Overview
Overview
SS‑31 (elamipretide) is a mitochondria‑targeted tetrapeptide that selectively binds cardiolipin in the inner mitochondrial membrane[1], stabilizing electron transport chain complexes and reducing reactive oxygen species production while enhancing ATP synthesis[2]. This peptide has demonstrated protective effects in preclinical models of heart failure, neurodegenerative disease, and age‑related muscle atrophy, and received FDA accelerated approval in 2025 as the first treatment for Barth syndrome
- Category
- Longevity
- Routes
- subcutaneous
Mechanism
SS-31
Mechanism of action
Mechanism of action
SS‑31 (elamipretide) is a cell‑permeable tetrapeptide with a unique mechanism of action targeting mitochondrial dysfunction [1] . The peptide selectively accumulates in the inner mitochondrial membrane where it binds to cardiolipin, a specialized phospholipid essential for organizing electron transport chain supercomplexes and maintaining cristae structure [2] [7] . By stabilizing cardiolipin‑protein interactions, SS‑31 optimizes electron transport efficiency, reduces pathological reactive oxygen species generation, and enhances ATP synthesis in metabolically active tissues [8] . Preclinical research demonstrated that SS‑31 protects against mitochondrial dysfunction across multiple disease models including heart failure, ischemia‑reperfusion injury, neurodegeneration, chronic kidney disease, and age‑related muscle atrophy [9] . In human clinical trials, SS‑31 showed favorable safety and tolerability profiles with no dose‑limiting toxicities [4] [5] . While Phase II trials in heart failure and primary mitochondrial myopathy did not meet primary efficacy endpoints, the TAZPOWER trial in Barth syndrome demonstrated significant improvements in muscle strength and six‑minute walk distance, leading to FDA accelerated approval in 2025 [3] [10] .
Key research findings
- 01
A mitochondria-targeting tetrapeptide (D-Arg-2',6'-dimethyl-Tyr-Lys-Phe-NH2) from the Szeto-Schiller (SS) peptide series; also known as elamipretide, MTP-131, and Bendavia. It concentrates in the inner mitochondrial membrane.
- 02
Mechanism: binds cardiolipin on the inner mitochondrial membrane, reported to stabilize cristae architecture, support electron-transport efficiency, and reduce mitochondrial reactive-oxygen-species production (in vitro and animal models).
- 03
Extensive preclinical literature across cardiac, renal, neural, ocular, and skeletal-muscle ischemia and aging models (animal studies).
- 04
Human trials (as elamipretide) have spanned heart failure, primary mitochondrial myopathy (MMPOWER series), dry age-related macular degeneration (ReCLAIM), and Barth syndrome (TAZPOWER); results were mixed, with some primary endpoints not met.
- 05
Regulatory milestone: in September 2025 the FDA granted accelerated approval to elamipretide (brand FORZINITY) for Barth syndrome; other indications remain investigational.
Primary source: Barth syndrome (FDA-approved): TAZPOWER (NCT03098797) is the pivotal Phase 2/3 trial. The 12-week randomized crossover phase did not reach statistical significance vs placebo on either co-primary endpoint. The 168-week open-label extension showed durable improvements in 6-minute walk distance and knee extensor muscle strength. The natural-history comparison study (8 OLE patients vs 19 untreated controls) reinforced these findings. FDA granted accelerated approval on September 19, 2025 based on knee extensor strength as an intermediate endpoint. Heart failure: Multiple Phase 1–2 elamipretide studies in heart failure with preserved ejection fraction (HFpEF) and reduced ejection fraction (HFrEF) reported mixed and mostly modest signals. As of June 2026, no FDA approval exists in this indication. Primary mitochondrial myopathy: MMPOWER and MMPOWER-3 Phase 3 trials evaluated elamipretide in primary mitochondrial myopathy. MMPOWER-3 did not meet its co-primary endpoints. Stealth has continued exploration but the indication is not FDA-approved as of June 2026. Dry age-related macular degeneration: ReCLAIM and ReCLAIM-2 evaluated elamipretide in dry AMD. Mixed signals; investigational. Not FDA-approved for AMD as of June 2026. Mechanism and preclinical evidence: Strong and consistent. Cardiolipin binding, cristae stabilization, ATP rescue, and ROS reduction have been confirmed across cell-culture and animal disease models including ischemia-reperfusion injury, doxorubicin cardiotoxicity, age-related muscle dysfunction, and acute kidney injury models. Healthy-adult anti-aging or performance use: No published human RCT supports an anti-aging or athletic-performance indication for SS-31 in healthy adults. Anecdotes and supplier marketing are not evidence.
