SS-31 Peptide: What It Is, How It Works, and What Research Shows

The SS-31 peptide is a synthetic tetrapeptide, also called elamipretide, that travels into mitochondria and binds cardiolipin on the inner mitochondrial membrane. Researchers study it for conditions driven by mitochondrial dysfunction, including heart failure, Barth syndrome, and age-related macular degeneration. SS-31 is not FDA-approved for human use in the United States and is sold to laboratories as a research chemical.

What Is the SS-31 Peptide?

SS-31 belongs to the Szeto-Schiller family of aromatic-cationic peptides. Its sequence is D-Arg-DimethylTyr-Lys-Phe-NH2, a chain of just four amino acids, which makes the molecule small, stable, and able to cross cell membranes. It also appears in the literature and on product labels as MTP-131, Bendavia, and Forzinity.

What separates the mitochondrial peptide ss-31 from most research peptides is where it accumulates. Instead of binding a receptor on the cell surface, it concentrates heavily on the inner mitochondrial membrane. That localization is the basis for nearly every study published on it.

How SS-31 Works Inside Mitochondria

Mitochondria produce ATP through the electron transport chain, and the inner membrane structure that makes this possible depends on cardiolipin. SS-31 binds cardiolipin directly.

• Cardiolipin stabilization: SS-31 helps keep cardiolipin in the correct configuration, supporting cristae shape and the activity of complexes I, III, and IV.
• Antioxidant activity: The dimethyltyrosine residue in the peptide scavenges reactive oxygen species and limits lipid peroxidation.
• Reduced electron leak: Stabilized membranes generate fewer free radicals per unit of ATP produced.
• No membrane potential requirement: Unlike many mitochondria-targeted compounds, SS-31 does not need a charged membrane to reach the inner membrane.

What Research Shows So Far

Published results are mixed. Several small trials reported improvements in functional measures, while larger trials missed their primary endpoints.

Condition	Study type	Reported outcome
Heart failure	PROGRESS-HF, 40 mg SC daily	Some functional and biomarker improvement; primary endpoint not met
Barth syndrome	TAZPOWER, 40 mg SC daily	Gains on some functional scales; FDA issued a complete response letter in 2024
Primary mitochondrial myopathy	MMPOWER-3	Missed the primary six-minute walk endpoint
Dry age-related macular degeneration	ReCLAIM, 40 mg SC daily	Improvements in some visual function measures
Cardiac ischemia-reperfusion	Animal and early human studies	Reduced infarct size in animal models

The FDA has not approved elamipretide for any indication. A complete response letter issued in 2024 means the agency asked for more evidence before it would consider approval for Barth syndrome.

SS-31 Peptide Dosing in Published Research

No standard human dose exists outside clinical trials. Published ss-31 peptide dosing depends on the model, the route of administration, and the endpoint being measured.

Setting	Typical dose	Route
Human trials (most programs)	40 mg once daily	Subcutaneous injection
Early human infusion studies	0.05 to 0.1 mg/kg per hour	Intravenous infusion
Rodent studies	1 to 5 mg/kg per day	Subcutaneous or intraperitoneal
Cell culture work	10 nM to 10 micromolar	Incubation

Most human protocols used a fixed dose rather than a weight-based one, so ss-31 peptide injection dosage in the literature does not scale with body weight. Researchers preparing solutions from lyophilized powder should account for peptide content, salt form, and reconstitution volume to avoid measurement errors.

Is SS-31 Legal to Buy in the USA?

SS-31 is not a scheduled drug under the Controlled Substances Act, but it is not an approved medicine either. Vendors sell it labeled for research use only and not for human consumption.

Researchers comparing suppliers typically check a certificate of analysis for HPLC purity above 98%, mass spectrometry confirmation, and endotoxin testing. Questions about where to buy ss-31 peptide usually come down to documentation quality rather than price. Anyone hoping to purchase SS-31 as a personal-use drug should understand that no US vendor can legally sell it that way.

Combining SS-31 With Other Mitochondrial Peptides

Some research protocols use ss-31 and mots-c together, because both compounds act on mitochondrial function through different mechanisms. MOTS-c is a mitochondrial-derived peptide that influences AMPK signaling and metabolic regulation, while SS-31 targets membrane cardiolipin.

No published human trial has tested the combination. Stacking two unapproved research peptides raises the chance of unanticipated interactions and makes it impossible to attribute any observed effect to one compound.

Safety Considerations

In clinical trials, the most frequently reported side effects were mild: injection site reactions, headache, and nausea. Long-term safety data in humans remain limited, and the effects of sustained use are unknown.

• SS-31 sold online is not manufactured to pharmaceutical sterility or purity standards.
• Reconstitution errors are common with lyophilized peptides.
• Any consideration of human use should involve a licensed healthcare professional.

SS-31 remains a promising research target rather than an established therapy. The cardiolipin-binding science is well documented; the clinical evidence is not yet conclusive.

COMMON QUESTIONS

Frequently Asked Questions

Is the SS-31 peptide FDA-approved?

No. The FDA has not approved elamipretide (SS-31) for any human condition, and Stealth BioTherapeutics received a complete response letter in 2024 for its Barth syndrome application. SS-31 sold online is labeled for research use only and is not a legal medicine.

What dose of SS-31 is used in studies?

Most human trials used 40 mg injected subcutaneously once daily, while earlier infusion studies used 0.05 to 0.1 mg/kg per hour. Animal research commonly uses 1 to 5 mg/kg per day. No standard human dose exists outside clinical trials.

Can SS-31 be taken as a pill or nasal spray?

No. SS-31 is a peptide with poor oral bioavailability, so researchers administer it by subcutaneous injection or intravenous infusion. Oral and nasal SS-31 products have no published pharmacokinetic data supporting them.