ss-31

Q: What is SS-31?

SS-31 is elamipretide, a cell-penetrating tetrapeptide that binds cardiolipin on the inner mitochondrial membrane. Developed at Cornell University Medical College by Hazel Szeto and Peter Schiller originally during opioid receptor research.

Q: What does SS-31 do?

Stabilizes cardiolipin and preserves mitochondrial cristae structure and function under metabolic stress. Clinical trials demonstrated efficacy in Barth syndrome, a rare genetic mitochondrial disease. Research and community applications target broader mitochondrial dysfunction, age-related metabolic decline, heart failure, and other conditions involving mitochondrial stress.

Q: How is SS-31 typically administered?

Approved clinical dosing for Barth syndrome (as Forzinity) is 40 mg subcutaneous injection daily in adult and pediatric patients weighing at least 30 kg. Community protocols and research peptide use vary, typically at lower doses. Administration outside the approved Barth syndrome indication is off-label or unsupervised research use.

Q: What are the side effects of SS-31?

Most common clinical trial side effects: injection-site reactions, nausea, and headache. Generally well-tolerated at approved doses. Long-term safety data exists primarily from the Barth syndrome clinical trial program.

Q: Is SS-31 FDA approved?

Yes, but narrowly. SS-31 (elamipretide) was FDA-approved in 2025 as Forzinity for Barth syndrome, a rare inherited mitochondrial disorder. It is not approved for general anti-aging, heart failure, or other mitochondrial-support indications in healthy adults.

Q: How much does SS-31 cost?

Branded Forzinity is priced at orphan-drug levels. Public cash-price listings put a 28-day supply around $59,000, which annualizes near $775,000 before insurance, assistance programs, or negotiated coverage. On the research-chemical market it sells at a different scale entirely, for a small fraction of the branded price.

the first mitochondria-targeted peptide drug. FDA-approved september 2025. for Barth syndrome, studied for heart failure.

tier A · healing · FDA '25 elamipretide · Barth syndrome

verdict

the first FDA-approved peptide drug that targets mitochondria. Forzinity for Barth syndrome, ~$800,000 a year.

if you're asking whether SS-31 is the longevity drug the press cycle made it sound like — not on the current evidence. the Barth syndrome approval (Sept 2025) is real and historic. it establishes the regulatory category for mitochondria-targeted peptides. but Forzinity is approved for fewer than 1,000 US patients with a specific genetic disease, on a TAZPOWER trial whose blinded phase missed primary endpoints and was salvaged by the open-label extension. for general anti-aging in healthy adults, controlled trials at scale do not exist yet.

if you're asking about the heart-failure and broader mitochondrial story — mixed. PROGRESS-HF gave an early signal in heart failure, RECLAIM-2 in HFrEF missed its primary endpoint, MMPOWER-3 in primary mitochondrial myopathy also failed. ReNEW phase 3 in dry AMD passed 50% enrollment in 2025, with an FDA-required post-marketing confirmatory trial set to start 2026. the cardiolipin mechanism is pharmacologically elegant. the clinical translation outside Barth is still being mapped.

if you came in via gray-market 'SS-31' vials — Forzinity is the approved branded product, AnovoRx is the exclusive specialty pharmacy, and the orphan-drug pricing reflects that. peptide-vendor 'SS-31' is a separate supply chain with no GMP, no FDA-reviewed label, and no controlled outcome data at the doses sold on that channel. the molecule is the same on a structure drawing; identity, purity, and dose-response at the vendor channel are not what the trials measured.

based on published evidence and disclosed clinical practice. not medical advice. dose and protocol conversations belong with a clinician.

why A-tier

A-tier because SS-31 now has FDA approval (September 2025) for a specific rare disease, plus substantial phase 2/3 clinical trial data across multiple indications. Not S-tier because the approved indication is extremely narrow (Barth syndrome, <1,000 US patients) and the broader phase 3 programs in more common conditions (heart failure, mitochondrial myopathy) have been mixed. Comparable in structure to sermorelin's tier placement: FDA approval for a narrow indication with widespread off-label interest. If heart failure or aging trials read out positively in future years, moves to S.

the core tension

SS-31 (elamipretide) is the only peptide on this list with a brand-new FDA approval (September 2025) for Barth syndrome, a rare genetic mitochondrial disease with fewer than 1,000 US patients. That approval validates 15+ years of development by Stealth BioTherapeutics and establishes mitochondria-targeted peptides as a real pharmaceutical category. The broader phase 3 programs in heart failure and mitochondrial myopathy have been mixed, but the Barth approval is real and the mechanism is well-characterized. The off-label use case is cardiac and longevity-focused.

what it is

SS-31, also known as elamipretide, MTP-131, and Bendavia, is a four-amino-acid cell-penetrating tetrapeptide (D-Arg-dimethylTyr-Lys-Phe-amide) that selectively binds cardiolipin on the inner mitochondrial membrane. discovered at Cornell University Medical College by Hazel Szeto and Peter Schiller during opioid receptor research. approved by the FDA in September 2025 as Forzinity for Barth syndrome.

what it does

binds cardiolipin in its damaged or oxidized state, stabilizing cristae structure, preserving electron transport chain supercomplexes, and restoring ATP output. crucially, it preferentially accumulates in dysfunctional mitochondria and largely ignores healthy ones, which explains the clean safety profile. the approved Forzinity dose is 40 mg subcutaneous daily for Barth syndrome patients weighing at least 30 kg.

origin

developed through 15+ years of clinical trials by Stealth BioTherapeutics. the regulatory path went through Fast Track in mitochondrial myopathy (2016), Orphan Drug status for Barth syndrome (2017), and accelerated approval September 19, 2025, based on TAZPOWER's 168-week extension data showing 96m average improvement on the 6-Minute Walk Test in 8 of 10 patients.

