SS-31

Elamipretide (Szeto-Schiller Peptide 31)

Evidence & Status

  • FDA Approved
  • Strong Human Evidence
  • Strong

At a Glance

Elamipretide (SS-31) is FDA-approved as FORZINITY for improving muscle strength in adult and pediatric patients (≥30 kg) with Barth syndrome. Its use for other mitochondrial conditions, aging, heart failure, and neurological indications remains investigational.

Plain English

SS-31, also called elamipretide, is FDA-approved as FORZINITY for improving muscle strength in adult and pediatric patients who weigh at least 30 kg and have Barth syndrome. That approval applies only to this labeled Barth syndrome population. Researchers continue to study elamipretide for other mitochondrial conditions, aging, heart failure, and neurological uses, but those uses are not FDA-approved.

Overview

A mitochondria-targeted tetrapeptide developed by Hazel Szeto that selectively concentrates in the inner mitochondrial membrane. Binds cardiolipin — a phospholipid critical for cristae architecture and electron transport chain efficiency — stabilizing mitochondrial structure, reducing ROS generation, and improving ATP production. FDA approved in September 2025 as FORZINITY (elamipretide) for improving muscle strength in adult and pediatric patients (≥30 kg) with Barth syndrome, a rare mitochondrial cardiomyopathy, under accelerated approval (NDA 215244). Under ongoing investigation for broader aging, heart failure, renal protection, and neurological indications.

Research Summary

SS-31 (Elamipretide) has strong mechanistic preclinical evidence for mitochondrial cardiolipin stabilization and ATP restoration across cardiac, renal, and neurological animal models. Phase 2/3 randomized clinical trials in Barth syndrome established safety and early efficacy signals; the TAZPOWER trial (NCT03098797, completed October 2021) did not meet its primary endpoint (6-minute walk test) but demonstrated significant improvements in secondary functional and quality-of-life outcomes. FDA granted accelerated approval in September 2025 for FORZINITY (elamipretide) for improving muscle strength in adult and pediatric patients (≥30 kg) with Barth syndrome — the first FDA-approved treatment for this condition (NDA 215244). Additional Phase III trials include NCT05162768 (completed December 2024) and NCT06373731 (active not recruiting as of August 2026, estimated completion September 2027). The previously stored PubMed identifiers (PMID 29668615 and PMID 31154001) were confirmed as entity mismatches and have been removed. The 168-week open-label extension of TAZPOWER (Thompson et al., 2024) provides long-term safety and efficacy data for elamipretide in Barth syndrome; as an open-label extension, these results are not randomized controlled evidence. Evidence for indications beyond Barth syndrome — including broader aging, heart failure, renal protection, and neurological disease — remains investigational and should not be characterized as established or approved.

Research Areas

  • Mitochondrial bioenergetics
  • Cardioprotection & heart failure
  • Longevity & aging
  • Renal protection
  • Neurodegeneration
  • Barth syndrome

Safety & Risks

Serious Risks

  • FORZINITY is approved under accelerated approval; continued approval may be contingent on post-approval clinical trial verification of clinical benefit
  • Insufficient long-term human safety data outside the Barth syndrome clinical trial context; long-term systemic effects in other indications are unknown

Reported Side Effects

  • Injection site reactions (mild)
  • Transient nausea (uncommon)
  • Fatigue (rare)
United States
FDA-approved as FORZINITY (elamipretide) injection for improving muscle strength in adult and pediatric patients (≥30 kg) with Barth syndrome, under accelerated approval (NDA 215244, September 2025). Other mitochondrial disease applications and broader aging, heart failure, and neurological indications remain investigational.
United Kingdom
Research only
Australia
Research only
Canada
Research only

Citations & Sources