The mitochondrial-targeted compound SS-31 re-energizes ischemic mitochondria by interacting with cardiolipin
Birk AV, Liu S, Soong Y, Mills W, Singh P, Warren JD, Seshan SV, Pardee JD, +1 more
Journal of the American Society of Nephrology (2013)
Birk and Szeto demonstrated that SS-31 binds cardiolipin selectively on the inner mitochondrial membrane, inhibits cytochrome c peroxidase activity, preserves cristae structure during ischemia, and accelerates ATP recovery after renal reperfusion — the foundational mechanism paper for every subsequent SS-31 indication.
This 2013 JASN paper from Hazel Szeto's laboratory at Weill Cornell is the foundational mechanism paper for SS-31 (elamipretide) and the single most-cited primary publication in the molecule's literature. The investigators demonstrate that SS-31 — a tetrapeptide composed of D-Arg-dimethyl-Tyr-Lys-Phe-NH2 — binds with high affinity to cardiolipin, the anionic phospholipid that is essentially restricted to the inner mitochondrial membrane and that scaffolds the electron-transport-chain supercomplexes responsible for oxidative phosphorylation. The binding is selective: SS-31 does not interact significantly with other inner-membrane phospholipids. The functional consequences mapped in this paper are extensive. SS-31 inhibits cytochrome c peroxidase activity (the cardiolipin-peroxidising reaction that releases cytochrome c into cytoplasm and initiates apoptosis), preserves cristae structure during ischemic insult, prevents mitochondrial swelling on reperfusion, accelerates ATP recovery after the ischemic period, reduces tubular-cell apoptosis, preserves tubular-barrier integrity, and mitigates renal dysfunction in a rat ischemia-reperfusion-injury model. The paper established cardiolipin as a tractable therapeutic target and SS-31 as the first-in-class cardiolipin-protective compound — the framework that motivated the entire subsequent SS-31 development programme through MMPOWER-2 (Karaa 2018), MMPOWER-3 (Karaa 2023), and the Barth-syndrome programme that ultimately received FDA approval in 2025.
This is a preclinical mechanism paper, not a clinical trial. The kidney-ischemia-reperfusion model is informative for the principle that SS-31 protects mitochondria from oxidative injury but it does not establish efficacy in any chronic mitochondrial-disease indication — the indication where the most rigorous subsequent human trial was conducted (primary mitochondrial myopathy, MMPOWER-3) ultimately did not meet its primary endpoints. The cardiolipin-binding-and-electron-transport-protection mechanism remains widely accepted and has been refined by subsequent biophysical work (Mitchell 2020 on electrostatic membrane modulation) but the precise relationship between the mechanism and clinical efficacy across SS-31's many candidate indications is incompletely settled. Hazel Szeto is the inventor of SS-31 and has commercial interests through Stealth BioTherapeutics; the paper's conflict-of-interest disclosures are routine but the molecule's development arc has been led by a single laboratory and a single commercial sponsor. The 2013 framing — that SS-31 should re-energise any tissue with ischemic or chronic mitochondrial dysfunction — has not survived contact with clinical-trial data in heart failure or unselected primary mitochondrial myopathy.
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