As of September 2026, the FDA has given elamipretide, also called SS-31, accelerated approval for Barth syndrome, a rare inherited disease. The approval rests on a trial of 12 patients, and a confirming trial is still required. Trial results for other conditions are mixed or failed. The approval covers Forzinity, the maker's product. A vial labeled SS-31 from another source is outside it, and you cannot see what it holds.
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What is SS-31?
SS-31 is another name for elamipretide, a small lab-made peptide designed to gather inside mitochondria. Hazel Szeto discovered it at Weill Cornell Medicine in 2004, and Stealth BioTherapeutics developed it. In September 2025 the FDA gave it accelerated approval for Barth syndrome under the brand Forzinity, with a confirming trial still required.
Does SS-31 work?
For Barth syndrome, the FDA reviewed a trial of 12 patients and gave accelerated approval, on the condition that the maker runs a confirming trial. In primary mitochondrial myopathy, a broader condition, larger trials failed to meet their main goals, and it is not approved for that.
What we found. 3 completed randomized trials counted on the record. 3 human study rows listed below, and one of them is an open-label follow-up.
| Study | Tested in | Status | What it shows |
|---|---|---|---|
| TAZPOWER trial in Barth syndrome | People | Completed. Randomized, 12 patients. The basis for the accelerated approval | Improved strength in the muscles that straighten the knee, compared with placebo |
| TAZPOWER open-label extension, 168 weeks | People | Completed | Long-term follow-up reported that strength and function measures were sustained, with no new safety signals |
| MMPOWER-3 trial in primary mitochondrial myopathy | People | Completed. It did not meet its main goal | The six-minute walk test and the other main goals were not met |
Is SS-31 safe?
The record names no side effects. The one safety finding it holds comes from the long follow-up of the Barth syndrome trial, which reported no new safety signals. That trial had 12 patients. Outside Barth syndrome, the record says human evidence remains limited. All of this describes the maker's product, Forzinity. A vial sold under the name SS-31 is a separate matter.
Is SS-31 legal?
- United States
- FDA accelerated approval in September 2025 as Forzinity, for Barth syndrome in patients who weigh 30 kg or more. A confirming trial is still required.
- European Union
- No EMA marketing authorisation.
- Sport
- Not named on WADA's list. That is not clearance.
- Other uses
- Investigational and not approved for other conditions. The record notes a failed trial in primary mitochondrial myopathy.
Not medical advice. Approval and sport status as of . Medical disclaimer
What is in a vial sold as SS-31?
The accelerated approval covers Forzinity, the maker's product. This record holds no sign that SS-31 is sold outside pharmacies. If a vial labeled SS-31 reached you another way, that approval does not cover it, and the checklist lists what to ask the seller.
What don't we know?
- Whether the confirming trial will back the approval. It has not reported yet.
- Whether stronger knee muscles mean better function. Strength was a stand-in measure.
- Whether it helps outside Barth syndrome. Results there are mixed or failed.
- What is in any vial that did not come from a pharmacy.
The other side
Forzinity comes with a prescription and a doctor's care, and the FDA reviewed a randomized trial before granting the accelerated approval. The open questions are the confirming trial still to come, and any vial sold as SS-31 from another source.
What would change this record?
- Results from the confirming trial in Barth syndrome that the FDA requires. They would either back the current approval or undercut it.
Three questions to ask next
- What does 'research use only' actually mean?
- How can you tell if a peptide vendor is legitimate?
- How do you read a certificate of analysis?
Ask better questions.
More questions about SS-31
Is SS-31 the same as elamipretide?
- Yes. SS-31 is another name for elamipretide. The record also lists MTP-131 and Bendavia as names, and Forzinity as the brand given accelerated approval.
Is SS-31 approved by the FDA?
- Only as Forzinity, and with a condition. The FDA gave elamipretide accelerated approval in September 2025 for Barth syndrome, and the maker must still run a confirming trial. It is not approved for any other condition.
Did SS-31 fail any trials?
- Yes. The MMPOWER-3 trial in primary mitochondrial myopathy did not meet its main goal. The record says larger trials in that condition failed to meet their main goals.
Is SS-31 approved in Europe?
- Not by the EMA. The record shows no EMA marketing authorisation.
Is SS-31 banned in sport?
- It is not named on WADA's list. That is not clearance. If you compete, check the current List.
Record checked on . Each source shows the date it was checked.
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