A Phase 2a Safety, Tolerability, Pharmacokinetic, and Pharmacodynamic Study in Individuals With Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like Episodes (MELAS)
Phase: PHASE2
Conditions: MELAS
Sponsor: Tisento Therapeutics



IW‑6463  
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Protocol: C6463-201, Amendment 3 
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1. 
PROTOCOL SUMMARY 
1.1. 
Synopsis 
 
Name of Sponsor/Company:  Cyclerion Therapeutics, Inc. 
Name of Investigational Product: IW-6463 
Name of Active Ingredient: 
IW-6463  
Protocol number: C6463‑201 
Phase: 2a 
Country: United States (US) 
Study title:  
A Phase 2a safety, tolerability, pharmacokinetic, and pharmacodynamic study in individuals with 
mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS)  
Primary objective and endpoints 
Objective:  
To evaluate the safety and tolerability of 
IW-6463 when administered to 
participants with MELAS 
Endpoints:  
● Number of participants with study drug dose reductions 
or discontinuations due to ≥1 TEAE 
● Incidence and severity of adverse events 
Study design:  
C6463-201 is an open-label, single-arm study evaluating the safety, tolerability, pharmacokinetics 
(PK), and pharmacodynamics (PD) of IW-6463 in participants diagnosed with mitochondrial 
encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS). Because this is the first study 
evaluating IW-6463 in a patient population, the primary objective is safety and tolerability. 
To complete the study, each participant will progress through 3 distinct periods: Screening, Treatment, 
and Follow-up. Specific procedures and assessments will be conducted according to the Schedule of 
Events (Table 1 of the protocol).  
Number of participants (planned):  
It is expected that approximately 20 participants will be included in the Safety Population to result in 
approximately 12 evaluable participants. 
Diagnosis and main criteria for study inclusion:  
Participants will be 18 years of age or older on the day of consent and will have prior genetic 
confirmation of a known mitochondrial disease mutation; neurological feature(s) of MELAS; and a 
plasma lactate level of at least 1.0 at Screening. 
Study drug and mode of administration:  
IW-6463 tablets will be administered orally on a once-daily (QD) regimen 
Duration of study drug dosing and study participation for each participant:  
Participants will receive QD doses for up to 29 days. The overall study duration per participant will be 
a maximum of 75 days, including the Screening, Treatment, and Follow-up periods. 
Reference therapy: Not applicable 
Safety assessments: Safety will be assessed by the monitoring of adverse events, clinical safety 
laboratory test results, vital signs, and 12-lead electrocardiograms. 

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Statistical methods: 
Sample size justification: The sample size selected is not based on statistical considerations due to the 
developmental stage of this study. A sample size of approximately 12 evaluable participants in a rare 
disease indication is considered sufficient to address the primary research objective. 
General considerations: Descriptive statistics (n, mean, standard deviation, minimum, maximum, 
median, and interquartile range) will be calculated to summarize continuous variables. Frequency and 
percentage of participants in each category will be calculated to summarize categorical variables.  
Due to the developmental stage of this study, no adjustments will be made for multiplicity. Details of 
the data handling methods will be specified in the statistical analysis plan. Inferential statistics will be 
used for descriptive purposes only. If not otherwise specified, the baseline value is defined as the last 
non-missing value measured before administration of study drug on Day 1. 
 
1.2. 
Study Schematic 
Figure 1: 
Study Schematic 
 
1.3. 
Schedule of Events  
Table 1 presents the Schedule of Events for this study. Please also refer to Section 7 as well as 
the study's scanning guidelines, and laboratory and pharmacy manuals and any other study-
specific manual(s) for additional details. 
Follow-up
Visit **
(Day 43 [±4])
Screening
Visit
(Day -28 to
Day -10) *
Clinic Visit
(Day 1)
End of Treatment
Clinic Visit
(Day 29 [-4])
Screening 
Period 
Treatment Period
Follow-up 
Period
≤28 days *
29 (-4) days
14 (±4) days
Day 8 (±2)
Visit
(home or clinic) **
Day 15 (±2)
Visit
(home or clinic) **
All participants will receive open-label IW-6463 once daily for up to 29 days during the Treatment Period.
*  Screening assessments may take place over more than 1 day. However, all Screening procedures must be 
completed at least 10 but not more than 28 days before the start of the Treatment Period.
** The Day 8, Day 15, and Follow-up visits can be conducted either at home or in the study clinic, per 
participant/Study Center preference.

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Table 1: 
Schedule of Events 
Study Period → 
 
Visit Type/Name → 
Screening 
Treatment Period (assessments are predose unless noted) 
F/U 
In-clinic 
Screening 
In-clinic 
Visit 
At-home 
Visit 1 
At-home 
Visit 1 
In-clinic 
EOT Visit 2 
At-home 
Visit 1 
Visit Day (window) → 
 
Study Procedure ↓ 
Day -28 
to 
Day -10 
Day 1  
 
Day 8 
(±2 
days) 
Day 15 
(±2 
days) 
Day 29 (-4 days) 
Day 43 
(±4 
days) 
Pre 
2 h 
4 h 
6 h 
(±30 m) 
ICF signed 
X 
 
 
 
 
 
 
 
 
Eligibility evaluation 
X 
X 
 
 
 
 
 
 
 
Demographics  
X 
 
 
 
 
 
 
 
 
Drug/alcohol screen 3 
X 
 
 
 
 
 
 
 
 
Medical history 
X 
X 
 
 
 
 
 
 
 
Physical examination 4 
X 
X 
X 
X 
X 
 
 
 
X 
Weight (W), height (H)  
W, H 
W 
 
W 
W 
 
 
 
W 
12-lead ECG 5 
X 
X 
 
 
X 
 
 
 
X 
ECHO 6  
X  
 
 
 
 
 
 
 
 
BP (including 
orthostatic) & pulse 7 
X 
X 
X 
X 
X 
 
 
X 
X 
Oral temp, O2, & RR 
X 
X 
X 
X 
X 
 
 
X 
X 
Clinical safety samples 8 
(chemistry, coag/ 
hematology, UA) 
X 
  X 9 
X 
X 
X 
 
 
 
X 
Pregnancy test 10 
X 
X 
X 
X 
X 
 
 
 
X 
C-SSRS  
 
At each scheduled and unscheduled visit 
Study drug supply/ 
accountability/return 11 
 
X 
X 
X 
X 
 
 
 
 
Participant diary 
(see Section 8.4) 
Issued at Screening; reviewed at each scheduled visit; collected at Follow-up 
Study drug dosing 11,12  
 
QD Days 2–28, including at 
home, at a consistent time (±1 h 
of Day 1 dose time) 
In clinic 
 
AE/SAE evaluation 
From Screening through Follow-up 
Prior/concom. med. rev. 
From Screening through Follow-up 
Blood sample for PK 
 
 
X 
X 
X 
X 
X 
X 
 
CSF sample for PK 
(optional) 
 
 
 
 
 
 
 
X 
 
Blood sample for 
PD biomarkers 8 
X 
X 
 
X 
X 
 
 
 
X 

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Table 1: 
Schedule of Events 
Study Period → 
 
Visit Type/Name → 
Screening 
Treatment Period (assessments are predose unless noted) 
F/U 
In-clinic 
Screening 
In-clinic 
Visit 
At-home 
Visit 1 
At-home 
Visit 1 
In-clinic 
EOT Visit 2 
At-home 
Visit 1 
Visit Day (window) → 
 
Study Procedure ↓ 
Day -28 
to 
Day -10 
Day 1  
 
Day 8 
(±2 
days) 
Day 15 
(±2 
days) 
Day 29 (-4 days) 
Day 43 
(±4 
days) 
Pre 
2 h 
4 h 
6 h 
(±30 m) 
Neuroimaging 13 
X 
X 
 
 
 
 
X 
 
 
MFIS 
 
X 
 
 
X 
 
 
 
 
PGIC 
 
 
 
 
X 
 
 
 
 
PROMIS–Cognitive 
function 
 
X 
 
 
X 
 
 
 
 
Visit discharge 14 
 
~4h post 
 
 
 
 
 
 
 
Study completion 
 
 
 
 
 
 
 
 
X 
AE=adverse event; BP=blood pressure; coag=coagulation; concom=concomitant; CSF=cerebral spinal fluid; 
C-SSRS=Columbia Suicide Severity Rating Scale; ECG=electrocardiogram; ECHO=echocardiogram; EOT=end of 
treatment; F/U=follow-up; h=hour(s); H=height; ICF=informed consent form; m=minute(s); med=medication(s); 
MFIS=Modified Fatigue Impact Scale; O2=oxygen saturation; PD=pharmacodynamic; PGIC=Patient Global 
Impression of Change; PK=pharmacokinetic(s); post=postdose; Pre=predose; PROMIS=Patient-Reported Outcomes 
Measurement Information System; QD=once daily; rev=review; RR=respiratory rate; SAE=serious adverse event; 
UA=urinalysis; VS=vital signs; W=weight 
1 Visit will be conducted within the allowable timeframe either at the participant’s home or in the Study Center, 
per participant/Study Center preference. If the Follow-up Visit is conducted at home: The investigator will 
perform a medical review of the safety assessments conducted during the at-home F/U visit and may contact the 
participant via telephone if further follow-up is needed.  
2 All participants will be asked to return to the Study Center for the EOT visit. For premature study drug 
discontinuations: If possible, participants who prematurely discontinue study drug will be asked to complete the 
EOT assessments prior to departure and then complete the Follow-up Visit as scheduled. 
3 See Section 8.3.6 for a list of drugs to be screened.  
4 A complete physical exam will be done at Screening and at Follow-up; a symptom-directed exam can be 
performed at all other visits. 
5 ECGs will be performed after the participant has been resting supine for ≥5 minutes and should be obtained 
before blood draws (or ≥10 m after a blood draw, if necessary). See Section 8.3.4 for details. When timing 
coincides, ECGs and vital signs can be assessed together. 
6 Screening ECHO is necessary only in the absence of a documented ECHO performed within 3 months of Day 1  
7 All BP and pulse measurements will be obtained with an automated BP device (left arm preferred) prior to blood 
draws (or ≥10 m after a blood draw, if necessary). Manual readings are allowed only if automatic is not 
available.  
--Supine BP at Screening (only): Record the average of 2 measurements obtained at 2-minute intervals after the 
participant has rested quietly in a semi-recumbent/supine position for ≥5 minutes 
--Orthostatic vital signs (all scheduled visits): Participant must rest quietly in a supine/semi-recumbent position 
for ≥5 minutes before supine measurements are recorded, then assume sitting position for ≥1 minute, and finally 
assume standing position for 2 (±1) minute before standing measurements are recorded. Results will be used to 
calculate and record orthostatic BP and pulse. 
8 Although IW-6463 can be taken with or without food, participants are requested to fast for 3 to 4 hours prior to 
all clinical safety and PD laboratory sample collections. Water and a light snack (if previously approved) are 
allowed upon awakening on the morning of the visit. For in-clinic visits, because participants may be vulnerable 

