SLU-PP-332 for Muscle Growth

Evidence Review created on 09/13/2026 using AI4L / Opus 5

Also known as: SR9861, 4-hydroxy-N’-(naphthalen-2-ylmethylene)benzohydrazide, 4-hydroxybenzoic acid 2-(2-naphthalenylmethylene)hydrazide

Motivation

SLU-PP-332 is a laboratory-made compound that switches on a family of control proteins inside muscle cells called the estrogen-related receptors. When a person trains for endurance, those proteins turn up the genes that build the structures muscle uses to generate energy and to burn fuel. SLU-PP-332 turns the same proteins up without the training, which is why researchers describe it as an exercise mimetic.

The compound came out of drug-discovery work published in 2023 and was built as a research tool for studying how muscle controls its own energy supply, not as a treatment. Injected into sedentary mice, it made them run considerably longer and pushed their muscle toward a more endurance-like makeup. It is now sold as a research chemical and discussed in fitness and longevity circles as a route to more muscle without resistance training.

This review examines what the published record does and does not establish about SLU-PP-332 and muscle growth: how the compound acts on muscle cells and muscle fibers, how far the evidence reaches, what is known about its safety, and where the muscle-building claim currently rests.

Benefits - Risks - Protocol - Conclusion

Grokipedia

SLU-PP-332

A dedicated reference entry giving the compound’s chemistry, receptor potencies, preclinical results and research-tool status in one place — useful for orientation before reading the primary papers.

Examine

No Examine article exists for SLU-PP-332. Examine covers dietary supplements and food-derived compounds, and does not cover unapproved investigational compounds or prescription-only agents, which is the category this molecule falls into.

ConsumerLab

No ConsumerLab article exists for SLU-PP-332. ConsumerLab tests commercially sold supplements and consumer health products for identity and purity, and does not cover unapproved investigational compounds or prescription-only agents.

Systematic Reviews

Two systematic reviews bear on SLU-PP-332 — one covering the compound directly, one covering the exercise-mimetic category it belongs to; no meta-analysis exists for either.

Pharmacological Activation of ERRα/β/γ as an Exercise Mimetic: Potential Therapeutic Applications - de Souza-Lima et al., 2026

Spanish-language systematic review of preclinical pan-ERR agonist evidence, SLU-PP-332 included; concludes clinical trials are absent.
Exercise Mimetics in Aging: Suggestions from a Systematic Review - Giacomello et al., 2025

Surveys 97 exercise-mimetic papers across the category; positions the drug class but does not assess SLU-PP-332 itself.

Note on the trade-off: only the benefit side is represented above. No systematic review or meta-analysis exists on the risks, adverse effects or toxicology of SLU-PP-332 or of any pan-ERR agonist, so the risk side of the trade-off is unrepresented in this literature.

Mechanism of Action

SLU-PP-332 is an agonist (an activator) of all three estrogen-related receptors. These are nuclear receptors (proteins that bind directly to DNA and switch genes on). It is most potent at ERRα, the subtype most abundant in skeletal muscle, with a half-maximal effective concentration (EC50, the concentration producing half the maximum response) of 98 nanomolar, against 230 nanomolar at ERRβ and 430 nanomolar at ERRγ, and it does not activate the estrogen receptors themselves or other nuclear receptors (Billon et al., 2023).

Downstream, it induces Ddit4 (a gene that directs the acute endurance-exercise response) and Slc25a25 (a mitochondrial transporter gene) as strongly as a treadmill run, alongside PGC-1α (a master switch for building new mitochondria) and Pdk4 (which shifts cells toward burning fat). Distribution favours the target tissue: two hours after injection in mice, muscle concentrations run roughly threefold above plasma. Metabolism is hepatic and extensive — hydroxylation followed by glucuronide and sulfate conjugation, with more than twenty metabolites identified in human liver preparations, though the responsible enzymes have not been assigned (Avliyakulov et al., 2026). No terminal half-life has been published; twice-daily injection was needed in animals, the gene response fades within six hours, and oral absorption is poor.

