SLU-PP-332

Origin and structure

SLU-PP-332 is a small synthetic molecule, not a peptide: it contains no amino acids and weighs about 290 daltons (formula C18H14N2O2). Chemically it is an acyl hydrazone: a phenol ring and a naphthalene ring joined by a short –CO–NH–N=CH– link. It was designed by researchers in St. Louis, Missouri, led by the pharmacologist Thomas Burris, starting from GSK4716, an older GlaxoSmithKline compound that activates ERRβ and ERRγ but barely touches ERRα. Swapping the isopropylphenyl group of GSK4716 for a naphthalene group made the molecule about 50 times more potent at ERRα. The first full description appeared in ACS Chemical Biology in 2023.

The name causes confusion. Every scientific paper calls the compound SLU-PP-332; 'SLU-PP-322', a name used on some product listings, swaps two digits, and no compound of that name appears in the scientific literature. The same team later made SLU-PP-915, a chemically different ERR agonist that does work when given by mouth in mice; it is a separate substance, not a form of SLU-PP-332.

How it is thought to work

The estrogen-related receptors ERRα, ERRβ and ERRγ are nuclear receptors: proteins that bind DNA and switch genes on. Despite the name they do not respond to oestrogen; they owe the name to their resemblance to the oestrogen receptors. They are active even without a ligand, and ERRα and ERRγ are most abundant in tissues that use a lot of energy, such as heart, skeletal muscle and liver, where they drive genes for new mitochondria, fat oxidation and the respiratory chain. Mice lacking ERRα have less muscle and less endurance.

SLU-PP-332 binds these receptors and pushes their activity higher still. In cell tests it was most potent at ERRα (half-maximal effect at 98 nanomolar), then at ERRβ (230 nM) and ERRγ (430 nM). In mouse muscle it switched on part of the gene programme that a single bout of aerobic exercise switches on, including the gene Ddit4, and its effect on endurance disappeared in mice whose muscle lacked ERRα. In the heart, by contrast, its protective effect ran mainly through ERRγ.

Is SLU-PP-332 approved?

No. SLU-PP-332 is not authorised as a medicine anywhere, no clinical trial of it is registered on ClinicalTrials.gov, and no study in people has been published. Its own developers treat it as a laboratory tool: they report that it lacks oral bioavailability, and a 2026 review co-written by Burris says it is not metabolically stable enough to be a conventional drug candidate without further chemistry. The team has since moved on to SLU-PP-915 and newer analogues.

• EU and the Netherlands: not a registered medicine, with no marketing authorisation for any product containing it.
• US: not FDA-approved, and no clinical trial is registered on ClinicalTrials.gov.
• Sport: prohibited at all times. On the 2026 list it falls under S0, the class for substances with no approval for human therapeutic use. The 2027 list, in force from 1 January 2027, names 'SLU-PP-332, SLU-PP-915 and related substances' in class S4.4.1, metabolic modulators, next to AICAR, MOTS-c, the PPARδ agonist GW1516 and the REV-ERBα agonists SR9009 and SR9011. In the Netherlands the WADA list is an annex to the National Doping Regulations and applies to every sports federation that recognises the World Anti-Doping Code.
• Doping control: researchers at the German Sport University Cologne identified nine breakdown products that human liver enzymes make from SLU-PP-332 in the test tube (six phase I and three phase II), as a basis for detecting it in athletes' samples.

What the research shows

All published work on SLU-PP-332 is in cells and animals. There are five mouse studies, and every one has members of the team that developed it among the authors; no independent group has yet repeated the animal results. Groups were small: six to eight mice per group in the endurance and obesity studies. The main findings:

• Endurance (ACS Chemical Biology 2023): mice injected twice a day for about a week ran about 70% longer and about 45% further on a treadmill than untreated mice (six per group). After about two weeks of injections their thigh muscle had more oxidative type IIa fibres and their grip strength was higher. In mice whose muscle lacked ERRα the endurance gain disappeared.
• Obesity (Journal of Pharmacology and Experimental Therapeutics 2024): after four weeks of injections, diet-induced obese mice weighed about 12% less than untreated obese mice; untreated mice gained about 5 g of fat against less than 0.5 g on SLU-PP-332, with no difference in food intake or lean mass (seven per group). Fasting glucose and insulin were lower. In lean mice on normal food body weight did not change, but fat oxidation rose by 25%.
• Heart failure (Circulation 2024): in mice with heart failure from a surgically narrowed aorta, six weeks of treatment improved the heart's pumping function (ejection fraction) from week four and reduced scarring, but did not stop the heart wall from thickening. Survival was better in treated mice, but the paper shows that result only with SLU-PP-332 and its sister compound SLU-PP-915 pooled.
• Ageing kidney (American Journal of Pathology 2023): in 21-month-old mice, eight weeks of treatment reversed age-related protein loss in the urine, loss of podocytes (filter cells), mitochondrial dysfunction and inflammatory signals. ERR levels were lower in old human and mouse kidneys.
• Oral successor (Journal of Pharmacology and Experimental Therapeutics 2026): SLU-PP-915 matched SLU-PP-332's effect on running distance and duration when both were injected, and kept it when given by mouth, which SLU-PP-332 cannot do.
• Human cells (Frontiers in Physiology 2025): muscle precursor cells taken during hip replacement from physically inactive women in their late seventies were treated in the dish for two days; SLU-PP-332 raised levels of PGC-1α, SIRT1 and ERRα, lowered oxidative stress and helped the cells fuse into muscle fibres. This is cell work, not a study in people.

Safety, limits and the idea of an 'exercise pill'

There are no human safety data. In mice, ten days of twice-daily injections caused no obvious toxicity, with normal blood counts and electrolytes and no rise in creatine kinase, a marker of muscle damage. Genetically obese ob/ob mice tolerated twice-daily injections less well, and that part of the obesity study was cut to 12 days. No long-term or formal toxicology studies have been published.

The chemistry adds caveats. The hydrazone link in its structure is regarded in medicinal chemistry as a weak point, because such links are metabolised quickly and may be toxic. SLU-PP-332 also barely dissolves in water: in a 2026 analysis its kinetic solubility was 0.2 micromolar, and human liver microsomes broke half of it down in about 31 minutes.

Calling it an exercise pill overstates what was shown. The mice did not train: the compound reproduced part of the gene response to one bout of exercise and improved a treadmill test in small groups of animals. Whether any of this happens in people, at what dose and with what side effects, has never been tested.

Frequently asked questions

Is SLU-PP-332 a peptide?

No. It is a small synthetic molecule of about 290 daltons (C18H14N2O2), an acyl hydrazone without a single amino acid. It is often listed next to peptides, but chemically it has nothing in common with them.

Has SLU-PP-332 been tested in humans?

No. No clinical trial is registered on ClinicalTrials.gov and no study in people has been published. The closest anyone has come is human material in the laboratory: muscle precursor cells from inactive women treated in the dish, and human liver enzymes used in the test tube to see how it is broken down. Everything else is in mice.

Is SLU-PP-332 absorbed when swallowed?

According to its developers, not in useful amounts: they report that SLU-PP-332 lacks oral bioavailability, and every animal study gave it by injection into the abdominal cavity. It also barely dissolves in water. That is why the team made SLU-PP-915, a chemically different ERR agonist that does work by mouth in mice. No absorption data exist for SLU-PP-332 taken by mouth.

Is SLU-PP-332 legal in the Netherlands?

SLU-PP-332 is not a registered medicine in the Netherlands or anywhere else, so it may not be sold, advertised or supplied for use in people. Buying and selling it as research material is a different status, which our guide on research-use-only products in the Netherlands explains. For athletes it is prohibited under the anti-doping rules, however it was obtained.

Is SLU-PP-332 banned in sport?

Yes, at all times, in and out of competition. Under the 2026 WADA list it is covered by S0, which bans any substance without approval for human therapeutic use. The 2027 list, in force from 1 January 2027, names 'SLU-PP-332, SLU-PP-915 and related substances' in class S4.4.1, metabolic modulators. In the Netherlands the same list applies through the National Doping Regulations, and the anti-doping laboratory in Cologne has already mapped which breakdown products to look for.

SLU-PP-322 or SLU-PP-332: which is right?

SLU-PP-332. That is the name in every scientific paper and on the WADA list. 'SLU-PP-322' swaps two digits; it is used on some product listings, but no compound with that name appears in the scientific literature. A label alone says nothing about what is in a vial; only analysis can confirm identity and purity.

Storage and handling

Store according to product-label instructions and batch handling notes. Lyophilized research peptides are commonly kept dry, protected from light, and handled with clean laboratory technique.

References

Checked against these sources on 28 October 2026.