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to metabolic decompensation during any catabolic state, a standardized meal with a low glycemic index will be 
administered just prior to the start of this fasting period. For at-home visits, participants will either be counseled 
on what to consume prior to the fasting period or will be given a standardized meal by home health services. For 
details regarding standardized snacks and meals, see the Nutrition Guidelines for this study. 
9 Safety laboratory results must be assessed for clinical significance prior to initiation of study drug dosing on 
Day 1; local laboratory results can be used for the Day 1 eligibility assessments; a second set of samples must 
also be sent to the Central laboratory. 
10 For women of reproductive potential (defined in Section 5.3.4.1), a serum pregnancy test will be conducted at 
Screening and at the Follow-up Visit; urine-based pregnancy tests will be acceptable at all other scheduled visits 
(unless serum testing is required by local regulation or the institutional review board/independent ethics 
committee [IRB/IEC]). A reviewed and documented negative result is required at Screening and again prior to 
study drug initiation on Day 1. A confirmed positive result at any time during the study will result in immediate 
discontinuation of study drug. See Section 8.3.6.1. 
11 Study drug supply will be distributed on Day 1 and will be resupplied as applicable. Dosing compliance (via 
tablet count) will be recorded at each scheduled visit during the Treatment Period. Participant diaries will also be 
checked at each visit for completeness. Participants will be instructed to bring in any unused study drug supply 
and their diary to each scheduled visit through EOT. 
12  Participants will be instructed to take their study drug dose on Days 2 through 28 at a consistent time each day, 
corresponding to the Day 1 dose administration time (±1 h). Exception/Note: For the Days 8, 15, and 29/EOT 
visits, they will take their dose during the visit to allow for appropriate timing of pre- and postdose assessments. 
Attempts should be made to schedule the Day 8 and 15 visits (at home or in clinic) such that dosing can still 
occur at approximately the same time as the Day 1 and subsequent doses. 
13  Includes magnetic resonance spectroscopy (MRS), arterial spin labeling (ASL), and functional magnetic 
resonance imaging blood-oxygen-level-dependent (fMRI-BOLD) imaging. Scanners that lack fMRI capabilities 
may be considered for use in this study with Sponsor approval. See Section 8.7 and the study’s scanning 
guidelines document for details. 
14 Participants will be observed for ≥4 hours postdose and thereafter may be released from the study center per 
Investigator discretion 
 
 
 

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TABLE OF CONTENTS 
TITLE PAGE .............................................................................................................................. 1 
1. 
PROTOCOL SUMMARY ........................................................................................ 2 
1.1. 
Synopsis ................................................................................................................... 2 
1.2. 
Study Schematic ....................................................................................................... 3 
1.3. 
Schedule of Events ................................................................................................... 3 
LIST OF ABBREVIATIONS AND DEFINITIONS OF TERMS .............................................. 12 
2. 
BACKGROUND INFORMATION AND STUDY RATIONALE .......................... 14 
2.1. 
Name and Description of Study Drug ..................................................................... 14 
2.2. 
Introduction and Rationale ...................................................................................... 14 
2.3. 
Findings from Nonclinical and Clinical Studies ...................................................... 14 
2.3.1. 
Nonclinical Studies ................................................................................................. 14 
2.3.2. 
Clinical Studies....................................................................................................... 15 
2.3.2.1. 
Clinical Studies in Children .................................................................................... 15 
2.4. 
Selection of Study Drug Dosage Regimen .............................................................. 15 
2.5. 
Risk Assessment ..................................................................................................... 15 
2.5.1. 
Potential Benefits of Study Participation ................................................................. 15 
2.5.2. 
Risk-Benefit Assessment ........................................................................................ 16 
2.6. 
Compliance Statement ............................................................................................ 16 
3. 
OBJECTIVES AND ENDPOINTS ......................................................................... 17 
4. 
INVESTIGATIONAL PLAN ................................................................................. 18 
4.1. 
Overall Study Design .............................................................................................. 18 
4.1.1. 
Screening Period ..................................................................................................... 18 
4.1.2. 
Treatment Period .................................................................................................... 18 
4.1.3. 
Follow-up Period .................................................................................................... 18 
4.2. 
Estimated Total Blood and CSF Volumes to be Collected from 
Each Participant ...................................................................................................... 19 
4.3. 
Number of Study Centers and Participants .............................................................. 19 
4.4. 
Treatment Assignment and Blinding ....................................................................... 19 
4.5. 
Safety Stopping Criteria for the Overall Study ........................................................ 19 
4.6. 
Duration of Individual Participation ........................................................................ 19 
4.7. 
End of Study Definition .......................................................................................... 19 

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5. 
PARTICIPANT SELECTION, LIFESTYLE RESTRICTIONS, AND 
DISCONTINUATION............................................................................................ 19 
5.1. 
Inclusion Criteria .................................................................................................... 20 
5.2. 
Exclusion Criteria ................................................................................................... 21 
5.3. 
Lifestyle Restrictions .............................................................................................. 23 
5.3.1. 
Meals and Dietary Restrictions ............................................................................... 23 
5.3.2. 
Caffeine, Alcohol, and Tobacco .............................................................................. 24 
5.3.3. 
Medications, Vitamins, Supplements, and other Substances .................................... 24 
5.3.4. 
Contraception Requirements (Both Sexes) .............................................................. 24 
5.3.4.1. 
Definition of Reproductive Potential in Female Participants ................................... 24 
5.3.5. 
Breastfeeding .......................................................................................................... 25 
5.3.6. 
Strenuous Activity .................................................................................................. 25 
5.4. 
Screen Failures ....................................................................................................... 25 
5.5. 
Lost to Follow-up ................................................................................................... 25 
5.6. 
Participant Completion/Withdrawal ........................................................................ 26 
5.6.1. 
Completion ............................................................................................................. 26 
5.6.2. 
Premature Study Drug Discontinuation for Individual Participants.......................... 26 
5.7. 
Replacement of Prematurely Discontinued Participants .......................................... 27 
6. 
TREATMENT OF PARTICIPANTS ...................................................................... 27 
6.1. 
Study Drug Regimen and Administration................................................................ 27 
6.2. 
Dose Adjustment Criteria for Individual Participants .............................................. 27 
6.2.1. 
Safety Criteria ........................................................................................................ 27 
6.2.2. 
PK Criteria ............................................................................................................. 28 
6.3. 
Concomitant Medications and Procedures ............................................................... 28 
6.3.1. 
Recording of Medications ....................................................................................... 28 
6.3.2. 
Prohibited Medications ........................................................................................... 28 
7. 
STUDY DRUG MATERIALS AND MANAGEMENT ......................................... 29 
7.1. 
Description of Study Drug ...................................................................................... 29 
7.2. 
Packaging and Labeling .......................................................................................... 29 
7.3. 
Storage ................................................................................................................... 29 
7.4. 
Treatment Compliance and Adherence.................................................................... 29 
7.5. 
Accountability ........................................................................................................ 30 
7.6. 
Handling and Disposal ............................................................................................ 30 

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8. 
STUDY EVALUATIONS AND MEASUREMENTS ............................................ 30 
8.1. 
Informed Consent ................................................................................................... 30 
8.2. 
Efficacy Evaluations ............................................................................................... 30 
8.3. 
Safety Evaluations and Parameters.......................................................................... 30 
8.3.1. 
Demographic and Medical Record Review (Screening Visit only) .......................... 30 
8.3.2. 
Physical Examination ............................................................................................. 31 
8.3.3. 
Height and Weight .................................................................................................. 31 
8.3.4. 
Electrocardiogram (ECG) and Echocardiogram (ECHO) ........................................ 31 
8.3.5. 
Vital Signs .............................................................................................................. 32 
8.3.5.1. 
Blood Pressure and Heart Rate (Pulse) .................................................................... 32 
8.3.5.2. 
Respiratory Rate, Oxygen Saturation, and Temperature .......................................... 32 
8.3.6. 
Clinical Laboratory Assessments ............................................................................ 32 
8.3.6.1. 
Pregnancy Testing .................................................................................................. 33 
8.3.6.2. 
Genetic Evaluations ................................................................................................ 34 
8.3.7. 
Suicidality .............................................................................................................. 34 
8.3.8. 
Adverse Event and SAE Monitoring ....................................................................... 34 
8.4. 
Participant Diary for Recording Changes in Health Status, Daily Dosing, and 
Concomitant Medications ....................................................................................... 34 
8.5. 
Clinical Outcomes Assessments/Participant Questionnaires .................................... 35 
8.5.1. 
Patient-reported Outcomes Measurement Information System (PROMIS)–
Cognitive Function ................................................................................................. 35 
8.5.2. 
Patient Global Impression of Change (PGIC) .......................................................... 35 
8.5.3. 
Modified Fatigue Impact Scale (MFIS) ................................................................... 35 
8.6. 
PK Evaluations (Plasma and CSF) .......................................................................... 35 
8.7. 
PD Evaluations and Parameters (Neuroimaging) ..................................................... 36 
8.8. 
Immunogenicity ...................................................................................................... 36 
8.9. 
Biomarkers ............................................................................................................. 36 
8.9.1. 
Circulating Biomarkers in Blood ............................................................................ 36 
8.9.2. 
Brain Metabolites ................................................................................................... 36 
8.10. 
Medical Resource Utilization and Health Economics .............................................. 36 
9. 
STATISTICAL CONSIDERATIONS .................................................................... 37 
9.1. 
Statistical Hypotheses ............................................................................................. 37 
9.2. 
Sample Size and Power ........................................................................................... 37 

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9.3. 
Statistical Methods ................................................................................................. 37 
9.3.1. 
General Considerations ........................................................................................... 37 
9.3.2. 
Populations for Analyses ........................................................................................ 38 
9.3.3. 
Disposition ............................................................................................................. 38 
9.3.4. 
Baseline Data.......................................................................................................... 38 
9.3.5. 
Drug Exposure and Compliance.............................................................................. 38 
9.3.6. 
Prior and Concomitant Medications and Procedures ............................................... 38 
9.3.7. 
Major Protocol Deviations ...................................................................................... 38 
9.3.8. 
Safety Analyses ...................................................................................................... 39 
9.3.8.1. 
ECGs ...................................................................................................................... 39 
9.3.9. 
Patient-Reported Outcomes Analyses ..................................................................... 39 
9.3.10. 
PK Analyses ........................................................................................................... 39 
9.3.11. 
PD Analyses ........................................................................................................... 40 
9.4. 
Controlling for Multiplicity .................................................................................... 40 
9.5. 
Interim Analysis ..................................................................................................... 40 
9.6. 
Independent Data Monitoring Committee ............................................................... 40 
10. 
SAFETY MANAGEMENT AND REPORTING OF ADVERSE EVENTS ............ 40 
10.1. 
Monitoring and Reporting Details ........................................................................... 40 
10.1.1. 
SAE Reporting ....................................................................................................... 41 
10.1.2. 
IRB/IEC Notification of SAEs and Other Unanticipated Events .............................. 41 
10.1.3. 
Follow-up Reports .................................................................................................. 41 
10.1.4. 
Reporting of Pregnancy in a Participant or Participant’s Partner ............................. 41 
10.2. 
Definition of Adverse Events .................................................................................. 42 
10.2.1. 
Adverse Event (AE) ................................................................................................ 42 
10.2.1.1. 
Definition of TEAE ................................................................................................ 42 
10.2.2. 
Serious Adverse Event (SAE) ................................................................................. 42 
10.2.3. 
Adverse Events of Special Interest (AESIs) ............................................................ 42 
10.3. 
Categorization of Events ......................................................................................... 43 
10.3.1. 
Relationship to Study Drug ..................................................................................... 43 
10.3.2. 
Severity (Intensity) ................................................................................................. 43 
11. 
STUDY ADMINISTRATION AND ETHICAL CONSIDERATIONS ................... 43 
11.1. 
Data Collection and Management ........................................................................... 43 

