MOTS-c vs SS-31: How Two Mitochondrial Peptides Compare

MOTS-c vs SS-31 is a comparison of two very different mitochondrial peptides. MOTS-c is a 16-amino-acid peptide made from mitochondrial DNA and studied, mostly in mice, as a metabolic signal. SS-31 (elamipretide) is a synthetic peptide that binds cardiolipin in the mitochondrial membrane, and it holds one narrow FDA approval, for Barth syndrome.

The MOTS-c vs SS-31 question usually comes from people reading about mitochondria and longevity. Both are short peptides, both are linked to mitochondria, and both get described as "mitochondrial peptides." That shared label hides how differently they work.

This guide compares their mechanisms, the evidence, their regulatory status and what that means in practice. Also searched as: mots c vs ss-31, motsc vs ss31, elamipretide vs mots-c, ss-31 peptide vs mots-c peptide, peptide mots-c vs ss 31.

MOTS-c vs SS-31 at a glance

A simple way to frame MOTS-c vs SS-31: MOTS-c is a messenger that mitochondria send out, while SS-31 is a drug sent in to shore up the mitochondrial membrane.

• MOTS-c is naturally produced by your own cells, coded in mitochondrial DNA, and studied as a signal that changes how cells handle energy.
• SS-31 is lab-designed, not found in the body, and built to target cardiolipin, a fat that holds the energy-making machinery in place.

What MOTS-c is: a mitochondrial-derived signal

MOTS-c stands for mitochondrial open reading frame of the 12S rRNA type-c. It was first described in 2015 as a 16-amino-acid peptide coded in the mitochondrial genome (Lee et al., 2015). In mice, its main target appeared to be skeletal muscle, where it acted on the folate cycle and led to AMPK activation, an energy-sensing switch. Treated mice were protected from diet-induced and age-related insulin resistance.

On the MOTS-c side of MOTS-c vs SS-31, later work found that under metabolic stress MOTS-c can move into the cell nucleus and influence gene expression (Kim et al., 2018). In humans, exercise raised natural MOTS-c levels in muscle and blood, and in older mice treatment was linked to better physical capacity (Reynolds et al., 2021).

You can read about the MOTS-c protocol at telos rx, and for more on the MOTS-c peptide itself, see our MOTS-c metabolic research overview and the guide to mitochondrial-derived peptides like MOTS-c and humanin.

What the SS-31 peptide is: a cardiolipin-targeting drug

The SS-31 peptide, drug name elamipretide, is a synthetic tetrapeptide, a chain of four amino acids. "SS" refers to Szeto-Schiller, the scientists behind the peptide family. It is small enough to enter cells and concentrates at the inner mitochondrial membrane.

Its target is cardiolipin, a phospholipid found almost only in that inner membrane. Cardiolipin helps form the cristae, the folds where energy is made, and organizes the respiratory complexes. When cardiolipin is damaged, energy production can suffer. SS-31 was developed as the first cardiolipin-protective compound (Szeto, 2014).

That design is why MOTS-c vs SS-31 is really signal versus structure. Our explainer on the SS-31 peptide (elamipretide) covers its background in more detail.

Mechanisms: how MOTS-c vs SS-31 work

The mechanism gap is the heart of MOTS-c vs SS-31. One changes the cell's metabolic program, the other props up the mitochondrial structure.

• Where they act. MOTS-c research focuses on skeletal muscle signalling and, under stress, the nucleus. SS-31 acts at the inner mitochondrial membrane.
• What they do. MOTS-c is linked to AMPK activation and insulin sensitivity in mice. SS-31 binds cardiolipin and, in lab studies, appears to stabilize cristae and reduce oxidative stress.
• Where they come from. MOTS-c is made by the body. SS-31 is made only in a lab.

Because of this, MOTS-c vs SS-31 is not a contest between two versions of one idea. They are two separate approaches that happen to share the word "mitochondrial."

The evidence for each

MOTS-c. Most data come from mice and cells. Human studies mostly measure natural MOTS-c levels, for example after exercise, rather than testing injected MOTS-c. There is no published controlled trial showing what injected MOTS-c does in people, and no established human dose.

SS-31. On human data, MOTS-c vs SS-31 tilts toward SS-31, which has been through formal clinical trials, mostly in rare mitochondrial diseases. The results are mixed:

• MMPOWER-3. In a phase 3, placebo-controlled trial in adults with primary mitochondrial myopathy, elamipretide did not meet its primary endpoints on the 6-minute walk test or fatigue score, though it was well tolerated (Karaa et al., 2023).
• TAZPOWER. In Barth syndrome, a 168-week open-label extension followed 10 patients, 8 of whom reached week 168. Injection-site reactions were the most common adverse events, and walking distance improved from extension baseline (Thompson et al., 2024). Open-label results without a control group are weaker evidence than a blinded trial.

No published trial has tested either peptide as an anti-aging therapy in healthy adults. That is an important shared limit in any MOTS-c vs SS-31 discussion.

MOTS-c vs SS-31 comparison table

Regulatory status: MOTS-c vs SS-31

On regulation, MOTS-c vs SS-31 is a real contrast. On September 19, 2025, the FDA granted accelerated approval to Forzinity (elamipretide) as the first treatment for Barth syndrome, in patients weighing at least 30 kg. The approval was based on improved knee extensor muscle strength, and FDA requires a randomized, placebo-controlled confirmatory trial. It is not approved for aging, energy or performance, and SS-31 sold online as "research use only" is not the approved product.