Pharmacokinetic profile
Single-dose plasma curve over 24h. Shaded band = commonly-cited therapeutic window. Illustrative only.
Protocol Reference
Protocol reference
Commonly cited research range: 5–20 mg, daily.
Reference figures reported in the research literature — not a dosing recommendation. For interactive vial math and scheduling, see the Calculator and Schedule tabs.
Cited protocol & reconstitution guide
Source-backed reference fields by phase, including any volume fields authored in the cited guide.
Tier 1 — Micro / sensitivity start
0.1-1 mg
Tier 2 — Low-dose maintenance (Weeks 8–12, with breaks)
0.5-1 mg
Tier 3 — Common reported range (Weeks 4–8)
1-5 mg
Tier 4 — Standard reported range
5-10 mg
| Phase | Reference amount | Units / volume |
|---|---|---|
| Tier 1 — Micro / sensitivity start | 0.1-1 mg | 1–10 units (0.01–0.10 mL) |
| Tier 2 — Low-dose maintenance (Weeks 8–12, with breaks) | 0.5-1 mg | 5–10 units (0.05–0.10 mL) |
| Tier 3 — Common reported range (Weeks 4–8) | 1-5 mg | 10–50 units (0.10–0.50 mL) |
| Tier 4 — Standard reported range | 5-10 mg | 50–100 units (0.50–1.00 mL) |
Titration protocol
- Micro / sensitivity startStart0.1-1 mg
Subcutaneous. Daily or several times weekly. Rotate injection sites.
- Weeks 8–12 (with breaks)Build0.5-1 mg
Subcutaneous, 3-5x/week. Observe the scheduled breaks as written; rotate sites.
- Weeks 4–8Build1-5 mg
Subcutaneous, once daily at the same time each day. Skip a missed dose; do not double up.
- Standard reported rangeBuild5-10 mg
Subcutaneous, once daily, often morning. Hold at this step before moving up.
- Weeks 4–12Maintenance10-20 mg
Subcutaneous, once daily or pre-workout. At this vial's 10 mg/mL, any dose above 10 mg exceeds 100 units — split into two equal draws at separate sites (20 mg = 100 units (1.00 mL) × 2).
Storage & Handling
Storage requirements(typical for most peptides)
Can be stored for extended periods. Protect from moisture.
Store in refrigerator door. Never freeze after reconstitution.
Label vials with reconstitution date. Discard if cloudy.
Reconstitution steps
- 01🌡️01 Inspect the vial — Check the label, lot, and that the powder cake is intact and uncracked. Discard if damaged.
- 02🧴02 Bring to room temperature — Let the vial sit out 10–20 minutes after refrigeration so condensation does not form when you remove the cap.
- 03💉03 Wipe both stoppers — Use a fresh alcohol swab on the SS-31 vial stopper and on the BAC water vial stopper.
- 04💧Draw 1 mL bacteriostatic water into a sterile syringe — this 10 mg vial yields 10 mg/mL.
- 05🔄05 Inject slowly down the vial wall — Aim the stream against the inner glass wall, not directly onto the powder. This reduces foaming.
- 06🏷️06 Swirl, do not shake — Roll or gently swirl the vial until the solution is fully clear. Do not vortex or shake hard.