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11.1.1. 
Participant Confidentiality and Data Protection ....................................................... 44 
11.2. 
Monitoring and Inspection of Data and Study Centers ............................................ 44 
11.2.1. 
Monitoring of Study Center and Inspection of Records ........................................... 44 
11.2.2. 
Audits and Inspections ............................................................................................ 45 
11.2.3. 
Retention and Archiving of Records ....................................................................... 45 
11.2.4. 
Quality Control and Quality Assurance ................................................................... 46 
11.3. 
Ethics ..................................................................................................................... 46 
11.3.1. 
IRB/IEC and Investigator Requirements ................................................................. 46 
11.3.2. 
Ethical Conduct of the Study/Compliance Statement .............................................. 46 
11.3.3. 
Written Informed Consent ...................................................................................... 46 
11.4. 
Changes in the Conduct of the Study or Planned Analyses ...................................... 47 
11.5. 
Trial Safety Committee Structure and Safety Data Reviews .................................... 47 
 
 
13. 
LIST OF REFERENCES ........................................................................................ 48 
APPENDIX 1. CONCOMITANT MEDICATIONS AND SUPPLEMENTS .......................... 50 
 
 
 
LIST OF TABLES 
Table 1: 
Schedule of Events ................................................................................................... 4 
Table 2: 
Study Drug Description .......................................................................................... 29 
Table 3: 
Protocol-Required Safety Laboratory Assessments ................................................. 33 
 
LIST OF FIGURES 
Figure 1: 
Study Schematic ....................................................................................................... 3 
  

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LIST OF ABBREVIATIONS AND DEFINITIONS OF TERMS 
Abbreviation/Term 
Definition 
AE 
adverse event 
ASL 
arterial spin labeling 
AUC 
area under the plasma concentration time curve 
AUCtau 
area under the concentration-time curve during a dosing interval 
BOLD 
blood-oxygen-level-dependent 
BP 
blood pressure 
CBF 
cerebral blood flow 
CFB 
change from baseline 
CFR 
Code of Federal Regulations 
cGMP 
cyclic guanosine 3’,5’-monophosphate 
CL/F 
apparent total plasma clearance 
Cmax 
maximum observed plasma concentration 
CNS 
central nervous system 
CRO 
clinical research organization 
CSF 
cerebral spinal fluid 
C-SSRS 
Columbia Suicide Severity Rating Scale 
Ctrough 
plasma concentration observed at the end of a dosing interval (ie, trough; 
collected before the next administration) 
ECG 
electrocardiogram 
ECHO 
echocardiogram 
eCRF 
electronic case report form 
EOT 
end of treatment 
FDA 
Food and Drug Administration 
FIH 
first in human 
fMRI 
functional magnetic resonance imaging 
FSH 
follicle-stimulating hormone 
GCP 
Good Clinical Practice 
h 
hour(s) 
HRT 
hormone replacement therapy 
IB 
Investigator's Brochure 
ICF 
informed consent form 

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Abbreviation/Term 
Definition 
ICH 
International Council on Harmonisation 
IEC 
Independent Ethics Committee 
IRB 
Institutional Review Board 
m 
minute(s) 
MELAS 
mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes 
MFIS 
Modified Fatigue Impact Scale 
MRI 
magnetic resonance imaging 
MRS 
magnetic resonance spectroscopy 
NO 
nitric oxide   
PD 
pharmacodynamic(s) 
PDE5 
phosphodiesterase 5 
PGIC 
Patient Global Impression of Change 
PK 
pharmacokinetic(s) 
PROMIS 
Patient-Reported Outcomes Measurement Information System 
QD 
once daily 
QT 
the time between the beginning of the QRS (ventricular polarization) complex 
and the end of the T-wave 
QTcF 
QT interval corrected for HR using Fridericia’s formula 
SAE 
serious adverse event 
SD 
standard deviation 
sGC 
soluble guanylate cyclase 
SLE 
stroke-like episode 
SOP 
standard operating procedure 
t1/2 
apparent terminal half-life 
TEAE 
treatment-emergent adverse event 
Tmax 
time to Cmax 
Vz/F 
apparent volume of distribution 

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2. 
BACKGROUND INFORMATION AND STUDY RATIONALE 
2.1. 
Name and Description of Study Drug 
IW-6463 is being investigated as a treatment for mitochondrial diseases. It is intended for 
administration only to eligible study participants in accordance with this protocol. Additional 
drug product details are provided in Section 7.  
2.2. 
Introduction and Rationale 
IW-6463 is an orally administered central nervous system (CNS)-penetrant stimulator of soluble 
guanylate cyclase (sGC), a signaling enzyme that catalyzes the formation of cyclic guanosine 
3’,5’-monophosphate (cGMP) from guanosine triphosphate in response to nitric oxide (NO) 
binding. Intracellular cGMP regulates vascular tone and regional blood flow, fibrosis, and 
inflammation, and has been implicated in neuronal survival and cognitive function. Impaired 
NO-sGC-cGMP signaling is believed to play an important role in the pathogenesis of 
mitochondrial diseases such as mitochondrial encephalomyopathy with lactic acidosis and 
stroke-like episodes (MELAS).(1)  
Mitochondrial diseases are a group of rare genetic disorders that occur when mitochondria fail to 
produce enough energy for the body to function properly. The NO signaling pathway is critical 
for the regulation of mitochondrial function and mitochondrial biogenesis.(2-6) NO pathway 
dysregulation is recognized as a major contributing factor in mitochondrial disease, and leads to 
impaired cerebral blood flow (CBF), oxidative stress, inflammation and metabolic crises.(7, 8) 
There are clear links observed between NO signaling, stroke-like episodes (SLEs), and 
dysregulated CBF in patients with mitochondrial disease.(9)  
In the absence of approved therapies for MELAS, citrulline and L-arginine, precursors of NO, 
are hypothesized to provide benefit in this patient population. The consensus guidelines from the 
Mitochondrial Medicine Society recommend acute arginine administration to improve clinical 
symptoms associated with SLEs in patients with MELAS.(9-12) Mechanistically, L-arginine is 
converted directly into NO, the starting point of the NO-sGC-cGMP pathway. sGC stimulators 
act synergistically with NO on the native, heme-containing form of the enzyme to produce 
cGMP and thereby increase NO signaling. As a core node in the NO-sGC-cGMP pathway, it is 
hypothesized that an sGC stimulator is in a key position to potentially enhance mitochondrial 
function and biogenesis.(6) 
As the first CNS-targeted sGC stimulator, IW-6463 may offer unique therapeutic benefit for 
patients with mitochondrial disease. Data from nonclinical studies evaluating IW-6463 support 
the hypothesis that sGC stimulation may have beneficial effects on several key mechanisms of 
mitochondrial disease pathologies and thus may be of value in treating mitochondrial diseases. 
Please see the IW-6463 Investigator’s Brochure (IB) for details. 
2.3. 
Findings from Nonclinical and Clinical Studies  
2.3.1. 
Nonclinical Studies 
Results from nonclinical studies of IW-6463 supporting the evaluation of IW-6463 in this 
clinical study population are summarized in the IW-6463 IB. 

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2.5.2. 
Risk-Benefit Assessment 
Because this is the first study of IW-6463 in this population, a full risk-benefit assessment cannot 
be conducted. However, evaluation of IW-6463 in individuals with mitochondrial disease is 
justified based on the minimal risk profile reported in healthy participants who have received 
IW-6463, along with the potential benefit to study participants based on the pharmacological 
effects observed in nonclinical studies. Results from the nonclinical efficacy and safety 
assessment program support a favorable benefit:risk assessment; see the IB for more 
information. 
2.6. 
Compliance Statement 
See Section 11.3.2.  

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4. 
INVESTIGATIONAL PLAN 
4.1. 
Overall Study Design 
C6463-201 is an open-label, single-arm study evaluating the safety, tolerability, PK, and 
pharmacodynamics (PD) of IW-6463 when administered for up to 29 days to participants 
diagnosed with MELAS. Because this is the first study evaluating IW-6463 in a patient 
population, the primary objective is safety and tolerability; see Section 3 for a complete list of 
study objectives and their corresponding endpoints. 
To complete the study, each participant will progress through 3 distinct periods as described 
below. For details regarding the timing of the specific procedures and assessments, see the 
Schedule of Events (Table 1). A study schematic is shown in Figure 1.  
Criteria for premature discontinuation of individual participants are provided in Section 6.2.  
4.1.1. 
Screening Period 
The Screening Period begins with the execution of the informed consent form (ICF) at the 
Screening Visit. After signing the ICF, each participant’s study eligibility will be assessed 
according to the protocol inclusion and exclusion criteria (Section 5).  
Screening assessments may be conducted over more than 1 day. However, all Screening 
procedures must be completed at least 10 but not more than 28 days before the start of the 
Treatment Period. 
After the Screening Visit, participants who are eligible for the study must begin complying with 
the lifestyle restrictions detailed in Section 5.3. They will also begin completing their daily diary 
for this study (see Section 8.4).  
The end of the Screening Period will coincide with the start of the Treatment Period. 
Collection of adverse events (AEs) will begin after the ICF is signed and will continue through 
the Follow-up Period. 
4.1.2. 
Treatment Period 
The Treatment Period begins on Day 1 (there is no “Day 0”) when participants return to the 
Study Center to undergo baseline procedures and receive their first daily dose of study drug. 
Participants will return to the Study Center on Day 29 (-4 days) for the End-of-Treatment (EOT) 
Visit; all other scheduled visits during this period will be completed within the allowable 
timeframe either at home or in the study center, per participant preference. Throughout the 
Treatment Period, participants will continue completing their daily diary (see Section 8.4).  
The end of the Treatment Period coincides with the beginning of the Follow-up Period. 
4.1.3. 
Follow-up Period 
The Follow-up Period begins immediately after the EOT Visit. During this period, participants 
will continue to comply with all lifestyle restrictions as detailed in Section 5.3 and will continue 
to complete their daily diary (Section 8.4).  
See Table 1 for Follow-up Visit instructions. 

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4.2. 
Estimated Total Blood and CSF Volumes to be Collected from 
Each Participant 
An estimate of the total blood volume that will be collected from each participant over the course 
of the study will be a minimum of approximately 100 mL and will not exceed 500 mL. In 
addition to the blood samples, 1 CSF sample (~4 mL) will be collected from each participant 
who does not withhold consent for the procedure. Collection timepoints are detailed in Table 1. 
Biological samples collected from participants in this study may be stored for up to 5 years for 
future analysis. 
4.3. 
Number of Study Centers and Participants 
The study will be conducted at approximately 5 investigative sites in the United States. It is 
expected that approximately 20 participants will be included in the Safety Population to result in 
approximately 12 evaluable participants.  
4.4. 
Treatment Assignment and Blinding 
Not applicable; this is an open-label study. 
4.5. 
Safety Stopping Criteria for the Overall Study 
The decision to prematurely terminate this study for safety reasons will be made by the Sponsor 
after consultation with the Trial Safety Committee (Section 11.5).  
All dosing will be stopped and the study will be terminated if an overall pattern of clinically 
significant TEAEs or changes in any safety parameter occurs that may appear minor in terms of 
an individual event but, in the opinion of the Sponsor, collectively represent a safety concern. 
See Section 5.6 for discontinuation criteria for individual participants. 
4.6. 
Duration of Individual Participation  
The overall study duration per participant will be a maximum of 75 days, including the 
Screening (≤28 days), Treatment (≤29 days), and Follow-up (≤18 days) periods. 
4.7. 
End of Study Definition  
The end of the study is defined as the date of the last visit of the last participant in the study. 
5. 
PARTICIPANT SELECTION, LIFESTYLE RESTRICTIONS, 
AND DISCONTINUATION 
Please note:  
• Screening assessments may take place over more than 1 day. However, all Screening 
procedures must be completed at least 10 but not more than 28 days before the start of 
the Treatment Period. 

