LongevityElamipretideMTP-131

SS-31 (Elamipretide)

Mitochondria-targeting tetrapeptide · failed most trials · narrow 2025 FDA approval

SS-31 (elamipretide) is the clearest case study in this library for separating a real pharmaceutical program from peptide-community myth. It is a genuine, heavily studied mitochondria-targeting tetrapeptide developed by Stealth BioTherapeutics that binds cardiolipin — a key fat in the inner membrane of the mitochondria, the cell's power plants — and is proposed to protect their structure and reduce oxidative damage. The biochemistry is real. The clinical record is the problem: SS-31 FAILED the main (primary) goal of nearly every large randomized human trial it entered — in primary mitochondrial myopathy (MMPOWER-3, 218 patients), in heart failure (PROGRESS-HF, 71 patients), in dry age-related macular degeneration (ReCLAIM-2, 176 patients), and in the randomized portion of the Barth syndrome trial (12 patients). Its single regulatory success is narrow and recent: in September 2025 the FDA granted accelerated approval (brand name Forzinity) to improve muscle strength in Barth syndrome — an ultra-rare genetic disease affecting roughly 150 US patients — and even that came only after a 2021 refuse-to-file and a May 2025 Complete Response Letter, was based on a small open-label study and a surrogate strength measure, and remains contingent on a confirmatory trial. It is NOT approved for mitochondrial myopathy, heart failure, macular degeneration, or any 'anti-aging' use. The community framing of SS-31 as a general mitochondrial-repair or anti-aging compound has no primary-source human efficacy behind it, and there is no validated wellness dose — every human dose on record is the 40 mg/day subcutaneous trial dose.

The short version

SS-31 is a tiny engineered peptide — just four amino acids — built to home in on mitochondria, the structures inside your cells that produce energy. It works by sticking to cardiolipin, a signature fat found only in the inner mitochondrial membrane that the cell's energy machinery needs to assemble correctly. By stabilizing cardiolipin, SS-31 is proposed to keep mitochondria structurally intact and cut down on the harmful 'reactive oxygen species' (oxidative damage) they can leak. That part — the biochemistry — is genuinely well supported.

Where the honesty matters is the jump from mechanism to benefit. A drug having a real mechanism does not mean it helps patients, and SS-31 is the textbook example. It was put through a series of large, well-run randomized human trials — for a muscle-wasting mitochondrial disease, for heart failure, and for a common cause of vision loss (dry macular degeneration) — and it missed the main goal in essentially all of them. The biggest trials simply did not beat placebo on what they set out to measure.

There is one place SS-31 did cross the regulatory finish line. In September 2025 the FDA gave it accelerated approval, under the brand name Forzinity, to improve muscle strength in Barth syndrome — an ultra-rare inherited disease in which a gene defect lowers cardiolipin, so the mechanism fits unusually well. But this approval is narrow and hard-won: it followed a 2021 refusal to even file the application and a 2025 rejection letter, it rests on a small open-label study (no placebo group) of roughly eight to ten patients and a surrogate strength measurement, and it is conditional on a future confirmatory trial. So the honest one-liner is: a real, FDA-approved drug for one ultra-rare disease — and an investigational compound with a track record of failed trials for everything else. The popular image of SS-31 as a general 'mitochondrial repair' or anti-aging peptide has no human efficacy evidence behind it.

Molecular identity

Specs

Molecular formula: C₃₂H₄₉N₉O₅ (free base)
Monoisotopic mass: 639.3857 Da (free base)
Topological polar surface area: 267 Å²
CAS / UNII: 736992-21-5 · 87GWG91S09
PubChem CID: 11764719

Sequence: D-Arg-Dmt-Lys-Phe-NH₂ (4 AA; non-standard residues: D-arginine + 2,6-dimethyltyrosine)PubChem CID 11764719
Type: Aromatic-cationic, cell-permeable tetrapeptide (mitochondria-targeting)Elamipretide review, Int J Mol Sci 2025 (PMID 39940712)
Molecular weight: 639.8 g/mol (free base; the approved HCl salt differs)PubChem CID 11764719
Molecular target: Cardiolipin on the inner mitochondrial membrane (stabilizes cristae / electron-transport chain)Elamipretide review, Int J Mol Sci 2025 (PMID 39940712)
Half-life: Short — ~2 h elimination in animals (rat/dog/monkey), renal excretion; rapid SC absorption (Tmax ~1–2 h) in humansResearch literature; PMID 29500292Half-life curve →
Regulatory status: FDA accelerated approval Sept 2025 (Forzinity) — Barth syndrome ONLY; investigational/not approved for all other usesFDA; Drugs@FDA NDA 215244

