AC-262536

Overview

AC-262536 (also written AC-262,536) is a nonsteroidal selective androgen receptor modulator (SARM) that acts as a partial agonist at the androgen receptor (AR). It is not a peptide — it is a small synthetic molecule — and it is not an approved medicine anywhere in the world.

Everything currently known about AC-262536 traces back to a single published preclinical study: Piu et al., Journal of Steroid Biochemistry and Molecular Biology, 2008 (PMID 18164613), from ACADIA Pharmaceuticals. That paper characterized the compound in binding assays, cell-based assays, and castrated-rat models. There are no published human trials, and it does not appear to have advanced beyond that early characterization.

Chemistry and structure

Structurally, AC-262536 belongs to an aniline / azabicyclooctane class related to ACADIA's ACP-105 and, more loosely, to RAD140 (testolone). PubChem confirms the identity as 4-(3-endo-hydroxy-8-azabicyclo[3.2.1]oct-8-yl)naphthalene-1-carbonitrile (C18H18N2O, CID 44512434).

Mechanism of action

AC-262536 works by binding and partially activating the androgen receptor. Its defining feature — like other SARMs — is tissue selectivity: relatively strong action on muscle-type (anabolic) tissue and weaker action on prostate-type (androgenic) tissue. All of the following is preclinical.

• Androgen receptor — partial agonist [In vitro]. Binds the AR with high affinity (Ki ~5 nM) and activates it partially relative to testosterone. It was selective for the AR across a panel of 47 nuclear receptors, with no significant affinity for the others tested. (Source: PMID 18164613.)
• Muscle (levator ani) vs prostate — tissue selectivity [Animal]. In castrated rats it produced ~66% of testosterone's maximal levator-ani (anabolic) effect but only ~27% of its maximal prostate (androgenic) effect — the defining SARM tissue-selectivity profile. (Source: PMID 18164613.)
• HPTA axis — central suppression [Animal]. It reduced elevated plasma luteinizing hormone (LH) in castrated rats, indicating central negative feedback on gonadotropin signaling. This is the mechanistic basis for the HPTA / testosterone suppression seen across the SARM class. (Source: PMID 18164613.)
• LNCaP prostate-cancer cells — anti-proliferative [In vitro]. It inhibited dihydrotestosterone (DHT)-induced proliferation of androgen-sensitive LNCaP prostate cancer cells at 0.1 and 1 µM in vitro. (Source: PMID 18164613.)

Research and evidence

Honestly stated: the entire evidence base for AC-262536 is one 2008 preclinical paper. It shows an interesting tissue-selective anabolic signature in castrated rats and clean AR selectivity in vitro — but there is no human efficacy or safety data of any kind, and development does not appear to have progressed to published human trials.

Status and regulation

• Preclinical only. No human trials identified on ClinicalTrials.gov or PubMed. AC-262536 is not in clinical development in any indication that these sources record.
• Not an approved medicine. It is not approved by the FDA, EMA, or any other regulator, and has no approved indication.
• Research reagent framing. Where AC-262536 is sold, it is sold as a research chemical ("not for human consumption"). That framing does not make human use safe or lawful.
• Prohibited in sport. It is banned by WADA under S1.2 (Other Anabolic Agents — SARMs) at all times, and USADA lists SARMs as a prohibited anabolic class.

Safety

AC-262536 has no human safety data. The signals below are either compound-specific but animal-only, or class-level for SARMs.

• No human safety data [Human]. AC-262536 has never been studied in humans. Any statement that it is "safe" is unknown, not reassuring — untested is not the same as safe.
• SARM-class liver injury / DILI [Human — class-level]. The FDA has warned that products containing SARMs are associated with serious liver injury, including cases requiring hospitalization and acute liver failure. This is a class-level signal; AC-262536 itself has no human liver-safety data. (Source: FDA SARM consumer warning.)
• Testosterone / HPTA suppression [Animal — compound; Human — class]. AC-262536 reduced plasma LH in castrated rats, consistent with central suppression of the HPTA axis. Across the SARM class this manifests as suppression of the body's own testosterone; the extent in humans is unknown for this specific compound.
• Broader SARM-class adverse events [Human — class-level]. SARM use as a class has been linked in FDA communications and case reports to increased risk of heart attack or stroke, psychiatric effects, sexual dysfunction, infertility, and testicular shrinkage — not specifically demonstrated for AC-262536, but relevant to anyone exposed to a product labelled as a SARM.

Legal status

AC-262536 is best understood as a research-reagent-classified compound: it is not an approved medicine, and in most jurisdictions selling or using an unapproved compound in humans falls under unauthorised-medicine rules. This page does not assess the legality of any particular use in any particular country. Separately — and on a different axis from legality — AC-262536 is prohibited in sport by WADA under S1.2 (Other Anabolic Agents). Being on the WADA list governs sport eligibility, not general legality. Nothing here is legal advice (dated 2026-07-10).

How it compares

AC-262536 sits in the same nonsteroidal SARM bucket as several better-known compounds. The honest distinction is evidence stage: AC-262536 is purely preclinical, whereas some peers at least reached early human trials.

Takeaways:

• Same class, different maturity. AC-262536 is the least-studied of these — a single preclinical paper versus human-trial data for ostarine and testolone.
• None is approved. No SARM here is an approved medicine, and all are WADA-prohibited.
• No "prostate-sparing" claim in humans. The tissue selectivity is a rat/in-vitro finding for AC-262536 — not a demonstrated human safety property.

Common misconceptions

• "AC-262536 is a peptide." No. It is a nonsteroidal small molecule (C18H18N2O), a SARM. It is listed here because SARMs are frequently discussed alongside peptides in muscle/performance contexts.
• "It's an approved or clinically proven drug." No. It is a preclinical research chemical with one 2008 study and zero human trials.
• "It's a safer, milder, or legal alternative to steroids." No. It carries the SARM-class liver and HPTA-suppression warnings, has no human safety data, and is WADA-banned.
• "The prostate-sparing profile means it's safe." That profile is a castrated-rat / in-vitro result — it says nothing verified about human safety.
• "A vial labelled AC-262536 contains AC-262536." Often not — the JAMA analysis found the label was wrong about half the time.