SS-31 and MOTS-c are compared because both are sold as "mitochondrial peptides". On the record they could hardly be further apart. SS-31 is elamipretide, a drug with an FDA label, a fixed 40 mg daily dose and more than twenty registered trials. MOTS-c is a peptide found inside the mitochondrial genome in 2015, studied in mice and cells, with no human dose published anywhere. This page sets the two side by side from the label, the registry and the papers read on 2026-10-28, and converts the figures in circulation into molecules and syringe units. It reports; it recommends no dose for anyone.
Each has its own page with the full sources: SS-31 dosage and MOTS-c dosage. Mixing figures for SS-31 are on SS-31 reconstitution.
Side by side
| SS-31 (elamipretide) | MOTS-c | |
|---|---|---|
| What it is | Synthetic tetrapeptide, 639.8 g/mol | 16-amino-acid peptide encoded in mitochondrial 12S rRNA, 2,174.6 g/mol |
| Where it acts | Binds cardiolipin, inner mitochondrial membrane (label) | Inhibits the folate cycle, activates AMPK; skeletal muscle in mice (Lee 2015) |
| Approval | Forzinity, accelerated approval 2025-09-19, Barth syndrome | None |
| Labelled dose | 40 mg SC once daily; 20 mg in severe renal impairment | — |
| Human trial dose | 40 mg SC daily in every registered programme read (TAZPOWER, MMPOWER-3) | None published; one 2026 registration states no dose |
| Animal doses on record | — (approved drug) | 15 mg/kg/day in mice; 5 mg/kg in rats |
| Registry records (2026-10-28) | 21 | 5 |
| Vendor figures | 5–10 mg a day | 5–10 mg a week, split over 2–3 injections |
The vendor figure for SS-31 is the one place the two records look alike, and it is the figure with no trial behind it: every elamipretide trial read for this site's SS-31 page used 40 mg, four to eight times the vendor range.
Two different jobs inside the mitochondrion
Elamipretide's mechanism is stated on its label: it localises to the inner mitochondrial membrane, binds cardiolipin and "improves mitochondrial morphology and function". Its approval rests on muscle strength in Barth syndrome, a cardiolipin disorder, which is why the label limits it to that disease. MOTS-c works, in the discovery paper's description, more like a hormone: it is made from the mitochondria's own DNA, its primary target organ "appears to be the skeletal muscle", and its effects in mice ran through the folate cycle and AMPK, preventing diet-induced obesity and insulin resistance. One is a membrane-targeted drug, the other a signalling peptide; "mitochondrial" names where each comes from or goes, not a shared action.
Molecules, not milligrams
| Amount | Molecular weight | Micromoles |
|---|---|---|
| 40 mg elamipretide (label dose) | 639.8 | 62.5 |
| 10 mg elamipretide (top of vendor range) | 639.8 | 15.6 |
| 10 mg MOTS-c (top of vendor weekly range) | 2,174.6 | 4.6 |
| 5 mg MOTS-c | 2,174.6 | 2.3 |
Micromoles = mg ÷ molecular weight × 1,000, using PubChem's free-base weights; the label's 40 mg may be stated as the hydrochloride salt, which would lower the elamipretide row slightly. A milligram of MOTS-c holds about a third as many molecules as a milligram of elamipretide.
The amounts, as syringe units
Units on a U-100 syringe = milligrams ÷ concentration in mg/mL × 100.
| Amount | 5 mg/mL | 10 mg/mL | 50 mg/mL | 80 mg/mL (Forzinity) |
|---|---|---|---|---|
| 2.5 mg | 50 units | 25 | 5 | — |
| 5 mg | 100 | 50 | 10 | — |
| 10 mg | — | 100 | 20 | — |
| 40 mg (label, SS-31) | — | — | 80 | 50 |
5 mg/mL is a 10 mg vial with 2 mL of water (or 5 mg with 1 mL); 10 mg/mL a 10 mg vial with 1 mL; 50 mg/mL a 50 mg SS-31 vial with 1 mL. A dash marks a draw larger than one 100-unit syringe or a vial that cannot hold the amount. The SS-31 vial arithmetic and the MOTS-c calculator work any other vial and volume.
What is not established
Any human dose of MOTS-c: none published. Any use of elamipretide outside Barth syndrome: the label covers that one disease, and the larger mitochondrial-myopathy trial (MMPOWER-3) was terminated. The 5 to 10 mg SS-31 figures: no trial. Any study of the two together: none found. MOTS-c is also set against a small-molecule NNMT inhibitor on the page comparing it with 5-amino-1MQ. Medibact's MOTS-c guide covers that compound. Decisions about whether to use either belong with a clinician.