Trial Outcomes & Findings for A Trial to Evaluate Safety, Tolerability and Efficacy of Elamipretide in Subjects With Barth Syndrome (NCT NCT03098797)

Last Updated: 2024-04-16

Results Overview

Average distance walked in meters during the 6-minute walk test (6MWT) at end of treatment, where end of treatment means end of Visit 5 (Week 12) for Period 1 and end of Visit 10 (Week 12) for Period 2. Results were pooled for each 12 week period.

Recruitment status

COMPLETED

Study phase

PHASE2/PHASE3

Target enrollment

12 participants

Primary outcome timeframe

Pre-dose to Week 12 (end of treatment)

Results posted on

2024-04-16

Participant Flow

Participant milestones

Participant milestones
Measure	Experimental: Elamipretide, Then Placebo Part 1: Patients will be randomized to receive 12 weeks of elamipretide in one of the two treatment periods. All subjects will receive 12 weeks of elamipretide, 4 weeks of washout, then 12 weeks of placebo followed by a 4-week washout period before Part 2. Elamipretide: 40 mg daily subcutaneous injection for 12 weeks Placebo: subcutaneous injection for 12 weeks Part 2: Open Label Extension: Subjects are to be treated with daily 40 mg SC elamipretide for up to 192 weeks.	Placebo, Then Elamipretide Patients will be randomized to receive 12 weeks of placebo in one of the two treatment periods. All subjects will receive 12 weeks of placebo, followed by a 4 week washout period and then 12 weeks of elamipretide followed by a 4-week washout period before Part 2. Placebo: subcutaneous injection for 12 weeks Elamipretide: 40 mg daily subcutaneous injection for 12 weeks Part 2: Open Label Extension: Subjects are to be treated with 40 mg SC elamipretide for up to 192 weeks.
First Intervention (12 Weeks) STARTED	6	6
First Intervention (12 Weeks) COMPLETED	6	6
First Intervention (12 Weeks) NOT COMPLETED	0	0
Washout (4 Weeks) STARTED	6	6
Washout (4 Weeks) COMPLETED	6	6
Washout (4 Weeks) NOT COMPLETED	0	0
Second Intervention (12 Weeks) STARTED	6	6
Second Intervention (12 Weeks) COMPLETED	6	6
Second Intervention (12 Weeks) NOT COMPLETED	0	0
Part 2 Open Label Extension STARTED	5	5
Part 2 Open Label Extension Week 12	5	5
Part 2 Open Label Extension Week 36	3	5
Part 2 Open Label Extension Week 168	3	5
Part 2 Open Label Extension COMPLETED	3	5
Part 2 Open Label Extension NOT COMPLETED	2	0

Reasons for withdrawal

Reasons for withdrawal
Measure	Experimental: Elamipretide, Then Placebo Part 1: Patients will be randomized to receive 12 weeks of elamipretide in one of the two treatment periods. All subjects will receive 12 weeks of elamipretide, 4 weeks of washout, then 12 weeks of placebo followed by a 4-week washout period before Part 2. Elamipretide: 40 mg daily subcutaneous injection for 12 weeks Placebo: subcutaneous injection for 12 weeks Part 2: Open Label Extension: Subjects are to be treated with daily 40 mg SC elamipretide for up to 192 weeks.	Placebo, Then Elamipretide Patients will be randomized to receive 12 weeks of placebo in one of the two treatment periods. All subjects will receive 12 weeks of placebo, followed by a 4 week washout period and then 12 weeks of elamipretide followed by a 4-week washout period before Part 2. Placebo: subcutaneous injection for 12 weeks Elamipretide: 40 mg daily subcutaneous injection for 12 weeks Part 2: Open Label Extension: Subjects are to be treated with 40 mg SC elamipretide for up to 192 weeks.
Part 2 Open Label Extension Adverse Event	2	0

Baseline Characteristics

All participants for whom Age was measured.

Baseline characteristics by cohort

PRIMARY outcome

Timeframe: Pre-dose to Week 12 (end of treatment)

Population: All participants for whom 6MWT was measured.

Outcome measures

Outcome measures
Measure	Experimental: Elamipretide n=12 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-week washout period).	Placebo n=12 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-weekwashout period).
Part 1: Distance Walked During the 6-Minute Walk Test (6MWT) by Visit Pre-dose	400.1 meters Standard Deviation 55.07	412.6 meters Standard Deviation 60.16
Part 1: Distance Walked During the 6-Minute Walk Test (6MWT) by Visit Week 12 (End of Treatment	443.1 meters Standard Deviation 65.43	443.9 meters Standard Deviation 77.10

PRIMARY outcome

Timeframe: Pre-dose, Weeks 1, 4, 8, and 12 (end of treatment)

Population: All participants for whom Total Fatigue Score was measured

Total Fatigue Score (Q1, Q2, and Q4) Based on the BarTH Syndrome Symptom Assessment (BTHS-SA) by visit at predose, Weeks 1, 4, 8, and 12 (end of treatment). The BTHS-SA is 3-question fatigue assessment using a 0 to 4-point scale for each question where no fatigue =0 and very severe fatigue =4, with scores from all 3 questions combined and averaged for all subjects; a lower score means better outcome, higher score means a worse outcome. Combined Min score=0, max score =12. Weekly values are based on the weekly average of the last 7 days before the site or visiting nurse visit for both periods. Results from each 12-week period were combined, where end of treatment for Period 1 =Visit 5 (week 12), and End of Period 2 = Visit 10 (week 12)

