TL;DR: SLU-PP-332 is not a peptide. It has no amino-acid backbone at all — it is a small synthetic molecule, roughly 290 Da, that activates the estrogen-related receptors (ERRα, ERRβ, ERRγ). In mice, it switches on an aerobic-exercise gene program: more oxidative muscle fibers, more fat burning, better endurance, less fat mass. Every one of those results comes from mouse studies. There is no human dosing data, no FDA approval, and no registered clinical trial.
The first thing to get right: it isn’t a peptide
Search volume for “SLU-PP-332 peptide” is climbing fast in Germany right now, and a fair number of research-chemical vendors list it right alongside actual peptides like BPC-157 or Ipamorelin. That label is wrong, and it isn’t a minor technicality.
A peptide is a chain of amino acids linked by peptide bonds — MOTS-c is 16 amino acids, SS-31 is four. SLU-PP-332 has none of that. It’s a small organic molecule with the formula C18H14N2O2, built around a hydrazide linkage connecting a hydroxybenzene ring to a naphthalene group. Chemically, it has more in common with a small-molecule drug like ibuprofen than with any peptide on this site. It doesn’t get broken down by peptidases the way a peptide does, it isn’t dosed by reconstituting a lyophilized vial the same way, and its pharmacology follows small-molecule rules: oral bioavailability, hepatic metabolism, and receptor binding kinetics rather than proteolytic degradation.
Why the confusion? Partly naming: the “SLU” prefix (Saint Louis University, where the compound was characterized) reads like a peptide code to anyone used to seeing CJC-1295 or GHK-Cu. Partly marketing: it gets sold in the same capsule and vial formats, on the same storefronts, next to genuine research peptides, so it inherits the category by association. Neither reason makes it one.
What it actually does: the ERR pathway
SLU-PP-332 is a pan-agonist of the estrogen-related receptors — ERRα, ERRβ, and ERRγ — a family of orphan nuclear receptors (no confirmed natural hormone binds them) that sit upstream of mitochondrial biogenesis and fatty-acid oxidation. ERRα in particular is a well-established co-regulator of PGC-1α, the transcriptional program that endurance training itself switches on in muscle.
In binding assays, SLU-PP-332 activates all three receptors with EC50 values of about 98 nM at ERRα, 230 nM at ERRβ, and 430 nM at ERRγ — meaning it’s most potent at ERRα, the subtype most tied to the aerobic-exercise gene program.
EC50 in nanomolar; lower means more potent activation. ERRα is the primary driver of the exercise-linked gene program.
By flipping on this receptor family pharmacologically, SLU-PP-332 mimics part of what a training block does biologically — hence “exercise mimetic” or, in the more breathless corners of the internet, “exercise in a pill.”
What the mouse data shows
The published effects are genuinely striking, and it’s worth being specific about them rather than hand-waving.
In the foundational 2023 characterization from the Burris lab at Saint Louis University (published in ACS Chemical Biology), SLU-PP-332 induced an ERRα-dependent acute aerobic-exercise gene program in mouse skeletal muscle, increased the proportion of oxidative (type IIa) muscle fibers, and enhanced treadmill exercise capacity. A follow-up 2024 paper in the Journal of Pharmacology and Experimental Therapeutics tested it in a diet-induced obesity model: over 28 days, control mice gained roughly 5 grams of fat mass while treated mice gained under half a gram, total body weight ran about 12% lower, and fasting insulin was reduced. Separate work reports roughly a 25% increase in fatty-acid oxidation in muscle cells treated with the compound.
That’s a compelling phenotype. It is also, without exception, a mouse phenotype.
That gap matters more here than it does for some other research compounds, because ERR agonism touches broad metabolic machinery. Mouse muscle physiology and human muscle physiology diverge in fiber-type composition, in relative reliance on ERRα versus other pathways, and in dose-scaling — none of which can be resolved by reading across from a mouse study, no matter how well designed. Until a controlled human trial exists, “exercise in a pill” is a hypothesis generated in mice, not a demonstrated human effect.
The research history so far
- 1
2014
The parent chemical scaffold is patented by Ligand Pharmaceuticals, developed in unrelated hematopoietic growth factor research — nothing to do with exercise yet.
- 2
2020
A medicinal chemistry paper converts a selective ERR-beta/gamma ligand into a pan-ERR agonist chemotype, laying the groundwork for the SLU-PP series.
- 3
2023
Billon et al. in ACS Chemical Biology first characterize SLU-PP-332 as an exercise mimetic: ERR-alpha-dependent gene program, oxidative fiber switching, enhanced endurance in mice.
- 4
2024
A follow-up paper in the Journal of Pharmacology and Experimental Therapeutics shows SLU-PP-332 blunts diet-induced fat-mass gain and improves insulin measures in obese mice.
- 5
2026
The International Journal of Biological Macromolecules publishes the first systematic structure-activity relationship (SAR) analysis of the scaffold, mapping which structural features drive potency, selectivity, and drug-like properties.
- 6
2026
Drug Testing and Analysis characterizes SLU-PP-332's in-vitro metabolites specifically for doping-control purposes, an early sign that anti-doping laboratories are building detection assays for this compound class.
That last entry is worth a single factual note and nothing more: it tells you analytical chemists are treating SLU-PP-332 as detectable and relevant enough to build assays for, not that this article is taking a position on competitive-sport rules. That’s a separate topic from what this compound is and what the science shows.
