ACP-105 Half-Life: What the Research Actually Shows

Key takeaways

What Is ACP-105?

ACP-105 is a nonsteroidal selective androgen receptor modulator (SARM) first reported by researchers at Acadia Pharmaceuticals. In a 2008 conference abstract, the company described it as a tissue-selective, orally bioavailable, nonsteroidal androgen receptor modulator that was found to be a potent and selective androgen receptor agonist in cell-based assays, with studies in castrated rats showing that it potently suppressed the luteinizing hormone surge and produced anabolic effects. A related synthesis and structure-activity paper by the same group, published in the Journal of Medicinal Chemistry, characterized the compound alongside a series of related nonsteroidal androgen receptor modulators.

ACP-105 has never advanced through a published human clinical trial and is not approved by the FDA or any other regulatory agency for any indication. It is sold online labeled as a research chemical, a marketing pattern documented across the SARM class generally, with products typically labeled 'not for human consumption' or 'for research use only.' It falls within the class of substances prohibited in sport by the World Anti-Doping Agency.

Does ACP-105 Have a Confirmed Human Half-Life?

No. Because ACP-105 has never been tested in a published human clinical pharmacokinetic study, there is no validated, peer-reviewed elimination half-life for the intact drug in living people. Numbers that circulate online, most commonly somewhere between 4 and 6 hours, trace back either to a single in vitro assay, a 2025 computational prediction, or unsourced commercial copy rather than to a clinical dosing study in humans.

This distinction matters because in vitro and in silico estimates routinely diverge from what would be measured in an actual human dosing study with timed blood draws, and the existing ACP-105 data illustrate that gap clearly.

The In Vitro Data: 5 Hours in Human Liver Cells

The earliest pharmacokinetic-adjacent data point for ACP-105 comes from a human hepatocyte stability assay tied to the compound's original medicinal chemistry characterization. Multiple chemical-supplier reference sheets citing this source report that the half-life of ACP-105 in human hepatocytes was measured and found to be 5.0 hours.

This is an in vitro metabolic stability assay: isolated human liver cells are incubated with the compound and its disappearance over time is tracked in a dish. It gives an estimate of how quickly liver enzymes would metabolize the compound if exposure were comparable in a whole organism, but it does not account for absorption, distribution, plasma protein binding, or renal handling in an intact human body. It is not equivalent to a true in vivo elimination half-life.

The 2025 In Silico ADME Prediction: About 1.2 Hours

A 2025 paper in Archives of Toxicology set out to build the first comprehensive ADME (absorption, distribution, metabolism, excretion) profile of ACP-105, noting that the compound is increasingly detected in anti-doping analyses despite lacking such a profile. The authors used seven independent computational platforms, ADMETlab 3.0, ADMET Predictor 12.0, ACD/Percepta, SwissADME, pkCSM, XenoSite, and DruMAP, to model the compound's likely pharmacokinetic behavior in the absence of any in vivo human data.

Clearance predictions varied widely across the different models (roughly 7.175 to 3.86 × 10⁻⁵ mL/min/kg), but converged on a short predicted half-life of approximately 1.18 hours, with no expected renal excretion via the OCT2 transporter. The same analysis predicted high gastrointestinal absorption of up to 100%, moderate lipophilicity (LogP roughly 3.0 to 3.52), strong plasma protein binding (77% to 99%) with a minimal free plasma fraction below 1%, and a variable predicted volume of distribution (0.18 to 12 L/kg), along with predicted blood-brain barrier penetration in most models.

The paper also modeled metabolism, identifying six predicted metabolites (M1 to M6) formed primarily via CYP3A4, for which ACP-105 was a consistent substrate (82% to 100%), with additional minor contributions from CYP2C9, CYP2C19, and CYP2D6, and predicted pathways including oxygenation, N-dealkylation, and UGT (glucuronide) conjugation.

These figures are computational predictions generated from chemical structure, not measurements taken from blood samples in a living organism. The authors themselves frame the analysis as filling a gap left by the absence of real pharmacokinetic data, intended to support interpretation of exposure in clinical and forensic toxicology rather than to guide human use of the compound.

What Equine Doping-Control Studies Show About Clearance

The only in vivo dosing data for ACP-105 that could be identified come from two separate equine studies conducted for anti-doping purposes, not from human trials. One study administered ACP-105 orally to horses and analyzed urine using LC-MS/MS, detecting a total of 19 metabolites in ACP-105-administered equine urine samples. That study reported that ACP-105 and its metabolites were detected for up to 72 hours in urine, describing the finding as a valuable tool for evaluating the compound's use in sport.

A separate equine study, published in the journal Metabolites, administered ACP-105 orally to horses and collected blood and urine samples over a 96-hour window, comparing the in vivo findings against five in vitro liver-metabolism models. That study tentatively identified 21 metabolites, labeled M1a through M9b, including several novel glucuronide conjugates in plasma and urine, with hydroxylated metabolites dominating in hydrolyzed urine samples. The major plasma metabolite M1a had a detection time of 24 hours in plasma, but was also tentatively identified in hydrolyzed urine with a detection time exceeding 96 hours, the outer limit of the study's own testing window, meaning the true detection window for this metabolite could not be fully established and may extend further.

Taken together, these detection-window findings do not directly equal an elimination half-life, since detection windows depend on assay sensitivity as well as clearance. But they are broadly consistent with the pattern suggested by the human hepatocyte and in silico work: the parent ACP-105 molecule appears to be metabolized relatively quickly, while several downstream metabolites persist in urine for considerably longer, which is why metabolites rather than the parent compound are the preferred targets for doping laboratories.

Why Commercial Half-Life Claims Should Be Treated With Caution

Numerous SARM retailer and blog websites state that ACP-105 has a half-life of roughly 4 to 6 hours, sometimes rounded to 6 hours, and use this figure to recommend split or twice-daily dosing schedules. None of the vendor or blog sources identified link back to an actual dataset or acknowledge the 2025 in silico prediction of roughly 1.2 hours, which is a substantially shorter figure derived from a peer-reviewed toxicology publication.

Because these websites typically sell the compound, their stated half-lives and any accompanying dosing suggestions carry an inherent commercial interest and should not be treated as clinical fact. A genuine human half-life would require a controlled pharmacokinetic study with timed blood draws in volunteers, and no such study of ACP-105 has been published.

Regulatory Status and Safety Context

ACP-105 belongs to the broader SARM class, about which the FDA has issued repeated warnings. The FDA has stated that SARMs are considered unapproved drugs and cannot be legally marketed in the United States as a dietary supplement or drug, and has separately warned that these products are not worth risking a person's health for a few extra likes on social media, citing risks including increased risk of heart attack or stroke, psychosis and hallucinations, sleep disturbances, sexual dysfunction, and liver injury.

SARMs as a class are listed as 'Other Anabolic Agents' under Section S1.2 of the World Anti-Doping Agency's Prohibited List and have been banned at all times, in and out of competition, since 2008. A 2023 systematic review of SARM safety in healthy adults found that SARMs are not FDA approved and that obtaining them for personal use is illegal, and documented case reports of drug-induced liver injury and tendon rupture associated with SARM use, concluding that recreational use should be strongly discouraged.

No published clinical trial has evaluated ACP-105 specifically in humans, so its long-term safety, hepatic effects, and hormonal suppression profile in people remain unstudied outside preclinical rodent and equine work.

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