SS-31 (Elamipretide): Forzinity Approval and Research

Abstract still life: four tiny beads on a fine thread weaving through the folds of a pleated paper membrane — **SS-31.** Illustration, not a product photo.

Research compound. Not approved by FDA Philippines for human use unless stated. Nothing here is a dosing recommendation or medical advice.

What it is

SS-31 is a small synthetic peptide of four amino acids, one of the Szeto-Schiller (SS) series of mitochondria-targeted peptides. Its drug name is elamipretide, and it has also carried the development codes MTP-131 and Bendavia. The developer is Stealth BioTherapeutics.

It is the only compound on this site's longevity list that is now an approved medicine. On 19 September 2025 the US FDA granted it accelerated approval under the brand name Forzinity for Barth syndrome, an ultra-rare inherited disorder of cardiolipin metabolism that affects males and causes muscle weakness and heart disease. It was the first treatment approved specifically for that disease.

How it works

Mitochondria have an inner membrane folded into ridges called cristae, where the machinery that makes ATP sits. That membrane is rich in cardiolipin, a lipid that holds the energy-producing protein complexes in place. When cardiolipin is damaged or abnormal, cristae lose their shape and energy output falls.

SS-31 is drawn to the inner mitochondrial membrane and binds cardiolipin. In a 2013 rat kidney study, Birk and colleagues showed that this binding blocked the cytochrome c peroxidase activity that oxidises cardiolipin during ischaemia. Treated rats kept intact cristae, avoided mitochondrial swelling and recovered ATP faster after blood flow returned. The FDA label describes the drug the same way: a mitochondrial cardiolipin binder.

That mechanism is why the ageing community is interested. Declining mitochondrial function is a feature of ageing tissue, and SS-31 is one of the few compounds with a well-defined mitochondrial target. The approval, however, is for a genetic disease, not for ageing.

What the research found

Barth syndrome (the approval)

TAZPOWER (Thompson and colleagues, 2021) enrolled 12 males aged 12 to 35 with Barth syndrome. In the 12-week randomised crossover part, elamipretide did not beat placebo on the six-minute walk test or the other primary endpoint. In the open-label extension, after 36 weeks on the drug, the eight who completed it walked 95.9 metres farther than at the start and knee strength rose by 56 newtons.
FDA's decision rested on knee extensor strength. The Drug Trials Snapshot states plainly that strength gains were not seen during the randomised period but were seen during the long extension, which ran to 192 weeks. FDA judged the strength effect reasonably likely to predict benefit and required a confirmatory randomised, placebo-controlled trial.

Other human trials

MMPOWER-3 (Karaa and colleagues, 2023) randomised 218 adults with primary mitochondrial myopathy to elamipretide or placebo for six months. It missed both primary endpoints, the six-minute walk test and fatigue. A post-hoc look suggested benefit in people with nuclear DNA mutations, which a follow-up trial is testing.
A 2025 review lists phase 3 work in dry age-related macular degeneration, and earlier study in Leber's hereditary optic neuropathy.

Animal studies

Most of the ageing interest comes from animal work, including the rat kidney ischaemia study above. No human trial has tested SS-31 as a longevity or general anti-ageing treatment.

Side effects reported in studies

Injection-site reactions dominate. In the Barth syndrome trial every person on the drug had local reactions, with redness in all, pain in 75% and hardening of the skin in 66.7%, according to FDA. Two people in TAZPOWER stopped during the extension because of injection-site reactions. The label also warns of allergic reactions, some serious enough to need emergency care, which can appear from minutes to months after starting. MMPOWER-3 reported the drug as well tolerated over six months.

SS-31 vs other mitochondrial compounds

Compound	Target	Status
SS-31 (elamipretide)	Cardiolipin, inner membrane	FDA accelerated approval, Barth syndrome
MOTS-c	Folate cycle, AMPK	Mouse data; analogue phase 1
NAD+	Energy and DNA-repair coenzyme	Small human trials of precursors
Epitalon	Telomerase, pineal gland	Small reports from one group

Status in the Philippines

The FDA approval applies in the US. Stealth licensed elamipretide to Pharmanovia in 2023 to commercialise it in Europe and other territories, but we found no registration of Forzinity with FDA Philippines. SS-31 sold in the Philippines comes through research-chemical suppliers and is not the approved, sterile-manufactured product. For Barth syndrome, prescribing belongs with a licensed Philippine physician. SS-31 is not a controlled substance under RA 9165.

Storage

The approved product is stored refrigerated at 2 to 8°C and must not be frozen. Once a vial is opened, the label allows refrigeration or room temperature and says to discard it after 8 days. Philippine room temperature often runs above the label's 20 to 25°C, so a fridge is the safer choice, especially during brownouts. See the beginner guide for handling basics.

Doses used in published research

What investigators actually administered, as reported in the cited study. This is a record of the literature, not a recommendation.

Study	Population	Regimen
Thompson et al., Genet Med 2021 (TAZPOWER)	12 males aged 12 to 35 with Barth syndrome	40 mg subcutaneous once daily; 12-week crossover vs placebo, then 36-week open-label extension
FDA label, Forzinity (2025)	Adults and children with Barth syndrome weighing at least 30 kg	40 mg subcutaneous once daily (approved dose; prescribing belongs with a licensed physician)

Common questions

Is SS-31 FDA approved?

Yes, for one use. On 19 September 2025 the FDA granted accelerated approval to elamipretide, sold as Forzinity, to improve muscle strength in people with Barth syndrome weighing at least 30 kg. It is not approved for ageing, heart health or any other condition.

What does accelerated approval mean for Forzinity?

The approval rests on improved knee extensor muscle strength, which FDA judged reasonably likely to predict real benefit such as walking farther. The company must run a confirmatory randomised, placebo-controlled trial, and the approval can be withdrawn if that trial fails.

Did SS-31 work in mitochondrial myopathy?

Not in the main trial. MMPOWER-3 gave 218 adults with primary mitochondrial myopathy elamipretide or placebo for six months, and neither the six-minute walk test nor fatigue scores improved significantly.

Is SS-31 available in the Philippines?

Forzinity is not registered with FDA Philippines as far as we could find. SS-31 sold locally comes through research-chemical channels and is not the approved product.