Mechanistically the muscle-growth case is contested. The same programme that adds mitochondria drives fibres toward a smaller, more oxidative phenotype, while separate work shows ERRα is required for muscle-precursor proliferation and differentiation — a pro-growth role (Nguyen et al., 2025).

Historical Context & Evolution

The ERRs were classified as orphan receptors (nuclear receptors with no known natural binding partner) and were long treated as undruggable, ERRα especially. Two findings changed that: GSK4716, an agonist selective for ERRβ and ERRγ, and C29, an ERRα inverse agonist (a molecule that shuts down a receptor’s built-in activity), which proved ERRα could be engaged at all. From the GSK4716 scaffold and a crystal structure of the ERRγ binding pocket, the Saint Louis University and Washington University group added a naphthalene group predicted to stack against a phenylalanine unique to ERRα, gaining roughly fiftyfold potency. The result was SLU-PP-332 (Billon et al., 2023).

Its original use was as a chemical probe (an injectable tool for asking what ERR activation does in a living animal) and secondarily as a metabolic-disease lead. Muscle and longevity interest followed the probe rather than preceding it. It was then reported to cut fat mass and improve insulin sensitivity in obese mice (Billon et al., 2024), to improve ejection fraction (the share of blood the heart expels per beat) in pressure-overload heart failure (Xu et al., 2024), and to reverse mitochondrial decline in aged kidneys (Wang et al., 2023).

None of that work has been retracted or overturned; what shifted is emphasis. Because oral absorption was poor, the originating group moved to a successor, SLU-PP-915 (Billon et al., 2026). That left the parent as a research tool, which grey-market vendors adopted and anti-doping laboratories began characterising in 2026 (Möller et al., 2026).

Expected Benefits

High 🟩 🟩 🟩

No benefit reaches High: the class of evidence that would be needed — a human clinical endpoint or a validated clinical surrogate replicated across more than one trial — does not exist here, because the compound has never been administered to a human in a reported study, the only human material studied being primary muscle-cell culture, an in-vitro assay.

Medium 🟩 🟩

No benefit reaches Medium either: there is no single human trial and no observational human cohort measuring any muscle outcome on this compound, every controlled dataset being rodent in-vivo work or cell culture.

Low 🟩

Speculative 🟨

Skeletal Muscle Hypertrophy ⚠️ Conflicted

In cultured human muscle-precursor cells the compound drove abundant muscle-fibre formation and raised growth-signalling proteins; in mice, chronic dosing left fibres thinner. Net: no study shows it enlarges muscle (Bonanni et al., 2025).

Muscle Regeneration After Injury

Increasing ERRα genetically boosted repair, blood-vessel growth and function in injured and dystrophic rodent muscle. Basis is genetic overexpression, not the compound: no regeneration model has been run with SLU-PP-332 (Nguyen et al., 2025).

Grip Strength

Sedentary mice injected twice daily for two weeks showed higher grip strength than vehicle controls in one controlled experiment. Mechanism is presumed oxidative remodelling. No human strength measurement exists (Billon et al., 2023).

Aerobic Exercise Capacity ⭕️ Not Central to Muscle Growth

Sedentary mice injected twice daily ran substantially longer and further than vehicle controls, the compound’s most replicated effect. This bears on endurance performance, not muscle size (Billon et al., 2023).

Cardiac and Renal Mitochondrial Function ⭕️ Not Central to Muscle Growth

In pressure-overload heart failure the compound raised ejection fraction (Xu et al., 2024); in aged mice it reversed kidney mitochondrial decline (Wang et al., 2023). Both bear on organ function, not muscle size.

Oxidative Fibre-Type Remodelling ⭕️ Not Central to Muscle Growth

Two weeks of injection raised type IIa fibres (the fatigue-resistant, oxygen-using kind) plus mitochondrial number and content, while fibre diameter fell. This bears on endurance capacity, not muscle size (Billon et al., 2023).