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• Participants may be rescreened per Investigator judgment after consultation with the 
Sponsor’s Medical Monitor. Laboratory assessments may be repeated if an error is 
suspected. Laboratory, electrocardiogram (ECG), or blood pressure (BP) values that 
are outside of the range specified in the protocol’s eligibility criteria may be repeated 
after consultation with the contract research organization (CRO)-based medical 
monitor. 
• Supine BP measurement at Screening (only): Record the average of 2 measurements 
obtained using an automated BP device (left arm preferred) at 2-minute intervals after 
the participant has rested quietly for ≥5 minutes in a semi-recumbent/supine position.  
• Orthostatic vital sign measurements (all scheduled visits): Participant must rest 
quietly in a supine/semi-recumbent position for ≥5 minutes before supine 
measurements are recorded, then assume sitting position for ≥1 minute, and finally 
assume a standing position for 2 (±1) minutes before standing measurements are 
recorded. Results will be used to calculate and record orthostatic BP and pulse. 
• The Investigator will determine whether a particular finding is clinically significant. 
In making this determination, the Investigator will consider whether the finding could 
prevent the participant from performing any of the protocol-specified assessments, 
could represent a condition that would exclude the participant from the study, could 
represent a safety concern if the participant participates in the study, or could 
confound the study-specified assessments. 
5.1. 
Inclusion Criteria 
Each participant must meet each of the following criteria to be eligible for entering this study. 
1. Signed an ICF (either the participant or his/her legal representative/guardian, where 
appropriate) before any study-specific procedures are performed 
2. 18 years of age or older on the day of consent 
3. Prior genetic confirmation of a known mitochondrial disease mutation 
4. Neurological features of MELAS (can be based on medical history) 
5. Elevated plasma lactate during Screening (≥1.0 mmol/L) 
6. Agrees to adhere to all study requirements, including lifestyle restrictions noted in 
Section 5.3 
7. Agrees to refrain from making any major lifestyle changes (eg, start a new diet or change 
an exercise pattern) from the time of the ICF signature until after the Follow-up Visit 
(and beyond, vis-à-vis the contraception requirements) 
8. If receiving chronic medication(s), has had no change in regimen(s) for ≥4 weeks before 
first day of dosing and has no plans to change regimen(s) during the study 

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9. If female, meets 1 of the 2 following criteria: 
a. Confirmed as being postmenopausal (no menses for ≥1 year or ≥12 consecutive 
months) or surgically sterile (bilateral oophorectomy, hysterectomy, or tubal 
sterilization [tie, clip, band, or burn]) 
—or— 
b. If of reproductive potential (see Section 5.3.4.1): 
i. Is not pregnant or breastfeeding at the time of the Screening Visit and 
ii. Has negative pregnancy test results at the Screening Visit and predose at 
Day 1 
iii. Agrees to contraception (see Inclusion #10) for duration of study and for 
≥90 days after the final study drug dose 
10. Male and female participants of reproductive potential must agree to use ≥1 of the 
following effective contraception methods from the date of signing the ICF until 
≥90 days after receiving his/her final study drug dose: 
a. Completely abstain from heterosexual intercourse  
—or— 
b. If heterosexually active, use: 
i. Intrauterine device (“IUD”) and/or a progesterone implant –or— 
ii. Combination of 2 highly effective birth control methods (eg, condom with 
spermicide + diaphragm or cervical cap; hormonal contraceptive [eg, oral 
or transdermal patch or progesterone implant] + barrier method) –or— 
iii. Maintenance of a monogamous relationship with a partner who has been 
surgically sterilized either by vasectomy (conducted ≥60 days before the 
Screening Visit or confirmed via sperm analysis) or by bilateral 
oophorectomy, hysterectomy or tubal sterilization; or is not sterile due to 
postmenopausal status 
11. Male participants must agree to refrain from donating sperm from the Screening Visit 
through 90 days after their final dose of study drug 
12. Agrees to not receive an investigational therapy or device in any other study while 
participating in this study, through the Follow-up Visit 
13. No clinically significant findings on ECG (as assessed at Screening and predose on 
Day 1) and echocardiogram (ECHO; within 3 months of Day 1) 
5.2. 
Exclusion Criteria 
A participant who meets any of the following criteria will be excluded from entering this study.  
1. Severe visual, auditory, or cognitive impairment as determined by the Investigator that 
may affect the ability to adhere to protocol requirements or to complete required 
assessments 

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2. Used any nicotine-containing products (eg, cigarettes, e-cigarettes, vape pens, cigars, 
chewing tobacco, gum, patches) within 1 month of enrollment 
3. Positive pregnancy test at Screening or on Day 1 (or at any other point during the study) 
4. Inpatient hospitalization for alcoholism or drug addiction in the 12 months before the 
Screening Visit and/or has positive drug or alcohol test results at Screening or predose at 
Day 1. Drug screen will include amphetamines, cocaine, opiates, and cannabinoids. 
Note:  
− Use of cannabis and cannabidiol products for medical purposes is permitted in 
this study except for 24 hours before the Screening, Day 1, and EOT visits, and 
for 4 hours prior to all other visits.  
− A participant should be excluded from study entry if there is a known cannabis 
abuse or dependence that, in the opinion of the Investigator, will impact the 
ability of that individual to comply with the protocol or may lead to harm to the 
individual. 
5. Clinically significant hypersensitivity or allergy to any of the inactive ingredients 
contained in the IW-6463 drug product 
6. Hypotension, defined as systolic BP ≤90 mmHg or diastolic BP ≤60 mmHg at Screening 
or predose at Day 1 
7. Hypertension, defined as systolic BP >160 mmHg or diastolic BP >100 mmHg, at 
Screening or predose at Day 1 
8. Orthostatic hypotension at Screening or predose at Day 1, defined as a decrease in 
systolic BP of ≥20 mmHg or a decrease in diastolic BP of ≥10 mmHg when measured 
after assuming a standing position from a semi-recumbent/supine position  
9. Uncontrolled diabetes mellitus with an HbA1c >11% or as determined by the Investigator 
10. Lymphoma, leukemia, or any malignancy within the past 5 years  
Exception: Basal cell or squamous epithelial carcinomas of the skin that have been 
resected with no evidence of metastatic disease for 3 years 
11. Severe gastrointestinal dysmotility (eg, history of dyspepsia, stomach aches, nausea, 
vomiting, recurrent pancreatitis, constipation) as determined by the Investigator that may 
impact compliance and/or oral drug administration, absorption, and exposure 
12. Unable to fast (ie, no food or fluid; water allowed as required) for 3 to 4 hours after a 
meal 
13. Family history of short QT syndrome or long QT syndrome 
14. Clinically significant cardiac involvement or an ECG with corrected QT interval using 
Fridericia’s formula (QTcF interval) >500 ms 
15. Current or past history of clinically significant cardiomyopathy and/or cardiac conduction 
abnormality  

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16. History of platelet dysfunction, hemophilia, von Willebrand disease, coagulation 
disorder, other bleeding diathesis condition(s), or significant, nontraumatic bleeding 
episodes 
17. Current use of aspirin ≥325 mg/day, any P2Y12 inhibitor, any anticoagulant medication, 
specific inhibitors of phosphodiesterase 5 (PDE5), nonspecific inhibitors of PDE5 
(including dipyridamole and theophylline), any supplement for the treatment of erectile 
dysfunction, riociguat, and/or any nitrate. These medications are prohibited from the 
Screening Visit through the duration of the study. See Appendix 1 for details.  
Note: Participants who are taking arginine or citrulline for the treatment of mitochondrial 
disease will be eligible and allowed to continue these therapies.  
18. Participated in any study of investigational therapies for mitochondrial disease and/or for 
the symptoms of mitochondrial disease within 1 month before Day 1 
19. Any contraindication to MRI procedures 
20. Hospitalized for any illness, trauma, surgical procedure, or mitochondrial disease-related 
complication within 4 weeks before Screening 
21. Unable or unwilling to adhere to the study schedule, lifestyle restrictions 
(see Section 5.3), and assessment requirements or, in the clinical judgment of the 
Investigator, is otherwise not suitable for study participation 
22. Patient or his/her legal representative/guardian (where appropriate) is unable or unwilling 
to provide written, informed consent to participate in this study 
5.3. 
Lifestyle Restrictions 
Participants are to abide by the following lifestyle restrictions throughout the study, starting from 
the Screening Visit through the Follow-up Visit, unless otherwise indicated. 
5.3.1. 
Meals and Dietary Restrictions 
• Fasting (ie, no food or fluid; water allowed as required) is required for 3 to 4 hours 
prior to the collection of clinical safety and PD laboratory samples at each scheduled 
visit, including at any at-home visit.  
− Because participants may be vulnerable to metabolic decompensation during any 
catabolic state, on the day of each visit, participants will fast upon awakening 
(water and a light snack, if previously approved, are allowed) and then will be 
given a standardized meal with a low glycemic index in the clinic, 3 to 4 hours 
before the collection of clinical safety and PD laboratory samples. For at-home 
visits, participants will either be counseled on what to consume prior to the fasting 
period or will be given a standardized meal by home health services. 
− On days when neuroimaging is conducted (Screening, Day 1, and Day 29 visits): 
After the safety and PD laboratory samples have been collected, participants can 
eat a light standardized snack; heavy meals, however, should be avoided until 
after all imaging scans have been conducted. 

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− For more details regarding approved snacks and standardized meals, please refer 
to the Nutrition Guidelines for this study. 
5.3.2. 
Caffeine, Alcohol, and Tobacco 
• Caffeine- or xanthine-containing products (eg, coffee, tea, cola drinks, and chocolate) 
should not be ingested for 24 hours before the Screening, Day 1, and EOT visits, and 
for 4 hours prior to all other scheduled visits. These products can impact the 
assessments conducted in this study.  
• The use of alcohol is not permitted during the 24 hours prior to any scheduled visit 
• Tobacco- or nicotine-containing products (eg, e-cigarettes, patches) should not be 
used during this study until after the final study visit 
5.3.3. 
Medications, Vitamins, Supplements, and other Substances 
Participants are to be advised that the following are prohibited as indicated below. 
• Any medical treatment for erectile dysfunction beginning with Screening through the 
Follow-up Visit 
• “Illicit" drugs beginning 1 month before Screening through the Follow-up Visit.  
• Use of cannabis and cannabidiol products for medical purposes is permitted except 
for the 24-hour period before Screening, the Day 1 and EOT visits, and for 4 hours 
before all other visits. 
• Foods containing poppy seeds should be avoided throughout the study because they 
can cause a positive “drug” result 
Investigators must refer to Appendix 1 for comprehensive list of medications that are prohibited 
or are allowed with caution. Also see Section 6.3.  
5.3.4. 
Contraception Requirements (Both Sexes) 
Each participant (of either sex) of reproductive potential must use effective contraception as 
defined in Inclusion Criteria 10 and 11 (Section 5.1), as applicable. Details regarding pregnancy 
testing and reporting are provided in Section 8.3.6.1 and Section 10.1.4, respectively. 
5.3.4.1. 
Definition of Reproductive Potential in Female Participants 
A premenopausal woman is considered fertile following menarche unless she has undergone a 
documented hysterectomy, bilateral salpingectomy, or bilateral oophorectomy. (Documentation 
can come from the Study Center personnel’s review of the participant’s medical records, medical 
examination, or medical history interview.) 
A postmenopausal state is defined as no menses for ≥12 months without an alternative medical 
cause. A high follicle-stimulating hormone (FSH) level in the postmenopausal range may be 
used to confirm a postmenopausal state in women not using hormonal contraception or hormone 
replacement therapy (HRT). However, in the absence of 12 months of amenorrhea, a single FSH 
measurement is insufficient. A female participant on HRT whose menopausal status is in doubt 
is required to use 1 of the nonestrogen hormonal highly effective contraception methods if HRT 

