SS-31

Few peptides are aimed as precisely at a single cell compartment as SS-31, also listed in the literature as elamipretide or bendavia. The four-residue molecule (D-Arg-Dmt-Lys-Phe-NH2) carries modified amino acids that give it an unusual pharmacokinetic profile: it collects in mitochondria at roughly a thousand times the concentration found in the cytoplasm. It was developed in the laboratory of Hazel Szeto at Cornell University.

The target is cardiolipin, a phospholipid found almost only in the inner mitochondrial membrane and without which the respiratory chain and ATP synthase cannot work cleanly. SS-31 binds to it with high affinity and, in preclinical models, keeps the membrane architecture stable. In the studies this translates into preserved respiratory capacity and less oxidative stress.

Findings from animal models and cell systems:

• In isolated mitochondria, less ROS formation, less swelling and less release of cytochrome c; in an ex vivo heart model, stronger contractile force.
• In a rat model of kidney ischemia, inhibited peroxidase activity of cytochrome c, protected cristae and a quicker ATP recovery after reperfusion.
• In aged mice, a single dose brought ATP production in skeletal muscle up to the level of young animals within an hour; after eight days, endurance performance rose.
• Further models cover ischemia-reperfusion damage in the heart, age-related mitochondrial dysfunction and neurodegenerative questions.

Unlike most research peptides, SS-31 has gone through phase II and phase III clinical trials for various indications, which makes the data base unusually broad.

In the studies SS-31 counts as well tolerated, and thanks to the clinical programs it is documented better than many other peptides. What has been noticed:

• Local reactions: In the clinical trials, reactions at the injection site were the most frequently recorded observation: redness, pressure or a transient irritation.
• Circulation and head: Isolated reports mention a feeling of warmth, slight dizziness or headache shortly after dosing.
• Accumulation as a double-edged property: The massive concentration in mitochondria is mechanistically intended. What a sustained exposure of the organelle means for humans in the long run has not yet been fully described.
• Gap outside the clinic: Robust data on long-term use outside controlled trials are missing; the safety picture rests on trial results and animal models.

This summary is no substitute for medical advice.

• The mitochondrial-targeted compound SS-31 re-energizes ischemic mitochondria by interacting with cardiolipin - establishes the high-affinity cardiolipin binding and the protection of cristae in the rat kidney ischemia model.
• Mitochondrial-targeted peptide rapidly improves mitochondrial energetics and skeletal muscle performance in aged mice - documents the rapid normalization of muscle ATP production and the endurance gain in aged mice.
• First-in-class cardiolipin-protective compound as a therapeutic agent to restore mitochondrial bioenergetics - review of the discovery, mechanism of action and clinical development of the peptide.