Fat Mass Loss and Insulin Sensitivity ⭕️ Not Central to Muscle Growth

In diet-induced obese and leptin-deficient mice the compound raised energy expenditure and fat burning, cutting fat mass and improving insulin sensitivity. This bears on metabolic health and leanness, not muscle accretion (Billon et al., 2024).

Benefit-Modifying Factors

ESRRA and PPARGC1A variants: ESRRA encodes ERRα, the compound’s main target; PPARGC1A encodes PGC-1α, its partner in mitochondrial building. Common variants in both alter training response, but no pharmacogenetic study of this compound exists.
Baseline training and mitochondrial status: Muscle from inactive women showed suppressed ERRα, PGC-1α and SIRT1 (a repair-linked regulator) with raised NOX4 (a source of cellular oxidants); the compound’s in-vitro effect was on those deconditioned cells, implying more headroom in the untrained (Bonanni et al., 2025).
Sex: All in-vivo efficacy work used male mice; the only human-cell work used women exclusively. No direct comparison exists, and a sex difference in response can neither be claimed nor excluded.
Pre-existing health conditions: Response was demonstrated in obese and metabolically impaired animals. Whether an already lean, insulin-sensitive, trained person has anything left to gain from the same signal is untested.
Age: ERR expression declines with age and inactivity; 21-month-old mice responded in kidney tissue, so older, deconditioned users plausibly have the largest signal available — but no aged-muscle experiment with this compound has been reported.

Potential Risks & Side Effects

High 🟥 🟥 🟥

No risk reaches High: the class of evidence required — documented human adverse events or a validated clinical surrogate, replicated across more than one trial — cannot exist for a compound that has never been administered to a human in a reported study, leaving no safety-surveillance stream, no post-marketing report set and no clinical safety database.

Medium 🟥 🟥

No risk reaches Medium either: there is no single human trial and no observational human dataset reporting harms, the only safety readouts being blood counts, electrolytes, creatine kinase (an enzyme that leaks into the blood when muscle is damaged) and histology from short rodent courses.

Low 🟥

Speculative 🟨

Cancer Promotion Through ERRα Activation ⚠️ Conflicted

ERRα over-activity drives breast-cancer spread and treatment resistance, and inhibitors are in development — yet this agonist cut inflammation and ageing markers in aged mice. Net: adverse in direction, untested (Pradhan et al., 2026).

Counter-Productive Fibre Remodelling

Fifteen days of twice-daily injection left mouse quadriceps fibres measurably thinner, the expected consequence of a glycolytic-to-oxidative shift. For a muscle-size goal this is the intervention working against the objective (Billon et al., 2023).

Unknown Chronic and Human Toxicity

Ten-day dosing left mouse blood counts, electrolytes and creatine kinase normal (Billon et al., 2023); eight weeks was tolerated in aged mice (Wang et al., 2023). No chronic, reproductive, genotoxicity or cancer study exists.

Unselective Activation of ERRs Outside Muscle

All three receptor subtypes are activated, and they are abundant in heart, kidney, liver and brain. Cardiac and renal effects helped in disease models; chronic activation of healthy organs is unstudied (Xu et al., 2024).

Contamination and Unsterile Injection of Research-Grade Material

Poor oral absorption pushes users toward injecting a powder sold for laboratory use only, with no sterility, endotoxin or identity guarantee. Basis is the compound’s pharmacology and market status; no case reports have been published.

Risk-Modifying Factors

Genetic polymorphisms: Variants in ESRRA and ESRRG (the ERRα and ERRγ genes) plausibly alter sensitivity, and cytochrome P450 (CYP) variants alter clearance — but the enzymes handling this compound are unidentified, so no variant can be named as relevant.
Baseline biomarker levels: Baseline liver enzymes, creatine kinase and blood counts set the reference against which any organ signal would be read. Baseline oestrogen-receptor-driven cancer risk markers matter more than any metabolic marker here.
Sex: Every in-vivo safety observation comes from male mice. Because ERRα over-activity is a documented driver in breast cancer, women with a personal or family history of hormone-receptor-positive disease face a sex-specific concern that has never been quantified.
Pre-existing health conditions: Active or treated malignancy is the greatest concern, given the receptor’s cancer profile. Liver disease alters clearance of an extensively conjugated compound; kidney disease and heart failure already strain organs this compound acts on.
Age: Older users carry more undetected malignancy, more polypharmacy and less hepatic and renal reserve, so the same unquantified exposure carries more downside — while the eight-week aged-mouse course remains the only chronic-dosing data at any age.

