SS-31 (elamipretide) is a tiny peptide that concentrates inside mitochondria - the cell's power plants - and binds a special membrane lipid called cardiolipin to help them work better. In September 2025 it became the first FDA-approved mitochondria-targeted medicine (brand name Forzinity), for the rare genetic disease Barth syndrome. For every other use - aging, energy, heart, eyes - it remains investigational and unproven.
Elamipretide is a cell-permeable, mitochondria-targeting tetrapeptide that binds cardiolipin on the inner mitochondrial membrane, stabilizing cristae, supporting electron-transport-chain efficiency, and reducing reactive oxygen species. It received FDA accelerated approval (Forzinity) in 2025 to improve muscle strength in Barth syndrome patients weighing >=30 kg - but, importantly, its pivotal trials in Barth syndrome and primary mitochondrial myopathy did not meet their primary endpoints, so its broad clinical value remains unsettled.
SS-31 (D-Arg-Dmt-Lys-Phe-NH2) is the lead Szeto-Schiller peptide: an aromatic-cationic tetrapeptide (net charge +3) that crosses membranes energy-independently and accumulates 1,000-5,000-fold at the inner mitochondrial membrane via dual hydrophobic and electrostatic binding to cardiolipin. It modulates cardiolipin-protein interactions (including cytochrome c) and surface electrostatics rather than acting as a simple antioxidant, improving bioenergetics across a broad preclinical landscape.
SS-31 is the most clinically mature peptide in this atlas - the first and only FDA-approved mitochondria-targeted therapeutic - but its approval is narrow (one ultra-rare disease, accelerated pathway, an intermediate endpoint) and its pivotal trials largely missed their primary endpoints. The page keeps the genuine, well-characterized mechanism and approved use separate from the broad, unvalidated off-label use, and distinguishes the approved Forzinity product from gray-market research "SS-31."
Unlike most peptides that flip a switch on a cell-surface receptor, SS-31 slips inside the cell, concentrates in the mitochondria, and grabs onto cardiolipin - a lipid that helps hold the mitochondria's energy machinery together. By stabilizing that machinery, it helps cells make energy more cleanly.
SS-31 targets cardiolipin on the inner mitochondrial membrane. This stabilizes cristae architecture, improves electron-transport-chain coupling and ATP output, reduces reactive oxygen species, and helps keep the mitochondrial permeability transition pore (mPTP) closed under stress. Its effects are membrane- and bioenergetics-based rather than receptor-mediated.
As an amphipathic aromatic-cationic tetrapeptide (+3), SS-31 crosses the plasma membrane non-saturably and accumulates 1,000-5,000-fold at the IMM. It binds cardiolipin through combined hydrophobic and electrostatic interactions, modulating surface electrostatics and cardiolipin-protein contacts (including cytochrome c), which underlies its broad restoration of mitochondrial function.
SS-31 is unusual in this atlas because a real, approved dosing regimen exists - but only for one disease. Forzinity (elamipretide) is approved as a once-daily subcutaneous injection to improve muscle strength in Barth syndrome patients >=30 kg. Every other use - primary mitochondrial myopathy, heart failure, dry AMD, aging, performance - is investigational or off-label, with no validated dose. The clinical program standardized on 40 mg/day SC; community off-label use is lower and unproven.
| Context | Dose | Route | Status |
|---|---|---|---|
| Approved (Barth) | Per Forzinity label, once daily | SC | FDA-approved (>=30 kg) |
| Trial standard | 40 mg/day | SC | Investigational |
| Historical IV | 0.01-0.25 mg/kg/h | IV infusion | Historical / phase 1-2 |
| Community (off-label) | ~1-10 mg/day (cycled) | SC | Unvalidated - not recommended |
Only the approved Barth-syndrome regimen is a validated human dose. All other rows are research/historical or unvalidated and must not be read as recommendations.