- 07❄️07 Label and store — Write the reconstitution date on the vial. Store reconstituted SS-31 refrigerated at 35.6–46.4°F (2–8°C), protected from light. Do not freeze once reconstituted.
- 08💉Important: This guide is for educational purposes only and is not medical advice. For research use only. Not for human consumption.
- 09💉This 10mg vial covers the first 4 steps of the schedule; later steps exceed one vial.
Additional storage notes
Refrigerated 36–46°F (2–8°C); do not freeze — After first opening, may be stored refrigerated or at room temp 68–77°F (20–25°C). Discard 8 days after first opening per label.
-4°F (-20°C) long-term; refrigerated short-term — Use original sealed vial, away from light. Stability typically reported up to ~2 years frozen by suppliers, but verify supplier label and stability data.
35.6–46.4°F (2–8°C) — Do not freeze. Protect from light. Many suppliers and protocol references suggest using within ~28 days of reconstitution.
Clinical Evidence
Clinical evidence
Investigated in preclinical and clinical research for mitochondrial dysfunction in cardiac, muscle, and ophthalmic contexts.
Barth syndrome (FDA-approved): TAZPOWER (NCT03098797) is the pivotal Phase 2/3 trial. The 12-week randomized crossover phase did not reach statistical significance vs placebo on either co-primary endpoint. The 168-week open-label extension showed durable improvements in 6-minute walk distance and knee extensor muscle strength. The natural-history comparison study (8 OLE patients vs 19 untreated controls) reinforced these findings. FDA granted accelerated approval on September 19, 2025 based on knee extensor strength as an intermediate endpoint. Heart failure: Multiple Phase 1–2 elamipretide studies in heart failure with preserved ejection fraction (HFpEF) and reduced ejection fraction (HFrEF) reported mixed and mostly modest signals. As of June 2026, no FDA approval exists in this indication. Primary mitochondrial myopathy: MMPOWER and MMPOWER-3 Phase 3 trials evaluated elamipretide in primary mitochondrial myopathy. MMPOWER-3 did not meet its co-primary endpoints. Stealth has continued exploration but the indication is not FDA-approved as of June 2026. Dry age-related macular degeneration: ReCLAIM and ReCLAIM-2 evaluated elamipretide in dry AMD. Mixed signals; investigational. Not FDA-approved for AMD as of June 2026. Mechanism and preclinical evidence: Strong and consistent. Cardiolipin binding, cristae stabilization, ATP rescue, and ROS reduction have been confirmed across cell-culture and animal disease models including ischemia-reperfusion injury, doxorubicin cardiotoxicity, age-related muscle dysfunction, and acute kidney injury models. Healthy-adult anti-aging or performance use: No published human RCT supports an anti-aging or athletic-performance indication for SS-31 in healthy adults. Anecdotes and supplier marketing are not evidence.
- 01A mitochondria-targeting tetrapeptide (D-Arg-2',6'-dimethyl-Tyr-Lys-Phe-NH2) from the Szeto-Schiller (SS) peptide series; also known as elamipretide, MTP-131, and Bendavia. It concentrates in the inner mitochondrial membrane.
- 02Mechanism: binds cardiolipin on the inner mitochondrial membrane, reported to stabilize cristae architecture, support electron-transport efficiency, and reduce mitochondrial reactive-oxygen-species production (in vitro and animal models).
- 03Extensive preclinical literature across cardiac, renal, neural, ocular, and skeletal-muscle ischemia and aging models (animal studies).
- 04Human trials (as elamipretide) have spanned heart failure, primary mitochondrial myopathy (MMPOWER series), dry age-related macular degeneration (ReCLAIM), and Barth syndrome (TAZPOWER); results were mixed, with some primary endpoints not met.
- 05Regulatory milestone: in September 2025 the FDA granted accelerated approval to elamipretide (brand FORZINITY) for Barth syndrome; other indications remain investigational.
Evidence maturity varies by compound; much peptide research is preclinical (in vitro or animal-model). Where human data are limited, findings should be read as research observations, not clinical conclusions.
