SS-31 vs MOTS-c: the difference, the research and which to buy

In plain words: SS-31 is a structural helper. Cardiolipin is a fat molecule found almost only on the inner mitochondrial membrane, where it holds the folded membrane (the cristae) in shape; when cells are stressed it is damaged and energy production falters, and SS-31 binds it. MOTS-c is a messenger: in cultured cells under metabolic stress (glucose restriction) it moved into the nucleus and changed which genes were switched on, including genes for handling glucose and fat (Kim et al., 2018).

Decide on the compound first, then choose between its smaller and larger vial. Vendor pages often suggest using the two together; we found no published study testing that.

Cell and animal studies

Birk and colleagues (2013) showed in rats that SS-31 binds cardiolipin, protects the cristae during kidney ischaemia (blood supply cut off), speeds ATP recovery once blood flow returns, and reduces kidney dysfunction. Mitchell and colleagues (2020), using model membranes, yeast mitochondria and simulations, found that SS-31 binds lipid bilayers and changes the electrical charge at the membrane surface. These are findings in membranes and rats, not in people.

Human trials

As elamipretide, SS-31 has been tested in randomised, placebo-controlled trials. The three trials summarised here missed their primary endpoints.

• Heart failure (PROGRESS-HF): 71 patients received placebo or elamipretide for 28 days; it did not reduce the size of the heart's main pumping chamber at the end of each beat, the main measure (Butler et al., 2020).
• Primary mitochondrial myopathy (MMPOWER-3): 218 people with primary mitochondrial myopathy, an inherited group of muscle disorders, were randomised for 24 weeks. The trial missed both main measures, six-minute walk distance and fatigue score (Karaa et al., 2023).
• Barth syndrome (TAZPOWER): a small randomised crossover trial missed its primary endpoints. In the open-label extension, eight of ten participants reached 36 weeks and the authors reported improvements, weaker evidence without a placebo group (Thompson et al., 2021).

On 19 September 2025 the FDA granted accelerated approval to elamipretide, sold as Forzinity, for Barth syndrome in patients weighing at least 30 kg, based on improved knee-extension strength and conditional on a confirmatory trial (FDA, 2025).

Mouse studies

In the 2015 discovery paper, MOTS-c treatment in mice prevented age-dependent and diet-induced insulin resistance and obesity (Lee et al., 2015). Reynolds and colleagues (2021) showed that MOTS-c rises in mouse muscle with exercise and that giving old mice MOTS-c late in life increased their physical capacity; the authors declared commercial interests linked to a company developing MOTS-c analogues.

Human measurements

Human MOTS-c data measure the body's own peptide: Reynolds and colleagues sampled ten young men around exercise and found MOTS-c rose in blood and muscle afterwards; the men were not given MOTS-c. The cited studies do not establish clinical efficacy for administered native MOTS-c.

A lower cost per mg is a reason to pick the bigger vial of the compound you need, not a reason to swap one molecule for the other.

Both documents carry the footer "reference template for customer consultation purposes only": they are the manufacturer's reference reports, not tests of the vial you receive. The 0.1 point gap between the two purity figures says nothing about which compound is better.

One identity point on SS-31: the PDF prints the formula C34H56N10O6 and molecular weight 672.87 g/mol, but that formula calculates to about 701 g/mol, and PubChem lists elamipretide as C32H49N9O5 and 639.8 g/mol for the free base (no added salt). The formula and weight disagree with each other and with the reference identity, and no salt form is named to explain the gap, so the document does not establish the identity of the supplied material; obtain clarification and lot-linked evidence before relying on it. The SS-31 certificate of analysis guide covers the document line by line.

Both peptides ship from Australian stock with prices in A$ on the page: SS-31 at A$99.99 (10 mg) or A$189.99 (50 mg), supplier report batch SS-3-2026-242 at 99.1% by HPLC; MOTS-c at A$89.99 (10 mg) or A$189.99 (40 mg), batch MOTS-2026-274 at 99.2%. Each PDF is linked on its product page. For membrane and energy-production questions, open SS-31; for exercise-signalling and metabolism questions, open MOTS-c. Related reading: the MOTS-c benefits guide and the mitochondrial peptides guide.

Is SS-31 the same as elamipretide?

Yes. SS-31, elamipretide, MTP-131 and Bendavia name the same four-amino-acid peptide; Forzinity is the US brand approved for Barth syndrome in 2025. Research-grade SS-31 is not that medicine, and the supplier report's formula and weight do not match PubChem's entry or each other.

Is MOTS-c natural or synthetic?

MOTS-c occurs naturally, encoded in the mitochondrial 12S rRNA gene. The MOTS-c in a research vial is a synthetic copy of that 16-amino-acid sequence.

Which vial size has the lower unit price?

The larger vial of each: SS-31 50 mg at A$189.99 is A$3.80 per mg against A$10.00 for the 10 mg vial, and MOTS-c 40 mg at A$189.99 is A$4.75 per mg against A$9.00. Buy the 10 mg vial only if the work needs less.

Did the SS-31 human trials work?

The three trials summarised here missed their primary endpoints. Open-label follow-up in Barth syndrome and a knee-strength measure led to accelerated FDA approval in 2025, pending a confirmatory trial.

1. Birk AV et al. J Am Soc Nephrol (2013): SS-31 and cardiolipin in ischaemic kidney
2. Mitchell W et al. J Biol Chem (2020): SS-31 binds lipid bilayers
3. Butler J et al. J Card Fail (2020): PROGRESS-HF
4. Karaa A et al. Neurology (2023): MMPOWER-3
5. Thompson WR et al. Genet Med (2021): TAZPOWER
6. FDA press release, 19 September 2025: accelerated approval for Barth syndrome
7. Lee C et al. Cell Metab (2015): MOTS-c discovery paper
8. Kim KH et al. Cell Metab (2018): MOTS-c moves to the nucleus
9. Reynolds JC et al. Nat Commun (2021): MOTS-c and exercise
10. PubChem. Elamipretide, CID 11764719
11. PEPTALIAS SS-31 product page
12. PEPTALIAS MOTS-c product page
13. Supplier reference report for SS-31, batch SS-3-2026-242 (PDF)
14. Supplier reference report for MOTS-c, batch MOTS-2026-274 (PDF)