Outcome measures

Outcome measures
Measure	Experimental: Elamipretide n=12 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-week washout period).	Placebo n=12 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-weekwashout period).
Part 1: Total Fatigue Score Based on the BTHS-SA by Visit. Pre-dose	7.672 score on a scale Standard Deviation 1.9360	7.433 score on a scale Standard Deviation 1.3848
Part 1: Total Fatigue Score Based on the BTHS-SA by Visit. Week 1	6.837 score on a scale Standard Deviation 2.1114	6.994 score on a scale Standard Deviation 1.7093
Part 1: Total Fatigue Score Based on the BTHS-SA by Visit. Week 4	6.220 score on a scale Standard Deviation 2.3325	6.485 score on a scale Standard Deviation 1.4447
Part 1: Total Fatigue Score Based on the BTHS-SA by Visit. Week 8	6.089 score on a scale Standard Deviation 1.8344	6.196 score on a scale Standard Deviation 1.7815
Part 1: Total Fatigue Score Based on the BTHS-SA by Visit. Week 12	6.305 score on a scale Standard Deviation 2.0612	6.240 score on a scale Standard Deviation 1.6384

SECONDARY outcome

Timeframe: Baseline to Weeks 12, 24, 36, 48, 72, 96, 168, 192

Population: All participants for whom distance walked in 6MWT was measured.

Change from baseline for distance walked in meters during the 6-minute walk test (6MWT) by visit where Baseline= Part 1 Period 1 Pre-dose

Outcome measures

Outcome measures
Measure	Experimental: Elamipretide n=5 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-week washout period).	Placebo n=5 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-weekwashout period).
Part 2: Distance Walked During the 6MWT Part 2: Week 12	45.4 meters Standard Deviation 55.73	75.6 meters Standard Deviation 87.25
Part 2: Distance Walked During the 6MWT Part 2: Week 24	79.8 meters Standard Deviation 23.54	100.4 meters Standard Deviation 94.61
Part 2: Distance Walked During the 6MWT Part 2: Week 36	68.0 meters Standard Deviation 31.19	112.6 meters Standard Deviation 119.35
Part 2: Distance Walked During the 6MWT Part 2: Week 48	87.3 meters Standard Deviation 25.58	103.4 meters Standard Deviation 102.02
Part 2: Distance Walked During the 6MWT Part 2: Week 72	121.7 meters Standard Deviation 20.74	97.8 meters Standard Deviation 117.53
Part 2: Distance Walked During the 6MWT Part 2: Week 96	128.0 meters	63.7 meters Standard Deviation 69.14
Part 2: Distance Walked During the 6MWT Part 2: Week 168	89.3 meters Standard Deviation 32.75	100.2 meters Standard Deviation 78.10
Part 2: Distance Walked During the 6MWT Part 2: Week 192	118.0 meters	125.0 meters Standard Deviation 28.28

SECONDARY outcome

Timeframe: Baseline to Weeks 12, 24, 36, 48, 72, 96, 120, 144, 168, 192

Population: All participants for whom Total Fatigue Score was measured.

Change from Baseline (mean) in Total Fatigue Score (Q1, Q2, and Q4) Based on the BarTH Syndrome Symptom Assessment (BTHS-SA) by visit. The BTHS-SA is 3-question fatigue assessment using a 0-4 point scale for each question where no fatigue =0 and very severe fatigue =4, with scores from all 3 questions combined and averaged for all subjects by visit; a lower score means better outcome, higher score means a worse outcome. Change from baseline: an increase in scores would mean worse outcome, a decrease in scores means better outcome. Combined Min score=-12, max score =12. Weekly values are based on the weekly average of the last 7 days before the site or visiting nurse visit for both periods. Baseline= Period 1 Predose.

Outcome measures

Outcome measures
Measure	Experimental: Elamipretide n=5 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-week washout period).	Placebo n=5 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-weekwashout period).
Part 2: Change From Baseline: Total Fatigue Score (Q1, Q2, and Q4) Based on the BTHS-SA by Visit Baseline	-2.425 score on a scale Standard Deviation 2.0849	-1.540 score on a scale Standard Deviation 1.3653
Part 2: Change From Baseline: Total Fatigue Score (Q1, Q2, and Q4) Based on the BTHS-SA by Visit Week 12	-1.800 score on a scale Standard Deviation 2.4838	-1.314 score on a scale Standard Deviation 1.4237
Part 2: Change From Baseline: Total Fatigue Score (Q1, Q2, and Q4) Based on the BTHS-SA by Visit Week 24	-1.500 score on a scale Standard Deviation 2.0253	-0.314 score on a scale Standard Deviation 1.0816
Part 2: Change From Baseline: Total Fatigue Score (Q1, Q2, and Q4) Based on the BTHS-SA by Visit Week 36	-2.667 score on a scale Standard Deviation 3.6821	-1.714 score on a scale Standard Deviation 1.0583
Part 2: Change From Baseline: Total Fatigue Score (Q1, Q2, and Q4) Based on the BTHS-SA by Visit Week 48	-1.000 score on a scale Standard Deviation 2.9172	-0.314 score on a scale Standard Deviation 1.0650
Part 2: Change From Baseline: Total Fatigue Score (Q1, Q2, and Q4) Based on the BTHS-SA by Visit Week 72	-2.667 score on a scale Standard Deviation 3.4827	-1.114 score on a scale Standard Deviation 1.1301
Part 2: Change From Baseline: Total Fatigue Score (Q1, Q2, and Q4) Based on the BTHS-SA by Visit Week 96	-3.500 score on a scale Standard Deviation 2.5254	-0.357 score on a scale Standard Deviation 1.5763
Part 2: Change From Baseline: Total Fatigue Score (Q1, Q2, and Q4) Based on the BTHS-SA by Visit Week 120	-3.000 score on a scale Standard Deviation 2.9172	-0.114 score on a scale Standard Deviation 1.0309
Part 2: Change From Baseline: Total Fatigue Score (Q1, Q2, and Q4) Based on the BTHS-SA by Visit Week 144	-2.667 score on a scale Standard Deviation 2.2961	-0.314 score on a scale Standard Deviation 2.0067
Part 2: Change From Baseline: Total Fatigue Score (Q1, Q2, and Q4) Based on the BTHS-SA by Visit Week 168	-2.333 score on a scale Standard Deviation 4.0515	-0.514 score on a scale Standard Deviation 0.7309
Part 2: Change From Baseline: Total Fatigue Score (Q1, Q2, and Q4) Based on the BTHS-SA by Visit Week 192	-5.286 score on a scale	-1.107 score on a scale Standard Deviation 0.5556

