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Longevity & mitochondrial

SS-31 (elamipretide)

Also called elamipretide, Forzinity, Bendavia, MTP-131, D-Arg-Dmt-Lys-Phe-NH2

SS-31, now called elamipretide, is a small lab-made peptide that travels to the mitochondria, the cell's power plants. In September 2025 the FDA gave it accelerated approval, as Forzinity, to improve muscle strength in people with Barth syndrome, a rare inherited mitochondrial disease. It is also being studied in other mitochondrial and eye diseases.

FDA-approvedApproved by the FDA for at least one use after large human trials.

All printable flashcards

Drawn from its published sequence: 4 residues, one bead each.

Overview

SS-31, now called elamipretide, is a small lab-made peptide that travels to the mitochondria, the cell's power plants. In September 2025 the FDA gave it accelerated approval, as Forzinity, to improve muscle strength in people with Barth syndrome, a rare inherited mitochondrial disease. It is also being studied in other mitochondrial and eye diseases.

How it works

Established at the label level: the FDA label describes elamipretide as a mitochondrial cardiolipin binder that localizes to the inner mitochondrial membrane and improves mitochondrial structure and function. Cardiolipin is a fat that is abnormal in Barth syndrome. How this translates into clinical benefit is still being confirmed.

What research shows

  • Pivotal trial SPIBA-201: 12 males with Barth syndrome at one US site; in the randomized placebo-controlled crossover period the drug did not beat placebo on the primary endpoints (6-minute walk, fatigue score) 1.
  • Accelerated approval was based on improved knee extensor muscle strength seen during the long open-label extension (10 entered; 8 followed to week 168) 1.
  • Confirmatory Phase 4 trial (4TAZPower): 72-week randomized, double-blind, placebo-controlled study in patients aged 5+ 4.
  • Other programs listed by the company: POLG-related mitochondrial disease and dry age-related macular degeneration 4.

Doses studied in people

Study or labelDose usedSource
FDA label (Forzinity), Barth syndrome, patients ≥30 kg40 mg subcutaneously once daily2
FDA label, adults with eGFR <30 mL/min not on dialysis20 mg subcutaneously once daily2

Doses are from the FDA label for Barth syndrome only; no approved dose exists for other uses.

Read this first: these are the amounts given to participants in published studies or written on official prescribing labels, reported for reference. They are not recommendations. Trial doses were chosen for specific patients under medical supervision, and a dose that is safe in one person can be harmful in another.

Weekly protocol

How the schedule looks week by week. Each chart says where it comes from: a prescribing label, a clinical trial, or a protocol commonly reported online.

Forzinity (elamipretide) label

Prescribing label

One week

D1D2D3D4D5D6D7

Once daily, at the same time each day · Subcutaneous injection

Dose by week

40 mgwk 1+
Course
Ongoing
Note
FDA-approved (2025) only for Barth syndrome in patients weighing at least 30 kg. Adults with eGFR under 30 mL/min not on dialysis: 20 mg once daily.
Source
FORZINITY (elamipretide) prescribing information (rev. 9/2025)

Commonly reported research-community protocol

Commonly reported, not studied

One week

D1D2D3D4D5D6D7

Once daily · Subcutaneous injection

Syringe units (U-100)

Dose by week

5 mgwk 1–2
10 mgwk 3–8

Supplies for one course (estimate)

Counts only. This site does not sell or link to supplies.

Course
8 weeks
Note
Another guide describes 5–10 mg daily, 4 weeks on and 2 weeks off. These doses are not the approved Barth syndrome dose.
Source
PeptideDosages.com: SS-31 (10 mg vial) dosage protocol
Also: Peptide Protocol Wiki: SS-31 dosing protocols

Reference only, not a recommendation. Charts marked "commonly reported" describe what public sources say people use. They have not been tested in trials, and their safety and effect are unknown. Label and trial schedules were set for specific patients under medical supervision. Use the calculator only to understand the arithmetic.