References
Literature references
Published research articles and sources related to SS-31.
- 01U.S. Food and Drug Administration. FORZINITY (elamipretide) injection — Highlights of Prescribing Information. accessdata.fda.gov (2025)et al. (2025)
- 02U.S. Food and Drug Administration, Center for Drug Evaluation and Research. Approval Package for Application 215244Orig1s000 (FORZINITY). accessdata.fda.gov (2025)et al. (2025)
- 03Stealth BioTherapeutics Inc. FDA Accelerated Approval of FORZINITY (elamipretide HCl), the First Therapy for Barth Syndrome — News Release. PR Newswire (2025)et al. (2025)
- 04Shirley M. Elamipretide: First Approval. Drugs (PubMed) (2025)et al. (2025)
- 05Reid Thompson WR, Hornby B, Manuel R, et al. Long-term efficacy and safety of elamipretide in patients with Barth syndrome: 168-week open-label extension results of TAZPOWER. Genetics in Medicine (2024)et al. (2024)
- 06Reid Thompson WR, Manuel R, Abbruscato A, et al. Natural history comparison study to assess the efficacy of elamipretide in patients with Barth syndrome. Orphanet Journal of Rare Diseases (PMC) (2022)et al. (2022)
- 07Mitchell W, Ng EA, Tamucci JD, et al. The mitochondria-targeted peptide SS-31 binds lipid bilayers and modulates surface electrostatics as a key component of its mechanism of action. Journal of Biological Chemistry (PMC) (2020)et al. (2020)
- 08Chavez JD, Tang X, Campbell MD, et al. Mitochondrial protein interaction landscape of SS-31. Proceedings of the National Academy of Sciences (PNAS) (2020)et al. (2020)
- 09Daubert MA, Yow E, Dunn G, et al. Elamipretide: A Review of Its Structure, Mechanism of Action, and Therapeutic Potential. International Journal of Molecular Sciences (PMC) (2025)et al. (2025)
- 10Sabbah HN. Barth syndrome cardiomyopathy: targeting the mitochondria with elamipretide. Heart Failure Reviews (PubMed) (2021)et al. (2021)
- 11Barth Syndrome Foundation. FDA Approves First Medication for Barth Syndrome (FORZINITY). barthsyndrome.org (2025)et al. (2025)
- 12ClinicalTrials.gov. Study to Evaluate the Safety, Tolerability, and Efficacy of Elamipretide in Subjects With Barth Syndrome (TAZPOWER, NCT03098797). clinicaltrials.gov (2025)et al. (2025)
- 13Peptides Institute. SS-31: Research Profile & Guide. peptidesinstitute.org (2026)et al. (2026)
- 14Pep-Pedia. SS-31 (Elamipretide). pep-pedia.org (2026)et al. (2026)
- 15Peptide Protocol Wiki. SS-31: Community Protocols & Reports. peptideprotocolwiki.com (2026)et al. (2026)
- 16Reddit r/Peptides. SS-31 - Dosing and Results? reddit.com (2024)et al. (2024)
- 17Reddit r/Peptidesource. SS31 protocol. reddit.com (2026)et al. (2026)
Observed Effects
Observed effects in cited research
Most commonly reported in trials
- Injection-site reactions: redness, swelling, itching, or mild pain. These were the most common adverse events in TAZPOWER and the long-term extension.
- Headache, especially in the first weeks of dosing.
- Dizziness, mild nausea, or fatigue, mostly self-limited.
Notable per the Forzinity label
- Hypersensitivity reactions. Serious hypersensitivity has been observed; the label lists hypersensitivity as a contraindication for any ingredient.
- Benzyl alcohol content. Forzinity contains benzyl alcohol; not for use in neonates due to risk of metabolic acidosis and gasping syndrome with benzyl-alcohol-containing drugs.