Plain English

Mechanism

SS-31 is an aromatic-cationic tetrapeptide — a positively charged, fat-and-membrane-loving four-amino-acid chain — that crosses into mitochondria and binds cardiolipin on the inner mitochondrial membrane. Cardiolipin is the defining phospholipid of the cristae (the folded inner membranes where energy production happens) and is required for the electron transport chain to assemble into working 'supercomplexes.' This binding is the core, well-supported mechanism.

By stabilizing cardiolipin–protein interactions, SS-31 is proposed to preserve the folded architecture of the cristae, improve the efficiency of the electron transport chain, and reduce the leak of reactive oxygen species (ROS) and lipid peroxidation — in plain terms, to keep the power plant running cleanly and to cut oxidative wear. This is the rationale behind every clinical program.

The cleanest mechanistic fit is Barth syndrome, which is caused by mutations in the tafazzin (TAZ) gene that lower mature cardiolipin and raise an abnormal precursor (monolysocardiolipin). In the Barth open-label extension, SS-31 was reported to improve that cardiolipin ratio. But two honesty notes belong here. First, a real mechanism does not guarantee clinical benefit — the failed trials below are the direct counter-evidence. Second, the vendor claims that go beyond this biochemistry — 'reverses aging,' 'repairs mitochondria systemically,' 'boosts energy and performance' — have no primary-source human efficacy support and should be read as marketing extrapolation, not established fact.

Sources:PMID 39940712 PMID 38602181

Why people reach for it

Potential benefits

SS-31 is reached for as the mitochondria-targeting peptide — the one with a real pharma program behind it. Here's what draws people to it, kept strictly honest about where the human evidence stops.

Targeted mitochondrial support — Its defining appeal. SS-31 homes in on mitochondria and binds cardiolipin — the signature fat of the inner membrane — which is proposed to keep the cell's power plants structurally intact; this cardiolipin-binding mechanism is genuinely well supported.
Cleaner cellular energy — By stabilizing the cristae and the electron-transport chain, SS-31 is proposed to improve how efficiently mitochondria turn fuel into ATP — the energy angle most people pursue it for, reported at the mechanism level rather than proven in wellness trials.
Lower oxidative wear — A core part of its proposed action is reducing the leak of reactive oxygen species (oxidative damage) from mitochondria — the rationale behind reaching for it on cellular-aging and resilience goals.
A real, FDA-vetted molecule — Unlike most research peptides, SS-31 (elamipretide) is a genuine pharmaceutical compound with FDA accelerated approval for one ultra-rare disease (Barth syndrome) — part of its appeal, though that approval is narrow and it missed its primary endpoints in the larger trials.
A mitochondrial base that stacks well — Because it works on membrane structure rather than fuel or signaling, it pairs cleanly with other mito levers — most commonly NAD+ to fuel the chain it keeps intact and MOTS-c for the metabolic signal.

Sources:PMID 39940712 PMID 38602181 PMID 37268435

What people reach for SS-31 for, drawn from its well-supported cardiolipin/mitochondrial mechanism and how it's used — not proven outcomes. Honest limit: SS-31 missed the primary endpoints of nearly every large human trial, and its only positive efficacy data are from a small uncontrolled Barth extension. No anti-aging claims.

Implied timing

Best time to dose

Implied best time

Morning

Most people take SS-31 in the morning, lining the mitochondrial-energy support up with the active part of the day.

SS-31's proposed effect is supporting mitochondrial energy output (cardiolipin stabilization → cleaner electron-transport chain), which pairs logically with daytime activity rather than the evening wind-down.
Its action is short-lived — elimination half-life is roughly 2 hours in animals with rapid subcutaneous absorption (Tmax ~1–2 h) — so a once-daily morning dose puts the exposure during waking, active hours; some split a higher dose ~10–12 hours apart.
The human trials dosed once daily and did not specify a required time of day, so morning is a sensible community habit rather than a studied schedule.