Key Interactions & Contraindications

No interaction study of SLU-PP-332 has been performed in humans or animals. Every entry below is a mechanistic prediction, and its severity rating reflects the plausibility of the mechanism plus the absence of data, not an observed event.

Receptor-blocking agents (tamoxifen, 4-hydroxytamoxifen, XCT790-class inverse agonists): Caution, with loss of effect in both directions — these shut down the receptors the compound activates. Mitigation: co-administration is avoided; users on endocrine therapy fall under the avoid list below.
Narrow-therapeutic-index prescription drugs (warfarin, phenytoin, digoxin, tacrolimus): Caution, with unpredictable drug levels, because the conjugating and oxidising enzymes handling this compound are unassigned. Mitigation: co-use is avoided, or drug levels and the international normalised ratio (INR, a clotting-time index) are monitored closely.
Over-the-counter analgesics (acetaminophen, high-dose ibuprofen, naproxen, aspirin): Caution, with possible additive liver load, since both acetaminophen and this compound are cleared by glucuronide and sulfate conjugation. Mitigation: acetaminophen held under 2 g daily, with liver enzymes checked at 4 weeks.
Mitochondrial-biogenesis supplements (nicotinamide riboside, nicotinamide mononucleotide, resveratrol, urolithin A, pyrroloquinoline quinone): Caution, with additive signalling through the same PGC-1α axis and unknown combined toxicity. Mitigation: agents introduced one at a time, separated by at least two weeks.
High-dose antioxidant supplements (vitamin C above 1 g, vitamin E above 400 IU, N-acetylcysteine): Monitor, with possible blunting of benefit, as these damp the oxidant signalling that mitochondrial adaptation partly runs on. Mitigation: antioxidant doses held at food-level intakes.
Other interventions (endurance training, caloric restriction, resistance training): Monitor for additive effect — the oral successor compound amplified training-induced gene responses, and caloric restriction preserves ERR expression. Mitigation: none identified; resistance training remains the only proven muscle-growth stimulus, and displacing it forfeits that stimulus.

Populations who should avoid SLU-PP-332:

Anyone with active malignancy, or a personal history of hormone-receptor-positive breast cancer, or current endocrine therapy for it
Anyone with a first-degree relative diagnosed with hormone-receptor-positive breast cancer before age 50, or a known BRCA1 or BRCA2 variant (BRCA genes repair DNA breaks; faults raise breast and ovarian cancer risk)
Pregnant or breastfeeding women, and anyone under 18, given complete absence of developmental and reproductive data
People with liver impairment at Child-Pugh Class B or C (a scored measure of liver failure severity), given extensive hepatic conjugation
People with chronic kidney disease at an estimated glomerular filtration rate (eGFR, a measure of kidney filtering capacity) below 30 mL/min/1.73 m²
People with heart failure at New York Heart Association (NYHA) Class III or IV (marked symptoms on mild exertion, or symptoms at rest)
Competitive athletes subject to anti-doping testing, for whom validated detection assays now exist

