SS-31 benefits are best described as condition-specific, not as a general boost for energy or healthy aging. Elamipretide—the clinical name for SS-31—has its strongest human evidence in Barth syndrome, a rare mitochondrial disease. Even there, the randomized TAZPOWER phase missed its main outcomes before longer open-label follow-up showed gains. Larger studies in primary mitochondrial myopathy, heart failure, and dry age-related macular degeneration did not meet their primary endpoints.
For the molecule and terminology, see what SS-31 is. Questions about amounts and schedules belong in the separate SS-31 dosage guide.
SS-31 benefits start with a mitochondrial mechanism
SS-31 binds cardiolipin, a lipid in the inner mitochondrial membrane. That interaction is meant to support the membrane structure around the machinery that produces cellular energy. The mechanism is biologically plausible, but a mechanism is not a clinical outcome. Better mitochondrial measurements do not automatically mean less fatigue, longer walking distance, better vision, or improved heart function. Each benefit has to clear its own trial endpoint.
That distinction explains why the evidence looks inconsistent: SS-31 can affect a mitochondrial target without producing a measurable benefit in every disease driven partly by mitochondrial dysfunction.
The strongest case: Barth syndrome
TAZPOWER enrolled 12 males with genetically confirmed Barth syndrome. In its randomized, placebo-controlled crossover phase, elamipretide was not superior to placebo on either co-primary endpoint: six-minute walk distance or the Barth Syndrome Symptom Assessment fatigue score. That is the controlled result and it matters.
The signal appeared during the extension, when every participant knew they were receiving elamipretide. Ten people entered that phase and eight reached week 168. Their mean six-minute walk distance improved by 96.1 meters from the open-label baseline, while muscle-strength and some cardiac measures also moved in a favorable direction (Thompson et al., Genetics in Medicine 2024). With eight people and no concurrent placebo group, those gains are encouraging but cannot carry the certainty of a larger controlled trial.
The FDA trial summary is unusually direct: the randomized portion did not show a significant difference, and the knee-extensor strength increases used for accelerated approval emerged during the longer open-label period. A confirmatory randomized trial is still required.
What the broader human trials found
The larger programs tested whether mitochondrial targeting translated into outcomes people could feel or clinicians could measure. Their primary results set a clear ceiling on broad benefit claims.
| Program | Population | Main finding | Evidence reading |
|---|---|---|---|
| MMPOWER-3 | 218 adults with primary mitochondrial myopathy | No improvement in six-minute walk distance or total fatigue at 24 weeks | High-quality negative primary result |
| PROGRESS-HF | 71 adults with stable heart failure and reduced ejection fraction | No improvement in left-ventricular end-systolic volume or ejection fraction after four weeks | Short trial, but negative primary result |
| ReCLAIM-2 | 176 adults with dry AMD and geographic atrophy | No significant benefit on low-luminance visual acuity or geographic-atrophy area at 48 weeks | Negative co-primary results with exploratory retinal signals |
In MMPOWER-3, the between-group difference in six-minute walk distance was -3.2 meters and the fatigue-score difference was -0.07, neither statistically significant (Karaa et al., Neurology 2023). That result does not support SS-31 as a general treatment for fatigue in primary mitochondrial myopathy.
PROGRESS-HF likewise found no significant structural or functional heart benefit at four weeks compared with placebo (Butler et al., Journal of Cardiac Failure 2020). Earlier small studies produced mechanistic signals, but they did not establish a heart-failure benefit.
The eye study had a signal, not a clinical win
ReCLAIM-2 missed both primary endpoints. Exploratory imaging analyses did find 43% less progression of complete ellipsoid-zone loss and 47% less progression of partial loss with elamipretide than placebo. Those retinal-layer measures were secondary, nominal findings—not proof of preserved vision. The honest reading is that they justify another trial, not a benefit claim for dry AMD (Ehlers et al., Ophthalmology Science 2025).
Aging and skeletal muscle remain early evidence
The anti-aging interest comes largely from preclinical work. In aged mice, SS-31 reduced age-related redox stress and improved exercise tolerance (Campbell et al., Free Radical Biology and Medicine 2019). Mouse endurance is not evidence that a person will feel more energetic.
A randomized study in 39 healthy adults ages 60 to 85 gives a more useful bridge. A single elamipretide infusion increased a measure of muscle mitochondrial energy capacity immediately afterward, but the study found no significant improvement in fatigue resistance and no lasting difference at day seven (Roshanravan et al., PLOS ONE 2021). That separates a cellular effect from a practical benefit.
MOTS-c also appears in mitochondrial-health conversations, but it is a different peptide with a different signaling story. The MOTS-c benefit evidence should be judged on its own; it cannot fill gaps in the SS-31 trials.
What the approval does—and does not—establish
As of September 2026, Forzinity has accelerated approval to improve muscle strength in adults and children with Barth syndrome who weigh at least 30 kilograms. The decision was based on knee-extensor strength as an intermediate endpoint considered reasonably likely to predict benefit, not on a demonstrated advantage in the randomized phase. Continued approval may depend on a confirmatory trial.
Promise's SS-31 is dispensed as a compounded medication, which is different from an FDA-approved product: the formulation offered here is not FDA-approved. Forzinity's narrow indication and evidence do not transfer to a compounded preparation or to general fatigue, exercise performance, eye disease, heart failure, or healthy aging.
Regulatory status is one fact in the decision; a licensed provider may still prescribe a compounded formulation when appropriate, and that decision belongs to the patient and prescriber.
How to read an SS-31 benefit claim
First ask what population was studied. A result in Barth syndrome cannot be generalized to healthy adults. Next ask whether the result was a prespecified primary endpoint, a secondary signal, or a change seen only after an open-label extension. Finally, separate measurements of mitochondrial activity from outcomes such as fatigue, walking distance, vision, or heart function.
At Promise, a licensed provider reviews every request for SS-31 and prescribes only when medically appropriate. Not everyone qualifies. The useful conversation is not whether SS-31 supports mitochondria in theory; it is whether the evidence for a specific goal is strong enough to justify treatment in a specific person.