AC-262,536 (usually written AC-262536) is an experimental nonsteroidal selective androgen receptor modulator (SARM) discovered by ACADIA Pharmaceuticals. A SARM is a compound designed to activate the androgen receptor in muscle and bone while having less effect on tissues such as the prostate. AC-262536 was described in a single pharmacology paper in 2008 and was never developed into a medicine.
The most important fact about AC-262536 is how little is known. All published efficacy data come from one 2-week study in castrated rats. No human trial has been published or registered, so there are no human data on dosing, pharmacokinetics, effectiveness or safety. Even so, SARMs are widely sold online (Cutler et al., Drug Test Anal 2021), and anti-doping laboratories now screen for AC-262536.
This page summarizes what the original animal study, anti-doping research and regulators report. It is for education only and is not medical advice.
| Property | Detail |
|---|---|
| Drug class | Nonsteroidal SARM, tropanol (8-azabicyclo[3.2.1]octane) chemical class |
| Developer | ACADIA Pharmaceuticals; first described in 2008 |
| Chemistry | C₁₈H₁₈N₂O, 278.3 g/mol, CAS 870888-46-3 |
| Activity at the androgen receptor | Partial agonist relative to testosterone (cell-based assay) |
| Studied doses | Animal only: a 2-week study in castrated male rats; no human doses studied |
| Half-life | No published human or animal half-life in the sources reviewed |
| Human trials | None published; none found on ClinicalTrials.gov |
| US status | Not FDA-approved; FDA states SARMs cannot be legally marketed as dietary supplements or drugs; not named in DEA Schedule III |
| WADA status | Prohibited at all times as a SARM (class S1.2, other anabolic agents) |
What it is
AC-262536’s chemical name is 4-[(1R,5S)-3-hydroxy-8-azabicyclo[3.2.1]octan-8-yl]naphthalene-1-carbonitrile (PubChem). In plain terms, it is a naphthalene ring carrying a nitrile group, joined to a tropane-like bicyclic ring with a hydroxyl group in the “endo” position. It has no steroid skeleton, so it cannot be converted by the body into estrogen or dihydrotestosterone (DHT) the way testosterone can.
ACADIA scientists identified it using a functional cell-based assay of androgen receptor activation (Piu et al., J Steroid Biochem Mol Biol 2008). They reported that it was a potent and selective ligand of the androgen receptor, with partial agonist activity compared with testosterone. A partial agonist activates the receptor but produces a smaller maximal response than a full agonist.
Anti-doping chemists classify AC-262536 with ACADIA’s later compound ACP-105 as “tropanol” SARMs (Stacchini et al., J Pharm Biomed Anal 2021). ACP-105 came out of the same company’s screening program and was reported in 2009 (Schlienger et al., J Med Chem 2009). Other SARMs in the library, such as ostarine, ligandrol and RAD-140, belong to different chemical classes, and several of them have at least some human trial data. AC-262536 does not.
How it works in the body
There are no published human pharmacokinetic data for AC-262536: no measured absorption, peak level, half-life or route of elimination. Half-life figures that circulate online could not be traced to a primary source, so we do not repeat them.
The only in vivo metabolism study was done in horses, for doping-control purposes (Cutler et al., Drug Test Anal 2021). Two Thoroughbred horses received AC-262536 by mouth:
| Finding | Result in horses |
|---|---|
| Phase I metabolites found with liver preparations in vitro | 9 |
| Metabolites detected in urine | 4, plus the parent compound |
| Metabolites detected in plasma | 3, plus the parent compound |
| Main form in urine and plasma | Glucuronide conjugates |
| Longest-detectable marker | An epimer of the parent compound (an isomer differing at one stereocenter) |
| Hair | Parent compound incorporated; no metabolites |
These are horse data from two animals and do not establish how the compound behaves in people.