SECONDARY outcome

Timeframe: Pre-dose to Week 12 (end of treatment)

Population: All participants for whom muscle strength as measured by handheld dynamometry was measured.

Muscle strength as measured by handheld dynamometry (HHD) in Newtons, where end of treatment means end of Visit 5 (Week 12) for Period 1 and end of Visit 10 (Week 12) for Period 2. Results were pooled for each 12 week period. Handheld dynamometry assesses the average strength of the knee extensors of both legs.

Outcome measures

Outcome measures
Measure	Experimental: Elamipretide n=12 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-week washout period).	Placebo n=12 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-weekwashout period).
Part 1: Muscle Strength as Measured by HHD by Visit Pre-dose	131.236 Newtons Standard Deviation 29.9004	123.100 Newtons Standard Deviation 24.6762
Part 1: Muscle Strength as Measured by HHD by Visit Week 12	135.934 Newtons Standard Deviation 52.2796	129.253 Newtons Standard Deviation 34.2395

SECONDARY outcome

Timeframe: Baseline to Weeks 12, 24, 36, 48, 72, 96,168, 192

Population: All participants for whom Muscle Strength by HHD (Newtons) was measured.

Muscle strength as measured by handheld dynamometry (HHD) in Newtons. Handheld dynamometry assesses the average strength of the knee extensors of both legs. Change from baseline where Baseline= Part 1 Period 1 Pre-dose: the greater positive change, the better the outcome, the smaller positive change (or negative change) the number the worse the outcome.

Outcome measures

Outcome measures
Measure	Experimental: Elamipretide n=5 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-week washout period).	Placebo n=5 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-weekwashout period).
Part 2: Change From Baseline: Muscle Strength by HHD (Newtons) by Visit Week 36	68.798 Newtons Standard Deviation 22.8892	48.351 Newtons Standard Deviation 31.1331
Part 2: Change From Baseline: Muscle Strength by HHD (Newtons) by Visit Week 48	69.613 Newtons Standard Deviation 20.8788	45.704 Newtons Standard Deviation 56.8895
Part 2: Change From Baseline: Muscle Strength by HHD (Newtons) by Visit Week 72	62.089 Newtons Standard Deviation 33.4753	32.071 Newtons Standard Deviation 31.7087
Part 2: Change From Baseline: Muscle Strength by HHD (Newtons) by Visit Week 96	93.745 Newtons	38.848 Newtons Standard Deviation 18.1422
Part 2: Change From Baseline: Muscle Strength by HHD (Newtons) by Visit Week 168	57.751 Newtons Standard Deviation 17.7509	61.897 Newtons Standard Deviation 19.1573
Part 2: Change From Baseline: Muscle Strength by HHD (Newtons) by Visit Week 192	42.368 Newtons	32.140 Newtons Standard Deviation 17.9287
Part 2: Change From Baseline: Muscle Strength by HHD (Newtons) by Visit Week 12	33.606 Newtons Standard Deviation 24.7304	42.147 Newtons Standard Deviation 34.9498
Part 2: Change From Baseline: Muscle Strength by HHD (Newtons) by Visit Week 24	54.073 Newtons Standard Deviation 29.7699	54.068 Newtons Standard Deviation 37.3060

SECONDARY outcome

Timeframe: Pre-dose to Week 12 (end of treatment)

Population: All participants for whom 5XSST was measured.

Time (in seconds) to complete the Five Times Sit-To-Stand, where end of treatment means end of Visit 5 (Week 12) for Period 1 and end of Visit 10 (Week 12) for Period 2. Results were pooled for each 12 week period.

Outcome measures

Outcome measures
Measure	Experimental: Elamipretide n=12 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-week washout period).	Placebo n=12 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-weekwashout period).
Part 1: 5XSST by Visit Pre-dose	12.965 seconds Standard Deviation 3.3366	13.710 seconds Standard Deviation 5.3088
Part 1: 5XSST by Visit Week 12	14.023 seconds Standard Deviation 5.4508	13.749 seconds Standard Deviation 6.1024

SECONDARY outcome

Timeframe: Baseline to Weeks 12, 24, 36, 48, 72, 96, 168, 192

Population: All participants for whom 5X Sit to Stand was measured.

Change in baseline in time (in seconds), where Baseline= Part 1 Period 1 Pre-dose to complete the Five Times Sit-To-Stand by visit. More time means worse outcome, less time means better outcome.