Risk Mitigation Strategies

Per-lot identity and purity verification: A per-lot certificate of analysis showing high-resolution mass-spectrometry identity and chromatographic purity above 98%, or commissioned independent testing, mitigates the contamination and wrong-compound risk of research-grade powder.
Cancer screening before and during use: Age-appropriate screening at baseline (mammography from 40, prostate-specific antigen from 45), kept current annually, mitigates the receptor’s documented cancer-progression signal.
Shortest viable exposure: Use confined to discrete blocks of 4 to 8 weeks with equal off-periods, rather than continuous dosing, mitigates the entirely unstudied risk of chronic activation.
Baseline and scheduled organ panels: Liver enzymes, creatine kinase, a complete blood count and kidney filtration drawn at baseline, week 4 and week 12, then every 3 to 6 months, mitigate undetected liver, muscle, marrow or kidney injury.
Sterile administration or none: Where the compound is injected, single-use sterile equipment, a freshly filtered solution and a rotating site mitigate the abscess and bloodstream-infection risk that unsterile self-injection of laboratory powder carries.
Resistance training as the primary stimulus: Progressive resistance training maintained throughout mitigates the fibre-thinning that oxidative remodelling produces and the opportunity cost of substituting an unproven compound for a proven stimulus.

Therapeutic Protocol

No human protocol exists: No leading practitioner, clinic or guideline describes a human regimen, because no human has been dosed in a reported study. Everything below is what the literature and vendor practice describe, not a validated schedule.
Published animal regimen: The Saint Louis University and Washington University group, which originated the compound, dosed 50 mg/kg twice daily intraperitoneally for 7 to 15 days for efficacy work, and 30 mg/kg for pharmacokinetics (Billon et al., 2023).
Competing approaches: Three, with no default: body-weight scaling of the mouse injection dose, which grey-market practice uses; the orally active successor SLU-PP-915 (Billon et al., 2026); or training itself, which drives the same gene programme.
Best time of day: Animal work dosed morning and evening; the acute gene response peaks 1 to 3 hours after administration, so pre-training administration is the mechanistically coherent choice. No timing comparison has been run.
Half-life: No terminal half-life has been published in any species. Twice-daily dosing was required for effect, muscle levels exceeded plasma at 2 hours, and the induced gene response had disappeared by 6 hours — collectively implying short duration of action.
Single versus split dosing: Every positive animal result used split twice-daily administration. No single-daily-dose regimen has been tested, and the transient gene response argues against it.
Genetic polymorphisms: ESRRA and PPARGC1A variants and conjugating-enzyme variants are the plausible dose modifiers, but no pharmacogenetic dosing guidance exists for this compound and none can be inferred.
Sex-based differences: All in-vivo dosing data come from male mice. No female dosing, exposure or response data exist, so no sex-adjusted regimen can be described.
Age-related considerations: The longest reported course, eight weeks, was in 21-month-old mice for a kidney endpoint. Older adults have lower baseline receptor expression, which argues for more response and for more caution at once.
Baseline biomarker levels: Response in animals tracked baseline metabolic impairment — obese and diabetic models responded most. Lean, insulin-sensitive baselines have never been dosed, so expected response there is unknown.
Pre-existing health conditions: Heart failure, aged kidney disease and diet-induced obesity are the conditions in which effect was shown. None of those models informs dosing in a healthy adult seeking muscle growth.

Discontinuation & Cycling

Lifelong or short-term: No human data address duration. Reported animal courses ran 7 to 15 days for muscle endpoints and up to 8 weeks in aged mice, so the entire evidence base describes short-term use only.
Withdrawal effects: None have been reported in any species, and none is mechanistically expected: the compound activates a gene programme rather than replacing a hormone, so no rebound deficiency pathway exists.
Tapering: Not applicable. Every reported study stopped dosing abruptly with no adverse observation, and there is no dependence or downregulation mechanism that a taper would address.
Reversal of effect: The acute gene response fades within 6 hours of a dose, and fibre-type and mitochondrial changes would be expected to reverse on the timescale of detraining. No study has measured washout.
Cycling: Untested. No experiment has compared continuous with intermittent dosing, so the case for cycling rests only on limiting cumulative exposure to an untoxicologically characterised compound.

