What Is Ss 31?

Overview

SS-31 (elamipretide) is a synthetic, aromatic-cationic tetrapeptide belonging to the Szeto-Schiller (SS) family of mitochondria-targeted peptides. Its sequence — D-Arg-Dmt-Lys-Phe-NH₂ — alternates cationic residues (D-Arg, Lys) with aromatic residues (Dmt, Phe), an architectural pattern that confers selective, high-affinity binding to cardiolipin (CL) on the inner mitochondrial membrane (IMM).[1][2]

Discovery: SS-31 was identified serendipitously by Dr. Hazel Szeto (Weill Cornell Medical College) and Dr. Peter Schiller (Montreal IRCM) during research into opioid receptor agonists. It was derived from SS-02 ([Dmt¹]DALDA), a synthetic opioid peptide analog, but engineered to completely eliminate opioid receptor activity while retaining the aromatic-cationic motif required for mitochondrial targeting.[1]

Key distinguishing features: (1) Concentrates 5,000-fold in the IMM via cardiolipin binding; (2) Uptake is membrane-potential-independent (unlike MitoQ, which requires intact electrochemical gradient); (3) Has no effect on healthy mitochondria — improves bioenergetics only in aged/dysfunctional mitochondria; (4) Small, water-soluble, crosses the blood-brain barrier.[2][4]

Regulatory milestone: On September 19, 2025, the FDA granted Accelerated Approval to Forzinity™ (elamipretide) for Barth syndrome — a rare genetic disorder caused by TAFAZZIN gene mutations leading to cardiolipin deficiency. This made SS-31 the first drug ever authorized by the FDA specifically for Barth syndrome, and one of the first mitochondrially-targeted drugs to receive FDA approval for any indication.[3]

Compared to MOTS-c — another mitochondria-targeted research compound — SS-31 acts upstream at the level of cardiolipin and the electron transport chain itself, rather than via nuclear gene regulation.[1]