Outcome measures

Outcome measures
Measure	Experimental: Elamipretide n=5 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-week washout period).	Placebo n=5 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-weekwashout period).
Part 2: Change From Baseline: 5X Sit to Stand by Visit End of Part 1	-0.773 seconds Standard Deviation 2.5323	0.400 seconds Standard Deviation 2.7824
Part 2: Change From Baseline: 5X Sit to Stand by Visit Week 12	-1.505 seconds Standard Deviation 2.1843	0.384 seconds Standard Deviation 3.7167
Part 2: Change From Baseline: 5X Sit to Stand by Visit Week 24	-2.533 seconds Standard Deviation 2.7507	-1.160 seconds Standard Deviation 2.8668
Part 2: Change From Baseline: 5X Sit to Stand by Visit Week 36	-3.700 seconds Standard Deviation 3.7649	-0.344 seconds Standard Deviation 2.7035
Part 2: Change From Baseline: 5X Sit to Stand by Visit Week 48	-4.780 seconds Standard Deviation 2.9820	-0.082 seconds Standard Deviation 2.6625
Part 2: Change From Baseline: 5X Sit to Stand by Visit Week 72	-4.770 seconds Standard Deviation 3.2043	-0.454 seconds Standard Deviation 1.6369
Part 2: Change From Baseline: 5X Sit to Stand by Visit Week 96	-8.060 seconds	-0.397 seconds Standard Deviation 3.6036
Part 2: Change From Baseline: 5X Sit to Stand by Visit Week 168	-4.320 seconds Standard Deviation 4.0307	-0.986 seconds Standard Deviation 2.1857
Part 2: Change From Baseline: 5X Sit to Stand by Visit Week 192	-6.850 seconds	-0.390 seconds Standard Deviation 1.5839

SECONDARY outcome

Timeframe: Pre-dose to Week 12 (end of treatment)

Population: All participants for who SWAY application balance was measured.

SWAY application balance assessment consists of five stances each performed for 10 seconds and scores postural stability on a scale from 0-100 with higher scores indicating better postural stability from Pre-dose to Week 12 (end of treatment), where end of treatment means end of Visit 5 (Week 12) for Period 1 and end of Visit 10 (Week 12) for Period 2. Results were pooled for each 12 week period.

Outcome measures

Outcome measures
Measure	Experimental: Elamipretide n=12 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-week washout period).	Placebo n=12 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-weekwashout period).
Part 1: SWAY Application Balance Assessments by Visit Pre-dose	70.752 Score on a scale Standard Deviation 19.7199	68.820 Score on a scale Standard Deviation 24.7478
Part 1: SWAY Application Balance Assessments by Visit Week 12	78.698 Score on a scale Standard Deviation 15.1554	71.353 Score on a scale Standard Deviation 20.2515

SECONDARY outcome

Timeframe: Baseline to Weeks 12, 24, 36, 48, 72, 96,168, 192

Population: All participants for whom SWAY Application Balance Assessment was measured.

Change from Baseline: SWAY Application Balance Assessment,where Baseline= Part 1 Period 1 Pre-doseSWAY application balance assessment consists of five stances each performed for 10 seconds and scores postural stability on a scale from 0-100 with higher scores indicating better postural stability. An increase from baseline is a better outcome and a decrease in score is a worse outcome.

Outcome measures

Outcome measures
Measure	Experimental: Elamipretide n=5 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-week washout period).	Placebo n=5 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-weekwashout period).
Part 2: Change From Baseline: SWAY Application Balance Assessment Week 12	-3.152 score on a scale Standard Deviation 29.8419	10.464 score on a scale Standard Deviation 19.1971
Part 2: Change From Baseline: SWAY Application Balance Assessment Week 24	12.190 score on a scale Standard Deviation 9.6799	6.664 score on a scale Standard Deviation 9.5896
Part 2: Change From Baseline: SWAY Application Balance Assessment Week 36	0.807 score on a scale Standard Deviation 14.9493	9.484 score on a scale Standard Deviation 11.3834
Part 2: Change From Baseline: SWAY Application Balance Assessment Week 48	5.773 score on a scale Standard Deviation 7.8814	15.260 score on a scale Standard Deviation 16.2540
Part 2: Change From Baseline: SWAY Application Balance Assessment Week 72	10.420 score on a scale Standard Deviation 1.7501	15.240 score on a scale Standard Deviation 14.3557
Part 2: Change From Baseline: SWAY Application Balance Assessment Week 96	12.840 score on a scale	18.433 score on a scale Standard Deviation 21.3323
Part 2: Change From Baseline: SWAY Application Balance Assessment Week 168	21.127 score on a scale Standard Deviation 14.1854	19.644 score on a scale Standard Deviation 18.6821
Part 2: Change From Baseline: SWAY Application Balance Assessment Week 192	15.100 score on a scale	13.080 score on a scale Standard Deviation 16.3483

SECONDARY outcome

Timeframe: Pre-dose, Week 1, Week 12 (end of treatment)

Population: All participants for whom Patient Global Impression Scales of Symptoms was measured.

Patient-reported health status over the past week, by visit, where end of treatment means end of Visit 5 (Week 12) for Period 1 and end of Visit 10 (Week 12) for Period 2. Results were pooled for each 12 week period. Scores range from 0-40 for adolescents and 0-50 for adults. PGI Scale is as follows: 0=None, 1=Mild, 2=Moderate, 3=Severe, and 4=Very Severe. Higher score means worse health status, means worse outcome; lower score means better health status, means better outcome.

Outcome measures

Outcome measures
Measure	Experimental: Elamipretide n=12 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-week washout period).	Placebo n=12 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-weekwashout period).
Part 1: Patient Global Impression Scales of Symptoms Predose	1.7 Score on a scale Standard Deviation 0.65	1.8 Score on a scale Standard Deviation 0.83
Part 1: Patient Global Impression Scales of Symptoms Week 1	1.7 Score on a scale Standard Deviation 0.89	1.5 Score on a scale Standard Deviation 1.00
Part 1: Patient Global Impression Scales of Symptoms Week 12	1.4 Score on a scale Standard Deviation 0.79	1.6 Score on a scale Standard Deviation 0.67

SECONDARY outcome

Timeframe: Baseline to Weeks 12, 24, 36, 48, 72, 96, 120, 144, 168, 192

Population: All participants for whom Patient Global Impression Scales of Symptoms was measured.

