The main SS-31 news entering October 2026 is that Forzinity's follow-up trial has begun. It must check whether the early muscle-strength finding translates into everyday benefit. The trial concerns Barth syndrome, a rare inherited disorder affecting mitochondria, the parts of cells that make usable energy. New mouse and cell papers add research questions, not proof of broader benefits in people.
Changelog
As of September 30, 2026, the day this article was written, these were the key July–September developments.
September 17, 2026 — The Barth syndrome trial record lists recruitment underway. The 4TAZPower registry update lists an actual start of July 2 and a target of 48 participants. Treatment lasts 72 weeks. Its main measure combines walking, getting up and moving, and repeated sit-to-stand tests. There are no results posted yet.
September 17, 2026 — ReNEW continues with existing participants. The ReNEW eye-disease trial record lists 313 enrolled participants and the status “active, not recruiting.” ReNEW studies dry age-related macular degeneration, an eye disease that damages central vision. Its main measure tracks loss of light-sensing cells in the retina, the tissue at the back of the eye. Results are not posted.
August 31, 2026 — A fatty-liver paper added mouse findings. Researchers studied older female mice fed a fat- and sugar-rich diet. SS-31 was associated with less liver fat and changes in mitochondrial structure. These were animal findings, not a liver-treatment trial in people (Xiao et al., Physiological Research, 2026).
July 24, 2026 — A heart-cell paper examined radiation injury. Researchers tested rat-derived heart cells and human heart cells grown from stem cells in laboratory dishes. SS-31 reduced signs of senescence, a state in which cells stop dividing. Nobody received treatment in this study (Xie et al., Journal of Radiation Research, 2026).
July 8, 2026 — The first 4TAZPower participant had received treatment. Mighty Therapeutics announced the first participant was dosed. That announcement marks the follow-up study moving from a plan into treatment. It is a trial milestone, not a new benefit result.
What the SS-31 news means for Forzinity
SS-31, also called elamipretide, is a peptide, a short chain of amino acids, the building blocks of proteins. It contains four amino acids and binds cardiolipin, a fat that helps organize the inner mitochondrial membrane. That is its studied target; feeling less tired is a separate clinical question.
SS-31 is coming soon to Promise — add me to the list. Through Promise, SS-31 will be dispensed as a compounded medication, which is different from an FDA-approved product: the formulation Promise will offer is not FDA-approved. Forzinity is the manufactured elamipretide product with a narrow Barth syndrome label.
As of September 30, 2026, the day this article was written, DailyMed's current Forzinity label still says “Revised: 9/2025.” It covers improving muscle strength in adults and children with Barth syndrome weighing at least 30 kilograms, about 66 pounds.
The FDA's September 19, 2025 letter granted accelerated approval, a pathway allowing earlier access while another trial checks patient benefit. The Forzinity approval anniversary explains that history. This quarter's change is the follow-up trial getting underway; the label's indication remains narrow.
What 4TAZPower needs to answer
The original decision rested on knee-extensor strength, the force of the muscles that straighten the leg. The new trial asks whether treatment changes practical function, including walking and standing up.
Participants are assigned by chance to elamipretide or placebo, an inactive look-alike. Neither participants nor the people evaluating them know the assignment during the trial. That design helps distinguish a treatment effect from expectation, changing effort, or natural ups and downs.
The study includes males ages 5 to 55 with genetically confirmed Barth syndrome. Its 48-person enrollment figure is a target, not a count of people already treated. The FDA's ongoing accelerated-approval table lists the final confirmatory report due March 31, 2030. Starting recruitment does not mean the required benefit has been confirmed.
Other elamipretide studies remain separate
Primary mitochondrial myopathy means inherited muscle disease that disrupts cellular energy production. The MMPOWER-3 trial of 218 participants aged 16–75 did not improve walking distance or fatigue versus placebo after 24 weeks (Karaa et al., Neurology, 2023).
NuPOWER tested a narrower genetic group. Its registry record lists the trial as completed, with 102 participants and no posted results. “Completed” describes study activity; it does not tell us whether treatment helped.
The earlier 176-person ReCLAIM-2 eye trial missed its main outcomes for dim-light vision and the area of lost retinal tissue. Other retinal findings helped shape the next study (Ehlers et al., Ophthalmology Science, 2025). ReNEW's current record lists a main measurement at week 48 and treatment continuing for 96 weeks.
The SS-31 benefits guide covers the wider trial record. For this update, the distinction is straightforward: a study starting, continuing, or finishing is not the same as a positive result.
SS-31 and MOTS-c ask different questions
MOTS-c belongs in mitochondrial conversations, but it is a different peptide. It contains 16 amino acids and is studied as a signal through AMPK, the cell's fuel sensor. Its original treatment experiments used cells and mice (Lee et al., Cell Metabolism, 2015).
SS-31's membrane-binding mechanism and MOTS-c's signaling mechanism cannot substitute for each other's evidence. A Forzinity milestone does not establish a benefit for MOTS-c, or show that combining them helps. The SS-31 and MOTS-c comparison explains their separate evidence bases.
What a provider considers in October 2026
A clinical conversation starts with the goal and whether a study actually included people with that problem. It also covers kidney function, current medicines, allergy history, pregnancy or breastfeeding, and how side effects would be followed.
Forzinity's label reports local injection reactions in all 12 participants during elamipretide treatment, compared with eight during placebo treatment. It also warns about serious allergic reactions. Those findings belong to the manufactured product; the SS-31 side-effects guide explains the limits when considering a compounded prescription.
A licensed provider may still prescribe a compounded formulation; that decision is between the patient and the doctor. At Promise, a licensed provider reviews every SS-31 request and may prescribe or decline on medical eligibility; not everyone qualifies.
What to watch next
The next meaningful changes would be published trial results, a completed confirmatory report, or a revised label. ReNEW's registry estimates its main study completion in August 2027; that is an estimate, not a promised results date. For anyone following SS-31, the useful question remains whether a new finding changes an outcome people can feel or measure in daily life.