Sourcing and Quality

Research-chemical status only: There is no pharmaceutical-grade SLU-PP-332. The compound is sold by chemical suppliers as a powder labelled for laboratory research use only, outside good manufacturing practice (GMP, the regulated quality system for medicines).
What to look for: The relevant documentation is a per-lot certificate of analysis showing high-performance liquid chromatography purity above 98%, mass-spectrometric identity confirmation and ideally nuclear magnetic resonance structural confirmation, with the lot number matching the product received.
Independent verification: Vendor certificates are self-reported and frequently recycled between lots. Third-party analytical testing of the received material is the only meaningful check, and it is the single highest-value quality step available here.
Reputable sources: None can be named for human use. No compounding pharmacy can lawfully prepare an unapproved investigational compound in the United States, so every accessible supply route is a laboratory-reagent channel.
Formulation considerations: The molecule is a poorly water-soluble hydrazone with low oral bioavailability. Vendor powders require an organic co-solvent such as dimethyl sulfoxide for reconstitution, which introduces its own sterility and tolerability problems.
Degradation risk: Hydrazones are susceptible to hydrolysis in aqueous solution and to light. Storage is desiccated, cold and dark, and any reconstituted solution is short-lived rather than a stock preparation.

Practical Considerations

Time to effect: In mice, the acute gene response appears within 1 hour of a dose, fibre and mitochondrial remodelling after 7 to 15 days of twice-daily dosing, and endurance gains after 7 days. No human timeline exists for any endpoint.
Common pitfalls: Expecting hypertrophy from a compound whose demonstrated action is oxidative remodelling; oral dosing despite poor absorption by that route; substituting it for training; and trusting a vendor purity claim without independent testing.
Regulatory status: Not approved by any regulator, with no investigational new drug application and no registered human trial anywhere. It is not a dietary supplement and cannot lawfully be sold as one.
Anti-doping status: The World Anti-Doping Agency prohibits metabolic modulators and exercise mimetics, and validated detection assays for this compound and its metabolites were published in 2026 (Möller et al., 2026).
Anti-doping bodies have their own stake: Laboratories that characterise and list new compounds are funded to run detection programmes, so their output is no more a neutral read on risk than the originating laboratory’s is on benefit.
Cost and accessibility: Raw powder is inexpensive, but no legitimate clinical access route exists at any price, and no insurer or national health system reimburses it.
Payer incentives and funding bias: No institutional payer has a financial reason to favour either side — exercise, the direct competitor, costs a payer nothing — which is one reason research funding flows toward patentable exercise mimetics rather than exercise delivery.

Interaction with Foundational Habits

Sleep: Indirect and unquantified. The compound upregulated the clock genes Per1 and Per2 in mouse muscle, yet circadian locomotor activity was unchanged — a local muscle-clock effect rather than a systemic one. No human sleep data exist. Practically, evening dosing has no established sleep penalty and no established benefit.
Nutrition: Potentiating, through a substrate shift. Induction of Pdk4 and fat-oxidation genes pushes muscle toward using fat for fuel, which is what produced fat-mass loss in obese mice. Practical points: protein intake carries the entire anabolic load, since this compound supplies none; and carbohydrate restriction is not required for the effect.
Exercise: Potentiating and partly redundant. Acute running and the compound had additive effects on the Ddit4 exercise gene in mice, and the oral successor amplified training-induced mitochondrial gene expression (Billon et al., 2026). Practical point: it reproduces an endurance signal, so resistance training remains the non-substitutable stimulus for muscle size.
Stress management: No established interaction. No cortisol, adrenal or stress-axis measurement has been reported in any species, and the receptor family governs energy metabolism rather than glucocorticoid signalling. The reductions in oxidative stress and cell-ageing markers seen in cultured muscle cells are cellular events and say nothing about psychological stress.

Monitoring Protocol & Defining Success

Because no human dosing study exists, monitoring here is precautionary rather than protocol-driven: it borrows the endpoints the animal work tracked and the organ systems the receptor biology implicates. Baseline testing before any exposure establishes a personal reference for liver enzymes, muscle-damage markers, blood counts, kidney filtration, glucose handling and body composition, and settles whether age-appropriate cancer screening is current — the most consequential baseline item, given that this compound activates a receptor whose over-activity is a cancer-progression target.