Part 2: Change from Baseline: Patient Global Impression Scales of Symptoms by Visit Patient-reported health status over the past week where Baseline= Part 1 Period 1 Pre-dose, administered at Week 12 for Period 1 and Period 2. Scores range from 0-40 for adolescents and 0-50 for adults. PGI Scale is as follows: 1=None, 2=Mild, 3=Moderate, 4=Severe, and 5=Very Severe. Change from baseline: Higher score means worse health status, means worse outcome; lower score means better health status, means better outcome.

Outcome measures

Outcome measures
Measure	Experimental: Elamipretide n=5 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-week washout period).	Placebo n=5 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-weekwashout period).
Part 2: Change From Baseline: Patient Global Impression Scales of Symptoms by Visit End of Part 1	0.0 score on a scale Standard Deviation 0.00	-0.4 score on a scale Standard Deviation 0.55
Part 2: Change From Baseline: Patient Global Impression Scales of Symptoms by Visit Week 12	-0.2 score on a scale Standard Deviation 1.10	-0.6 score on a scale Standard Deviation 0.55
Part 2: Change From Baseline: Patient Global Impression Scales of Symptoms by Visit Week 24	-0.3 score on a scale Standard Deviation 0.50	-0.4 score on a scale Standard Deviation 0.55
Part 2: Change From Baseline: Patient Global Impression Scales of Symptoms by Visit Week 36	-0.7 score on a scale Standard Deviation 1.15	-0.6 score on a scale Standard Deviation 0.55
Part 2: Change From Baseline: Patient Global Impression Scales of Symptoms by Visit Week 48	-0.7 score on a scale Standard Deviation 1.15	0.0 score on a scale Standard Deviation 0.00
Part 2: Change From Baseline: Patient Global Impression Scales of Symptoms by Visit Week 72	-0.7 score on a scale Standard Deviation 1.15	-0.4 score on a scale Standard Deviation 0.55
Part 2: Change From Baseline: Patient Global Impression Scales of Symptoms by Visit Week 96	-0.5 score on a scale Standard Deviation 2.12	-0.3 score on a scale Standard Deviation 0.58
Part 2: Change From Baseline: Patient Global Impression Scales of Symptoms by Visit Week 120	-0.7 score on a scale Standard Deviation 1.15	-0.6 score on a scale Standard Deviation 0.55
Part 2: Change From Baseline: Patient Global Impression Scales of Symptoms by Visit Week 144	-1.0 score on a scale Standard Deviation 1.41	-0.8 score on a scale Standard Deviation 0.45
Part 2: Change From Baseline: Patient Global Impression Scales of Symptoms by Visit Week 168	-0.7 score on a scale Standard Deviation 1.15	-0.6 score on a scale Standard Deviation 0.55
Part 2: Change From Baseline: Patient Global Impression Scales of Symptoms by Visit Week 192	-2.0 score on a scale	-0.5 score on a scale Standard Deviation 0.71

SECONDARY outcome

Timeframe: Pre-dose to Week 12 (end of treatment)

Population: All participants for whom Patient Global Impression Scales of Symptoms was measured.

Clinician Global Impression Scale by visit: Clinician-reported overall health status at end of treatment, administered at Week 12 for Period 1 and Period 2. Scores range from 0-6 for both adolescents and adults. PGI Scale is as follows: 1= Very much Better, 2= Moderately Better, 3= A Little Better, 4= No Change, and 5= A Little Worse 6= Very much Worse. Higher score means worse health status, means worse outcome; lower score means better health status, means better outcome. End of treatment means end of Visit 5 (Week 12) for Period 1 and end of Visit 10 (Week 12) for Period 2. Results were pooled for each 12 week period.

Outcome measures

Outcome measures
Measure	Experimental: Elamipretide n=12 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-week washout period).	Placebo n=12 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-weekwashout period).
Part 1: Part 1: Clinician Global Impression Predose	1.8 Score on a scale Standard Deviation 0.45	1.4 Score on a scale Standard Deviation 0.51
Part 1: Part 1: Clinician Global Impression 12 weeks	1.6 Score on a scale Standard Deviation 0.51	1.6 Score on a scale Standard Deviation 0.51

SECONDARY outcome

Timeframe: Baseline to Weeks 12, 24, 36, 48, 72, 96, 120, 144, 168, 192

Population: All participants for whom Patient Global Impression Scales of Symptoms was measured.

Change from Baseline: CGI Symptom Scale by visit where Baseline= Part 1 Period 1 Pre-dose. Clinician Global Impression Scale: Clinician-reported overall health status at end of treatment, administered at Week 12 for Period 1 and Period 2. Scores range from 0-6 for both adolescents and adults. PGI Scale is as follows: 1= Very much Better, 2= Moderately Better, 3= A Little Better, 4= No Change, and 5= A Little Worse 6= Very much Worse. Change from baseline: higher score means worse health status, means worse outcome; lower score means better health status, means better outcome.