- Renal impairment. Elamipretide and inactive metabolites accumulate in severe renal impairment; the label requires a 20 mg/day dose in adults with eGFR <30 mL/min not on dialysis.
Theoretical and quality-control risks
- Drug interactions: per the FDA label and Epocrates, no significant interactions have been identified, but kidney-stressing co-medications deserve clinician attention because elamipretide is renally cleared.
- Quality control of research-use vials: research-use SS-31 is not subject to FDA manufacturing oversight. Purity, identity, and endotoxin content can vary by supplier and lot. Buyer-side verification (COA review) is the only consumer-side check.
- Long-term safety beyond ~3.5 years (the longest TAZPOWER OLE follow-up) in healthy adults is not established. The trial population was small and tightly defined.
Stop and seek qualified medical care for
- Any sign of allergic reaction, spreading or infected injection-site reactions, persistent severe headaches, new shortness of breath or chest symptoms, significant changes in urination or new swelling, or any observed effect that significantly affects daily function. PDP does not provide medical advice.
Research Considerations
Research considerations
Research Use Only - not for human or veterinary therapeutic use. Investigational compound currently in clinical development; not approved for general use. Consult a licensed healthcare professional for any clinical decisions.
- Patients with serious hypersensitivity to elamipretide or any ingredient in the formulation.
- Neonates (the vial contains benzyl alcohol; benzyl-alcohol-containing drugs have caused serious adverse reactions in low-birth-weight and preterm neonates).
- Adults with severe renal impairment (eGFR <30 mL/min, not on dialysis): the label specifies a 20 mg daily dose adjustment.
- Adults with eGFR <30 mL/min on dialysis: insufficient data per label; no recommended regimen.
- Pregnancy and lactation: data are limited; refer to the prescriber.
- Healthy adults seeking anti-aging, cognitive, or athletic-performance benefits.
- Patients with primary mitochondrial myopathy, heart failure, or dry age-related macular degeneration. Some of these have been studied (MMPOWER, MMPOWER-3, ReCLAIM/ReCLAIM-2), but as of June 2026 none has produced an FDA approval, and Stealth's continued investigation in dry AMD and primary mitochondrial myopathy remains exactly that — investigation.
- Patients under 30 kg.
Factors noted in the research literature; not patient-specific medical advice.
Regulatory Status
Regulatory status
RUO
Comparisons
Comparisons
| Compound | Mechanism | Route | Status |
|---|---|---|---|
| SS-31this | A mitochondria-targeted tetrapeptide that selectively binds cardiolipin in the inner mitochondrial membrane, stabilizing electron-transport-chain organization and reducing reactive oxygen species. | subcutaneous | Investigational / RUO |
| Testagen | A synthetic tetrapeptide bioregulator (Lys-Glu-Asp-Gly) studied for modulation of endocrine function, particularly pituitary-gonadal regulatory pathways. | subcutaneous | Investigational / RUO |
| Vesugen (Lys-Glu-Asp) | A synthetic tripeptide bioregulator (Lys-Glu-Asp) studied for gene-regulatory support of vascular endothelial tissue. | subcutaneous | Investigational / RUO |
| Vilon | A synthetic immunoregulatory dipeptide (Lys-Glu) studied for gene-regulatory and immunomodulatory activity, including effects on lymphocyte markers and chromatin structure. | subcutaneous | Investigational / RUO |
| Cartalax | A synthetic tripeptide bioregulator (Ala-Glu-Asp) studied for gene-regulatory activity in connective and cartilage tissue, with proposed anti-inflammatory and regenerative effects. | subcutaneous | Investigational / RUO |
| Survodutide | An investigational long-acting dual agonist of GLP-1 and glucagon receptors studied for appetite regulation and increased energy expenditure. | subcutaneous | Investigational / RUO |
| TB-500 | Upregulates actin, promotes cell migration, reduces inflammation, and stimulates wound healing and tissue repair. | subcutaneous, intramuscular | Investigational / RUO |
Attributes shown for research comparison only; not a statement of efficacy or therapeutic equivalence.
