Retatrutide vs SLU-PP-332
Retatrutide (LY3437943) is an investigational single peptide with balanced agonist activity at the GIP, GLP-1 and glucagon receptors, developed through rodent pharmacology, phase 1b and phase 2 randomised trials in obesity, type 2 diabetes and metabolic dysfunction-associated steatotic liver disease, and a phase 3 readout published in 2026. SLU-PP-332 is a synthetic small-molecule pan-agonist of the estrogen-related receptors ERRalpha, ERRbeta and ERRgamma, described as an exercise mimetic because it reproduces part of the acute aerobic exercise transcriptional programme in rodent skeletal muscle. They are compared because both are promoted as pharmacological routes to fat loss without training, one by suppressing intake and one by imitating exercise. No published paper names both. Full-text searching of Europe PMC found reviews that discuss SLU-PP-332 alongside incretin-based weight-loss drugs as a class, but none of those reviews names retatrutide, so the comparison here is drawn from two separate literatures.
No study has compared them directly.
Everything below is drawn from separate studies that used different models, endpoints and species. That is a real limit on what can be concluded, not a formality.
No study has administered retatrutide and SLU-PP-332 in the same experiment, and no publication names both compounds. Searches were run against PubMed by title and abstract and against Europe PMC across full text, using LY3437943 for the first compound and the descriptors pan-ERR agonist and exercise mimetic for the second. Full-text searching did locate a small set of reviews that place SLU-PP-332 alongside incretin-based weight-loss agents as a therapeutic class, including a 2026 commentary arguing that exercise pills cannot reproduce the exercise milieu and a 2025 systematic review of exercise mimetics in ageing; on direct checking, none of those records names retatrutide, so none of them engages both compounds and none is cited here as head-to-head evidence. The comparison below is indirect throughout, and the two literatures share no species, endpoint or comparator.
Side by side.
| Retatrutide | SLU-PP-332 | |
|---|---|---|
| Evidence maturity | Clinical | Preclinical only |
| Studies cited here | 15 | 13 |
| Published 2023 or later | 13 | 13 |
| Newest paper | 2026 | 2026 |
| Molecular class and origin | A synthetic single-chain peptide engineered to combine agonism at three receptors that normally respond to separate endogenous hormones. | A synthetic small molecule that activates a family of orphan nuclear receptors acting inside the cell with PGC-1 coactivators. It is not a peptide and has no endogenous counterpart. |
| Mechanism as described in the literature | Balanced agonism at the glucagon, GIP and GLP-1 receptors. In obese rodents the weight effect was attributed to both reduced calorie intake and increased energy expenditure, and a phase 2 patient-reported analysis found reductions in appetite, hunger and prospective food consumption that correlated with weight loss. | Pan-agonism at ERRalpha, ERRbeta and ERRgamma, reported to induce an acute aerobic exercise-like transcriptional signature in mouse skeletal muscle, increase type IIa oxidative fibres and raise fatty acid oxidation and energy expenditure. The exercise-capacity effect was reported to be ERRalpha-dependent. |
| Size of the evidence base | Fifteen studies in this library, the majority randomised controlled human trials, alongside two systematic reviews and rodent pharmacology. | Thirteen studies in this library, none of them clinical trials. The set is rodent in vivo work, cell-based experiments, medicinal chemistry and doping-control metabolite characterisation. |
| Best-characterised finding | Dose-dependent body-weight reduction in a 48-week phase 2 obesity trial, reaching -24.2% in the highest dose group versus -2.1% on placebo, with HbA1c and liver fat reductions reported in separate phase 2 trials. | Improved treadmill endurance and an acute exercise-like muscle transcriptional response in mice, plus increased energy expenditure, increased fatty acid oxidation and reduced fat mass in diet-induced obese and ob/ob mice. |
| Human data | Randomised, double-blind, placebo-controlled trials in obesity and type 2 diabetes, a MASLD phase 2a substudy, body-composition and renal analyses, and a published phase 3 trial in type 2 diabetes. | No human has been dosed. The closest human-derived work is a 2025 pilot study in which primary myoblasts isolated from physically inactive women were treated with the compound in culture; the authors stated explicitly that no participants received it. |
| Evidence maturity | Clinical, with a registrational phase 3 programme described in design papers and a first phase 3 result published in 2026. | Preclinical only. A ClinicalTrials.gov query returned no studies, so human pharmacokinetics, dosing, efficacy and safety are entirely unestablished. |
| Recency of primary research | Active and clinical: 2025 and 2026 publications include body-composition and kidney analyses, cardiovascular biomarker reports, a meta-analysis and the first phase 3 readout. | Active but preclinical and increasingly analytical: the 2026 literature is dominated by structure-activity optimisation, work on the related oral analogue SLU-PP-915, and two independent in vitro metabolite studies performed to support doping-control detection. |
| Safety signals reported | Predominantly gastrointestinal, dose-related adverse events in phase 2. Long-term safety and cardiovascular outcome data have not been established in peer-reviewed reports. | A 2026 systematic review of preclinical studies reported no evident toxicity in the rodent models surveyed, but long-term toxicity, carcinogenicity and reproductive effects have not been characterised and there is no human safety record at all. |
And what it does not.