| Item | Detail |
|---|---|
| Presentation | 280 mg/3.5 mL (80 mg/mL), single-patient-use vials |
| Route | SC, abdomen (>=2 in from navel) or outer thigh; rotate daily |
| Storage / use | Discard vial 8 days after first opening; do not mix other products |
| Renal impairment | Halve dose if eGFR <30 (not on dialysis); not studied on dialysis |
| Benzyl alcohol | Contains benzyl alcohol; not for neonates (gasping-syndrome risk) |
| Contraindication | Serious hypersensitivity to elamipretide or excipients |
| Trigger | Action | Rationale |
|---|---|---|
| Barth syndrome, >=30 kg, prescribed | Use the approved Forzinity regimen under clinician care | Only validated, approved use |
| Severe renal impairment (eGFR <30) | Halve dose; avoid if on dialysis (not studied) | Metabolite (M1/M2) exposure rises markedly |
| Neonate / low-birth-weight infant | HARD STOP - do not use | Benzyl alcohol gasping-syndrome risk |
| Injection-site reaction | Rotate sites; assess; usually mild-moderate | Most common adverse effect |
| Off-label aging/performance use | Not recommended; no human outcome data | Unvalidated dose and product |
| Gray-market product, no COA | Do not use; verify identity/purity first | Research-chemical quality risk |
| Marker / assessment | Why it matters | Note |
|---|---|---|
| Injection-site assessment | Most common adverse effect | Rotate sites; usually mild-moderate |
| Renal function (eGFR) | Drives dose adjustment | Halve dose if eGFR <30 not on dialysis |
| Muscle strength / 6MWT (Barth) | Approved-use efficacy context | Knee-extensor strength was the accelerated-approval endpoint |
| Cardiac function (Barth) | Disease involves cardiomyopathy | Clinician-directed in the approved population |
| Hypersensitivity | Contraindication if serious | Monitor for allergic reactions |
| Off-label biomarkers | No validated response marker | Not established outside trials |
For lyophilized research SS-31 reconstituted with bacteriostatic water. The approved Forzinity product is supplied pre-formulated at 80 mg/mL and does not require reconstitution. Formula: concentration = vial mg / BAC mL; draw mL = target mg / concentration; U-100 units = draw mL x 100.
The calculator handles reconstitution arithmetic for research vials. It is not a recommendation to dose SS-31 off-label. Only the approved Forzinity regimen for Barth syndrome (>=30 kg) is a validated human use; for everything else SS-31 is investigational, and gray-market product is not the approved drug. Use under appropriate medical and regulatory oversight.
Verify research vials against supplier COA and mass spec; SS-31's modified residues (D-Arg, Dmt) must be confirmed - gray-market quality varies.
Reconstitute with bacteriostatic water; SS-31's D-amino acid and dimethyl-Tyr improve stability, but avoid harsh agitation and store refrigerated.
Keep research "SS-31" separate from the approved Forzinity product in any record; they differ in formulation, concentration, and regulatory status.
Renally cleared; in renal impairment, parent and metabolite (M1/M2) exposure rises - the basis for the approved dose reduction.
The approved product contains benzyl alcohol and is contraindicated in neonates; research formulations vary and are unverified.
Approved use is clinician-directed; off-label use lacks outcome data and should not be self-directed.
The approved use of elamipretide is monotherapy under the Forzinity label. The "mitochondrial stacks" discussed in longevity circles - pairing SS-31 with other mito-support agents - are theoretical, drawn from complementary mechanisms rather than human combination trials. None is validated, and combining unapproved agents compounds unknown risk.
The approved Forzinity regimen is monotherapy; the label directs that it not be mixed with other products in the same syringe. The combinations above are mechanistic theory from the longevity space, not validated protocols - and stacking unapproved agents multiplies unknown risk. For the approved Barth-syndrome use, follow clinician guidance rather than community stacks. Keep the approved product distinct from gray-market "SS-31."
SS-31 has one of the better-characterized safety profiles in this atlas, because it went through a full clinical-trial program and an FDA review. Across trials it was generally well tolerated, with mild-to-moderate injection-site reactions as the most common adverse effect. The approved Forzinity label adds specific cautions - benzyl alcohol (no neonates), a hypersensitivity contraindication, and renal dose adjustment - while off-label use and gray-market product carry their own, less-characterized risks.
| Condition | Concern | Severity |
|---|---|---|
| Neonates / low-birth-weight infants | Benzyl alcohol gasping-syndrome risk | Contraindicated |
| Serious hypersensitivity to elamipretide/excipients | Allergic reaction | Contraindicated |
| Severe renal impairment (eGFR <30) | Increased parent/metabolite exposure | Halve dose |
| On dialysis | Not studied | Undefined |
| Off-label aging/performance use | No human outcome data; unknown long-term risk | Not recommended |
| Pregnancy / lactation | Limited human data (Barth syndrome is X-linked, largely affects males) | Clinician-directed |
| Gray-market product without COA | Identity / purity / sterility risk | Avoid |
| Competitive athletics | Verify current WADA status / TUE | Verify |
Most common adverse effect; rotate daily, avoid tender/bruised/scarred skin, and assess for persistent reactions.
Check eGFR; halve the dose if <30 (not on dialysis). Metabolite exposure rises substantially in severe impairment.
Stop and evaluate for serious allergic reactions; serious hypersensitivity is a contraindication to continued use.
Muscle strength (knee extensor) and functional measures anchor the approved use; confirmatory benefit is still being verified.
For research vials, confirm identity/purity by COA/MS; discard the approved vial 8 days after opening.
No validated monitoring or response marker exists outside the trial settings; off-label use is not clinician-supported.