Outcome measures

Outcome measures
Measure	Experimental: Elamipretide n=5 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-week washout period).	Placebo n=5 Participants Subjects were randomized (in a ratio of 1:1) to one of two sequence groups: * Sequence 1: 12 weeks of single daily SC doses of 40 mg elamipretide in Treatment Period 1 followed by 12 weeks of treatment with placebo in Treatment Period 2 (separated by a 4-week washout period). * Sequence 2: 12 weeks of single daily SC doses of placebo in Treatment Period 1 followed by 12 weeks of treatment with 40 mg elamipretide in Treatment Period 2 (separated by a 4-weekwashout period).
Part 2: Change From Baseline: CGI Symptom Scale Week 12	-0.4 score on a scale Standard Deviation 0.55	0.0 score on a scale Standard Deviation 0.00
Part 2: Change From Baseline: CGI Symptom Scale Week 24	-1.3 score on a scale Standard Deviation 0.96	-0.4 score on a scale Standard Deviation 0.55
Part 2: Change From Baseline: CGI Symptom Scale Week 36	-1.3 score on a scale Standard Deviation 0.58	-0.2 score on a scale Standard Deviation 0.84
Part 2: Change From Baseline: CGI Symptom Scale Week 48	-1.3 score on a scale Standard Deviation 0.58	-0.4 score on a scale Standard Deviation 0.55
Part 2: Change From Baseline: CGI Symptom Scale Week 72	-1.3 score on a scale Standard Deviation 0.58	-0.6 score on a scale Standard Deviation 0.55
Part 2: Change From Baseline: CGI Symptom Scale Week 96	-1.0 score on a scale Standard Deviation 0.00	-0.7 score on a scale Standard Deviation 0.58
Part 2: Change From Baseline: CGI Symptom Scale Week 120	-1.7 score on a scale Standard Deviation 0.58	-1.0 score on a scale Standard Deviation 0.71
Part 2: Change From Baseline: CGI Symptom Scale Week 144	-1.3 score on a scale Standard Deviation 0.58	-0.6 score on a scale Standard Deviation 0.55
Part 2: Change From Baseline: CGI Symptom Scale Week 168	-1.3 score on a scale Standard Deviation 0.58	-0.8 score on a scale Standard Deviation 0.84
Part 2: Change From Baseline: CGI Symptom Scale Week 192	-1.0 score on a scale	-1.5 score on a scale Standard Deviation 0.71

Adverse Events

Part 2 (OLE): Elamipretide (Sequence AB)

Serious events: 1 serious events

Other events: 5 other events

Deaths: 0 deaths

Part 2 (OLE): Elamipretide (Sequence BA)