why researchers are interested

first FDA-approved peptide drug targeting mitochondria, period. that approval establishes the regulatory category. the cardiolipin mechanism is precise and pharmacologically elegant, side effects across multiple phase 2/3 trials have been consistently mild, and the longevity-medicine community sees a clear theoretical fit for cardiovascular and age-related mitochondrial decline.

does it work

for Barth syndrome, yes, with caveats. accelerated approval in fewer than 1,000 US patients on a TAZPOWER trial whose initial blinded phase missed primary endpoints, salvaged by the open-label extension. outside Barth, the record is mixed: PROGRESS-HF gave early heart-failure signal, RECLAIM-2 in HFrEF missed its primary endpoint, and MMPOWER-3 in primary mitochondrial myopathy also failed. for general anti-aging in healthy adults, no controlled trials exist at scale, just preclinical extrapolation. the mitochondrial-peptide market runs heavy on industry-press mechanism claims; SS-31 has the rare distinction of an actual approval, but Forzinity itself is priced at roughly $800,000 per year in the US (orphan-drug economics, AnovoRx exclusive specialty pharmacy), and the approval is for a rare disease, not for the longevity use case at all. ReNEW phase 3 in dry AMD passed 50% enrollment in 2025; an FDA-required post-marketing confirmatory trial initiates 2026.

claims vs the data

FDA-approved for Barth syndrome — supported — Approved September 2025 for adult and pediatric Barth syndrome patients weighing at least 30 kg. The accelerated approval is based on knee-extensor muscle strength, with confirmatory evidence still required. First FDA approval for a mitochondria-targeted peptide.
binds cardiolipin on the inner mitochondrial membrane — supported — Well-characterized mechanism. SS-31's alternating aromatic-cationic structure allows selective accumulation at the inner mitochondrial membrane and electrostatic-plus-hydrophobic binding to cardiolipin. Published extensively by Szeto and others.
improves heart failure outcomes in clinical trials — weak — PROGRESS-HF showed an early heart-failure signal, but RECLAIM-2 in HFrEF missed its primary endpoint. MMPOWER-3 in primary mitochondrial myopathy also failed. The non-Barth record is scientifically interesting but clinically mixed.
safe across multiple populations with minimal side effects — supported — Across multiple phase 2/3 trials, side effect profile has been consistently mild, injection site reactions and headaches the most common. No serious adverse events pattern. Favorable across heart failure, mitochondrial myopathy, and Barth populations.
reverses age-related mitochondrial decline — partially true — Preclinical data is strong for age-related mitochondrial dysfunction reversal. Clinical trials in aging populations specifically have not been conducted at scale. Longevity claims are mechanistically reasonable but not clinically validated.
improves cognitive function in humans — weak — Preclinical rodent data supports cognitive benefit from mitochondrial stabilization. Human cognitive trials have been limited and have not confirmed the preclinical signal at the scale of other indications.
SS-31 is proven as a longevity peptide for healthy adults — overreach — Elamipretide has legitimate mitochondrial-drug evidence and a rare-disease approval context, but healthy-adult longevity is not the proven indication. The strongest human records sit in mitochondrial disease and specific clinical programs, not general anti-aging.

key facts

molecular formula: C32H49N9O5
molecular weight: 639.8 Da
amino acids: 4
half-life: 3-4 hours in circulation; functional effects persist 12-16 hours due to mitochondrial retention
type: cell-penetrating tetrapeptide (cardiolipin-binding)
CAS: 736992-21-5
Sep 2025 FDA approval for Barth syndrome
1st mitochondria-targeted peptide ever approved
<1000 US Barth syndrome patients (rare disease)
96m avg 6MWT improvement at 168 weeks (Barth extension)

frequently asked questions

What is SS-31?

SS-31 is elamipretide, a cell-penetrating tetrapeptide that binds cardiolipin on the inner mitochondrial membrane. Developed at Cornell University Medical College by Hazel Szeto and Peter Schiller originally during opioid receptor research.

What does SS-31 do?

Stabilizes cardiolipin and preserves mitochondrial cristae structure and function under metabolic stress. Clinical trials demonstrated efficacy in Barth syndrome, a rare genetic mitochondrial disease. Research and community applications target broader mitochondrial dysfunction, age-related metabolic decline, heart failure, and other conditions involving mitochondrial stress.

How is SS-31 typically administered?

Approved clinical dosing for Barth syndrome (as Forzinity) is 40 mg subcutaneous injection daily in adult and pediatric patients weighing at least 30 kg. Community protocols and research peptide use vary, typically at lower doses. Administration outside the approved Barth syndrome indication is off-label or unsupervised research use.

What are the side effects of SS-31?

Most common clinical trial side effects: injection-site reactions, nausea, and headache. Generally well-tolerated at approved doses. Long-term safety data exists primarily from the Barth syndrome clinical trial program.

Is SS-31 FDA approved?

Yes, but narrowly. SS-31 (elamipretide) was FDA-approved in 2025 as Forzinity for Barth syndrome, a rare inherited mitochondrial disorder. It is not approved for general anti-aging, heart failure, or other mitochondrial-support indications in healthy adults.

How much does SS-31 cost?

Branded Forzinity is priced at orphan-drug levels. Public cash-price listings put a 28-day supply around $59,000, which annualizes near $775,000 before insurance, assistance programs, or negotiated coverage. On the research-chemical market it sells at a different scale entirely, for a small fraction of the branded price.

related peptides

mots-c — companion mitochondrial peptide, FDA-approved vs preclinical-only
NAD+ — mitochondrial stack companion; often combined in longevity protocols
tesamorelin — other FDA-approved peptide with narrow primary indication

reptides grades the research record and cites the literature behind every call. research reference only; not medical advice.