MOTS-c is not FDA-approved for any use. In July 2026, the FDA's Pharmacy Compounding Advisory Committee voted to recommend adding MOTS-c to the list of bulk substances that can be used in compounding, although FDA's briefing documents had recommended against it. The vote is advisory and non-binding, pending FDA rulemaking. On October 28, 2026, HHS announced an interim enforcement discretion policy that includes MOTS-c: HHS does not intend to take enforcement action against state-licensed pharmacies that compound single-ingredient MOTS-c for subcutaneous or intramuscular injection with a valid prescription, if strict sourcing, testing and reporting conditions are met. It is temporary while FDA decides through rulemaking, it is not FDA approval, and HHS can revisit it. Our PCAC vote explainer has the details, and the upcoming MOTS-c legal status guide will follow what happens next.

For tested athletes, USADA notes that MOTS-c is prohibited at all times under WADA S4 hormone and metabolic modulators, as an AMPK activator. If you compete under the WADA Code, check the current list and your federation before using SS-31 or any other mitochondrial peptides.

Does telos rx offer SS-31?

No. In the MOTS-c vs SS-31 choice, telos rx only offers one side: it does not offer SS-31 or elamipretide in any form. The approved product is a prescription drug for Barth syndrome, managed by specialists.

What telos rx does offer is compounded MOTS-c, prepared by a licensed US pharmacy as a subcutaneous injection. There is no oral or tablet MOTS-c. The dose and schedule are set by your provider, not by a chart.

Side effects and safety

For SS-31, the most common side effects in trials were injection-site reactions, mostly mild to moderate. For MOTS-c, human safety data are very limited. Theorised or reported effects include injection-site reactions, fatigue, headache, nausea and changes in blood sugar, which matters for anyone on diabetes medication. Neither should be used during pregnancy or breastfeeding. Grey-market "research use only" vials add risks of wrong identity, wrong strength and contamination.

How MOTS-c works at telos rx

1. Online intake. You share your health history, medications and goals.
2. Asynchronous provider review. A US-licensed provider reviews your answers. A prescription is required, and every plan is subject to medical approval by a licensed provider. Approval is not guaranteed.
3. Licensed pharmacy. If approved, a licensed US pharmacy compounds MOTS-c, with dosing set by your provider.
4. Ongoing care. Plans can be cancelled from your portal.

If you are also weighing NAD+, our MOTS-c vs NAD+ comparison covers that question, and mitochondrial biogenesis explained covers the role of exercise.

Frequently asked questions about MOTS-c vs SS-31

What is the difference in MOTS-c vs SS-31?

MOTS-c is a 16-amino-acid peptide encoded in mitochondrial DNA and studied as a metabolic signal, linked in mice to AMPK activation and insulin sensitivity. SS-31, also called elamipretide, is a synthetic four-amino-acid peptide that binds cardiolipin in the inner mitochondrial membrane. One sends signals, the other is designed to protect membrane structure.

Is MOTS-c vs SS-31 a question of which works better?

No head-to-head trial exists, and the two act in different ways, so there is no evidence-based way to rank them. SS-31 has more human trial data, mostly in rare mitochondrial diseases. MOTS-c has mostly mouse and cell data. A licensed provider can decide whether anything is appropriate for you.

What is the SS-31 peptide approved for?

Elamipretide, sold as Forzinity, received FDA accelerated approval in September 2025 to improve muscle strength in people with Barth syndrome who weigh at least 30 kg. It is not FDA-approved for aging, energy, performance or longevity, and FDA requires a confirmatory trial.

Is ss31 the same as elamipretide?

Yes. ss31, SS 31 and SS-31 are the research names for the peptide whose drug name is elamipretide. Products sold online as SS-31 are not the FDA-approved product and are not regulated in the same way.

Is MOTS-c FDA-approved?

No. MOTS-c is not FDA-approved for any use. In July 2026 an FDA advisory committee voted to recommend adding it to the list of bulk substances for compounding, but that vote is non-binding and FDA rulemaking is still pending. Since October 28, 2026, an interim HHS enforcement discretion policy covers single-ingredient MOTS-c injections under strict conditions; it is temporary and is not FDA approval.

Does telos rx offer SS-31?

No. telos rx does not offer SS-31 or elamipretide. telos rx offers compounded MOTS-c as a subcutaneous injection, subject to medical approval by a licensed provider after an online, asynchronous intake.

Can athletes use MOTS-c or SS-31?

MOTS-c is prohibited at all times under WADA S4 hormone and metabolic modulators, as an AMPK activator, so tested athletes should not use it. For SS-31, check the current WADA Prohibited List and your federation's rules before use.

This article is for general education and is not medical advice. MOTS-c is not FDA-approved for any use, and compounded MOTS-c has not been evaluated by the FDA for safety, effectiveness or quality. Elamipretide is FDA-approved only for Barth syndrome, and telos rx does not offer SS-31 or elamipretide. All prescriptions are subject to medical approval by a licensed provider; approval is not guaranteed. Individual experiences vary. telos rx is an online-first, asynchronous telehealth service, and medications are compounded by a licensed US pharmacy. MOTS-c is prohibited in sport under the WADA Prohibited List.