FAQ
Frequently asked questions
Yes. SS-31 is the original research code (also written SS31). Elamipretide is the generic drug name. FORZINITY is the FDA-approved brand name marketed by Stealth BioTherapeutics. Earlier development codes were MTP-131 and Bendavia.
Partially. On September 19, 2025, the FDA granted accelerated approval to elamipretide as FORZINITY for Barth syndrome in patients weighing at least 30 kg. Outside of that indication, SS-31 is not FDA-approved and is sold by research suppliers as a research-use compound. See the FDA label at accessdata.fda.gov .
The TAZPOWER Phase 2/3 trial in Barth syndrome used 40 mg subcutaneously once daily, both in the 12-week randomized crossover phase and in the open-label extension that ran up to 168 weeks. The Forzinity FDA label uses the same 40 mg/day dose for patients ≥30 kg, with a 20 mg/day adjustment for adults with severe renal impairment. This is reported as label and trial information, not a PDP dosing recommendation.
Forzinity is supplied at 80 mg/mL ready-to-use and does not require reconstitution. Lyophilized research-use SS-31 vials commonly come in 10 mg or 50 mg sizes. A 10 mg vial reconstituted with 1.0 mL bacteriostatic water yields 10 mg/mL; a 50 mg vial reconstituted with 2.5 mL yields 20 mg/mL. Always verify your specific vial's label.
There is no PDP-endorsed personal-use cycle for SS-31. The Forzinity label uses continuous daily dosing in patients with Barth syndrome. The TAZPOWER trial structure was 12 weeks per period in the randomized phase, with up to 168 additional weeks in the open-label extension.
In TAZPOWER and other elamipretide trials, injection-site reactions (redness, swelling, itching) were the most common adverse events. Headaches, mild nausea, and fatigue have also been reported. Forzinity's label flags hypersensitivity and benzyl alcohol content (do not use in neonates) as specific concerns.
Per the Forzinity label, anyone with serious hypersensitivity to elamipretide or excipients should avoid it, and it should not be used in neonates because it contains benzyl alcohol. Adults with severe renal impairment require a dose reduction (20 mg/day at eGFR <30 mL/min not on dialysis), and there is insufficient information for adults on dialysis. Healthy adults seeking anti-aging or performance use are not within any FDA-approved population.
Both are studied in mitochondrial-research contexts, but they work differently. SS-31 binds cardiolipin in the inner mitochondrial membrane to stabilize structure. MOTS-c is a mitochondrial-derived peptide that signals through pathways like AMPK. SS-31 has Phase 2/3 human data and one FDA approval (Barth syndrome). MOTS-c has preclinical and small human studies but no Phase 3 outcome trial. They are not interchangeable. See the MOTS-c protocol for more detail.
There is no published human randomized controlled trial demonstrating an anti-aging or athletic-performance benefit for SS-31 in healthy adults. The mechanism (cardiolipin stabilization) is biologically plausible, but mechanism plausibility is not proof of benefit. Most online claims in this space cite preclinical or anecdotal data, not human RCTs.
No. This page is an educational research reference. It reports trial-context dosing, FDA-label information, mechanism, and safety data from published sources. It is not a personal-use protocol, a prescription, or a substitute for evaluation by a qualified clinician.
Forzinity (the FDA-approved drug) is stored refrigerated at 36–46°F (2–8°C) and discarded 8 days after first opening, per its label. Lyophilized research-use SS-31 vials are typically stored long-term frozen at -4°F (-20°C); once reconstituted, they are stored refrigerated at 35.6–46.4°F (2–8°C), protected from light, and not refrozen.
The full FDA-approved label is at accessdata.fda.gov . The FDA approval letter is in the same docket. Both should be considered the source of truth for current Forzinity dosing, indications, and safety information.
Research-use notice
Research Use Only. This educational content and calculation support is intended for private research documentation. It does not provide medical advice, human-use directions, or claims of safety or effectiveness.