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is continued during the study. Otherwise, HRT must be discontinued to allow confirmation of 
postmenopausal status before study enrollment. 
5.3.5. 
Breastfeeding 
Breastfeeding is not allowed from the Screening Visit through 90 days after the final dose of 
study drug. 
5.3.6. 
Strenuous Activity 
• Participants will abstain from strenuous exercise 48 hours before each blood 
collection for clinical laboratory tests 
• Participants may engage in light recreational activities during the study, but should 
maintain the same level of physical activity from Screening through their Follow-up 
Visit. 
5.4. 
Screen Failures 
Screen failures are defined as participants who consent to participate in the clinical study but are 
not subsequently administered study drug (ie, are not part of the Safety Population). A minimal 
set of screen failure information is required to ensure transparent reporting of screen failure 
participants in compliance with the Consolidated Standards of Reporting Trials requirements and 
to respond to queries from regulatory authorities. Minimal information includes reporting of 
demography, screen failure details, eligibility criteria, and any SAE. 
Individuals who do not meet the eligibility criteria for participation in this study (ie, screen 
failure) may be rescreened. Rescreened participants will be assigned a new screening number 
that is different from the number assigned at the initial screening. 
5.5. 
Lost to Follow-up 
The following actions must be taken if a participant fails to complete/be present for an at-home 
visit or fails to return to the clinic for a required visit: 
• The Study Center must attempt to contact the participant and reschedule the missed 
visit as soon as possible and counsel the participant on the importance of maintaining 
the assigned visit schedule. 
• Before a participant is deemed as being lost to follow-up, the Investigator or designee 
must make every effort to regain contact with the participant (where possible, 3 phone 
calls and, if necessary, a certified letter to the participant’s last known mailing 
address or local equivalent methods). These contact attempts should be documented 
in the participant’s electronic case report form (eCRF). 
• Should the participant continue to be unreachable, he/she will be considered to have 
withdrawn from the study. 

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5.6. 
Participant Completion/Withdrawal  
5.6.1. 
Completion 
A participant is considered to have completed the study after completing all study periods 
(Screening, Treatment, and Follow-up). It will be documented in the eCRF whether or not each 
participant completes the study. 
5.6.2. 
Premature Study Drug Discontinuation for Individual Participants  
Participants will be informed that they may withdraw from the study at any time without 
prejudice to their care.  
A confirmed positive pregnancy test result in a participant requires immediate discontinuation of 
study drug. See Section 8.3.6.1. 
The Investigator may discontinue study drug administration in an individual participant if, in the 
Investigator’s opinion, it is not in the best interest of that individual to continue. See Section 6.2 
for study drug dose adjustment instructions. 
Immediate safety concerns should be discussed with the study's designated contract research 
organization (CRO)-based Medical Monitor upon occurrence or awareness. Changes in the 
participant’s health status since the previous visit or previous study drug administration must be 
checked, including laboratory results, as applicable.   
Participants may also be discontinued from the study by the Investigator or the Sponsor at any 
time for any reason, including the following: 
• Adverse event(s)  
• Any symptomatic hypotension-related AE (eg, syncope) that requires intervention 
and is considered related to study drug  
• Any ECG change from baseline that is considered to be clinically meaningful by the 
Investigator (eg, abnormal Q waves, prolonged QT) 
• Protocol violation, including lack of compliance 
• Lost to follow-up (see Section 5.5) 
• Withdrawal of consent (attempts should be made to determine the reason for the 
withdrawal, if possible) 
Note: The participant may request destruction of any samples collected but not yet 
tested; the Investigator must document this request in the study records. If the 
participant withdraws consent for disclosure of future information, the Sponsor may 
retain and continue to use any data collected prior to the withdrawal of consent. 
• Symptomatic deterioration 
• Study termination by the Sponsor  
Participants who discontinue from study drug administration should complete all EOT Visit 
assessments, as appropriate, at the time of their discontinuation. If possible, they should also 

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return to the study center for the Follow-up Visit. Refer to Table 1 for the assessments to be 
conducted at EOT and Follow-up. 
Participants who discontinue from the study due to a TEAE will be followed until resolution of 
all of their TEAEs or until the unresolved TEAEs are judged by the Investigator to have 
stabilized. 
The Sponsor will be notified of any premature discontinuation. The date the participant is 
withdrawn from the study and the reason for discontinuation will be recorded on the study 
termination form of the eCRF.  
The Sponsor and/or Investigator may contact participants after completion of the study or 
participant discontinuations to inquire about health status and/or experiences in the study. 
5.7. 
Replacement of Prematurely Discontinued Participants 
Participants who withdraw from the study after receiving ≥1 dose of study drug will not be 
replaced. 
6. 
TREATMENT OF PARTICIPANTS 
6.1. 
Study Drug Regimen and Administration 
All eligible participants will receive open-label IW-6463 at a starting dose of 15 mg QD. 
Participants will be instructed to take IW-6463 once per day on Days 2 through 28 at a time 
consistent (preferably ±1 hour) with the in-clinic study drug administration on Day 1.  
Exception/Note: For the Day 8, 15, and 29/EOT visits, participants will take their dose during 
the visit to allow for the appropriate timing of pre- and postdose assessments. Attempts should be 
made to schedule the Day 8 and 15 visits (at home or in clinic) such that dosing can still occur at 
approximately the same time as the Day 1 and subsequent doses. 
Participants are to record the date and time of each at-home dose administration in their diary 
(Section 8.4).  
Permitted concomitant medications may be taken with study drug. Participants will be asked to 
record in their diary each dosing day, time, and dose strength of any concomitant medication(s) 
they take. 
While IW-6463 can be taken with or without food, participants are requested to fast for 3 to 
4 hours prior to in-clinic and at-home clinical safety and PD laboratory sample collections. 
Study drug supply and dosing compliance assessment details are provided in Section 7.4. 
6.2. 
Dose Adjustment Criteria for Individual Participants 
6.2.1. 
Safety Criteria 
The decision to de-escalate IW-6463 dosing in an individual participant will be made jointly by 
the Investigator and the designated CRO-based Medical Monitor, on a per-participant basis.  

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Participants who require a dose adjustment from the 15-mg QD dose will be de-escalated to a 
10-mg QD dose. Initiation of the new dose level should occur only after the TEAE(s) prompting 
the dose reduction has/have resolved or has improved to be considered mild in severity. 
If the 10-mg IW-6463 QD dose is not tolerated, the participant will be discontinued from study 
drug. See Section 5.6.2 for study drug discontinuation procedures for individual participants. 
6.2.2. 
PK Criteria  
No PK criteria will be used to inform dose adjustment or stopping decisions. All dose 
adjustments and stopping decisions will be based on emerging clinical findings and TEAEs. 
6.3. 
Concomitant Medications and Procedures 
6.3.1. 
Recording of Medications  
Any medication (including over-the-counter or prescription medicines, vitamins, and/or herbal 
supplements), vaccine, or other therapeutic/procedure that the participant is receiving at the time 
of Screening until the Follow-up Visit will be recorded along with: 
• Reason(s) for use 
• Dates of administration including start and end dates 
• Dosage information including dose, route of administration, and frequency 
6.3.2. 
Prohibited Medications  
Comprehensive drug-drug interaction studies with IW-6463 have not been conducted in humans. 
See Appendix 1 for a complete list of medications that are either prohibited or are allowed with 
caution.  
The decision and need to switch medications and/or dose-reduce concomitant medications prior 
to or during IW-6463 exposure will be made by the Investigator in consultation with the Study 
Center Pharmacist to assess the risk:benefit.  

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7. 
STUDY DRUG MATERIALS AND MANAGEMENT 
Please also refer to the study's pharmacy manual.  
7.1. 
Description of Study Drug 
Table 2 described the study drug and dosing regimen that will be administered in this study. 
Table 2: 
Study Drug Description  
Product name 
IW-6463 
Dosage form 
round tablet 
Unit dose and schedule 
15 mg once daily (QD) for up to 29 days 
Route of administration 
oral 
Physical description 
white to off-white solid 
 
Dose adjustment criteria are provided in Section 6.2. 
7.2. 
Packaging and Labeling 
IW-6463 tablets are supplied in white, induction-sealed 60-cc high-density polyethylene bottles 
that are fitted with a polypropylene child-resistant cap; each bottle contains a count of 35 tablets 
and a 3-g silica gel desiccant pack. 
7.3. 
Storage 
All study drug must be stored in a secure, monitored (manual or automated) area in accordance 
with the labeled storage conditions and with access limited to the Investigator and authorized 
Study Center staff. 
Study drug should be kept refrigerated (2°–8°C) until the bottles are opened (ie, the induction 
seal is broken). After the bottles have been opened, they should be stored at ambient 
temperatures and may be used for up to 30 days. The bottles must be kept tightly closed.  
Participants will be advised to maintain their study drug supply at room temperature (ie, 50°–
86°F), and to report any excursion outside of this temperature range to Study Center staff. 
7.4. 
Treatment Compliance and Adherence 
The appropriate amount of study drug will be dispensed to participants on Day 1 of the 
Treatment Period. Drug will be resupplied as needed. 
Participants will be asked to record the date and time of each at-home study drug administration 
in their daily diary (Section 8.4); these diaries will be checked for dosing compliance at each 
scheduled visit during the Treatment Period.  
Participants will be asked to bring their study drug supply and daily diary to each in-clinic visit 
during the Treatment Period.  

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Study drug dosing compliance in the eCRF will be based on tablet counts conducted at each 
scheduled in-clinic and at-home visit during the Treatment Period.  
7.5. 
Accountability 
The Investigator/designee must confirm appropriate temperature conditions have been 
maintained during transit for all study drug received and any discrepancies are reported and 
resolved before use of the study drug. 
Only participants who are eligible per this protocol for study drug administration may receive 
study drug. Only authorized Study Center staff may supply study drug to the participants. 
The Investigator, institution, or the head of the medical institution (where applicable) is 
responsible for study drug accountability, reconciliation, and record maintenance (ie, receipt, 
reconciliation, and final disposition records). A copy of the final Drug Accountability Log will 
be provided to the Sponsor or designee.  
7.6. 
Handling and Disposal 
All unused and reconciled study drug will be returned to the Sponsor or designee; refer to the 
study's Pharmacy Manual for instruction. No study drug is to be destroyed without prior written 
permission of the Sponsor.  
8. 
STUDY EVALUATIONS AND MEASUREMENTS 
The following safety, PK, and PD assessments/procedures are required per protocol and will be 
conducted according to Table 1 (Schedule of Events) and documented in the eCRF. Additional 
details are included below. 
During any unscheduled visit, safety assessments will be conducted per Investigator discretion; 
results will be documented in the source document and the appropriate eCRF. 
8.1. 
Informed Consent 
Before a potential study participant undergoes any study-specific evaluations or procedures, he 
or she (or his/her legal representative/guardian) must provide written, informed consent. 
See Section 11.3.3 for more information. 
8.2. 
Efficacy Evaluations 
Efficacy will not be evaluated in this study. 
8.3. 
Safety Evaluations and Parameters 
8.3.1. 
Demographic and Medical Record Review (Screening Visit only) 
At the Screening Visit, demographic characteristics (eg, age, sex, race) will be recorded along 
with a complete medical history that will include the participant’s diagnosis of MELAS, smoking 
history, prior and current medications, surgeries, and any additional relevant medical history. 