No study establishes an ideal time of day for SS-31 — this is reasoned from its mechanism and how it's used (the trials specified no time). As a rule of thumb most peptide dosing lands in the midday-to-evening window; for SS-31's energy angle the lean is morning.

Sources:PMID 39940712

How to run it

Dosing & protocol

SS-31 is dosed here as a subcutaneous injection — the route in every human trial and the only validated human route. There is no established wellness or anti-aging dose: every human dose on record is the 40 mg/day trial dose. The ranges below are community convention derived from the trial dose, not a tested longevity protocol — read this as a map of how people actually run injectable SS-31, with the failed-trial context kept front and center.

No validated wellness dose exists. The only human efficacy data outside the trial record comes from a small, uncontrolled open-label Barth syndrome extension. Community 'mitochondrial optimization' protocols are extrapolated from the trial dose with no controlled-trial efficacy support.

Tiered dose ranges

Trial anchor: 40 mg/day SC. Community convention scales below that; there is no pharmacological rationale for a specific lower threshold — these are usage patterns, not findings.

Exploratory / low:: 5–10 mg once daily — the lowest end some researchers use to test tolerance; no efficacy data at this range.
Mid-range convention:: 20 mg once daily — a common community starting point that splits the trial dose; no controlled trial at this level.
Trial dose:: 40 mg once daily SC — the dose in MMPOWER-3 (n=218, 24 weeks), TAZPOWER (n=12), PROGRESS-HF, and ReCLAIM-2. This is the anchor; it failed primary endpoints in every RCT except the narrow Barth open-label extension.

Subcutaneous administration

SS-31 is injected into subcutaneous fat; site, rotation, and timing are the actionable choices.

Injection site:: The abdomen (staying a couple of inches clear of the navel), the outer thigh, or the love-handle area. Rotate sites between doses — consistent use of one spot causes local irritation and lipohypertrophy over a long course.
Measuring the dose:: Drawn on a U-100 insulin syringe from the reconstituted vial. At the standard calculator-default mix (10 mg vial + 2 mL BAC = 5,000 mcg per mL): 5 mg = 10 IU · 10 mg = 20 IU · 20 mg = 40 IU. The live calculator converts any vial size.
Time of day:: Once-daily dosing is typically given in the morning in community use; the trials did not specify a required time. For a split-dose approach, space the two injections ~10–12 hours apart.
Food window:: Subcutaneous SS-31 is not influenced by the fed/fasted state — injections are independent of meals.

Cycle & washout

The trials ran continuous daily dosing for weeks to months (24 weeks in MMPOWER-3, 48 weeks in ReCLAIM-2) without a described washout. Community convention borrows peptide-cycle norms.

Standard cycle:: 4–12 weeks of daily use, then reassess. Longer continuous courses are consistent with the trial durations; intermittent cycling is convention, not SS-31-specific.
Washout:: 2–4 weeks off after a cycle, then re-evaluate baseline energy or functional markers. No trial-defined washout requirement exists.
Context note:: The Barth open-label extension ran continuous daily dosing for up to 168 weeks (≈3 years) in a small cohort — the longest documented human course. Applicability to community use is speculative.

Reconstitution at a glance

The on-page calculator does this live; the quick reference for a 10 mg vial at the default 2 mL BAC:

Mixing:: 10 mg vial + 2 mL bacteriostatic water = 5,000 mcg per mL. On a 100-unit (1 mL) insulin syringe: 5 mg = 10 IU · 10 mg = 20 IU · 20 mg = 40 IU · 40 mg = 80 IU (requires two vials at this dilution).
Why 2 mL:: A tighter dilution means higher drug concentration per syringe unit — keeps injection volumes small for the large trial dose. Use the calculator to adjust for your vial size and target dose.

Sources:PMID 37268435 PMID 38602181 PMID 39605874 PMID 32068002

Substrate the signal needs

Nutritional cofactor precision

SS-31's job is at the mitochondrion — it binds cardiolipin on the inner membrane to stabilize the electron transport chain (ETC) and cut oxidative leak. The logical cofactors are the nutrients that same ETC runs on: supply the substrates it consumes, and cover the antioxidant net it is trying to reinforce. Honest frame foregrounded: no cofactor changes the fact that SS-31 missed its primary endpoints in four controlled trials. These supplements support the underlying machinery; they do not rescue the clinical record.