Serious events: 4 serious events

Other events: 5 other events

Deaths: 0 deaths

Part 1: Elamipretide

Serious events: 0 serious events

Other events: 12 other events

Deaths: 0 deaths

Part 1: Placebo

Serious events: 0 serious events

Other events: 12 other events

Deaths: 0 deaths

Serious adverse events

Serious adverse events
Measure	Part 2 (OLE): Elamipretide (Sequence AB) n=5 participants at risk Part 2: Participants from Part 1 who received 12 weeks of elamipretide first, placebo for the last 12 weeks of treatment, then proceeded to Part 2 OLE and received up to 192 weeks of daily subcutaneous injections of 40mg elamipretide.	Part 2 (OLE): Elamipretide (Sequence BA) n=5 participants at risk Part 2: Participants from Part 1 who received 12 weeks of placebo first, then elamipretide for the last 12 weeks of treatment, then proceeded to Part 2 OLE and received up to 192 weeks of daily subcutaneous injections of 40mg elamipretide.	Part 1: Elamipretide n=12 participants at risk Participants who received Elamipretide either in the first or last 12 weeks of treatment.	Part 1: Placebo n=12 participants at risk Participants who received Placebo either in the first or last 12 weeks of treatment.
Respiratory, thoracic and mediastinal disorders Pneumothorax	0.00% 0/5 • Part 1: Participants were followed for a total of 28 weeks, they had a treatment period for 12 weeks, a washout period of 4 weeks, then another treatment period of 4 weeks. Part 2 OLE: Participants who agreed to proceed to Part 2 were followed for up to 192 weeks.	20.0% 1/5 • Part 1: Participants were followed for a total of 28 weeks, they had a treatment period for 12 weeks, a washout period of 4 weeks, then another treatment period of 4 weeks. Part 2 OLE: Participants who agreed to proceed to Part 2 were followed for up to 192 weeks.	0.00% 0/12 • Part 1: Participants were followed for a total of 28 weeks, they had a treatment period for 12 weeks, a washout period of 4 weeks, then another treatment period of 4 weeks. Part 2 OLE: Participants who agreed to proceed to Part 2 were followed for up to 192 weeks.	0.00% 0/12 • Part 1: Participants were followed for a total of 28 weeks, they had a treatment period for 12 weeks, a washout period of 4 weeks, then another treatment period of 4 weeks. Part 2 OLE: Participants who agreed to proceed to Part 2 were followed for up to 192 weeks.
General disorders Mucositis	0.00% 0/5 • Part 1: Participants were followed for a total of 28 weeks, they had a treatment period for 12 weeks, a washout period of 4 weeks, then another treatment period of 4 weeks. Part 2 OLE: Participants who agreed to proceed to Part 2 were followed for up to 192 weeks.	20.0% 1/5 • Part 1: Participants were followed for a total of 28 weeks, they had a treatment period for 12 weeks, a washout period of 4 weeks, then another treatment period of 4 weeks. Part 2 OLE: Participants who agreed to proceed to Part 2 were followed for up to 192 weeks.	0.00% 0/12 • Part 1: Participants were followed for a total of 28 weeks, they had a treatment period for 12 weeks, a washout period of 4 weeks, then another treatment period of 4 weeks. Part 2 OLE: Participants who agreed to proceed to Part 2 were followed for up to 192 weeks.	0.00% 0/12 • Part 1: Participants were followed for a total of 28 weeks, they had a treatment period for 12 weeks, a washout period of 4 weeks, then another treatment period of 4 weeks. Part 2 OLE: Participants who agreed to proceed to Part 2 were followed for up to 192 weeks.
Musculoskeletal and connective tissue disorders Costochondritis	0.00% 0/5 • Part 1: Participants were followed for a total of 28 weeks, they had a treatment period for 12 weeks, a washout period of 4 weeks, then another treatment period of 4 weeks. Part 2 OLE: Participants who agreed to proceed to Part 2 were followed for up to 192 weeks.	20.0% 1/5 • Part 1: Participants were followed for a total of 28 weeks, they had a treatment period for 12 weeks, a washout period of 4 weeks, then another treatment period of 4 weeks. Part 2 OLE: Participants who agreed to proceed to Part 2 were followed for up to 192 weeks.	0.00% 0/12 • Part 1: Participants were followed for a total of 28 weeks, they had a treatment period for 12 weeks, a washout period of 4 weeks, then another treatment period of 4 weeks. Part 2 OLE: Participants who agreed to proceed to Part 2 were followed for up to 192 weeks.	0.00% 0/12 • Part 1: Participants were followed for a total of 28 weeks, they had a treatment period for 12 weeks, a washout period of 4 weeks, then another treatment period of 4 weeks. Part 2 OLE: Participants who agreed to proceed to Part 2 were followed for up to 192 weeks.
Infections and infestations Abscess of Right Axilla	0.00% 0/5 • Part 1: Participants were followed for a total of 28 weeks, they had a treatment period for 12 weeks, a washout period of 4 weeks, then another treatment period of 4 weeks. Part 2 OLE: Participants who agreed to proceed to Part 2 were followed for up to 192 weeks.	20.0% 1/5 • Part 1: Participants were followed for a total of 28 weeks, they had a treatment period for 12 weeks, a washout period of 4 weeks, then another treatment period of 4 weeks. Part 2 OLE: Participants who agreed to proceed to Part 2 were followed for up to 192 weeks.	0.00% 0/12 • Part 1: Participants were followed for a total of 28 weeks, they had a treatment period for 12 weeks, a washout period of 4 weeks, then another treatment period of 4 weeks. Part 2 OLE: Participants who agreed to proceed to Part 2 were followed for up to 192 weeks.	0.00% 0/12 • Part 1: Participants were followed for a total of 28 weeks, they had a treatment period for 12 weeks, a washout period of 4 weeks, then another treatment period of 4 weeks. Part 2 OLE: Participants who agreed to proceed to Part 2 were followed for up to 192 weeks.
Infections and infestations Gastroenteritis	20.0% 1/5 • Part 1: Participants were followed for a total of 28 weeks, they had a treatment period for 12 weeks, a washout period of 4 weeks, then another treatment period of 4 weeks. Part 2 OLE: Participants who agreed to proceed to Part 2 were followed for up to 192 weeks.	0.00% 0/5 • Part 1: Participants were followed for a total of 28 weeks, they had a treatment period for 12 weeks, a washout period of 4 weeks, then another treatment period of 4 weeks. Part 2 OLE: Participants who agreed to proceed to Part 2 were followed for up to 192 weeks.	0.00% 0/12 • Part 1: Participants were followed for a total of 28 weeks, they had a treatment period for 12 weeks, a washout period of 4 weeks, then another treatment period of 4 weeks. Part 2 OLE: Participants who agreed to proceed to Part 2 were followed for up to 192 weeks.	0.00% 0/12 • Part 1: Participants were followed for a total of 28 weeks, they had a treatment period for 12 weeks, a washout period of 4 weeks, then another treatment period of 4 weeks. Part 2 OLE: Participants who agreed to proceed to Part 2 were followed for up to 192 weeks.

Other adverse events

Additional Information

Jim Carr, Pharm.D. Chief Clinical Development Officer

Stealth BioTherapeutics, Inc

Phone: 1-617-600-6888

Email: [email protected]

Results disclosure agreements

Principal investigator is a sponsor employee
Publication restrictions are in place

