Most of what's written about SS-31 online is about muscle, fatigue and "mitochondrial ageing". But the largest active trial programme for this peptide isn't aimed at any of those things — it's aimed at the back of the eye. If you're doing SS-31 research in 2026, the most informative story is a phase 2 trial in dry age-related macular degeneration that missed both of its primary endpoints and still produced a two-trial phase 3 programme. Understanding how that happened tells you more about the state of the evidence than any dosing forum ever will.

What is SS-31 (elamipretide), in one paragraph

SS-31 is a four–amino acid peptide, developed clinically as elamipretide by Stealth BioTherapeutics. It concentrates in the inner mitochondrial membrane and binds cardiolipin, a phospholipid that helps hold the electron transport chain in working shape. The theory is that stabilising cardiolipin improves mitochondrial structure and ATP output in tissues that are metabolically expensive — heart, skeletal muscle, and, relevantly here, retinal photoreceptors and retinal pigment epithelium. You can read our compound overview at /peptides/ss-31.

Regulatory reality check first: on 19 September 2025 the US FDA granted accelerated approval to elamipretide as Forzinity for Barth syndrome in patients weighing at least 30 kg, after an earlier complete response letter. That is an ultra-rare disease indication in a few dozen patients worldwide. Separately, its phase 3 in primary mitochondrial myopathy missed both of its endpoints. Neither result says anything about general wellness use, and elamipretide is not on the ARTG in Australia.

The dry AMD trial that missed — and what it found anyway

ReCLAIM-2 was a randomised, double-masked, placebo-controlled phase 2 trial in people aged 55 and over with dry AMD and non-central geographic atrophy (GA). Participants self-administered 40 mg of elamipretide subcutaneously, daily, for 48 weeks.

It had two co-primary endpoints: change in low-luminance best-corrected visual acuity, and change in the square-root-transformed area of geographic atrophy. It missed both. Under conventional reading, that's a negative trial.

What the investigators reported as secondary findings was a different kind of measurement. On spectral-domain OCT, they mapped the ellipsoid zone — the imaging band that corresponds to photoreceptor inner-segment mitochondria. Elamipretide was associated with a 43% reduction in the progression of total ellipsoid zone attenuation and a 47% reduction in partial attenuation versus placebo at week 48. A secondary visual measure also favoured treatment: 14.6% of treated participants gained at least 10 letters of low-luminance acuity versus 2.1% on placebo.

Say the obvious thing plainly: these are secondary outcomes from a single phase 2 trial that failed its primaries. They are hypothesis-generating, not confirmatory, and they have not been replicated. A 43% slowing of an imaging signal is not a demonstrated 43% preservation of anyone's sight.

Why the endpoint change matters more than the number

The reason the programme survived is regulatory, not promotional. In 2023 the FDA confirmed total ellipsoid zone attenuation as an approvable primary endpoint in dry AMD studies — on the logic that photoreceptor loss precedes and predicts the vision loss that follows. That single decision converted elamipretide's best-looking secondary measure into a legitimate primary endpoint for the next stage.

So the phase 3 programme — ReNEW (NCT06373731, ~360 participants) and its companion ReGAIN, both sponsored by Stealth BioTherapeutics, a real and listed company — is testing rate of change in the macular area of photoreceptor loss by SD-OCT and EZ mapping at week 48. In its April 2026 pipeline update the company said ReNEW remains on track and is expected to read out in late 2027, and that FDA guidance supports the potential for a single trial to serve as an approval basis. The same update described a phase 1 of bevemipretide eye drops completing enrolment, with phase 2 planned for late 2026 — an attempt to get the chemistry to the retina without a daily injection.

That's the honest framing for SS-31 in the eye: a well-designed, properly powered test of a plausible idea that has not yet succeeded on a clinical outcome anyone can see.

Is SS-31 legal in Australia, and what does GA treatment look like here?

Elamipretide is not registered with the TGA and is not on the ARTG. It has no Australian approved indication for Barth syndrome, mitochondrial myopathy, dry AMD or anything else. In practice it sits in the same bucket as most research peptides covered across /peptides: a prescription-only substance with no local marketing authorisation, accessible to individual patients only through pathways such as the Special Access Scheme or Authorised Prescriber, at a treating specialist's initiative — not something an individual sources for themselves. Material sold direct to consumers as "SS-31" is not the clinical product and carries no identity, purity or sterility assurance.

The Australian angle here is genuinely interesting, though, because geographic atrophy is one of the few areas where the local regulator moved early. In January 2025 the TGA approved pegcetacoplan (Syfovre) for GA secondary to AMD — Australia was the first country outside the United States to do so, based on the OAKS and DERBY phase 3 trials. So Australians with GA already have an approved, intravitreally injected, complement-pathway option.

Elamipretide, if ReNEW succeeds, would be something different: a daily subcutaneous injection aimed at photoreceptor mitochondria rather than the complement cascade. Whether Australian patients would tolerate a needle every day for an imaging-defined benefit is a question nobody has data on yet — and it only becomes a question at all if the phase 3 reads out positive in late 2027.

What this changes for how you read SS-31 claims

Three things worth carrying forward:

  • The approved indication is tiny. Accelerated approval in Barth syndrome is real, but it's an ultra-rare disease pathway with a confirmatory obligation still outstanding. It is not evidence for broad use.
  • The eye data are structural, not functional. Every strong number in the dry AMD story comes from OCT imaging, not from patients reading more letters on a chart in a primary analysis.
  • Failure is informative. A compound that missed in mitochondrial myopathy and missed both primaries in dry AMD is not a compound with a reliable across-the-board effect. It may be a compound with a narrow, tissue-specific one. That's the hypothesis on test.

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FAQ

What is SS-31 (elamipretide) used for?

Its only approval anywhere is a US accelerated approval (September 2025, as Forzinity) to improve muscle strength in Barth syndrome in patients weighing at least 30 kg. Every other use — mitochondrial myopathy, dry AMD, ageing — remains investigational or has failed its trials.

Does SS-31 work for macular degeneration?

Not proven. The phase 2 ReCLAIM-2 trial missed both primary endpoints, though it reported a 43% slowing of ellipsoid zone attenuation — an OCT imaging measure of photoreceptor loss — as a secondary finding. Two phase 3 trials are now testing that measure directly.

Is SS-31 legal in Australia?

Elamipretide is not on the ARTG and has no TGA-approved indication. It is a prescription-only substance with no local marketing authorisation; consumer-sold "SS-31" is not the clinical product.

When will the SS-31 dry AMD phase 3 results be released?

Stealth BioTherapeutics said in its April 2026 update that the phase 3 ReNEW trial is expected to read out in late 2027, with a second trial, ReGAIN, running alongside it.

Sources

Not medical advice. SS-31 (elamipretide) holds a US accelerated approval for Barth syndrome only and is not registered on the ARTG in Australia; all other uses discussed here are investigational. retatrutide.net.au is independent and does not sell or supply any compound.