Reasoned from SS-31's cardiolipin / ETC mechanism plus standard mitochondrial nutrition — not an SS-31 cofactor study. Supplement doses are common community ranges.

ETC substrate set (supply what the chain runs on)

The electron transport chain and ATP synthase need specific cofactors to function — these are the direct nutritional inputs to the system SS-31 is trying to preserve.

CoQ10 · 200 mg/day · with fat-containing meal:: Ubiquinone is the mobile electron carrier that shuttles between ETC Complexes I–III — it works in the exact system SS-31 targets. 200 mg/day (ubiquinol is better absorbed if CoQ10 blood levels are low). The overlap with SS-31 is direct: SS-31 stabilizes the inner membrane architecture; CoQ10 keeps the electrons moving through it.
Riboflavin (B2) · 100 mg/day · with meals:: Riboflavin is the backbone of FAD (flavin adenine dinucleotide), the electron carrier at ETC Complex II. Deficiency measurably impairs Complex II activity. This is the most mechanistically targeted B-vitamin for mitochondrial function.
Niacin (B3) / NAD precursor · 500 mg NR or NMN/day · morning:: Niacin feeds NAD, the electron carrier at Complexes I and III. Raising NAD via nicotinamide riboside (NR) or NMN supports ETC throughput — the same chain SS-31 is keeping structurally intact. (See NAD+ in stacks for the full NAD protocol.)
L-carnitine · 2 g/day · before meals:: Carnitine shuttles long-chain fatty acids into the mitochondrial matrix for beta-oxidation — the fuel input the ETC burns. Without adequate carnitine, mitochondria are substrate-starved regardless of structural integrity. Acetyl-L-carnitine also crosses the blood-brain barrier for additional CNS mitochondrial support.
Magnesium · 300–400 mg/day · evening:: Magnesium is the obligatory cofactor for ATP synthase and is required to stabilize ATP (the energy currency the ETC produces). Low magnesium impairs the output side of the system SS-31 works on.

Antioxidant net (amplify SS-31's ROS-reduction role)

Reducing mitochondrial ROS (reactive oxygen species) leak is half of SS-31's proposed mechanism. These supplements extend that antioxidant coverage into the cytosol and beyond.

Alpha-lipoic acid · 600 mg/day · with meals:: ALA is one of the few antioxidants that acts inside the mitochondrion itself and regenerates glutathione and vitamins C and E — directly reinforcing the endogenous antioxidant network that mops up what the ETC leaks. R-ALA is the active isomer; the racemic form at 600 mg is the standard dose.
NAC (N-acetyl cysteine) · 600–1,200 mg/day · away from meals:: NAC is the rate-limiting precursor to glutathione — the cell's master antioxidant. Raising intracellular glutathione gives the mitochondria more buffer against oxidative damage from ETC activity. 600–1,200 mg/day.
Vitamins C + E · 500 mg C / 200 IU mixed tocopherols · with fat:: Vitamins C and E work as the water-soluble and fat-soluble antioxidant front lines, scavenging ROS in the cytosol and membrane compartments respectively. Paired with ALA they form a regenerating network rather than a one-shot shield.

Combinations + timing

Stacking notes + timing windows

SS-31 locks onto the inner mitochondrial membrane and protects cardiolipin — that is the structural anchor. The complementary partners target different mitochondrial levers: NAD-level signaling, metabolic reprogramming, and stress-resilience peptides. Stacking two membrane-structure compounds would just double the same lever; the useful combinations cover the system from distinct angles.

These are user combinations reasoned from overlapping mechanism — never studied head-to-head, and SS-31's own controlled-trial record is mostly negative. A 'mito stack' is speculative on top of an already-unproven anti-aging premise. Doses are community convention; 'commonly combined for' describes where users go, not a proven indication.

SS-31 + NAD+ / NMN / NR

SS-31 keeps the electron-transport chain structurally intact; NAD+ fuels it. Two different angles on the same system.