Safety

  • Injection-site reactions in all 12 treated patients in the randomized trial (vs 8/12 on placebo), including redness, pain, hardening and itching 12.
  • Serious allergic reactions needing emergency care have occurred; contraindicated in people with serious hypersensitivity 2.
  • Eosinophil counts rose with courses of 30+ days, usually peaking around day 90 2.
  • Contains benzyl alcohol; not approved for neonates or for IV use 2.
  • Long-term benefit is still being confirmed (accelerated approval) 14.

Report side effects of any drug or product to the FDA through MedWatch. For a possible poisoning in the US, call Poison Control at 1-800-222-1222.

Storage and stability

Per label: refrigerate unopened vials at 2–8°C; do not freeze; opened vials may be refrigerated or kept at room temperature and discarded 8 days after first opening.

General lab handling, not instructions for personal use. See Storage and stability.

History

Developed by Stealth BioTherapeutics (now a subsidiary of Mighty Therapeutics). A Phase 2/3 study in Barth syndrome began in 2017; the NDA was submitted in 2021, an FDA advisory committee voted favorably in October 2024, action dates slipped in 2025, and after resubmission the FDA granted accelerated approval on September 19, 2025. A global Phase 4 confirmatory trial (4TAZPower) dosed its first patient in July 2026.

Common questions

Is SS-31 (elamipretide) FDA-approved?

Yes, with limits. FDA gave it accelerated approval as Forzinity on September 19, 2025, to improve muscle strength in people with Barth syndrome who weigh at least 30 kg 137. Keeping that approval depends on a confirmatory trial 1.

What does the research show?

In the randomized part of the 12-patient pivotal trial, it did not beat placebo on walking distance or fatigue 1. Approval was based on better knee muscle strength seen during a long open-label extension 1.

What dose is on the label?

The FDA label for Barth syndrome lists 40 mg injected under the skin once daily, or 20 mg for adults with severe kidney impairment not on dialysis 2. There is no approved dose for any other use 2.

What are the side effects?

Injection-site reactions occurred in all 12 treated patients in the randomized trial, versus 8 of 12 on placebo 12. Serious allergic reactions have occurred, and eosinophils (a type of white blood cell) rose with courses of 30 days or more 2.

How is elamipretide stored?

The label says to refrigerate unopened vials at 2 to 8°C and not freeze them 2. Opened vials can be refrigerated or kept at room temperature and should be thrown away 8 days after first opening 2.

Is SS-31 banned in sport?

It is not named on WADA's 2026 list, and as an FDA-approved drug it does not fall under the S0 non-approved substances rule 6.

Related compounds

Longevity & mitochondrialPreclinical onlyFlashcard

Humanin

HN · HNG (S14G analogue)

Humanin is a small peptide made from genetic code inside the mitochondria.

Longevity & mitochondrialEarly human dataFlashcard

NAD+

nicotinamide adenine dinucleotide · β-NAD

NAD+ is not a peptide but a small helper molecule that every cell uses to make energy and repair DNA.

Metabolic & weightPreclinical onlyFlashcard

MOTS-c

mitochondrial open reading frame of the 12S rRNA-c · MOTSc

MOTS-c is a small peptide made from instructions in mitochondrial DNA, the cell's 'power plant' genes.

Sources

  1. FDA Drug Trials Snapshots: Forzinity FDA label
  2. Forzinity (elamipretide) Prescribing Information (rev. 9/2025) FDA label
  3. Forzinity FDA approval history Regulatory
  4. Mighty Therapeutics: First Patient Dosed in Phase 4 Confirmatory Study of Elamipretide in Barth Syndrome (July 8, 2026) Regulatory
  5. FDA: Bulk Drug Substances Nominated for Use in Compounding Under Section 503A (updated May 14, 2026) Regulatory
  6. WADA 2026 Prohibited List (official English text, Dutch Treaty Series Trb. 2026, 25) Regulatory
  7. FDA approval letter, NDA 215244 Regulatory

Last reviewed 2026-10-25 · How we research · Found an error? See our corrections policy.