SS-31 vs MOTS-c: What’s the Difference?

SS-31 and MOTS-c are often mentioned together because both are connected with mitochondrial research. That can make them sound like two versions of the same thing. They aren’t.

Although both have been studied in relation to mitochondrial function, they come from different places, and researchers are interested in them for different reasons. SS-31 is a synthetic peptide designed to work directly within mitochondria, while MOTS-c is a naturally occurring mitochondrial-derived peptide that has mainly been studied for its role in cell signalling and metabolism.

So, when looking at SS-31 vs MOTS-c, the main difference is not simply what each peptide is supposed to do. It is also where the research currently stands.

What is SS-31?

SS-31 is also known as elamipretide, MTP-131, and, more recently, by its approved brand name, Forzinity. It is a small synthetic peptide made up of four amino acids.

One of the main reasons SS-31 has attracted attention is its ability to reach the mitochondria and interact with cardiolipin. Cardiolipin is a type of lipid found in the inner mitochondrial membrane. It helps maintain the structure of this membrane and supports some of the machinery involved in energy production.

Research has suggested that SS-31 can bind to cardiolipin and may help maintain the structure and function of mitochondria. Studies have looked at things such as mitochondrial energy production, oxidative stress and the condition of the mitochondrial membrane.

There is also a fairly large amount of human research on SS-31. It has been investigated in conditions including primary mitochondrial myopathy, Barth syndrome, heart failure and age-related macular degeneration. The results have varied, which is important to remember when reading about the peptide.

For example, some clinical studies failed to meet their main endpoints, showing that promising laboratory results do not automatically translate into the same results in people.

SS-31 has also moved beyond the purely experimental stage in one specific area. In September 2025, the US FDA granted accelerated approval to elamipretide, under the brand name Forzinity, for improving muscle strength in adults and children weighing at least 30 kg with Barth syndrome. The approval is specific to that condition, and the FDA requires a post-approval study to confirm the clinical benefit.

That does not mean SS-31 is an approved treatment for every condition it has been studied in. Its regulatory status is specific to the approved indication.

What is MOTS-c?

MOTS-c is quite different in origin.

MOTS-c stands for mitochondrial open reading frame of the 12S rRNA-c. It is one of the mitochondrial-derived peptides, sometimes called MDPs. Unlike SS-31, MOTS-c is produced naturally in the body.

A lot of interest in MOTS-c comes from its possible role as a signalling molecule. Researchers have studied its links with metabolism, glucose handling, cellular stress and exercise-related changes.

Some laboratory research has linked MOTS-c to pathways involved in energy metabolism, including AMPK-related signalling. Other work has looked at how MOTS-c may respond to stress and how it might influence activity in the nucleus. There is also research looking at its relationship with ageing and metabolic conditions.

Human studies do exist, but there is an important distinction here. Much of the human research has measured naturally occurring MOTS-c in blood or tissue rather than giving people MOTS-c as a treatment.

For example, researchers have measured circulating MOTS-c in people following different types of exercise. Other observational studies have looked at MOTS-c levels in people with particular health conditions. One registered study involving 120 people with type 2 diabetes and coronary artery disease was designed to measure MOTS-c levels and look at their association with cardiovascular outcomes. It was an observational study rather than a trial giving participants MOTS-c.

This distinction is easy to miss when reading online. Finding MOTS-c in a human study does not necessarily mean that it has been tested as a treatment in those people.

SS-31 vs MOTS-c: how are they different?

The simplest way to look at the difference is to consider what each peptide is being studied for.

SS-31 was designed as a synthetic mitochondria-targeting peptide. Much of the research focuses on its interaction with cardiolipin and the inner mitochondrial membrane. Researchers are interested in whether SS-31 can help support mitochondrial structure and energy-related processes.

MOTS-c, on the other hand, is a naturally occurring mitochondrial-derived peptide. Research has focused more on signalling, metabolism and the way cells respond to stress.

So while both are connected with mitochondria, they are not interchangeable peptides. They have different structures, origins and proposed mechanisms.

There is another major difference: the amount and type of clinical evidence available.

SS-31 has undergone multiple human clinical trials, including randomised controlled trials. Some results have been encouraging, while others have not shown a clear benefit on their main measures. Its development has also reached regulatory approval for a specific rare disease in the US.

MOTS-c remains much more heavily associated with laboratory and preclinical research. Human studies have helped researchers understand naturally occurring MOTS-c and its associations with different conditions, but that is not the same as having strong clinical evidence for administering MOTS-c as a treatment.

Why the research is often compared

The comparison primarily revolves around mitochondria.

Both peptides appear in discussions about mitochondrial health, energy production and cellular stress. That shared connection makes them easy to put in the same conversation.

But looking somewhat closer shows that researchers are asking different questions about them.

With SS-31, the focus is largely on whether targeting the mitochondrial membrane can help protect or improve mitochondrial function. With MOTS-c, researchers are looking at how a peptide produced by mitochondria itself may communicate with other parts of the cell and influence metabolism.

This complexity is also why it is difficult to say that one is simply “better” than the other. There has not been a direct head-to-head clinical trial comparing SS-31 and MOTS-c, and the research around the two peptides is at different stages.

The evidence regarding the effectiveness of SS-31 and MOTS-c is the most important aspect to consider.

When reading about SS-31 or MOTS-c online, it is useful to separate laboratory findings from human clinical results.

A result in cells or animals can help understand how a peptide works, but it doesn’t prove the same effect will occur in people. The same applies to studies that simply measure naturally occurring levels of a peptide.

SS-31 has a longer clinical development history, but even its human research has yielded mixed findings depending on the condition and outcome being studied. MOTS-c has intriguing lab and observational research, but we need much more to understand its potential as a human intervention.

In short, SS-31 and MOTS-c may sit under the same broad mitochondrial research umbrella, but they tell two quite different research stories. SS-31 is a synthetic peptide that targets the mitochondrial membrane and has progressed into clinical development and, for Barth syndrome, regulatory approval in the US. MOTS-c is a naturally occurring mitochondrial-derived peptide that remains a major area of preclinical and early-stage research.

For anyone comparing the two, looking at the type of evidence behind each peptide is probably more useful than focusing only on the fact that both are described as “mitochondrial peptides”.