Why it works:: NAD is the electron carrier at ETC Complexes I and III — it picks up electrons from metabolism and feeds them to the chain. When NAD levels decline (as they do with age), ETC throughput drops regardless of structural integrity. SS-31 addresses the structure; NAD precursors (NMN, NR) address the fuel supply. Distinct levers on the same machinery.
The protocol:: SS-31 20–40 mg SC once daily (morning) + NMN 500 mg orally once daily (morning, fasted) or NR 500 mg orally twice daily. The full NAD protocol is on the NAD+ page.
Outcome:: Commonly combined for mitochondrial optimization, age-related energy decline, and cognitive or physical performance goals. Evidence base for each compound is separate; the combination is unvalidated.

SS-31 + MOTS-c

SS-31 protects inner-membrane structure; MOTS-c drives mitochondrial metabolic signaling — different levers.

Why it works:: MOTS-c is a mitochondrially-encoded peptide that activates AMPK and metabolic stress-response pathways — it shifts cellular energy strategy, particularly under metabolic stress, rather than protecting the physical architecture. The combination logic is 'structural preservation + metabolic reprogramming' on the same organelle.
The protocol:: SS-31 20–40 mg SC once daily + MOTS-c 5–10 mg SC 3–5×/week (morning, fasted). Full MOTS-c dosing on the MOTS-c page.
Outcome:: Commonly combined for metabolic health, insulin sensitivity, and general mitochondrial longevity goals. Anti-doping caution: MOTS-c is explicitly prohibited under WADA S0 (non-approved substances). SS-31's own status is uncertain post-Forzinity approval — do not assume it is cleared. Athletes must consult their anti-doping authority before using either compound.

SS-31 + Humanin

Both are mitochondrially-encoded peptides; Humanin covers the stress-resilience and cytoprotection angle SS-31 does not directly address.

Why it works:: Humanin is another mitochondrially-derived peptide proposed to reduce cell death under metabolic stress (apoptosis signaling, unfolded-protein response). While SS-31 stabilizes inner-membrane architecture and reduces oxidative leak, humanin's mechanism is cytoprotective at the cell-survival signaling level — complementary, not redundant.
The protocol:: SS-31 20–40 mg SC once daily + Humanin 2–4 mg SC 3×/week. Full humanin dosing on the Humanin page.
Outcome:: Reached for in mitochondrial-cluster protocols focused on age-related cellular resilience, neuroprotection, and cardiometabolic support. All three stacks (SS-31, MOTS-c, humanin) are doubly-unproven — each compound's individual human evidence is limited or negative; the combined regimen is purely convention-and-mechanism.

Reconstitution math

Reconstitution calculator

Calculated for a 1 mL U-100 insulin syringe (100 units/mL).

Peptide per vial

BAC water added

Desired dose

Units per dose

Draw to this mark on a U-100 syringe

Volume per dose: 0.2 mL
Doses per vial: 10
Concentration: 5 mg/mL

One vial lasts

Daily: 10 days
Every other day: 20 days
5×/week: 14 days

Research use only. Not for human consumption. Outputs are reference values based on research literature — verify all measurements independently.

From the studies

Side effects from research

Across the randomized trials, SS-31 was generally well tolerated, with most adverse events mild to moderate and no major trial-stopping safety signal reported in the cited studies.

The most consistent side effect is injection-site reactions — redness, irritation or discomfort where the subcutaneous shot is given. In the macular-degeneration trial, adverse events occurred in about 86% of SS-31 patients versus 71% on placebo, a gap driven largely by these injection-site reactions.

Honest limits on the safety picture: long-term human safety data are thin, resting on small open-label cohorts of roughly eight to ten Barth patients. For the approved product's full warnings and precautions, the Forzinity prescribing information is the authoritative source — it was not reproduced here.

Sources:PMID 37268435 PMID 39605874

As reported in literature

Research dosing ranges

These are the doses tested in the published human trials, shown so the trial record is never mistaken for a recommended regimen. The pattern to foreground is stark: across the four largest randomized trials, every pre-specified primary endpoint was missed; the only positive efficacy data are small, uncontrolled, open-label (Barth) or nominal/exploratory secondary endpoints. All dosing was subcutaneous, under medical supervision.