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Note: Prior therapies, medications, surgeries, etc. (taken before initiation of study drug) 
should be differentiated from concomitant therapies (taken after initiation of study drug); see 
Section 6.3.1. 
8.3.2. 
Physical Examination 
At Screening and at Follow-up, a complete physical examination will be performed by the 
Investigator and documented on the appropriate eCRF. All other examinations may be symptom 
directed at the Investigator’s discretion. A complete physical examination should include 
examination and assessment of the following: 
General appearance 
Lymph nodes 
Nervous system  
Cardiovascular system 
Head, eyes, ears, nose, and throat 
Skin  
Respiratory system 
Neck 
Mental status  
Abdomen/liver/spleen 
Musculoskeletal system 
 
Breast, genitourinary, and rectal examinations are optional and may be performed at the 
discretion of the Investigator. 
Clinically significant changes since the Screening Visit that are not already associated with an 
ongoing AE will be recorded as AEs. 
8.3.3. 
Height and Weight 
Height will be measured only at Screening. Weight will be measured throughout the study per 
Table 1. 
8.3.4. 
Electrocardiogram (ECG) and Echocardiogram (ECHO) 
All ECGs and the Screening ECHO (if not documented in medical history within 3 months prior 
to Day 1; see Inclusion Criterion 13) must be obtained after the participant has rested supine for 
≥5 minutes and should be obtained before blood draws (or ≥10 m after a blood draw, if 
necessary). When timing coincides, ECGs and vital signs can be assessed together. 
If a QTc result (corrected using Fridericia’s formula) is outside of the normal range (>450 ms), 
the ECG should be repeated twice and the average of the 3 results calculated.  
All ECGs will be evaluated by an Investigator or qualified designee for the presence of 
abnormalities. Results will be reported as “normal,” “abnormal clinically significant,” or 
“abnormal not clinically significant.” Abnormalities of clinical significance will be recorded as 
an AE.  
If a confirmed clinically significant abnormal result is obtained, the Study Center should follow 
standard institutional procedure until the result resolves to baseline. If concerns remain, escalate 
the issue to the Sponsor’s Medical Monitor. 

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8.3.5. 
Vital Signs 
8.3.5.1. 
Blood Pressure and Heart Rate (Pulse) 
All BP and pulse measurements will be obtained with an automated BP device (left arm is 
preferred) prior to blood draws (or ≥10 m after a blood draw, if necessary). 
• Supine BP at Screening (only): Record the average of 2 measurements obtained at 
2-minute intervals after the participant has rested quietly in a semi-recumbent/supine 
position for ≥5 minutes. 
• Orthostatic vital signs (all scheduled visits: Participant must rest quietly in a 
supine/semi-recumbent position for ≥5 minutes before supine BP and pulse 
measurements are recorded, then assume sitting position for ≥1 minute, and finally 
assume a standing position for 2 (±1) minutes before standing measurements are 
recorded. Values from these measurements will be used to calculate and record 
orthostatic BP and pulse.  
8.3.5.2. 
Respiratory Rate, Oxygen Saturation, and Temperature 
Respiratory rate and oral temperature (°C) should be measured after the participant has been 
resting supine /seated for ≥5 minutes. 
Oxygen saturation measurements should be taken by pulse oximeter on room air. 
Note: If oxygen saturation declines <85% or if decreasing oxygen saturation (decreasing 
values across 2 sequential visits), the participant should be assessed (eg, cardiovascular 
exam, chest x-ray, as indicated) for pulmonary edema or other causes of decreased oxygen 
saturation. 
8.3.6. 
Clinical Laboratory Assessments 
Tests detailed in Table 3 will be performed by the Study Center and sent to the Central 
laboratory.  
Clinical safety laboratory (clinical chemistry, coagulation, hematology, and urinalysis) and 
pregnancy results on Day 1 must be reviewed and assessed for clinical significance prior to 
initiation of study drug dosing; local laboratory values may be used for this purpose. A separate 
set of Day 1 samples will be sent to the Central laboratory and processing for eCRF recording. 
Protocol-specific laboratory parameter requirements for inclusion or exclusion of participants are 
detailed in Section 5. 
Participants will fast for 3 to 4 hours before safety laboratory sample collections.  
Additional tests may be performed at any time during the study as determined necessary by the 
Investigator or as required by local regulations. Laboratory assessments may be repeated if an 
error is suspected. However, the maximum amount of blood collected from each participant over 
the duration of the study, including any extra assessments that may be required, will not exceed 
500 mL. 
Throughout the study, the Investigator must review each laboratory report, document this review, 
and file the laboratory reports with the source documents. 

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Table 3: 
Protocol-Required Safety Laboratory Assessments 
Assessment 
Parameter 
Hematology 
Hematocrit 
RBC indices: 
WBC count w/differential: 
 
Hemoglobin 
-- MCH 
-- Basophils 
-- Monocytes 
 
Platelet count 
-- MCV 
-- Eosinophils 
-- Neutrophils 
 
RBC count 
-- %Reticulocytes 
-- Lymphocytes 
Clinical 
chemistry 
(serum) 
Alkaline phosphatase 
BUN 
Creatine kinase 
Potassium 
ALT/SGPT 
Calcium 
GGT 
Protein (total) 
AST/SGOT 
Creatinine 
Glucose (fasting) 
Sodium 
Bilirubin (total, direct) 
 
 
Coagulation 
aPTT 
INR 
Prothrombin time 
Routine 
urinalysis 
-- Specific gravity 
-- pH, glucose, protein, blood, ketones, bilirubin, urobilinogen, nitrite, leukocyte esterase by 
dipstick 
-- Microscopic examination (if blood or protein is abnormal) 
Additional 
tests 
-- Follicle-stimulating hormone and estradiol (women of nonreproductive potential, only) 1 
-- Human chorionic gonadotropin (hCG) pregnancy test (for women of reproductive potential, 
only) 2 
-- Urine drug screen: amphetamines, cocaine, opiates, and cannabinoids 1 
ALT=alanine aminotransferase; aPTT=activated partial thromboplastin time AST=aspartate aminotransferase; 
BUN=blood urea nitrogen; GGT=gamma glutamyl transferase; INR=international normalized ratio; MCH=mean 
corpuscular hemoglobin; MCV=mean corpuscular volume; RBC=red blood cell; SGOT=serum glutamic-
oxaloacetic transaminase; SGPT=serum glutamic-pyruvic transaminase; WBC=white blood cell 
 Note: All events of ALT ≥3×upper limit of normal (ULN) and bilirubin ≥2×ULN (>35% direct bilirubin) or ALT 
≥3×ULN and international normalized ratio (INR) >1.5, which may indicate severe liver injury (possible Hy’s 
Law), must be reported as an SAE. 
1 Test is necessary at the Screening Visit, only 
2 Pregnancy tests will be serum based at Screening and at the Follow-up Visit. Urine-based tests are acceptable for 
all other visits unless serum testing is required by local regulation or IRB/IEC. Also see Section 8.3.6.1. 
 
8.3.6.1. 
Pregnancy Testing 
Contraception requirements for male and female participants are provided in Inclusion Criteria 9, 
10, and 11 (Section 5.1).  
For women of reproductive potential (defined in Section 5.3.4.1), a pregnancy test result from 
each scheduled visit must be documented in the eCRF. Negative results must be confirmed and 
documented at Screening and at predose on Day 1 for study entry eligibility. Additional testing 
will be performed when a menstrual cycle is missed or when pregnancy is otherwise suspected. 
A confirmed pregnancy test result will result in immediate discontinuation from study drug (see 
Section 5.6.2). See Section 10.1.4 for pregnancy reporting requirements. 

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8.3.6.2. 
Genetic Evaluations 
Genetic evaluation in this study is limited to confirmation of MELAS (by medical history) at 
Screening for study eligibility determination.  
8.3.7. 
Suicidality 
IW-6463 is a CNS-active investigational drug. Although IW-6463 and other similar drugs in this 
class have not been associated with an increased risk of suicidal thinking or behavior, the 
Sponsor considers it important to monitor for such ideation or behavior before and during this 
clinical study. Therefore, participants should be appropriately monitored and closely observed 
for suicidal ideation and behavior or any other unusual change in behavior. The Columbia 
Suicidality Severity Rating Scale (C-SSRS) (13, 14) will be administered according to Table 1, 
starting predose on Day 1 of the Treatment Period and at all subsequent visits where clinical 
assessments are conducted, including at any unscheduled visit. Immediate consultation with the 
Medical Monitor should be sought for participants who experience signs of suicidal ideation or 
behavior, and consideration given to discontinuing study drug. 
8.3.8. 
Adverse Event and SAE Monitoring 
Adverse events (AEs) will be monitored and recorded throughout the study starting from ICF 
execution through the Follow-up Visit. Care will be taken not to introduce bias when detecting 
AEs and/or SAEs. Open-ended and nonleading verbal questioning of the participant is the 
preferred method to inquire about AE occurrences.  
Investigators are not obligated to actively collect AE information after conclusion of the 
participant’s involvement in the study. However, if the Investigator learns of any SAE or death at 
any time after a participant has been discharged and the Investigator considers the event to be 
reasonably related to the study drug or to study participation, he/she must promptly notify 
the Sponsor. 
See Section 10 for details regarding AE management and reporting requirements. 
8.4. 
Participant Diary for Recording Changes in Health Status, Daily 
Dosing, and Concomitant Medications 
At the Screening Visit, each participant will be issued a paper (source) diary in which they (or 
their legal representative/guardian) will be asked to record on a daily basis the name of any other 
medication(s) they the take, along with the date, time, and dose strength of the medication(s); 
and any changes in their health status (including the dates, times, and brief descriptions).  
Starting on Day 1 of the Treatment Period, they will be instructed to also record the date and 
time of each study drug dose taken at home, in addition to any other medications they take 
(including name, date, time, and dose strength), and any changes in their health status  (including 
the dates, times, and brief descriptions).  
Participants will be asked to have the diaries available at each scheduled at-home and in-clinic 
visit during the Treatment Period for monitoring by the study staff.  

