SS-31: Cardiolipin Binding and the Elamipretide Clinical Programme

Targeting by design

The Szeto-Schiller peptides use an alternating aromatic-cationic motif that drives accumulation in the inner mitochondrial membrane. Uptake is not dependent on membrane potential, which distinguishes it from cationic mitochondrial targeting strategies that fail precisely when the membrane is depolarised and the target most needs intervention.

That property is the design's strongest feature: a compound intended to act on dysfunctional mitochondria should not require healthy mitochondria to reach them.

Cardiolipin as the binding target

Cardiolipin is a dimeric phospholipid nearly exclusive to the inner mitochondrial membrane, where it organises respiratory supercomplexes and anchors cytochrome c. Cardiolipin peroxidation disrupts supercomplex organisation, impairs electron transport and releases cytochrome c, which initiates apoptosis.

SS-31 binds cardiolipin and is reported to protect its structure, preserving supercomplex organisation and ATP production. Tung et al. (Int J Mol Sci, 2025) review structure, mechanism and therapeutic potential and are the best current single source.

Hao et al. (Cell Commun Signal, 2024) report on ALCAT1-mediated abnormal cardiolipin remodelling in podocytes in diabetic kidney disease, which approaches the same target from the pathology side.

Clinical evidence, including where it did not succeed

Karaa et al. (Neurology, 2023) report MMPOWER-3, a randomised clinical trial of elamipretide in primary mitochondrial myopathy. This is the most rigorous evidence available for any compound in this catalogue, and reading the actual outcome rather than a summary of it is essential: the trial's primary endpoints were not all met, and that result is as informative as the mechanism is elegant.

A well-characterised mechanism and a sound targeting strategy do not guarantee clinical benefit on a chosen endpoint in a chosen population. This compound is the clearest illustration of that gap in the catalogue.

Preclinical work continues across systems: Zhao et al. (J Neuroinflammation, 2019) on mitochondrial dysfunction and memory impairment in mice, Zheng et al. (Biomed Pharmacother, 2025) on ferroptosis in hypoxia-reoxygenation cardiomyocytes, and several reviews on age-related macular degeneration, where mitochondrial dysfunction in retinal pigment epithelium is the rationale.