The published record supports very different claims for these two compounds. For retatrutide it supports substantial, dose-dependent weight and glycaemic effects measured against placebo in randomised human trials, with a phase 3 result now in print, while leaving long-term safety, cardiovascular outcomes and post-discontinuation durability open. For SLU-PP-332 it supports a reproducible exercise-like transcriptional and metabolic response in rodents and in cultured cells, and nothing in humans: no trial has been published or registered, and the most recent work is medicinal chemistry and doping-detection method development rather than efficacy. The framing that sets them as competing routes to the same outcome has no basis in a shared experiment, and the two have never been measured on a common endpoint. It is also worth noting that the exercise-mimetic literature itself has attracted published scepticism about whether a drug can reproduce the systemic effects of training, and that question is unresolved for this compound.
Common questions.
- Is there any paper that discusses retatrutide and SLU-PP-332 together?
None was found. Full-text searching of Europe PMC did return reviews that place SLU-PP-332 next to incretin-based weight-loss drugs as a class, including a 2026 commentary on the limits of exercise pills and a 2025 systematic review of exercise mimetics in ageing. Each of those was checked individually and none names retatrutide. Discussing a drug class is not the same as engaging a specific compound, so those papers are not treated as head-to-head evidence on this page.
- What does the exercise-mimetic description actually rest on?
It rests on rodent transcriptomics. A 2023 study reported that SLU-PP-332 induced an acute aerobic exercise-like transcriptional signature in mouse skeletal muscle, increased type IIa oxidative fibres and improved treadmill endurance, with the exercise-capacity effect dependent on ERRalpha. Later mouse work extended the pattern to fatty acid oxidation, cardiac function in a pressure-overload model and the ageing kidney. The description summarises a gene-expression resemblance in animals rather than a demonstrated equivalence to training in people.
- Why does so much recent SLU-PP-332 research concern doping control?
Because anti-doping laboratories characterise emerging compounds before they appear in samples. Two independent 2026 studies incubated the compound with human liver preparations and catalogued its metabolites, one identifying nine metabolites of SLU-PP-332 alongside seven for the related agonist SLU-PP-915, and another characterising twenty-two in vitro metabolites and proposing eight as screening targets. Both studies addressed detectability only and neither assessed efficacy or safety, so they add analytical knowledge rather than evidence of benefit.
- Has either compound been shown to preserve lean mass during weight loss?
Only retatrutide has been examined for this in humans. A phase 2 body-composition substudy in adults with type 2 diabetes reported that total fat mass decreased 23.2% in the highest dose group, a least-squares mean difference of -18.7% versus placebo, and characterised the relative contribution of fat and lean tissue to total weight change. For SLU-PP-332 the corresponding evidence is a rodent fat-mass reduction alongside increased oxidative fibre type, with no human body-composition measurement of any kind.
- Do the two act on the same part of metabolism?
Not as described in the literature. Retatrutide engages cell-surface incretin and glucagon receptors, and its published human effects include reduced appetite ratings, weight loss, lower HbA1c and reduced liver fat. SLU-PP-332 acts on intracellular nuclear receptors that regulate mitochondrial biogenesis and oxidative metabolism with PGC-1 coactivators, and its published effects are transcriptional and metabolic changes in rodent muscle, heart and kidney. No study has tested whether the two pathways overlap or interact.
For research purposes only. Not for human consumption, diagnosis, treatment, or prevention of any condition. Nothing on this page is medical advice, and no comparison here should be read as a recommendation of either compound.