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During the Follow-up Period, participants will be asked to continue to record in the same manner 
any concomitant medications and changes in their health status. The diaries will be collected 
from the participants at the Follow-up Visit. 
8.5. 
Clinical Outcomes Assessments/Participant Questionnaires 
8.5.1. 
Patient-reported Outcomes Measurement Information System (PROMIS)–
Cognitive Function 
The Patient-reported Outcomes Measurement Information System (PROMIS) Item Bank v2.0–
Cognitive Function is a self-administered questionnaire that assesses multiple aspects of mental 
fatigue and cognitive function in the past 7 days prior to the administration of the questionnaire. 
It uses a Likert-type rating scale (eg, "Never" to "Very often"). 
8.5.2. 
Patient Global Impression of Change (PGIC) 
The Patient Global Impression of Change (PGIC) is a single-item questionnaire that assesses the 
participant's perception of change in his/her overall health status since the start of the study using 
a Likert-type rating scale (eg, "Very much improved" to "Very much worse").  
8.5.3. 
Modified Fatigue Impact Scale (MFIS) 
The Modified Fatigue Impact Scale (MFIS) is a self-administered questionnaire that assesses the 
impact of fatigue in terms of physical, cognitive, and psychosocial functioning over the past 
4 weeks. Patients respond using a Likert-type rating scale. (eg, "Never" to "Almost always"). 
8.6. 
PK Evaluations (Plasma and CSF) 
PK samples will be collected as scheduled in Table 1. The actual date and time (24-h clock time) 
of each sample collection will be recorded in the source documents and eCRF. Each sample will 
be divided into 2 aliquots (1 each for PK and a back-up). Specific instructions for the collection 
and handling of biological samples are provided in the study's laboratory manual. 
• Sparse whole-blood samples of approximately 2 mL will be collected for 
measurement of plasma concentrations of IW-6463 using a validated liquid 
chromatography-tandem mass spectrometry bioanalytical method.  
• From each participant who does not withhold consent for the procedure, a CSF 
sample of approximately 4 mL will be collected for measurement of IW-6463 CSF 
concentration using a validated liquid chromatography-tandem mass spectrometry 
bioanalytical method.  
The timing of sampling may be altered during the course of the study based on emerging data 
(eg, to obtain data closer to the time of peak plasma concentrations) to ensure appropriate 
monitoring. Samples collected for analyses of IW-6463 concentration may also be used to 
evaluate safety aspects related to concerns arising during or after the study. 
Biological samples collected from participants in this study may be stored for future analysis for 
not more than 5 years. 

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9. 
STATISTICAL CONSIDERATIONS 
See Section 3 for a list of the study objectives and their corresponding endpoints. Section 4.5 
provides overall study stopping criteria.  
9.1. 
Statistical Hypotheses 
Within-treatment statistical hypothesis testing will be performed on postdose change from 
baseline (CFB) exploratory endpoint. The null hypothesis assumes the CFB=0; rejecting the null 
hypothesis supports the alternative hypothesis (CFB≠0).  
9.2. 
Sample Size and Power 
A maximum of 20 participants will be assigned to receive IW-6463 such that approximately 
12 evaluable participants complete the study. 
The sample size selected is not based on statistical considerations. A sample size of 
approximately 12 evaluable participants in a rare disease indication is considered sufficient to 
address the primary and research objective.  
9.3. 
Statistical Methods 
9.3.1. 
General Considerations 
Descriptive statistics (n, mean, standard deviation [SD], minimum, maximum, median, and 
interquartile range) will be calculated to summarize continuous variables. Frequency and 
percentage of participants in each category will be calculated to summarize categorical variables.  
Due to the developmental stage of this study, no adjustments will be made for multiplicity. 
Details of the data handling methods will be specified in the statistical analysis plan. Inferential 
statistics will be used for descriptive purposes only. If not otherwise specified, the baseline value 
is defined as the last non-missing value measured before administration of study drug on Day 1. 

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9.3.2. 
Populations for Analyses 
Analysis populations are defined as follows. 
Population 
Description 
Screened  
All participants who sign the ICF 
Safety 
All participants who sign the ICF and take ≥1 dose of study drug  
PD Evaluable 
All participants who complete the baseline and EOT Visit assessments, 
have ≥80% compliance with study drug dosing, and do not have any 
major protocol violation(s) that could affect their PD assessment 
PK Evaluable 
All participants who complete the EOT Visit and have ≥1 evaluable 
postdose PK assessment 
9.3.3. 
Disposition 
The total number of screened participants and the number of participants who are screen failures 
will be tabulated. The number and percentage of participants included in each population 
(Screened, Safety, PD Evaluable, and PK Evaluable) will be presented. The number and 
percentage of participants who completed the study or discontinued early, as well as the reasons 
for discontinuation will be presented for the Safety Population.  
9.3.4. 
Baseline Data  
Baseline and demographic characteristics will be summarized by standard descriptive summaries 
(eg, means and SDs for continuous variables such as age and percentages for categorical 
variables such as sex). 
9.3.5. 
Drug Exposure and Compliance 
Exposure to open-label study drug, calculated as the number of days from the first dose taken to 
the date of the last dose taken, inclusive, will be summarized for the Safety Population. The total 
number of doses taken between specified visits and overall for the entire study will be calculated 
for each participant. Compliance will be based on the number of doses expected to be taken. 
Percent compliance will be summarized for each scheduled visit and overall. Compliance rates 
will also be categorized as missing, <80%, ≥80% and ≤120%, and >120% and will be 
summarized. 
9.3.6. 
Prior and Concomitant Medications and Procedures 
See definitions for prior and concomitant medications and procedures in Section 6.3. Prior and 
concomitant medication use will be summarized for the Safety Population by the number and 
percentage of participants receiving each medication within each therapeutic class. Multiple 
medications used by a participant in the same category (based on Anatomical-Therapeutic-
Chemical classification) will be counted only once. 
9.3.7. 
Major Protocol Deviations 
Major protocol deviations will be identified and documented based on review of protocol 
deviations before database lock, and will be used to define the PD Evaluable Population. The 

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categories of major protocol deviations to be reviewed include, but are not limited to, 
participants who: 
• Did not meet key inclusion/exclusion criteria in the judgment of the evaluability 
committee 
• Received disallowed concomitant medication that could meaningfully impact results 
• Had overall treatment compliance rate <80% or >120% 
The number and percentage of participants with major protocol deviations will be summarized 
for the Safety Population by type of deviation. All major protocol deviations will be presented in 
a data listing. 
9.3.8. 
Safety Analyses 
Incidence of AEs will be summarized by Medical Dictionary for Regulatory Activities system 
organ class and preferred term. By-participant listings will be provided for pretreatment AEs, 
TEAEs, severe AEs, drug-related AEs, SAEs, and AEs leading to study discontinuation or death. 
All safety analyses will be conducted on the Safety Population. 
ECGs, vital signs, and clinical laboratory tests (in International System [SI] units) at each 
assessment time point and the change from baseline at each postbaseline time point will be 
summarized using descriptive statistics unless noted otherwise. Listings will be provided for 
participants with abnormal values. 
A TEAE is defined as an adverse event that emerges during treatment, having been absent 
pretreatment, or that worsens relative to the pretreatment state.  
9.3.8.1. 
ECGs 
The number and percentage of participants with absolute QTcF intervals in the following 
categories will be examined: QTcF≤450 ms, 450 ms<QTcF≤480 ms, 480 ms<QTcF≤500 ms, 
and QTcF>500 ms. Shift tables will be presented comparing values between baseline and end 
of study. 
Additionally, the number and percentage of participants with a change from baseline in QTcF 
interval according to the following categories will be examined: QTcF interval increases by 
>30 ms, but ≤60 ms, and QTcF interval increases by >60 ms. Shift tables will be presented 
comparing values between baseline and end of study. 
9.3.9. 
Patient-Reported Outcomes Analyses 
Health outcomes analyses (Section 8.5) will be based on the PD Evaluable Population. 
Descriptive summaries for each domain of the questionnaires will be presented for each 
assessment time point and the change from baseline at each postbaseline time point, unless noted 
otherwise. 
9.3.10. 
PK Analyses 
Descriptive statistics will be calculated and summarized for plasma and CSF concentrations of 
IW-6463 at each assessed timepoint.   

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A population PK approach based on sparse PK data will be used to determine exposure and oral 
clearance of IW-6463. If data allow, influence of participant demographics (eg, age, race) and 
effects of concomitant medications on IW-6463 PK exposure will be evaluated. In addition, 
exposure-effect relationships (such as hemodynamic, biomarkers, and safety parameters) may 
also be explored. The results of these analyses may be reported separately outside of the clinical 
study report. 
PK parameters of interest include but are not limited to the area under the concentration-time 
curve from time zero (predose) to 24 hours postdose (AUCtau), time to Cmax (Tmax), t1/2, 
maximum observed plasma concentration (Cmax), plasma concentration observed at the end of a 
dosing interval (Ctrough), apparent total plasma clearance (CL/F), apparent volume of distribution 
(Vz/F), and CSF:plasma concentration ratio, and will be calculated and presented as data permit. 
9.3.11. 
PD Analyses 
Pharmacodynamic analyses will be conducted using the Safety and PD populations.   
Plasma biomarkers and imaging endpoints at each assessment time point and the change from 
baseline at each postbaseline time point will be summarized using descriptive statistics unless 
noted otherwise. Listings will be provided for all participants. 
9.4. 
Controlling for Multiplicity 
Due to the developmental stage of this study, no adjustments will be made for multiple 
comparisons. 
9.5. 
Interim Analysis 
An interim analysis is not planned. 
9.6. 
Independent Data Monitoring Committee 
Because this is an open-label study, a data monitoring committee will not be utilized. 
10. 
SAFETY MANAGEMENT AND REPORTING OF ADVERSE 
EVENTS 
10.1. 
Monitoring and Reporting Details 
All AEs (related and unrelated; serious or nonserious) will be monitored and recorded from the 
signing of the ICF until the Follow-up Visit in accordance with regulatory, Sponsor, and Good 
Clinical Practice (GCP) guidelines and requirements.  
Changes in laboratory values that are not already part of an ongoing AE and that are considered 
clinically significant are to be reported as AEs. For example, an ALT >3×the upper limit of 
normal range in the context of a diagnosis of hepatitis would not be reported as an AE. However, 
if the same elevation occurs outside of the context of an existing diagnosis and is considered 
clinically significant, it would be reported as an AE. 

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The AE term should be reported in standard medical terminology. For each AE, the Investigator 
will evaluate and report the onset (date and time), outcome/resolution (date and time), 
seriousness, severity (intensity), causality, action(s) taken with study drug, and whether any 
therapies or medications were administered in response to the AE. 
10.1.1. 
SAE Reporting  
All SAEs must be reported to the Sponsor using the AE eCRF page within 24 hours of the 
Investigator’s first awareness of the event. In all cases, the Investigator must verify the accuracy 
of the information with the corresponding source documents. 
10.1.2. 
IRB/IEC Notification of SAEs and Other Unanticipated Events 
The Sponsor or designee will notify FDA and all investigators of all unexpected, serious, study 
drug-related (per Sponsor assessment) events (ie, 7- or 15-day FDA safety reports) that occur at 
any Study Center during the study. The Principal Investigator at each site will be responsible for 
notifying the relevant IRB/IEC of these additional SAEs, according to local standard operating 
procedures (SOPs). 
10.1.3. 
Follow-up Reports 
The Investigator is responsible for ensuring that all AESIs and SAEs are followed until 
resolution, stabilization, the event is otherwise explained, or the participant is lost to follow-up 
(see Section 5.5).  
The investigator will submit via the AE eCRF any updated SAE information within 24 hours of 
the investigator’s first awareness of the information. 
10.1.4. 
Reporting of Pregnancy in a Participant or Participant’s Partner 
A female participant who reports pregnancy before initiation of study drug dosing on Day 1 will 
be withdrawn from study participation; the discontinuation will be recorded as a screen failure. 
Should a pregnancy occur in either a participant or a participant’s partner after initiation of study 
drug, it must be reported and recorded on the study-specific pregnancy form. The Study Center 
must notify Syneos Health GSPV (see Section 10.1.1 for contact details) within 24 hours from 
the time that Center personnel first learn of the pregnancy.  
The Study Center should make reasonable efforts to follow the pregnancy to term, notifying 
Syneos Health GSPV of the pregnancy outcome (spontaneous miscarriage, elective termination, 
normal birth, or congenital abnormality) within 24 hours of awareness.  
All reports of congenital abnormalities/birth defects and still births will be considered SAEs. 
Spontaneous miscarriages, elective termination without complications, and normal births without 
congenital abnormality will not be reported or handled as SAEs, but will be reported as the 
outcome of the respective pregnancy.  
If the pregnancy is associated with an SAE, a separate SAE form will be completed. 

