ACP-105

Overview

ACP-105 is a nonsteroidal selective androgen receptor modulator (SARM) — a true SARM, not a peptide. It was discovered by ACADIA Pharmaceuticals Inc. and nominated as a development candidate around 2006. In laboratory assays it behaves as a potent partial agonist of the androgen receptor (AR), and in rodent studies it was anabolic on muscle and bone while relatively sparing the prostate — the profile that defines the "SARM" concept.

It is important to be precise about what ACP-105 is and is not:

• It is not a peptide. It is a small-molecule benzonitrile bearing an azabicyclo-octane (tropane-like) group — formula C16H19ClN2O — not a chain of amino acids.
• It is a genuine SARM. Unlike some compounds mislabeled "SARMs" online, ACP-105 really does act on the androgen receptor.
• It is not an approved medicine. Its highest development phase was preclinical. It never reached an IND, never entered a human clinical trial, and has no ClinicalTrials.gov record. It is not authorized by any regulator anywhere.

In short, ACP-105 is a preclinical research reagent that was never validated in humans. Today it appears mainly in two places: as a compound sold online as a "SARM," and as a reference target in anti-doping science, where its metabolites have been characterized specifically so it can be detected.

Chemistry and structure

ACP-105 is a nonsteroidal, non-peptide small molecule. Its published identity is a benzonitrile substituted with a hydroxy-methyl 8-azabicyclo[3.2.1]octane (tropane-type) ring.

A note on the registry number: the widely-documented primary CAS is 899821-23-9. A 2025 forensic-toxicology paper lists an alternate CAS, 1048998-11-3. Whether that alternate denotes a stereochemical or salt variant versus the primary is not resolved in the available sources and is left as an open question below.

Mechanism of action

ACP-105's molecular target is the androgen receptor (AR) — the same receptor that testosterone acts on. As a partial agonist, it switches the receptor on, but with a tissue-selective pattern that is the whole point of the SARM concept.

• Androgen receptor (AR) — partial agonist / tissue-selective modulator. ACP-105 binds the AR with high affinity and acts as a nonsteroidal partial agonist. It is reported as orally available with pEC50 ~9.0 (wild-type AR) and ~9.4 (the T877A mutant) in reporter assays, and described as roughly as potent and efficacious as testosterone in vitro, without interacting with other steroid-hormone receptors. [In vitro]
• Skeletal muscle and bone AR signaling — anabolic gene program with tissue selectivity. In rodent models, ACP-105 produced anabolic effects on muscle and bone (e.g. lean mass / grip strength) at doses below those causing androgenic effects in the prostate — the basis for the "muscle/bone-selective, prostate-sparing" profile. This selectivity is relative, not absolute, and was shown only in animals. [Animal]
• CNS / hippocampal androgen signaling — exploratory neuroprotection. ACP-105 was also explored around cognition: it was reported to affect rotorod (sensorimotor) performance and cued fear conditioning in cranially-irradiated female mice, suggesting AR activity in CNS tissue. This is exploratory animal work only; no cognitive benefit has been shown in humans. [Animal]

Research and evidence

ACP-105 has never been tested in a human clinical trial. There is no IND, no registered study, and no ClinicalTrials.gov record. Its entire evidence base is preclinical — cells and animals — supplemented by computational predictions and anti-doping analytical work.

What exists includes:

• Developer preclinical characterization [Animal] — ACADIA presented preclinical data on ACP-105 (alongside ACP-104) at Experimental Biology 2008, describing it as anabolic on muscle and bone with minimal prostate effect. No IND or human trial followed.
• In vitro pharmacology [In vitro] — an oral, nonsteroidal AR partial agonist with pEC50 ~9.0 (wild-type) / ~9.4 (T877A) and reproductive-tissue selectivity, roughly as potent as testosterone in assays.
• CNS / cognition exploration [Animal] — Brain Research (2011; PMID 21219889) reported effects of ACP-105 on rotorod performance and cued fear conditioning in sham-irradiated and irradiated female mice.
• Anti-doping metabolite work [Animal] — Metabolites (2021; PMC7912737) characterized equine in-vivo/in-vitro metabolites of ACP-105 (tentatively identifying multiple metabolites, with monohydroxylated species as urinary detection targets) to support doping control; see also the Slíž et al. 2025 review.
• In-silico toxicology [In vitro] — Archives of Toxicology (2025; PMID 40064700) ran computational Ames/hERG/organ-toxicity/acute-toxicity predictions precisely because empirical human safety data are absent.