What the research shows
The rat study
The only published efficacy data come from ACADIA’s 2-week chronic study in castrated male rats (Piu et al., 2008). Castration removes the animals’ own testosterone, so any androgen-like effect can be attributed to the test compound. According to the paper’s abstract, AC-262536:
- significantly improved anabolic measures, especially growth of the levator ani, a small androgen-sensitive muscle in the rat pelvis;
- suppressed the elevated luteinizing hormone (LH) levels that follow castration;
- had only weak androgenic effects on prostate and seminal vesicle weight, in “sharp contrast” to testosterone.
The LH finding matters. LH is the pituitary signal that tells the testes to make testosterone. A compound that lowers LH acts on this feedback loop, which in intact animals or people would be expected to reduce natural testosterone production. How much AC-262536 does this in humans has never been measured.
About anabolic:androgenic ratios. Online sources often quote a precise anabolic:androgenic ratio for AC-262536. The published abstract reports only that androgenic effects were “weak” compared with testosterone in castrated rats. We could not verify any numeric ratio, so we do not repeat one. Rat organ-weight ratios also do not predict tissue selectivity or side effects in humans.
Human evidence
None. We found no published human study of AC-262536, and a search of ClinicalTrials.gov returned no registered trials. A 2023 systematic review of SARM safety in healthy adults included 18 clinical trials and 15 case reports or case series; none involved AC-262536 (Vignali et al., J Xenobiot 2023).
Claims about muscle gain, fat loss, strength, recovery or “joint healing” from AC-262536 in people are therefore not based on controlled evidence.
Side effects and risks
No compound-specific human safety data
Because AC-262536 has never been tested in humans, its side effects, safe dose range and interactions are unknown. What is known comes from the SARM class as a whole, and it cannot be assumed to apply equally to every compound.
Class-level risks
FDA warns that SARMs are not FDA-approved and that studies and reports link them to serious or life-threatening problems (FDA, 2023), including:
- increased risk of heart attack or stroke;
- liver injury and acute liver failure;
- psychosis or hallucinations, and sleep disturbances;
- sexual dysfunction, infertility and testicular shrinkage;
- miscarriage.
Published case data center on the liver:
| Source | What it found (SARMs as a class) |
|---|---|
| Vignali et al., 2023, systematic review, 33 studies | 15 reported cases of drug-induced liver injury, 1 Achilles tendon rupture, 1 rhabdomyolysis; ALT (a liver enzyme) elevation in a mean 7.1% of SARM-exposed trial participants |
| Leciejewska et al., Eur J Clin Pharmacol 2024, review of reported cases | 20 published adverse-event reports since 2020, mostly cholestatic or hepatocellular liver injury with jaundice |
Product quality
AC-262536 is not made under pharmaceutical quality control. In a JAMA analysis of 44 products sold online as SARMs, only 52% contained a SARM, 25% contained substances not listed on the label, 9% contained no active compound, and only 41% matched their labeled amount (Van Wagoner et al., JAMA 2017). A buyer therefore cannot be sure what a product labeled as AC-262536 actually contains, or how much.
Legal status and anti-doping
- United States. AC-262536 is not an approved drug. FDA states that SARMs “cannot be legally marketed in the U.S. as a dietary supplement or drug” (FDA, 2023). It is not named among the anabolic steroids in DEA Schedule III (21 CFR 1308.13).
- Sport. SARMs have been on the WADA Prohibited List since 2008 (Thevis and Schänzer, Mol Cell Endocrinol 2018). The 2026 list prohibits SARMs at all times, in and out of competition, under S1.2 “Other anabolic agents,” as non-specified substances (WADA 2026 Prohibited List). The list’s examples are not exhaustive, so AC-262536 is covered even though it is not named.
Laboratories have built tests that include AC-262536:
| Matrix | Context | Source |
|---|---|---|
| Human urine | Validated multi-SARM method; detection capability 0.1–1.0 ng/mL across the screened compounds | Stacchini et al., 2021 |
| Human hair | Validated screen of 9 SARMs and 2 metabolic modulators | Gheddar et al., J Chromatogr B 2021 |
| Horse and cattle blood | Screening method; detection capability 1 ng/mL for AC-262536 | Ventura et al., Drug Test Anal 2020 |
| Horse urine, plasma and hair | Metabolite identification after oral dosing | Cutler et al., 2021 |
Key takeaways
- An abandoned research compound. AC-262536 is a nonsteroidal SARM from ACADIA Pharmaceuticals that was never developed into a medicine.