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10.2. 
Definition of Adverse Events 
10.2.1. 
Adverse Event (AE) 
An adverse event is any untoward medical occurrence in a patient or clinical investigation 
participant administered a pharmaceutical product and which does not necessarily have a causal 
relationship with this treatment. An AE can therefore be any unfavorable and unintended sign 
(including an abnormal laboratory finding), symptom, or disease temporally associated with the 
use of a medicinal (investigational) product, whether or not related to the medicinal 
(investigational) product. Regardless of causality, all AEs must be recorded and reported on the 
forms provided by the Sponsor from the time that a participant signs the ICF at the Screening 
Visit until completion of the Follow-up Visit. 
10.2.1.1. Definition of TEAE 
A TEAE is defined as an adverse event that emerges during treatment, having been absent 
pretreatment, or that worsens relative to the pretreatment state.  
10.2.2. 
Serious Adverse Event (SAE) 
An SAE is an AE occurring during any study phase (ie, baseline, treatment, washout, or follow-
up), and at any dose of the study drug, comparator or placebo, that fulfills 1 or more of the 
following: 
• Results in death 
• Is immediately life-threatening 
• Requires inpatient hospitalization or prolongation of existing hospitalization 
• Results in persistent or significant disability or incapacity: a substantial disruption of a 
person’s ability to conduct normal daily functions 
• Results in a congenital abnormality or birth defect 
• Is an important medical event that may jeopardize the participant or may require medical 
intervention to prevent 1 of the outcomes listed above. 
All SAEs that occur after any participant has been enrolled, before treatment, during treatment, 
or within the Follow-up Period after the cessation of treatment, whether or not they are related to 
the study, must be recorded on forms provided by the Sponsor. 
10.2.3. 
Adverse Events of Special Interest (AESIs) 
Based on the mechanism of action of sGC and anticipated vasodilation effects and based on the 
fact that IW-6463 is a CNS-penetrant stimulator of sGC, the Sponsor will collect AESIs in a 
timely manner. 
The AESIs relate to symptomatic hypotensive events and/or tachycardia, dizziness, syncope, and 
TEAEs related to change of neurobehaviors (ie, suicidality or euphoria). In addition, because 
riociguat, a marketed sGC stimulator, includes bleeding events as a warning and precaution on 
its prescribing information (15), bleeding events will also be considered AESIs for IW-6463 in 

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this study. The specific list of TEAE terms will be provided in the C6463-201 safety 
management plan.   
An AESI classification means that although an event might be nonserious, it will nonetheless be 
reported to the Sponsor by completing an SAE form, filling in the AESI box, and submitting to 
Syneos Health (see Section 10.1.1) within 5 business days of the Investigator’s awareness of the 
event.  
10.3. 
Categorization of Events 
10.3.1. 
Relationship to Study Drug 
For all TEAEs, the Investigator must provide an assessment of causal relationship to study drug. 
The causality assessment must be recorded in the patient’s source documentation and on the AE 
page of the subject’s eCRF. Causal relationship must be assessed according to the following: 
Related: 
An event where there is at least a reasonable possibility of a causal 
relationship between the event and the study drug. “Reasonable possibility” 
means there is evidence to suggest a potential causal relationship between 
the drug and the TEAE. 
Unrelated: 
Any other event 
10.3.2. 
Severity (Intensity) 
The intensity (severity) of each AE will be assessed according to the following scale: 
• Mild (awareness of sign or symptom, but easily tolerated) 
• Moderate (discomfort sufficient to cause interference with normal activities) 
• Severe (incapacitating, with inability to perform normal activities) 
Severity is different than seriousness. Severity is a measure of intensity whereas seriousness is 
defined by the criteria under Section 10.2.2. An AE of severe intensity may not necessarily be 
considered serious, and vice versa. 
11. 
STUDY ADMINISTRATION AND ETHICAL CONSIDERATIONS 
11.1. 
Data Collection and Management  
• The Sponsor’s procedures include quality control and assurance checks on all clinical 
studies that it conducts. Before enrolling any participants into this study, Sponsor 
personnel and/or a trained designated representative will review with the Investigator: 
the protocol, the IB, the eCRFs and instructions for their completion, the procedure 
for obtaining informed consent, and the procedure for reporting AEs and SAEs. 
• All participant data relating to the study will be recorded on eCRFs unless transmitted 
electronically to the Sponsor or designee (eg, laboratory data). 

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− The Investigator is responsible for verifying that all data entries on the eCRFs are 
accurate and correct and ensure that all data are entered in a timely manner, as 
soon as possible after information is collected. An explanation should be provided 
for all missing data. 
− The Investigator must maintain accurate documentation (source data) that 
supports the information entered in the eCRF. 
− Data entered into the eCRF that are transcribed from source documents must be 
consistent with the source documents or the discrepancies must be explained. The 
Investigator may need to request previous medical records or transfer records. In 
addition, current medical records must be available.  
11.1.1. 
Participant Confidentiality and Data Protection 
• After ICF execution (see Section 11.3.3), each participant will be assigned a unique 
identifier by the Study Center. Any participant records or datasets that are transferred 
to the Sponsor will contain only the identifier; participant names or any information 
that would make the participant identifiable will not be transferred. 
• The participant must be informed that his/her personal study-related data will be used 
by the Sponsor in accordance with local data protection law. The level of disclosure 
must also be explained to the participant. 
• The participant must be informed that his/her medical records (eg, eCRFs) recorded 
during the study may be examined by Research Quality Assurance auditors or other 
authorized personnel appointed by the Sponsor, by appropriate IRB/IEC members, 
and by inspectors from regulatory authorities. 
11.2. 
Monitoring and Inspection of Data and Study Centers  
11.2.1. 
Monitoring of Study Center and Inspection of Records 
The Sponsor will be allowed to conduct site visits to the study center(s) for the purpose of 
monitoring any aspect of the study. The Investigator agrees to allow the monitor to inspect the 
drug storage area, study drug stocks, drug accountability records, participant charts and study 
source documents, and other records relative to study conduct. 
Before the Study Center can enter a participant into the study, a representative of the Sponsor 
will visit the Center to: 
• Determine the adequacy of the facilities 
• Discuss with the Investigator(s) and other personnel their responsibilities with regard 
to protocol adherence, and the responsibilities of the Sponsor or its representatives. 
This will be documented in a Clinical Study Agreement between the Sponsor and the 
Investigator. 
During the study, a monitor from the Sponsor or its representative will have regular contacts with 
the Study Center, for the following: 
• Provide information and support to the Investigator(s) 

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• Confirm that facilities remain acceptable 
• Confirm that the study team is adhering to the protocol, that data are being accurately 
recorded in the eCRFs, and that study drug accountability checks are being performed 
• Perform source data verification. This includes a comparison of the data in the eCRFs 
with the participant’s medical records at the hospital or practice, and other records 
relevant to the study. This will require direct access to all original records for each 
participant (eg, clinic charts). 
• Record and report any protocol deviations not previously sent to the Sponsor. 
• Confirm AEs, AESIs, and SAEs have been properly documented on eCRFs and 
confirm that:  
− All SAEs and AESIs have been forwarded to the Sponsor within the requested 
timelines 
− SAEs that met criteria for reporting have been forwarded to the IRB 
The monitor will be available between visits if the investigator(s) or other staff needs 
information or advice. 
11.2.2. 
Audits and Inspections 
Authorized representatives of the Sponsor, regulatory authority, IEC, or IRB may visit the Study 
Center to perform audits or inspections, including source data verification. The purpose of an 
audit or inspection by the Sponsor is to systematically and independently examine all study-
related activities and documents to determine whether these activities were conducted and that 
data were recorded, analyzed, and accurately reported according to the protocol, International 
Council on Harmonisation (ICH) GCP guidelines, and any applicable regulatory requirements.  
The Investigator should immediately contact the Sponsor if contacted by a regulatory agency 
about an inspection. 
11.2.3. 
Retention and Archiving of Records 
The Principal Investigator at each Study Center must maintain all documentation relating to the 
study including eCRFs, source documents (including signed ICFs, laboratory test results, and 
medication inventory records), and audit trails, in accordance with locally applicable regulatory 
requirements; and, in any event, for a period of 2 years after the last marketing application 
approval, or if not approved, 2 years after the discontinuance of the study drug for investigation.  
If it becomes necessary for the Sponsor or Regulatory Authority to review any documentation 
relating to the study, the Investigator must permit access to such records. 
No study records will be destroyed without notifying the Sponsor and giving the Sponsor the 
opportunity to take such study records or authorizing in writing the destruction of records after 
the required retention period. 

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11.2.4. 
Quality Control and Quality Assurance 
To ensure compliance with GCP and all applicable regulatory requirements, the Sponsor may 
conduct a quality assurance audit. See Section 11.2.2 for details. 
11.3. 
Ethics 
11.3.1. 
IRB/IEC and Investigator Requirements 
The Principal Investigator at each Study Center must obtain IRB approval for the investigation. 
Initial IRB approval, and all materials approved by the IRB for this study including the final 
version of the ICF and recruitment materials must be maintained by the Principal Investigator 
and made available for inspection.  
The final study protocol, including the final version of the ICF, must be approved or given a 
favorable opinion in writing by the IRB/IEC as appropriate. The Principal Investigator at a given 
Study Center must submit written approval to the Sponsor before enrolling any participant into 
the study. 
The Principal Investigator is responsible for informing the IRB/IEC of any amendment to the 
protocol in accordance with local requirements. In addition, the IRB/IEC must approve all 
advertising used to recruit participants for the study. The protocol must be re-approved by the 
IRB/IEC upon receipt of amendments and annually, as local regulations require. 
Progress reports and notifications of SAEs will be provided to the IRB or IEC by the Investigator 
according to local regulations and guidelines. 
11.3.2. 
Ethical Conduct of the Study/Compliance Statement 
This study will be conducted in full accordance all applicable local, state, and federal laws, in 
addition to 45 Code of Federal Regulations (CFR) 46, 21 CFR Parts 50, 54, 56, 312, and 314 and 
ICH GCPs. All episodes of noncompliance will be documented. 
All Investigators will perform the study in accordance with this protocol, will obtain written, 
informed consent, and will report unanticipated problems involving risks to participants or others 
in accordance with local SOPs and federal requirements. Collection, recording, and reporting of 
data will be accurate and will ensure the privacy, health, and welfare of research participants 
during and after the study.  
11.3.3. 
Written Informed Consent 
Informed consent procedures will comply with the CFR 21, Parts 50 and 312, and ICH E6(R2) 
guidelines. The written ICF must be pre-approved by the IRB/IEC for the purposes of obtaining 
and documenting consent. 
Before entry into the study, the Investigator(s) at each Study Center will ensure that each 
participant, if applicable, is given full and adequate oral and written information about the 
nature, purpose, possible risk and benefit of the study. All participants must be notified that they 
are free to discontinue from the study at any time. They must be given the opportunity to ask 
questions and allowed time to consider the information provided. 

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