Ongoing testing follows a front-loaded cadence: the liver, muscle and blood-count panel is repeated at 4 weeks, then at 12 weeks, then every 3 to 6 months while exposure continues; body composition and strength are reassessed every 12 weeks; glucose markers and kidney filtration are rechecked every 6 months; and cancer screening stays on the schedule set by age and family history rather than by the compound.

Biomarker	Optimal Functional Range	Why Measure It?	Context/Notes
Alanine aminotransferase	Under 20 U/L	Hepatic clearance is extensive and the responsible enzymes are unidentified	This enzyme leaks into the blood when liver cells are injured; conventional laboratory range extends to 40–50 U/L, which is far looser; requires a 10–12 hour fast; best paired with gamma-glutamyl transferase (GGT) and aspartate aminotransferase (AST), the two enzymes that separate liver from muscle or biliary sources
Creatine kinase	40–150 U/L (men), 30–120 U/L (women)	Detects muscle breakdown; this marker was unchanged in treated mice, so a rise is a genuine signal	Stays elevated up to 72 hours after hard training, so a sample taken after 48 hours of rest is the interpretable one
Complete blood count	All indices within reference, haemoglobin in the upper half	The rodent safety readout was a normal blood count, making this the closest available toxicity comparator	Non-fasting; best paired with ferritin, the iron-storage protein, to interpret any haemoglobin shift
Estimated glomerular filtration rate	Above 90 mL/min/1.73 m²	ERR activation acts directly on kidney mitochondria	Creatinine-based estimates fall transiently after high protein intake or heavy training; cystatin C is the better confirmatory measure
Fasting insulin	Under 5 µIU/mL	Improved insulin sensitivity was the clearest metabolic effect in animals	10–12 hour fast; best paired with fasting glucose to derive HOMA-IR, a calculated index of insulin resistance
Haemoglobin A1c	4.8–5.3%	Captures glucose control over roughly three months	Conventional cut-off is under 5.7%, which is looser; falsely low when red cells are short-lived
Lean body mass by dual-energy X-ray absorptiometry	No established target exists for this compound — change from the individual’s own baseline is the reference instead	The actual goal endpoint, which no study has ever measured on this compound	Requires the same machine and the same hydration and training state; 12-week intervals, since shorter intervals sit inside measurement error
Grip strength	Above 40 kg (men), above 25 kg (women)	Functional muscle output, and the one strength signal observed in mice	Age-related muscle-loss thresholds are much lower, under 27 kg and under 16 kg; the recorded value is the best of three attempts on the dominant hand
Prostate-specific antigen, men from 45	Under 1.0 ng/mL before 60, and stable year on year	Cancer surveillance, given that this receptor’s over-activity drives tumour progression	Unreliable within 48 hours of ejaculation or cycling; the equivalent for women is mammography on the age-based schedule, not a blood marker

Qualitative markers worth tracking alongside the panel:

Perceived effort during steady-state cardiovascular work at a fixed pace or power
Recovery between training sessions, and next-day readiness
Sleep quality, time to fall asleep and night waking
Appetite, and tolerance of cold, since fat oxidation and heat production shift together
Training motivation and adherence, which no laboratory value captures
Injection-site appearance, if the compound is injected

