The most-quoted line about SS-31 (elamipretide) online is that it "recharges mitochondria". The most important line in 2026 is much narrower: the compound now has one US approval in an ultra-rare genetic disease, one failed phase 3 in mitochondrial myopathy, and one large phase 3 in eye disease whose result is expected this year. If you want to know what SS-31 research actually says — rather than what a supplier's landing page says — the eye trial is where the next real answer comes from.

This piece looks at why elamipretide's decisive evidence is now an OCT scan of the retina, not a strength test, and what that means for Australian readers asking "what is SS-31" and "is SS-31 legal in Australia". Background on the compound sits on our SS-31 profile.

What SS-31 is, in one paragraph

Elamipretide (SS-31) is a synthetic four–amino-acid peptide that concentrates in the inner mitochondrial membrane and binds reversibly to cardiolipin, the phospholipid that helps organise the electron transport chain. The pitch is that stabilising cardiolipin improves the efficiency of energy production in cells where mitochondria are structurally damaged. It is given as a daily subcutaneous injection in the trials that matter — not a weekly or occasional dose.

On 19 September 2025 the FDA granted accelerated approval to elamipretide as Forzinity for improving muscle strength in adults and children with Barth syndrome weighing at least 30 kg, following an earlier complete response letter. That is the entire approved use worldwide. Accelerated approval also means a confirmatory trial is still owed; the sponsor presented that study's design at the Euromit mitochondrial meeting in mid-2026.

Why the eye became the main event

Elamipretide's phase 3 in primary mitochondrial myopathy missed both of its primary endpoints — a result worth remembering whenever "SS-31 for fatigue and muscle function" is asserted as settled. The programme with the largest patient numbers now is dry age-related macular degeneration with geographic atrophy (GA), where photoreceptors sit among the most metabolically demanding cells in the body.

The phase 2 ReCLAIM-2 trial (176 participants; 117 on 40 mg daily subcutaneous elamipretide, 59 on placebo, 48 weeks) did not meet either co-primary endpoint — low-luminance best-corrected visual acuity or GA lesion area. Its interest lies in secondary structural outcomes: a reported 43% reduction in progression of total ellipsoid zone (EZ) attenuation versus placebo (P = 0.003) and 47% for partial EZ attenuation (P = 0.004), with EZ change correlating with low-luminance acuity change. Those are secondary findings from a trial that failed its primaries — hypothesis-generating, not proof.

The regulatory bet inside the phase 3

The phase 3 ReNEW study (NCT06373731, sponsored by Stealth BioTherapeutics — a real, listed developer, worth checking given the fictional demonstration records that circulate on trial registries) takes that secondary signal and makes it the primary endpoint: rate of change in the macular area of photoreceptor loss measured by SD-OCT and ellipsoid zone mapping, over 96 weeks, randomised 2:1 to 40 mg daily subcutaneous elamipretide or placebo, with a companion study, ReGAIN.

That is an unusual bet. Approved GA therapies were built on lesion-area endpoints; elamipretide is being tested against a photoreceptor-integrity measure that is closer to the mechanism but has a shorter regulatory track record. The company has said FDA feedback supports the possibility of a single trial supporting approval — that statement comes from a company release, not a published regulatory decision, and should be read that way. Enrolment passed the 50% mark of a roughly 360-participant target in March 2025, and data have been guided for 2026. As of writing, no topline result has been published.

What the human "anti-ageing" evidence actually is

Ask what SS-31 does for healthy ageing muscle and you get one small, well-conducted randomised study, not a literature. Thirty-nine adults aged 60–85 with poor baseline mitochondrial function received a single two-hour infusion of elamipretide or placebo. Mitochondrial capacity (ATPmax) rose immediately after infusion versus placebo. By day 7 the difference was gone — consistent with the drug's blood half-life. Resting mitochondrial coupling did not change, and fatigue resistance did not improve.

That is a genuine finding: pharmacological reversal of a mitochondrial deficit measured in vivo. It is also a single dose, a single site, an intravenous route, unreplicated at scale, and with no functional benefit demonstrated. Anyone extrapolating from it to a subcutaneous "longevity" course is doing the extrapolating, not the researchers.

Is SS-31 legal in Australia? The regulatory position

Elamipretide is not on the Australian Register of Therapeutic Goods. The US Forzinity approval carries no automatic weight here — a sponsor must apply to the TGA separately, and there is no public Australian submission. Barth syndrome affects a very small number of people, so an Australian filing on that indication alone is far from guaranteed; a positive dry AMD result would be the first thing to give a sponsor a commercial reason to seek broader market approvals.

In the meantime, elamipretide would be handled as an unapproved therapeutic good. Injectable therapeutic peptides in Australia are generally prescription-only (Schedule 4) under the Poisons Standard, and unapproved products can only be lawfully supplied through pathways such as the Special Access Scheme or Authorised Prescriber, with a valid prescription. The TGA has published specific guidance warning importers, compounders and suppliers about their obligations for unapproved peptide products, including that "research use only" labelling does not exempt anyone from the Therapeutic Goods Act. Material sold online as research peptide is not quality-assured, is not the clinical formulation, and is not covered by any Australian approval.

There is also a practical point for the eye indication: a daily subcutaneous injection over 96 weeks is a heavier ask than the intravitreal dosing schedules used by approved GA drugs. If ReNEW reads out positive, that trade-off — systemic daily injection versus in-eye injection — becomes a real clinical conversation rather than a hypothetical.

What to watch next

  1. ReNEW topline. Does the EZ endpoint hold up when it is the primary, in a bigger, longer trial?
  2. Whether structure translates to sight. Slowing photoreceptor loss only matters if patients see better or lose vision more slowly.
  3. The Barth confirmatory study. Accelerated approval is provisional; the confirmatory trial determines whether it stays.
  4. Any Australian filing. Nothing is in motion publicly; a positive AMD result is the plausible trigger.

More compound profiles are in our peptides section, and you can join the free updates list for plain-English coverage of readouts like ReNEW as they land.

FAQ

What is SS-31 (elamipretide)?

SS-31, or elamipretide, is a synthetic tetrapeptide that binds cardiolipin in the inner mitochondrial membrane, with the aim of improving mitochondrial energy production. Its only approval anywhere is US accelerated approval as Forzinity for muscle strength in Barth syndrome patients weighing at least 30 kg.

Is SS-31 legal in Australia?

Elamipretide is not on the ARTG, so it is an unapproved therapeutic good in Australia. Injectable peptides are generally Schedule 4 prescription-only, and unapproved products can only be supplied lawfully via pathways such as the Special Access Scheme or Authorised Prescriber with a valid prescription.

Does SS-31 work for anti-ageing or muscle performance?

There is no human evidence supporting that use. The main ageing study was a single infusion in 39 older adults: mitochondrial capacity rose immediately but was back to baseline by day 7, with no improvement in fatigue resistance. A phase 3 in primary mitochondrial myopathy missed both primary endpoints.

When will the elamipretide dry AMD trial results be released?

Data from the phase 3 ReNEW study in dry AMD with geographic atrophy have been guided for 2026, following a phase 2 that missed both co-primary endpoints but showed secondary signals on ellipsoid zone preservation. No topline result had been published as of September 2026.

Sources

This article is information only, not medical advice. Elamipretide holds US accelerated approval for Barth syndrome only and is not on the ARTG — it remains investigational for every other use. retatrutide.net.au is independent and does not sell or source any compound.