Restriction type: GT60

Measure	Experimental: Elamipretide (Treatment AB) n=6 Participants Patients will be randomized to receive 12 weeks of elamipretide in one of the two treatment periods. All subjects will receive 12 weeks of elamipretide, 4 weeks of washout, and 12 weeks of placebo and 4 weeks of follow up (for those not continuing to Part 2). Elamipretide: 40 mg daily subcutaneous injection for 12 weeks Placebo: daily subcutaneous injection for 12 weeks	Experimental Placebo (Treatment BA) n=6 Participants Patients will be randomized to receive 12 weeks of placebo in one of the two treatment periods. All subjects will receive 12 weeks of placebo, 4 weeks of washout, and 12 weeks of elamipretide, and 4 weeks of follow up (for those not continuing to Part 2). Placebo: daily subcutaneous injection for 12 weeks Elamipretide: 40 mg daily subcutaneous injection for 12 weeks	Total n=12 Participants Total of all reporting groups
Age, Continuous Part 1	23.3 years STANDARD_DEVIATION 9.07 • n=6 Participants • All participants for whom Age was measured.	15.7 years STANDARD_DEVIATION 3.33 • n=6 Participants • All participants for whom Age was measured.	19.5 years STANDARD_DEVIATION 7.65 • n=12 Participants • All participants for whom Age was measured.
Age, Continuous PART 2: OLE	21.8 years STANDARD_DEVIATION 9.23 • n=5 Participants • All participants for whom Age was measured.	16.2 years STANDARD_DEVIATION 3.42 • n=5 Participants • All participants for whom Age was measured.	19.0 years STANDARD_DEVIATION 7.20 • n=10 Participants • All participants for whom Age was measured.
Sex: Female, Male Part 1 · Female	0 Participants n=6 Participants • All participants for whom sex was measured.	0 Participants n=6 Participants • All participants for whom sex was measured.	0 Participants n=12 Participants • All participants for whom sex was measured.
Sex: Female, Male Part 1 · Male	6 Participants n=6 Participants • All participants for whom sex was measured.	6 Participants n=6 Participants • All participants for whom sex was measured.	12 Participants n=12 Participants • All participants for whom sex was measured.
Sex: Female, Male Part 2 (OLE) · Female	0 Participants n=5 Participants • All participants for whom sex was measured.	0 Participants n=5 Participants • All participants for whom sex was measured.	0 Participants n=10 Participants • All participants for whom sex was measured.
Sex: Female, Male Part 2 (OLE) · Male	5 Participants n=5 Participants • All participants for whom sex was measured.	5 Participants n=5 Participants • All participants for whom sex was measured.	10 Participants n=10 Participants • All participants for whom sex was measured.
Race (NIH/OMB) Part 1 · American Indian or Alaska Native	0 Participants n=6 Participants • All individuals for whom race was measured.	0 Participants n=6 Participants • All individuals for whom race was measured.	0 Participants n=12 Participants • All individuals for whom race was measured.
Race (NIH/OMB) Part 1 · Asian	0 Participants n=6 Participants • All individuals for whom race was measured.	0 Participants n=6 Participants • All individuals for whom race was measured.	0 Participants n=12 Participants • All individuals for whom race was measured.
Race (NIH/OMB) Part 1 · Native Hawaiian or Other Pacific Islander	0 Participants n=6 Participants • All individuals for whom race was measured.	0 Participants n=6 Participants • All individuals for whom race was measured.	0 Participants n=12 Participants • All individuals for whom race was measured.
Race (NIH/OMB) Part 1 · Black or African American	0 Participants n=6 Participants • All individuals for whom race was measured.	0 Participants n=6 Participants • All individuals for whom race was measured.	0 Participants n=12 Participants • All individuals for whom race was measured.
Race (NIH/OMB) Part 1 · White	6 Participants n=6 Participants • All individuals for whom race was measured.	5 Participants n=6 Participants • All individuals for whom race was measured.	11 Participants n=12 Participants • All individuals for whom race was measured.
Race (NIH/OMB) Part 1 · More than one race	0 Participants n=6 Participants • All individuals for whom race was measured.	1 Participants n=6 Participants • All individuals for whom race was measured.	1 Participants n=12 Participants • All individuals for whom race was measured.
Race (NIH/OMB) Part 1 · Unknown or Not Reported	0 Participants n=6 Participants • All individuals for whom race was measured.	0 Participants n=6 Participants • All individuals for whom race was measured.	0 Participants n=12 Participants • All individuals for whom race was measured.
Race (NIH/OMB) Part 2 (OLE) · American Indian or Alaska Native	0 Participants n=5 Participants • All individuals for whom race was measured.	0 Participants n=5 Participants • All individuals for whom race was measured.	0 Participants n=10 Participants • All individuals for whom race was measured.
Race (NIH/OMB) Part 2 (OLE) · Asian	0 Participants n=5 Participants • All individuals for whom race was measured.	0 Participants n=5 Participants • All individuals for whom race was measured.	0 Participants n=10 Participants • All individuals for whom race was measured.
Race (NIH/OMB) Part 2 (OLE) · Native Hawaiian or Other Pacific Islander	0 Participants n=5 Participants • All individuals for whom race was measured.	0 Participants n=5 Participants • All individuals for whom race was measured.	0 Participants n=10 Participants • All individuals for whom race was measured.
Race (NIH/OMB) Part 2 (OLE) · Black or African American	0 Participants n=5 Participants • All individuals for whom race was measured.	0 Participants n=5 Participants • All individuals for whom race was measured.	0 Participants n=10 Participants • All individuals for whom race was measured.
Race (NIH/OMB) Part 2 (OLE) · White	5 Participants n=5 Participants • All individuals for whom race was measured.	4 Participants n=5 Participants • All individuals for whom race was measured.	9 Participants n=10 Participants • All individuals for whom race was measured.
Race (NIH/OMB) Part 2 (OLE) · More than one race	0 Participants n=5 Participants • All individuals for whom race was measured.	1 Participants n=5 Participants • All individuals for whom race was measured.	1 Participants n=10 Participants • All individuals for whom race was measured.
Race (NIH/OMB) Part 2 (OLE) · Unknown or Not Reported	0 Participants n=5 Participants • All individuals for whom race was measured.	0 Participants n=5 Participants • All individuals for whom race was measured.	0 Participants n=10 Participants • All individuals for whom race was measured.
Region of Enrollment United States	6 participants n=6 Participants	6 participants n=6 Participants	12 participants n=12 Participants
Body Mass Index Part 1	18.23 kg/m^2 STANDARD_DEVIATION 3.677 • n=6 Participants • All participants for whom Body Mass Index was measured.	16.88 kg/m^2 STANDARD_DEVIATION 4.179 • n=6 Participants • All participants for whom Body Mass Index was measured.	17.56 kg/m^2 STANDARD_DEVIATION 3.818 • n=12 Participants • All participants for whom Body Mass Index was measured.
Body Mass Index Part 2 OLE	18.14 kg/m^2 STANDARD_DEVIATION 4.103 • n=5 Participants • All participants for whom Body Mass Index was measured.	17.54 kg/m^2 STANDARD_DEVIATION 4.313 • n=5 Participants • All participants for whom Body Mass Index was measured.	17.84 kg/m^2 STANDARD_DEVIATION 3.981 • n=10 Participants • All participants for whom Body Mass Index was measured.