Emerging Research

No registered human trial: A clinicaltrials.gov search on 13 September 2026 returned no study of SLU-PP-332 under any name, so no NCT identifier exists for this compound. The compound has not entered clinical development, and nothing in the registry suggests it will.
Orally active successor: SLU-PP-915 matches the parent compound’s endurance effect when administered orally and amplifies training-induced mitochondrial gene expression (Billon et al., 2026). Chronic-dosing and human work will likely move to this molecule, which could leave the parent a permanent laboratory tool.
Structure-activity roadmap: The first systematic structure-activity relationship analysis of the scaffold found analogues matching its transcriptional effect with better solubility and metabolic stability (Okda et al., 2026). This weakens the case for the parent compound specifically.
Muscle regeneration as the decisive test: Genetic ERRα elevation drives muscle repair and mitigates dystrophy in rodents (Nguyen et al., 2025). A pharmacological version of that experiment is the single study most likely to settle whether receptor activation can build muscle.
Subtype division of labour: Both ERRα and ERRγ are required for training-induced mitochondrial building, while only ERRα carries the PGC-1α-driven programme in cultured muscle cells (Fan et al., 2025). Which subtypes a muscle-directed successor should hit therefore remains open.
Oncology counter-signal: Work pursuing ERRα inhibition as a breast-cancer strategy is expanding (Pradhan et al., 2026). Anything that firms up ERRα as an oncogenic driver weakens the case for deliberately activating it in healthy people.
Detection now exists: Two independent laboratories have mapped the compound’s human in-vitro metabolites for anti-doping use (Avliyakulov et al., 2026). Undetectable use is no longer a realistic assumption for anyone subject to testing.
Nearest registered human work: NCT05814705, an active 24-participant trial of protein with or without urolithin A during single-leg immobilisation, with mitochondrial respiration as its primary endpoint, tests the mitochondrial-remodelling premise in human muscle — without using SLU-PP-332.

Conclusion

SLU-PP-332 is a synthetic compound that switches on a family of control proteins in muscle cells, reproducing part of the signal endurance training sends. The animal and cell work behind it is internally consistent: muscle builds more energy-producing structures, shifts toward a more endurance-like fibre makeup, uses more fat for fuel, and in mice runs longer and shows greater grip strength.

For the goal of building muscle, that record points in an awkward direction. The same treatment that made mouse muscle more endurance-like also left its fibres thinner, and the one experiment on human muscle material — showing abundant new muscle-fibre formation — was done in cell culture rather than in a person. No one has given this compound to a human being in a registered study, so no human measurement of muscle size, strength or safety exists at all.

The safety picture is thin rather than reassuring. Short courses in mice produced no visible harm, but the receptor this compound switches on is the same one whose over-activity is being targeted in aggressive breast cancer, and no long-term or cancer-safety study has been done. Two interests sit on the evidence: almost all supporting work comes from the academic group that designed the compound, and the sports-testing laboratories documenting it run their own funded detection programmes. What is sold today is unregulated laboratory powder.

Top - Benefits - Risks - Protocol

SLU-PP-332 for Muscle Growth

Motivation

Recommended Reading

Grokipedia

Examine

ConsumerLab

Systematic Reviews

Mechanism of Action

Historical Context & Evolution

Expected Benefits

High 🟩 🟩 🟩

Medium 🟩 🟩

Low 🟩

Speculative 🟨

Skeletal Muscle Hypertrophy ⚠️ Conflicted

Muscle Regeneration After Injury

Grip Strength

Aerobic Exercise Capacity ⭕️ Not Central to Muscle Growth

Cardiac and Renal Mitochondrial Function ⭕️ Not Central to Muscle Growth

Oxidative Fibre-Type Remodelling ⭕️ Not Central to Muscle Growth

Fat Mass Loss and Insulin Sensitivity ⭕️ Not Central to Muscle Growth

Benefit-Modifying Factors

Potential Risks & Side Effects

High 🟥 🟥 🟥

Medium 🟥 🟥

Low 🟥

Speculative 🟨

Cancer Promotion Through ERRα Activation ⚠️ Conflicted

Counter-Productive Fibre Remodelling

Unknown Chronic and Human Toxicity

Unselective Activation of ERRs Outside Muscle

Contamination and Unsterile Injection of Research-Grade Material

Risk-Modifying Factors

Key Interactions & Contraindications

Risk Mitigation Strategies

Therapeutic Protocol

Discontinuation & Cycling

Sourcing and Quality

Practical Considerations

Interaction with Foundational Habits

Monitoring Protocol & Defining Success

Emerging Research

Conclusion