How it compares to genuine mitochondrial peptides
Because SLU-PP-332 gets marketed alongside mitochondria-focused peptides, the contrast is useful. MOTS-c is a 16-amino-acid peptide encoded in mitochondrial DNA that activates AMPK signaling and is itself studied as an exercise-responsive metabolic messenger — genuinely a peptide, working through a different pathway entirely. SS-31 is a synthetic four-amino-acid peptide that binds cardiolipin to stabilize the inner mitochondrial membrane, a structural rather than transcriptional mechanism. Humanin is another mitochondrial-derived peptide, studied for cytoprotective and longevity-adjacent signaling. Our mitochondrial peptides overview lays these out side by side.
SLU-PP-332 sits in the same conversation — mitochondrial function, exercise biology, metabolic health — but it gets there through nuclear-receptor transcriptional activation rather than any peptide mechanism. It’s a useful case study in why chemical class matters more than which shelf a compound sits on: two molecules can be discussed in the same breath and still belong to entirely different pharmacological categories, with different handling, different degradation behavior, and different evidence bases behind them. If you’re evaluating any research compound sold online, our guide to vetting a peptide vendor is a reasonable starting checklist, and “does the listing correctly identify what class of molecule this is” belongs near the top of it.
Where the science actually stands
Strip away the “exercise in a pill” framing and what’s left is a legitimate, still-early pharmacology story: a synthetic pan-ERR agonist that reproduces part of the aerobic-training transcriptional program in mouse muscle, with a 2026 SAR paper now mapping the chemistry systematically enough that better-optimized analogues are plausible. That’s real progress for a research tool compound. It is not evidence of a human performance or metabolic benefit, because that evidence doesn’t exist yet. The honest way to hold this one is: interesting mouse pharmacology, unbuilt human bridge.
Frequently asked questions
Is SLU-PP-332 a peptide?
No. It has no amino-acid chain — its formula is C18H14N2O2, a synthetic small molecule with a molecular weight around 290 Da. It gets called a peptide in search terms and some vendor listings because it’s discussed alongside genuine peptides for similar research goals, but chemically it belongs to an entirely different class: a nuclear-receptor agonist, not a peptide.
What does SLU-PP-332 actually do?
It activates the estrogen-related receptors ERRα, ERRβ, and ERRγ, nuclear receptors that sit upstream of mitochondrial biogenesis and fatty-acid oxidation. In mice, this switches on much of the gene program that endurance exercise itself activates in muscle, producing more oxidative fibers, greater fat oxidation, and improved treadmill endurance.
Has SLU-PP-332 been tested in humans?
Not that has been published. Every efficacy finding — fiber-type switching, fat-mass reduction, improved insulin measures, enhanced endurance — comes from mouse and cell-culture studies. There is no FDA approval for any indication, no publicly registered clinical trial, and no published human dosing or safety data.
How is SLU-PP-332 different from mitochondrial peptides like MOTS-c or SS-31?
MOTS-c and SS-31 are genuine peptides — short amino-acid chains — that act through mitochondrial signaling (AMPK activation) and membrane structure (cardiolipin binding), respectively. SLU-PP-332 is a small molecule that works through nuclear-receptor transcriptional activation instead. They’re discussed in similar research contexts, but they’re different molecule classes with different mechanisms.
Why are anti-doping labs studying SLU-PP-332?
A 2026 paper in Drug Testing and Analysis characterized SLU-PP-332’s in-vitro metabolites specifically to support doping-control detection assays. That’s a factual indication that analytical chemists consider it relevant enough to build detection methods for — it’s a side note about the state of the analytical science, not a statement about competitive-sport eligibility rules.
Where did SLU-PP-332 come from?
Its core chemical scaffold traces to a 2014 patent from Ligand Pharmaceuticals, originally explored in unrelated research. Researchers at Saint Louis University later optimized it into a pan-ERR agonist and first characterized its exercise-mimetic effects in a 2023 ACS Chemical Biology paper, with a 2026 paper providing the first systematic structure-activity relationship analysis of the scaffold.
References
- Billon C, Sitaula S, Banerjee S, et al. Synthetic ERRα/β/γ Agonist Induces an ERRα-Dependent Acute Aerobic Exercise Response and Enhances Exercise Capacity. ACS Chemical Biology. 2023;18(4):756-771.
- Billon C, Schoepke E, Avdagic A, et al. A Synthetic ERR Agonist Alleviates Metabolic Syndrome. Journal of Pharmacology and Experimental Therapeutics. 2024;388(2):232-240.
- Chemical optimization of the exercise mimetic SLU-PP-332 enables insight into estrogen-related receptor signaling. International Journal of Biological Macromolecules. 2026;355:151450.
- Avliyakulov N, et al. Analysis and Identification of In Vitro Metabolites of Exercise Mimetic SLU-PP-332 ERRα/β/γ Agonist for Doping-Control Purposes. Drug Testing and Analysis. 2026.
- Shahien M, Elagawany M, Sitaula S, et al. Bioorganic Chemistry. 2020 (conversion of a selective ERRβ/γ ligand to a pan-ERR agonist chemotype).
- PubChem CID 5338394, SLU-PP-332. National Center for Biotechnology Information.