What is the difference between SS-31 and Elamipretide?

It is the same substance under two names. SS-31 is the research designation of the cardiolipin-binding peptide, Elamipretide is the clinical development name.

NuPOWER is a Phase 3 study of Elamipretide in primary mitochondrial disease. The overall results and a subgroup signal regarding the POLG1 group will be presented at Euromit 2026.

Does this mean SS-31 is approved?

No. SS-31 is a research peptide. The Euromit announcement concerns the presentation of study data and study designs at a conference, not a new approval.

What does genotype-dependent response mean?

It means that the underlying genetic cause, here POLG1 mutations, could co-determine the extent of the treatment response. This is an indication from a subgroup that has to be tested in confirmatory studies.

How reliable is this information?

It comes from a press release announcing upcoming conference presentations. A reliable assessment is only possible after the full data presentation and peer review.

SS-31 (Elamipretide): NuPOWER Phase 3 Data and Genotype-Dependent Response in POLG at Euromit 2026

Important note: This article is intended solely for scientific information and research purposes. SS-31 is a research peptide and is not intended for human consumption. No therapeutic recommendations are given.

TL;DR: What was announced

Date: May 26, 2026, press release from Stealth BioTherapeutics. What: At Euromit 2026 (May 31 to June 4, Angers, France), new Elamipretide data will be presented, including the NuPOWER Phase 3 results in primary mitochondrial disease with indications of a genotype-dependent response in the POLG1 subgroup. Also: the design of a confirmatory study in Barth syndrome as well as preclinical POLG models. Context: This is an announcement of upcoming conference presentations, not a full data release. SS-31 is the cardiolipin-binding research twin of Elamipretide.

SS-31longevity

Mitochondria-targeted tetrapeptide (Elamipretide) that stabilizes cardiolipin and prevents ROS formation at the source.

SS-31 and Elamipretide: the same mechanism, two names

SS-31 (also known as Elamipretide) is a small, mitochondria-targeted peptide. It binds to cardiolipin in the inner mitochondrial membrane, a phospholipid that is crucial for organizing the respiratory chain and for the efficiency of energy production. Through this cardiolipin binding, SS-31 is thought to stabilize the membrane structure and improve mitochondrial function in stressed tissue. It is precisely this mechanism that makes the peptide interesting for research into mitochondrial diseases.

What will be shown at Euromit 2026

According to Stealth BioTherapeutics, the presentations will take place on June 4, 2026, in a session on therapeutic and diagnostic developments. Three topics are at the center:

NuPOWER Phase 3: overall results of a Phase 3 study of Elamipretide in primary mitochondrial disease, presented among other things in a poster on the overall results.
Genotype-dependent response: an emerging signal that the underlying mutation could co-determine the treatment response, with a focus on the POLG1 subgroup.
Barth syndrome: the design of a confirmatory study as well as preclinical POLG models as the next steps of the pipeline.

Important: announcement, not full publication

This is the announcement of upcoming conference presentations, not a complete, peer-reviewed data release. Terms such as "emerging indications" and "supports the potential" come from the release and are deliberately phrased with caution. Reliable conclusions are only possible after the full data presentation and peer review.

Why the POLG1 subgroup is interesting

POLG encodes the catalytic subunit of the mitochondrial DNA polymerase gamma. Mutations in POLG are among the most common causes of primary mitochondrial disease. A "genotype-dependent response" would mean that patients with a particular genetic cause respond more strongly or more weakly to a cardiolipin-targeted strategy than others.

From a research perspective, this is an important point: mitochondrial diseases are genetically very heterogeneous, and studies in mixed populations can easily dilute effects. If a subgroup (here POLG1) turns out to be particularly responsive, this provides a hypothesis for more targeted confirmatory studies. This is exactly the path Stealth outlines with the announced confirmatory Barth design and the preclinical POLG models.

Placing it within the SS-31 pipeline

Where NuPOWER stands

NuPOWER addresses primary mitochondrial disease as an indication. This is to be distinguished from other Elamipretide programs that have been reported on separately, for example in Barth syndrome and in ophthalmology. The POLG1 findings announced here are a new subgroup signal from the primary mitochondrial disease study and are not identical to those earlier readouts.

For research on SS-31 as a longevity- and mitochondria-relevant peptide, the Euromit 2026 announcement is notable above all because it links the cardiolipin mechanism to a genetically defined patient group. This is the transition from "does it work" to "in whom does it work," which is necessary for any targeted further development.