
– 
– 
– 
Definition: A finding based on laboratory test results that indicate a decrease in levels of haptoglobin in a blood specimen. 
Hemoglobin increased 
Increase in >0–2 
g/dL 
Increase in >2–4 
g/dL 
Increase in >4 g/dL  
– 
– 
Definition: A finding based on laboratory test results that indicate increased levels of hemoglobin above normal. 
Lipase increased 
>ULN –1.5 × ULN  
>1.5–2.0 × ULN; 
>2.0-5.0 x ULN 
and asymptomatic 
>2.0–5.0 × ULN 
with signs or 
symptoms; >5.0 x 
ULN and 
asymptomatic 
>5.0 × ULN and 
with signs or 
symptoms 
– 
Definition: A finding based on laboratory test results that indicate an increase in the level of lipase in a biological specimen. 
Lymphocyte count 
decreased 
<LLN–800/mm3; 
<LLN–0.8 × 10e9/L 
<800–500/mm3; 
<0.8–0.5 × 10e9/L 
<500–200/mm3; 
<0.5–0.2 × 10e9/L 
<200/mm3; <0.2 × 
10e9/L 
– 
Definition: A finding based on laboratory test results that indicate a decrease in number of lymphocytes in a blood specimen. 
Lymphocyte count 
increased 
– 
>4000/mm3–
20,000/mm3 
>20,000/mm3 
– 
– 
Definition: A finding based on laboratory test results that indicate an abnormal increase in the number of lymphocytes in the 
blood, effusions or bone marrow.  

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Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 119 of 127 
Confidential 
19.7 
Appendix 7: ePRO Teaching Tool 
 

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 120 of 127 
Confidential 
19.7 
Appendix 7: ePRO Teaching Tool cont. 
 

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 121 of 127 
Confidential 
19.7 
Appendix 7: ePRO Teaching Tool cont. 
 

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 122 of 127 
Confidential 
19.7 Appendix 7: ePRO Teaching Tool cont. 
 

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 1 2 3  of 1 2 7  
C o nfi d e nti al  
C CI

 
Pr ot oc ol A K 0 0 2 -0 1 6  
A me n d me nt 4  
Date: 2 6  Oct  2 0 2 1  
Alla k os I nc.  
P a ge 1 2 4  of 1 2 7  
C o nfi d e nti al  
C CI

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 125 of 127 
Confidential 
19.10 Appendix 10: Additional Questions for Atopic Conditions  
 

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 126 of 127 
Confidential 
19.11 Appendix 11: Previous Treatments Review 
Instructions: To be completed by Study Personnel through direct interview with Study 
Participant. Please ask questions to Study Participants, much as they appear below. This Review 
should be conducted anytime during the Screening Period. 
1. 
Were you clinically diagnosed with EG and/or EoD (sometimes called EGE) before 
participating in this study? 
Yes  
 
No 
 
2. 
Have you previously taken prescription medications specifically for the diagnosis of 
EG/EoD?  
Yes* 
 
No 
 
N/A, not previously diagnosed with EG/EoD 
 
 
If yes*please list:___________________________________________________________ 
 
All medications taken for EG/EoD or EG/EoD symptoms at any time should be listed on the 
Con-Med Log. 
3. 
Have you previously taken over-the-counter (OTC) medications for symptoms of EG/EoD 
(i.e., Zantac®, Tylenol®, Tums®)? 
Yes* 
 
No 
 
 
If yes*please list:___________________________________________________________ 
 
All medications taken for EG/EoD symptoms at any time should be listed on the Con-Med 
Log. 
4. 
Have you previously tried changing your diet to help improve the symptoms of EG/EoD?  
 
Yes* 
 
No 
 
 
If yes*please describe:_______________________________________________________ 
5. 
Have you previously tried changing your eating habits to help improve the symptoms of 
EG/EoD?  
Yes* 
 
No 
 
 
If yes*please describe:_______________________________________________________ 
6. 
Have you previously tried other methods to help improve the symptoms of EG/EoD 
(i.e., acupuncture, pressure point therapy)?  
Yes* 
 
No 
 
 
If yes*please describe:_______________________________________________________ 
Additional Comments  
 
 
 
 
 
_______________________________________________________ 
 
Name of Person completing the Previous Treatments Review 

 
Protocol AK002-016 
Amendment 4 
Date: 26 Oct 2021 
Allakos Inc. 
Page 127 of 127 
Confidential 
19.12 Appendix 12: Hepatitis B and Hepatitis C Serological Testing Details 
19.12.1 Hepatitis B Testing 
HBsAg positive patients are excluded. However, in case of past infections/vaccination in order to 
qualify, the patient’s testing status needs to align with the information in Table 5.  
Table 5 
Hepatitis B Reflex Testing 
Past Infection (Resolved) 
Or 
Vaccinated 
HBsAg 
Negative 
HBsAg 
Negative 
Anti-HBc 
Positive 
Anti-HBc 
Negative 
Anti-HBs 
Positive 
Anti-HBs 
Positive 
19.12.2 Hepatitis C Testing 
Anti-HCV positive and HCV-RNA positive patients are excluded. In order to qualify, the 
patient’s testing status needs to align with the information in Table 6.  
Table 6 
Hepatitis C Reflex Testing 
Non-Reactive 
Or 
Past Infection (Resolved) 
Anti- HCV 
Negative 
Anti- HCV 
Positive 
HCV RNA 
Negative