SS-31 has the deepest clinical dossier in this atlas - a decade of randomized trials across mitochondrial myopathy, Barth syndrome, heart failure, and dry AMD. The honest summary: the mechanism is strong and the program is mature, but the pivotal phase-3 trials largely missed their primary endpoints, and the 2025 FDA approval rests on the accelerated pathway using an intermediate endpoint (knee-extensor strength) in one ultra-rare disease. Benefit beyond that narrow use remains unproven.
FDA granted accelerated approval in September 2025 for muscle strength in Barth syndrome (>=30 kg) - the first approved mitochondria-targeted therapeutic, based on TAZPOWER plus the SPIBA-001 natural-history control, with continued approval potentially contingent on confirmatory trials.
A pivotal phase-3, randomized, double-blind, placebo-controlled trial of 40 mg/day SC elamipretide over 24 weeks; it did not meet its co-primary endpoints (6-minute walk test and PMM symptom fatigue), tempering enthusiasm despite a strong mechanistic rationale.
In 36 genetically confirmed PMM patients, IV elamipretide (0.01-0.25 mg/kg/h) improved exercise performance dose-dependently versus placebo, providing Class I evidence of tolerability and a functional signal - the foundation for later SC development.
A randomized crossover trial (40 mg/day) plus open-label extension; not superior to placebo on the primary 6MWT and fatigue endpoints, but knee-extensor muscle-strength gains in the extension - alongside a natural-history control - underpinned the accelerated approval.
Trials in dry AMD explored preservation of the photoreceptor ellipsoid zone and slowing of degeneration, with preliminary signals supporting continued development - an indication still in active clinical study, not approved.
Heart-failure programs (e.g. PROGRESS-HF and predecessors) examined peak VO2 and mitochondrial function in HFrEF/HFpEF with mixed results, and the EMBRACE STEMI reperfusion-injury trial did not meet its primary endpoint.
SS-31 pairs a strong, well-characterized mechanism (cardiolipin binding, cristae stabilization, ETC support) with the most mature clinical program in this atlas - yet its pivotal phase-3 trials largely missed their primary endpoints (MMPOWER-3 and TAZPOWER primaries not met). The 2025 FDA approval is real but narrow: accelerated, intermediate-endpoint-based, and limited to Barth syndrome >=30 kg, arriving only after a contested advisory-committee vote and complete-response letters, with confirmatory benefit still to be verified. It belongs on the Atlas as a genuinely approved mito-targeted drug for one ultra-rare disease - and an investigational, unproven agent for the broad uses (aging, heart failure, performance) it is popularly associated with.
| Study / source | Setting | Result | Grade |
|---|---|---|---|
| FDA Forzinity approval | Barth syndrome (accelerated) | Approved on intermediate endpoint (muscle strength) | A |
| MMPOWER-3 | Phase 3 PMM, 40 mg/d SC | Co-primary endpoints not met | A |
| MMPOWER-1 | Phase 1/2 PMM, IV | Dose-dependent exercise gain (Class I) | B |
| TAZPOWER | Barth crossover + OLE | Primaries not met; strength gains in extension | B |
| ReCLAIM / ReCLAIM-2 | Dry AMD | Photoreceptor-preservation signals; in development | B/C |
| Heart-failure programs | HFrEF / HFpEF | Peak VO2 / mito function, mixed | B/C |
| EMBRACE STEMI | Reperfusion injury | Primary endpoint not met | B |
| Preclinical (aging/cardiac) | Animal / cell | Broad mitochondrial-function restoration | P/C |
SS-31's distinguishing feature is that it is the only FDA-approved member of the mitochondria-targeted class, and it works on a lipid (cardiolipin) rather than a receptor. MOTS-c and humanin are mitochondrial-derived signaling peptides with different mechanisms; SBT-272 is the next-generation Szeto-Schiller analog; and CoQ10/ubiquinol is the familiar supplement-grade mitochondrial adjunct.
| Feature | SS-31 / Elamipretide | MOTS-c | SBT-272 | CoQ10 / ubiquinol |
|---|---|---|---|---|
| Class | Mito-targeted tetrapeptide | Mitochondrial-derived peptide | Next-gen Szeto-Schiller analog | Endogenous quinone / supplement |
| Primary mechanism | Cardiolipin binding / cristae stabilization | AMPK-linked metabolic signaling | Cardiolipin-targeting (improved properties) | Electron carrier / antioxidant |
| Target | Cardiolipin (lipid) | Nuclear/metabolic signaling | Cardiolipin (lipid) | ETC (Complex I-III) |
| Evidence tier | A (approved, narrow) + B RCTs | P/C (preclinical/early) | P (preclinical) | B/C (supplement trials) |
| Regulatory status | FDA-approved (Barth only); else investigational | Not approved; research | Investigational | Dietary supplement |
| Route | SC (approved); IV historical | SC (research) | Preclinical | Oral |
| Key caution | Missed primaries; off-label unproven | Minimal human data | Early-stage | Modest, variable evidence |