Retatrutide + SLU-PP-332
Five Phase 3 trials on one side, and none at all on the other.
Sold as the easy fat loss stack: the drug that suppresses appetite, plus a compound said to give the body the effects of exercise. The second half has never been given to a person in a trial, is not a peptide, and anti-doping laboratories are already building tests to detect it.
Eat less, and skip the training.
The pitch is tidy. Retatrutide handles appetite and SLU-PP-332 handles the part people find hardest, by producing the metabolic changes endurance training produces.
It also answers a real complaint about the GLP-1 drugs. Losing weight on them takes muscle along with fat, and a compound that increases oxidative muscle fibres sounds like the answer to that. The muscle preservation question has its own page.
The two halves could not be further apart on evidence. One has five positive Phase 3 trials and a filing planned. The other has never been given to a person in a trial of any kind.
Four benefits, and how well each one holds up.
The top row is the strongest evidence on this site. The bottom three are among the weakest. Both on one page.
Three questions, answered before anything else.
A small molecule, sold as a peptide, tested only in mice.
SLU-PP-332 activates all three estrogen-related receptors, most strongly ERR-alpha.[1] Those receptors control the genes muscle switches on during endurance exercise, which is the entire basis of the exercise mimetic idea.
The animal work is striking. In mice it increased oxidative muscle fibres and endurance, raised energy expenditure and insulin sensitivity, and protected the heart against pressure overload.[2] A separate study reported it induced an acute aerobic exercise response and enhanced exercise capacity.[3]
None of it has been repeated in a person. One assessment states that as of September 2026 no completed or registered human efficacy trial has been published. There is no investigational new drug application, and no human has been studied with the compound in a controlled clinical setting.[4]
It is also not a peptide, which matters on a site about peptides. It is a synthetic small molecule with a CAS number and a drug design history, sold on the same pages as the peptides and counted among them.[5] One vendor page calls it a groundbreaking oral peptide, which is wrong twice over.[6]
The gap between the mouse data and the sales page is the whole story here. One guide says so directly: real and exciting animal data on one side, almost no human evidence on the other, and most pages selling it skate past the second part.[7]
Laboratories are building tests before anyone has run a trial.
WADA prohibits exercise mimetics and metabolic modulators as a class.[2] That already covers SLU-PP-332, and the anti-doping world is treating it as a live problem.
Two separate 2026 papers in Drug Testing and Analysis and Rapid Communications in Mass Spectrometry characterise the compound and map its breakdown products specifically so that laboratories can detect its use.[2][8] One identified twelve hydroxylated metabolites plus direct glucuronidation and sulfation products.[2]
That is an unusual sequence. Detection methods usually follow clinical development. Here the testing infrastructure is being built for a compound with no human trial behind it, because enough people are taking it to make detection worth the work.
Anyone subject to testing should treat this pairing as a violation on both counts. Retatrutide sits in the same prohibited class.
Heart tissue uses the same receptors.
ERR-alpha is not confined to skeletal muscle. It governs metabolism in cardiac tissue too, which is why one assessment notes that any human exposure would happen without cardiovascular safety monitoring.[4]
The mouse work points the encouraging way on this, reporting cardiac protection against pressure overload.[2] A benefit in mouse hearts is not a safety clearance in human ones, and the two can diverge.
The comparison worth knowing is cardarine. It was the previous exercise mimetic to reach the grey market, and it carried a cancer signal in rodent studies that ended its development. One guide notes SLU-PP-332 has not shown that signal so far, while sharing the same core caveat: impressive in mice, unproven and unapproved in people.[7]
Grey-market material adds its own problem. One source points out that compounds sold as SLU-PP-332 carry no verified identity, purity or amount. That is true of everything on this site, and more consequential for something nobody has characterised in people.[4]
Retatrutide is the opposite problem.
Retatrutide has five positive Phase 3 trials and reached 28.3 percent average weight loss over 80 weeks at the top dose, the largest result published for any weight loss drug. Lilly plans to file for US approval in the first quarter of 2027.
It is still not approved anywhere, so everything sold online is research chemical material. Its side effect profile is well documented from the trials: nausea in 42.4 percent at the top dose against 14.8 on placebo, and about 11.3 percent stopping because of side effects.
So the stack pairs the best-evidenced compound in the category with one of the least-evidenced. Pairing retatrutide with cagrilintide and with tesamorelin are the versions with more behind them, and pairing it with tirzepatide is the version the approved drug's label argues against.
Two purchases, and no premixed version.
Nobody sells this pair ready-mixed, and we track no blend containing SLU-PP-332 at all.[9]
SLU-PP-332 is the more expensive half at the cheapest listings, despite being a small molecule rather than a peptide. Its price spread is wide, running to more than five times its own floor.
The comparison that matters is not between the two vials. Endurance training produces the effects SLU-PP-332 is sold for, has overwhelming human evidence, and costs nothing.
Neither approved, and one not even in development for people.
Retatrutide is approved nowhere and is in late-stage trials. SLU-PP-332 is approved nowhere and has no registered human trial, which is a different kind of unapproved.
One source states there is no population for whom use of SLU-PP-332 is supported by evidence.[4] That is unusually blunt for a page about a compound it also describes.
Both are prohibited in sport at all times, and detection methods for the second are published.
Anyone considering this has a reason to separate the two questions. Retatrutide has real trial data and a real side effect profile to discuss with a doctor. The other half has nothing to discuss yet.
