Mitochondria and cellular energy

SS-31

Approved on eight patients, and sold as a different salt

7 sections

Top of article
What it actually is
What it is supposed to do
What people take it for
The dose question
How to check you have the right molecule
What people get wrong
What is known about harm

What circulates: 0.1 to 40 mg a day under the skin
What was studied: 40 mg a day under the skin
The gap: Convention runs below the studied dose
How long it lasts: This entry publishes no figure for how long it lasts in the body. What it reports instead is how fast the effect came and went: after a single two hour infusion into a vein, a laboratory measure of energy production rose immediately afterwards and the difference was gone by day 7.

What it actually is

SS-31 is a chain of four amino acids, the small building blocks proteins are made from, and it collects inside mitochondria, the compartments in a cell that turn food into usable energy. It has four names and they are all the same molecule: elamipretide, MTP-131 and Bendavia are SS-31. In September 2025 it became an approved medicine in the United States, sold as Forzinity, for Barth syndrome, a rare inherited heart and muscle disease. That approval covers that one disease and nothing else.

What it is supposed to do

The story changed once. The 2004 founding paper from the Cornell laboratory that made it calls this class antioxidants, and it is where the line about concentrating a thousandfold in the inner membrane of mitochondria comes from. Ten years on the same laboratory restated it as binding to cardiolipin, a fat found almost nowhere except that inner membrane, where it holds the energy machinery in shape. Both accounts come from the same laboratory, and the vendor pages I read all trace back to the second one.

What people take it for

People buy it for energy, for recovery and for ageing. The only human study I found in people without a diagnosed disease gave a single infusion into a vein to 39 adults aged 60 to 85 picked for poorly working mitochondria: a laboratory measure of energy production rose straight after, the difference was gone a week later, and how tired the muscle got did not change. That study was funded by the drug's sponsor. Every positive human result in this entry is in patients with a diagnosed disease.

The dose question

What circulates: 0.1 to 40 mg a day under the skin
What was studied: 40 mg a day under the skin; Five published trials and the approved label, every one in people with a diagnosed disease

Below the studied dose

The headline number is real for once. Forty milligrams a day under the skin is the dose in five published trials and on the approved label, and every one of those was in people with a diagnosed disease. Where the convention departs, it departs downward. I could find no human trial reporting a clinical result at 2, 5 or 10 mg a day, and the label mentions that lower range only as a span over which blood levels were measured, so somebody has given 2 mg a day and published nothing but the blood levels. I looked for a study in any species testing the three times weekly schedule several pages give, and could not find one.

Reported because it is what people use. Nothing here recommends any amount.

How long it lasts

This entry publishes no figure for how long it lasts in the body. What it reports instead is how fast the effect came and went: after a single two hour infusion into a vein, a laboratory measure of energy production rose immediately afterwards and the difference was gone by day 7.

Route studied

Injected under the skin once a day at 40 mg in the later trials, and infused into a vein by body weight in the earlier ones. The mouse ageing result used an injection into the abdominal cavity, a route people do not use.

Route used

Injected under the skin from grey market vials, daily to three times a week, sometimes in cycles that one vendor page itself admits are not scientifically established.

How to check you have the right molecule

Ask what salt the certificate of analysis names. That is the one place the four names come apart. The approved injection is elamipretide hydrochloride, and four of the six bulk powder listings in the American drug regulator's directory are elamipretide acetate, which that regulator named in a warning letter of 8 December 2025 as ineligible for use in pharmacy compounding. On the molecule itself the public chemistry database holds one record covering all four names, CID 11764719, CAS 736992-21-5. A clean report still only describes the sample that was tested, and I could find no independent laboratory analysis of a grey market vial: no purity, content, sterility or bacterial contamination result.

Walked through on two real certificates in how to read a certificate of analysis.

What people get wrong

Treating the approval as though it covers what is in the vial. What was approved is one salt, elamipretide hydrochloride, and a salt is the same active molecule paired with a partner that makes it a stable powder, which a regulator treats as its own product. Most bulk powder sold to compounding pharmacies is the acetate, and eighty days after the approval the American drug regulator wrote to a Florida distributor naming elamipretide (SS-31) acetate as ineligible for compounding. In that listing the active ingredient named in the filing was something called peptide B27PD. I could find no published comparison of the two salts in people, and nothing describing what peptide B27PD is.

What is known about harm

Injection site reactions are close to universal. In the 12 patient Barth syndrome trial at 40 mg a day under the skin, redness occurred in every patient on the drug against 25 percent on the dummy injection, pain in 75 against 42, hardening of the tissue in 67 against 17, itching in 67 against 17. Two thirds of the dummy injections produced a local reaction too, which is the number that keeps the first one honest. Two warnings sit on the approved label: serious allergic reactions needing emergency treatment, and benzyl alcohol in the vial, which causes a life threatening condition in newborns and is why the product is not approved for them. The label also states the drug was not studied in patients aged 65 and over, the population most of the grey market interest comes from.

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Everything on this page is a summary. The citations, the studies and the reasoning live in the full entry.

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