- Animal data only. Everything known about its effects comes from one 2-week study in castrated rats, which reported anabolic effects on a pelvic muscle with weak effects on the prostate.
- No human trials. There are no published human data on dose, half-life, effectiveness or safety, and no registered trials.
- It acts on the hormone axis. It lowered LH in rats, which signals the potential to suppress natural testosterone production.
- Class risks and unreliable products. FDA links SARMs to liver injury and other serious harms, and products sold as SARMs are often mislabeled.
- Prohibited in sport. WADA bans all SARMs at all times, and anti-doping methods already include AC-262536.
Sources
- Piu F, Gardell LR, Son T, et al. Pharmacological characterization of AC-262536, a novel selective androgen receptor modulator. J Steroid Biochem Mol Biol. 2008;109(1-2):129–137. PubMed.
- National Center for Biotechnology Information. AC-262536, PubChem CID 44512434. PubChem.
- Schlienger N, Lund BW, Pawlas J, et al. Synthesis, structure-activity relationships, and characterization of novel nonsteroidal and selective androgen receptor modulators. J Med Chem. 2009;52(22):7186–7191. PubMed.
- Stacchini C, Botrè F, Comunità F, et al. Simultaneous detection of different chemical classes of selective androgen receptor modulators in urine by liquid chromatography-mass spectrometry-based techniques. J Pharm Biomed Anal. 2021;195:113849. PubMed.
- Cutler C, Viljanto M, Taylor P, et al. Equine metabolism of the selective androgen receptor modulator AC-262536 in vitro and in urine, plasma and hair following oral administration. Drug Test Anal. 2021;13(2):369–385. PubMed.
- Ventura E, Gadaj A, Buckley T, Mooney MH. Development of a multi-residue high-throughput UHPLC-MS/MS method for routine monitoring of SARM compounds in equine and bovine blood. Drug Test Anal. 2020;12(9):1373–1379. PubMed.
- Gheddar L, Raul JS, Kintz P. Development and validation of SARMs and metabolic modulators screening in hair using UHPLC-MS/MS: application to a doping case and first identification of S23 in authentic human hair. J Chromatogr B Analyt Technol Biomed Life Sci. 2021;1187:123048. PubMed.
- Vignali JD, Pak KC, Beverley HR, et al. Systematic review of safety of selective androgen receptor modulators in healthy adults: implications for recreational users. J Xenobiot. 2023;13(2):218–236. PubMed.
- Leciejewska N, Jędrejko K, Gómez-Renaud VM, et al. Selective androgen receptor modulator use and related adverse events including drug-induced liver injury: analysis of suspected cases. Eur J Clin Pharmacol. 2024;80(2):185–202. PubMed.
- Van Wagoner RM, Eichner A, Bhasin S, Deuster PA, Eichner D. Chemical composition and labeling of substances marketed as selective androgen receptor modulators and sold via the internet. JAMA. 2017;318(20):2004–2010. PubMed.
- Thevis M, Schänzer W. Detection of SARMs in doping control analysis. Mol Cell Endocrinol. 2018;464:34–45. PubMed.
- US Food and Drug Administration. FDA warns of use of selective androgen receptor modulators (SARMs) among teens, young adults. Consumer update, content current as of April 26, 2023. FDA.
- Drug Enforcement Administration. Schedules of controlled substances: Schedule III. 21 CFR 1308.13. eCFR.
- World Anti-Doping Agency. The 2026 Prohibited List, in effect from January 1, 2026. WADA 2026 Prohibited List.
- US National Library of Medicine. ClinicalTrials.gov search for “AC-262536.” ClinicalTrials.gov.