What people ask about this stack
Does SLU-PP-332 work in humans?
Nobody knows, because the studies do not exist. As of September 2026 no completed or registered human efficacy trial of SLU-PP-332 has been published, and there is no investigational new drug application. The animal data is striking: in mice the compound increased oxidative muscle fibres and endurance, raised energy expenditure and insulin sensitivity, and protected the heart against pressure overload. Mechanistic plausibility in animals does not predict clinical benefit in people.
Is SLU-PP-332 a peptide?
No. SLU-PP-332 is a synthetic small molecule that activates the estrogen-related receptors, with a CAS number and a rational drug design history rather than an amino acid sequence. It is sold on peptide vendor sites and counted among peptides, and at least one page describes it as a groundbreaking oral peptide, which is inaccurate on both counts.
Why are laboratories building tests for SLU-PP-332?
WADA prohibits exercise mimetics and metabolic modulators as a class, so SLU-PP-332 is already banned. Two separate 2026 papers characterise the compound and map its breakdown products specifically so anti-doping laboratories can detect its use, with one identifying twelve hydroxylated metabolites plus glucuronidation and sulfation products. Detection work usually follows clinical development, so building it for a compound with no human trial is unusual.
What are the safety concerns?
The honest answer is that the human safety profile is unknown because the studies do not exist. The specific concern raised is cardiac: ERR-alpha governs metabolism in heart tissue as well as skeletal muscle, so any human exposure happens without cardiovascular safety monitoring. The mouse work points the encouraging way, reporting cardiac protection, though a benefit in mouse hearts is not a clearance in human ones.
How does SLU-PP-332 compare to cardarine?
Cardarine was the previous exercise mimetic to reach the grey market, and a cancer signal in rodent studies ended its development. One guide notes SLU-PP-332 has not shown that signal so far, and acts on a different target, the estrogen-related receptors rather than PPAR-delta. It shares the same core caveat: impressive in mice, unproven and unapproved in people.
Is there a better-evidenced pairing for retatrutide?
Two have more behind them. Pairing retatrutide with cagrilintide uses a second appetite pathway that has been tested in combination with a GLP-1 drug, and pairing it with tesamorelin targets visceral fat through a separate mechanism. Both pages cover the gaps in each. For the effects SLU-PP-332 is sold for, endurance training has overwhelming human evidence and costs nothing. Compare against the other stacks.
What this page is built on
- 01SLU-PP-332, compound entry. A potent but non-selective estrogen-related receptor agonist acting most strongly at ERR-alpha, with an EC50 of 98 nanomolar. CAS number 303760-60-3. Encyclopaedia entry citing the primary pharmacology papers.
- 02Avliyakulov N et al. Analysis and identification of in vitro metabolites of exercise mimetic SLU-PP-332 for doping-control purposes. Drug Testing and Analysis, 2026. DOI 10.1002/dta.70035. Source for WADA prohibiting exercise mimetics and metabolic modulators, for SLU-PP-332 increasing oxidative muscle fibres, fatty acid oxidation and exercise endurance, for increased energy expenditure and insulin sensitivity and cardiac protection against pressure overload in mouse models of metabolic syndrome, and for the identification of twelve hydroxylated metabolites plus glucuronidation and sulfation products using human liver fractions.
- 03Billon C, Sitaula S, Banerjee S, Welch R, Elgendy B, Hegazy L, et al. A synthetic ERR agonist induces an acute aerobic exercise response and enhances exercise capacity. PMC11584170. Characterisation of SLU-PP-332 as an ERR-alpha agonist, with repeated pharmacological activation appearing to mimic repeated bouts of aerobic training in terms of skeletal muscle oxidative capacity and endurance.
- 04SLU-PP-332 research assessment, September 2026. Source for no completed or registered human efficacy trials having been published, no investigational new drug application, no human having been studied with the compound in a controlled clinical setting, ERR agonism affecting cardiac metabolism in addition to skeletal muscle so that any human exposure would occur without cardiovascular safety monitoring, grey-market material carrying no verified identity, purity or amount, and the statement that there is no population for whom use is supported by evidence.
- 05Source for SLU-PP-332 being an experimental small-molecule agonist of ERR-alpha, beta and gamma rather than a peptide, and for human pharmacokinetics, effective exposure, long-term safety, cardiovascular effects, interactions and clinical benefit not having been established by the cited mouse studies.
- 06A vendor page describing SLU-PP-332 as a groundbreaking oral peptide. Recorded here because the compound is a small molecule rather than a peptide.
- 07SLU-PP-332 evidence review. Source for there being no published human trial, for the observation that pages selling the compound skate past that gap, for no human research establishing a safe or effective dose, for the comparison with cardarine including its cancer signal and the note that SLU-PP-332 has not carried that signal so far, and for the comparison table listing exercise as having overwhelming human evidence and being free and irreplaceable.
- 08In vitro metabolism and analytical characterisation of SLU-PP-332 and SLU-PP-915, novel pan-ERR agonists with doping potential. Rapid Communications in Mass Spectrometry. PMC12835572. Both compounds target all three ERR isoforms and are under investigation as exercise mimetics. Source for SLU-PP-332 promoting an increase in type IIa oxidative skeletal muscle fibres and improving exercise endurance in animal models, and for limited metabolism data being available.
- 09Peptide Decoding vendor pricing data. Lowest in-stock single-compound listings for retatrutide and SLU-PP-332, with listing counts, computed at page load. No premixed listing contains SLU-PP-332 in any combination.