Elamipretide (SS-31)

Elamipretide, developed originally as SS-31, is a four-amino-acid peptide designed to accumulate inside mitochondria — hundreds of times more concentrated there than in the surrounding cytoplasm — and to bind cardiolipin, the phospholipid that anchors and stabilises the proteins of the electron transport chain. The logic is unusually tidy for a peptide: if energy production fails because the inner membrane's organisation breaks down, then a molecule that holds that organisation together should help. In cells and animals it does. In patients with mitochondrial disease, the results have been far harder to demonstrate, which makes it one of the most instructive compounds in this library about the gap between mechanism and outcome.

Elamipretide is a cell-permeable tetrapeptide with alternating aromatic and basic residues that give it a strong affinity for cardiolipin on the inner mitochondrial membrane. By stabilising cardiolipin–protein interactions it is thought to improve electron transport efficiency, restore ATP production and reduce the leakage of reactive oxygen species from complex I. It does not act on a receptor; it works on membrane architecture, which is part of why its effects are easier to see in damaged cells than in whole patients.

• Improved mitochondrial bioenergetics in preclinical models of oxidative stress
• Reduced ischaemia-reperfusion injury in cardiac and renal animal models
• Improved several secondary functional measures in a small Barth syndrome trial
• Reached late-stage human testing, which very few research peptides ever do

Reported benefits describe what the published literature and user reports suggest — not a promise of outcome for any individual.

Elamipretide has been tested in primary mitochondrial myopathy, Barth syndrome, ophthalmic mitochondrial disease, heart failure and progeria. The pattern has been consistent: encouraging preclinical and early-phase signals followed by pivotal trials that missed their primary endpoints. The largest primary mitochondrial myopathy trial did not meet its primary endpoint, and a heart failure study failed as well. In a small Barth syndrome trial, several secondary measures improved, but the trial was not powered to demonstrate changes in the disease's clinical course, and regulators have not approved the drug. For a reader, elamipretide is a compound of genuine scientific interest with no established human benefit — the opposite of what its grey-market listings imply.

• Injection-site reactions, the most common finding in trials
• Headache
• Nausea
• Transient blood-pressure or heart-rate changes during infusion in some studies

Not approved anywhere. Although the trial safety record is relatively bland, that record comes from closely monitored patients, and the studies were designed to look for short-term harm rather than long-term effects of chronic mitochondrial modulation. Its use as a longevity or performance aid is entirely unsupported by human evidence.

Not part of any studied combination. Layering it with other mitochondrial or metabolic compounds would combine unapproved interventions with no way to attribute effects or harms.