SLU-PP-332: The Exercise Mimetic Research Update

Key Takeaways

In 2026 the laboratory that created SLU-PP-332 published a new paper. Its purpose was to introduce a successor compound, and in explaining why a successor was needed, the authors wrote that SLU-PP-332 "improves aerobic performance in mice but lacks oral bioavailability."

That sentence is the most useful thing anyone considering this compound can read, and it comes from the people who know it best. SLU-PP-332 is sold online in oral form as an "exercise mimetic." Its inventors needed to build a different molecule to get an oral one.

PubMed indexes ten papers that name SLU-PP-332. This article reads all ten: four animal studies that made its reputation, one cell study using human tissue, one paper on its successor, one chemistry paper, two anti-doping papers and one systematic review. None is a human trial.

What an ERR Agonist Is

Skeletal muscle adapts to aerobic training by building mitochondria and shifting toward fibres that burn fat efficiently. A family of nuclear receptors — the estrogen-related receptors, ERRα, ERRβ and ERRγ — sits near the top of that programme, switching on genes for mitochondrial biogenesis, oxidative phosphorylation, fatty acid oxidation and the Krebs cycle.

The name misleads. ERRs resemble the oestrogen receptor in structure but do not bind oestrogen. They are "orphan" receptors: no natural hormone that activates them has been identified.

Genetic evidence had long suggested that activating ERRs should mimic some of the effects of training. The obstacle was chemistry. Agonists for ERRβ and ERRγ existed, but designing one that activated ERRα had proved difficult, and few compounds were usable in a living animal at all. SLU-PP-332 was the solution: a pan-agonist of all three receptors, with the highest potency at ERRα, and — in its authors' words — "sufficient pharmacokinetic properties to be used as an in vivo chemical tool."

Note the phrase. A chemical tool is built to ask a question in a laboratory. It is not a drug candidate, and it is certainly not a supplement. It is also not a peptide, despite being sold on peptide sites: it is a small synthetic molecule.

Study 1 — Endurance (2023)

The founding paper did three things. In a skeletal muscle cell line, the compound increased mitochondrial function and cellular respiration. In mice, it increased type IIa oxidative muscle fibres and enhanced exercise endurance. And it induced a gene programme characteristic of acute aerobic exercise that was specific to ERRα — with ERRα activation shown to be critical for the endurance gain.

That last point is what made the paper matter scientifically. It was a proof that ERRα could be drugged and that doing so reproduced part of an exercise response.

What it cannot tell you: anything about humans, about doses, about duration beyond the experiment, or about what happens to an animal that is also training.

Study 2 — Metabolic Syndrome (2024)

The second paper moved to disease models: diet-induced obese mice and ob/ob mice, which are genetically obese. Treatment increased whole-body energy expenditure and fatty acid oxidation, reduced fat mass accumulation, reduced obesity and improved insulin sensitivity.

This is the source of the compound's reputation as a fat-loss agent. It is a result in obese mice.

Study 3 — Heart Failure (2024)

Published in Circulation, this is the most rigorous paper of the set. Using two structurally distinct agonists — SLU-PP-332 and SLU-PP-915 — in a pressure-overload model of heart failure, the group found that both significantly improved ejection fraction, reduced fibrosis and increased survival, without affecting cardiac hypertrophy.

The mechanism work is thorough: RNA sequencing, metabolomics, and genetic dependency experiments showing that ERRγ — not ERRα — was the main mediator of the cardiac effect. Metabolic profiles in fatty acid and oxidative phosphorylation pathways were substantially normalised.

Two things follow. A pan-agonist does different things through different subtypes in different organs. And the fact that two unrelated chemical structures produced the same result is good evidence the effect runs through the receptor rather than through some off-target quirk of one molecule.

Study 4 — The Ageing Kidney (2023)

ERR levels fall in ageing human and mouse kidneys and are preserved in mice on lifelong caloric restriction. Treating 21-month-old mice with SLU-PP-332 for eight weeks reversed age-related increases in albuminuria, podocyte loss, mitochondrial dysfunction and inflammatory cytokines. The authors described ERRs as caloric-restriction mimetics.

Eight weeks in old mice is the longest exposure in this literature that reports functional outcomes. It is also the entire long-term safety record.

Study 5 — The Only Human Tissue (2025)

Twenty women undergoing hip replacement were divided into physically active and inactive groups. Muscle biopsies from inactive women showed lower SIRT1, PGC-1α and ERRα and higher NOX4. When myoblasts cultured from those biopsies were treated with SLU-PP-332, the pattern moved in the opposite direction.