Dose	Route	Model	Outcome	Sources:
40 mg/day × 24 wk	SC	Human RCT — MMPOWER-3, primary mitochondrial myopathy (n=218)	FAILED both co-primary endpoints — 6-minute walk difference −3.2 m (p=0.69); fatigue-score difference p=0.37. Well tolerated	PMID 37268435
40 mg/day, 12-wk crossover	SC	Human RCT — TAZPOWER Part 1, Barth syndrome (n=12)	FAILED randomized endpoints — 6-minute walk difference −0.8 m (p=0.97)	PMID 33077895
40 mg/day, open-label	SC	TAZPOWER open-label extension, Barth (≈8–10 pts, no placebo)	POSITIVE but uncontrolled — cumulative +96.1 m walk distance by week 168 (p=0.003), improved fatigue and cardiolipin ratio; basis for accelerated approval	PMID 38602181
4 mg & 40 mg/day × 28 d	SC	Human RCT — PROGRESS-HF, heart failure / HFrEF (n=71)	FAILED — no change in left-ventricular end-systolic volume vs placebo (40 mg p=0.28). Well tolerated	PMID 32068002
40 mg/day × 48 wk	SC	Human RCT — ReCLAIM-2, dry AMD / geographic atrophy (n=176)	FAILED both co-primary endpoints; only nominal (non-confirmatory) secondary signals on ellipsoid-zone loss	PMID 39605874

Quick answers

Frequently asked

Is SS-31 FDA-approved?

Only for one ultra-rare disease. In September 2025 the FDA granted accelerated approval (brand name Forzinity) to improve muscle strength in Barth syndrome. It is NOT approved for mitochondrial myopathy, heart failure, macular degeneration, anti-aging, or any wellness use — for all of those it is investigational, and 'research-use' SS-31 sold in the peptide market is not the approved product.

Does SS-31 reverse aging or repair mitochondria?

There is no primary-source human evidence for general anti-aging or systemic 'mitochondrial repair' use. The cardiolipin-binding mechanism is real biochemistry, but the leap to reversing aging is vendor marketing. In its large human trials SS-31 missed the main goal for mitochondrial myopathy, heart failure, and macular degeneration.

If it failed so many trials, why was it approved?

The Barth syndrome approval rests on a different, much narrower basis: a small open-label study (no placebo group, roughly eight to ten patients) plus a surrogate strength measurement, in a disease where the cardiolipin mechanism fits unusually well. It is an accelerated approval contingent on a confirmatory trial, and it followed a 2021 refuse-to-file and a 2025 rejection letter.

What dose is used?

Every human dose on record is a trial dose — 40 mg once daily by subcutaneous injection in the major trials (the heart-failure trial also tested 4 mg). There is no validated wellness or anti-aging dose. The approved Barth product has its own labelled dose in the prescribing information.

Is SS-31 banned in sport?

It is not specifically named on the 2026 WADA Prohibited List, but its status is genuinely uncertain rather than clearly allowed — before approval it could plausibly fall under the non-approved-substances category for athletes. Treat it as a risk and seek a ruling from your anti-doping authority. Do not assume it is permitted because the related peptide MOTS-c is prohibited (MOTS-c is explicitly banned).

Primary sources

References

PMID 37268435Karaa et al., Neurology 2023 — MMPOWER-3, elamipretide in primary mitochondrial myopathy (n=218, failed co-primaries)
PMID 33077895Reid Thompson et al., Genet Med 2021 — TAZPOWER phase 2/3, elamipretide in Barth syndrome (n=12, randomized arm negative)
PMID 38602181Reid Thompson et al., Genet Med 2024 — TAZPOWER 168-week open-label extension, Barth (uncontrolled, positive)
PMID 32068002Butler et al., J Card Fail 2020 — PROGRESS-HF, elamipretide in heart failure / HFrEF (n=71, failed LVESV)
PMID 39605874ReCLAIM-2, Ophthalmol Sci 2025 — elamipretide in dry AMD / geographic atrophy (n=176, failed co-primaries)
PMID 39940712Elamipretide review — structure / mechanism of action (cardiolipin binding)
PubChem CID 11764719PubChem record — CID, CAS, formula, MW, sequence
FDA; Drugs@FDA NDA 215244FDA — accelerated approval of first treatment for Barth syndrome (Forzinity, Sept 2025)
WADA 2026WADA 2026 Prohibited List (elamipretide not individually named; status by inference)

Research use only · Not medical advice · Updated 2026-06-01