mots-c vs ss-31

updated October 25, 2026

mots-c (tier B) vs ss-31 (tier A): what each is, why each got its grade, half-life and source counts side by side.

mots-c · tier B

mitochondrial peptide your body makes during exercise. restores metabolic health in mice. never given to a person in a trial.

tier rationale

B-tier because the preclinical evidence is genuinely novel and interesting (mitochondrial-encoded peptide, exercise-induced, age-declining, aging-reversing in mice), but parent-molecule human results have not read out. Not C-tier because the mechanism is well-characterized and the animal data is extensive. Not A-tier because the jump from mouse to human requires completed clinical testing. MOTS-c sits in an unusual category: exceptional biology, and a therapeutic record that has not begun.

ss-31 · tier A

the first mitochondria-targeted peptide drug. FDA-approved september 2025. for Barth syndrome, studied for heart failure.

tier rationale

A-tier because SS-31 now has FDA approval (September 2025) for a specific rare disease, plus substantial phase 2/3 clinical trial data across multiple indications. Not S-tier because the approved indication is extremely narrow (Barth syndrome, <1,000 US patients) and the broader phase 3 programs in more common conditions (heart failure, mitochondrial myopathy) have been mixed. Comparable in structure to sermorelin's tier placement: FDA approval for a narrow indication with widespread off-label interest. If heart failure or aging trials read out positively in future years, moves to S.

at a glance

reptides grades the research record and cites the literature behind every call. research reference only; not medical advice.