It is easy to see how this becomes "tested in humans" in a product description. It was tested on cells in a dish that came from humans. Nobody swallowed or injected anything.

The 2026 Papers — Where the Story Turned

The successor. The developers characterised SLU-PP-915, a chemically distinct pan-agonist that is orally bioavailable. Given by injection it matched SLU-PP-332 on distance and duration; given orally it kept comparable efficacy when adjusted for exposure. Both compounds induced Ddit4 — a gene switched on by acute aerobic exercise — to levels matching or exceeding treadmill running, depending on the muscle. And SLU-PP-915 synergised with exercise training, further raising Ddit4 and mitochondrial gene expression.

That synergy result deserves attention. The best outcome in the paper came from the compound plus training, not the compound instead of it.

The chemistry. A structure–activity study mapped which parts of the SLU-PP-332 scaffold control potency and selectivity. It called the compound a "widely used chemical probe" and reported analogues with better solubility, ligand efficiency or metabolic stability. Researchers are already improving on it.

The anti-doping work. Two laboratories independently mapped how human liver enzymes break the compound down — one identifying nine metabolites, the other twenty-two — so that its use can be detected in athletes. One of the papers states plainly that the World Anti-Doping Agency prohibits exercise mimetics and metabolic modulators.

The systematic review. A review covering 2020–2024 found the evidence base to be experimental studies in animals and cell models. It reported no evident toxicity in those models and concluded that clinical trials are needed to confirm efficacy and safety in humans.

What Is Missing

"No evident toxicity" in short mouse experiments is not a safety profile. Nuclear receptors control broad gene programmes. An earlier nuclear-receptor "exercise mimetic", the PPARδ agonist GW501516, was abandoned in development after long-term animal studies raised cancer concerns — the kind of finding that experiments lasting weeks cannot produce. A pan-agonist that acts through ERRα in muscle and ERRγ in heart is, by design, doing several things at once.

Why "Exercise Mimetic" Oversells It

The term is the authors' own and it is used carefully in the papers: the compound induces an acute aerobic exercise gene programme. That is a transcriptional signature in mouse muscle. It is not the cardiovascular, skeletal, neurological and psychological package that training delivers to a person.

The same label is attached to MOTS-c, which reaches a similar destination through AMPK rather than nuclear receptors, and whose evidence is at a comparable stage — see Humanin and MOTS-c: Mitochondrial-Derived Peptides Explained. Two different molecules carrying one marketing phrase is a reason to be more sceptical of the phrase, not less.

What to Watch For

Three developments would change this assessment:

1. A registered Phase 1 trial of SLU-PP-915 or a later analogue, with published pharmacokinetics.
2. Long-duration animal toxicology — months, not weeks, including cardiac and cancer endpoints.
3. A human indication. The preclinical data point most strongly at heart failure and metabolic disease, where a drug would be developed under supervision and with a comparator.

Until then the evidence-based route to activating ERRs is the one the compound was designed to copy. If you want that built into a plan with honest grades on every layer, it is Layer 0 of the Advanced Mitochondrial Stack.

Frequently Asked Questions

Is SLU-PP-332 a peptide? No. It is a synthetic small molecule. It is often sold alongside peptides, which is where the confusion comes from.

Does it affect oestrogen? There is no evidence that it does. Estrogen-related receptors are named for structural similarity and do not bind oestrogen.

Has it been tested in humans? No published study has administered it to a person. One 2025 study treated muscle cells cultured from human biopsies.

Do oral capsules work? The developers report that the compound lacks oral bioavailability, and their mouse studies used injection. No human absorption data exist either way.

Is it banned in sport? Substances without regulatory approval for human use are prohibited at all times, exercise mimetics and metabolic modulators are prohibited, and detection methods were published in 2026.

What is SLU-PP-915? A chemically distinct, orally active ERR pan-agonist from the same programme. It is equally unstudied in humans.

What does our profile grade it? Evidence grade D and safety tier D — see the SLU-PP-332 profile.

Related Research

• SLU-PP-332
• Humanin and MOTS-c: Mitochondrial-Derived Peptides Explained
• The Advanced Mitochondrial Stack: Mito-Peptides + Cofactors
• MOTS-c: Exercise in a Vial
• The Mito-Peptide Advanced Protocol