Status and regulation

ACP-105 is not an approved medicine anywhere. Its highest development phase was preclinical: a development candidate nominated around 2006 by ACADIA Pharmaceuticals that never reached an IND or any human trial. It is handled as a research reagent, not a pharmaceutical product.

Separately, ACP-105 is prohibited in sport. It is detected as a doping agent and is banned by the World Anti-Doping Agency (WADA) under class S1.2 (Other Anabolic Agents — SARMs), at all times, in and out of competition. Anti-doping status is a sport-eligibility matter and is separate from any question of legality for possession or sale.

Safety

The honest summary: ACP-105 has no human safety data at all, and it belongs to a compound class with documented serious harms. Signals below are tagged by evidence type.

No human safety data [Hypothesis — data absent]

ACP-105 has never been administered to humans in a registered trial. There are no human pharmacokinetic, efficacy, or safety data. Its half-life, human dose, and adverse-event profile are unknown. Any human use is uncontrolled self-experimentation with an unstudied compound.

SARM-class hepatotoxicity / drug-induced liver injury [Human — class level]

The FDA has warned that SARMs are associated with serious harms including liver injury and cases of acute liver failure requiring hospitalization, and multiple case reports document SARM-associated drug-induced liver injury (DILI). No ACP-105-specific human liver data exist, but it is a member of this class.

Testosterone / HPTA suppression [Hypothesis — class level, inferred]

As an AR agonist, ACP-105 would be expected — like other SARMs — to suppress the hypothalamic-pituitary-testicular axis and endogenous testosterone. This is a documented class effect of SARMs; it has not been measured for ACP-105 in humans.

Predicted (in-silico) toxicity flags [In vitro]

The 2025 Archives of Toxicology study ran computational Ames (genotoxicity), hERG (cardiotoxicity), organ-toxicity, and irritation predictions specifically because empirical human data are missing. These are predictions, not measured outcomes, and were undertaken to fill a data gap — they underscore uncertainty rather than establish safety.

Contamination reality — "SARM" labels are unreliable [Human]

Products sold as "SARMs" are frequently mislabeled. In a landmark analysis, Van Wagoner et al. (JAMA 2017;318(20):2004–2010; PMID 29183075) chemically tested products sold as SARMs and found that only 52% contained the labeled SARM, 39% contained a different unapproved drug, and 9% contained no active compound at all. A label is therefore not a reliable statement of contents — anything sold as "ACP-105" may contain something else entirely.

Legal status

Regulatory: ACP-105 is not an approved medicine in the United States, the European Union, or anywhere else. It is not a licensed drug or a dietary-supplement ingredient; it is handled as a research reagent. Framing on this site is research-reagent classification, not human-use legality — the per-market legality context is separate from, and does not endorse, human use. Legal status for possession or sale varies by jurisdiction and is not a single settled value.

Anti-doping (a separate axis): ACP-105 is on the WADA Prohibited List, class S1.2 (Other Anabolic Agents — SARMs), banned at all times in sport. Being WADA-listed is a sport-eligibility fact — distinct from whether a substance is legal to possess or handle in a given country.

How it compares

ACP-105 is one of many nonsteroidal SARMs that were characterized preclinically. Compared with the better-known members of the class, its distinguishing feature is how little human data exists — it never left the laboratory, whereas some SARMs (for example ostarine/enobosarm) reached early human studies.

The point of the comparison is not that any SARM here is safe — none is an approved medicine — but that ACP-105 sits at the least-studied end even of this class.

Common misconceptions

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This article is provided for educational purposes only and is not medical, legal, or performance advice (reviewed 2026-07-10). ACP-105 is an unapproved laboratory research compound that has never been tested in humans and has no human safety data. Nothing here is an endorsement or instruction to obtain or use it, and the mechanism, evidence, and safety points above are drawn from preclinical literature, in-silico predictions, and class-based inference, not from human clinical data.