GSK2881078

Overview

GSK2881078 (also written GSK-2881078 or GSK 2881078) is a nonsteroidal, orally active selective androgen receptor modulator (SARM) developed by GlaxoSmithKline (GSK) as an investigational treatment for muscle wasting and weakness. It is a true SARM — a small-molecule androgen receptor ligand. It is NOT a peptide (it is not an amino-acid chain) and NOT an anabolic steroid (its scaffold is nonsteroidal).

Unlike most SARMs sold on the grey market, GSK2881078 has a genuine clinical development history: a first-in-human Phase 1 study (Clark et al., Br J Clin Pharmacol 2017) and a 13-week Phase 2 randomized, placebo-controlled trial in patients with COPD and muscle weakness (Thorax 2022; NCT03359473). In those trials it increased lean body mass by roughly 2 kg and produced a signal toward increased quadriceps strength (statistically supported in men, not women). It appears on this peptide reference because it is frequently discussed and stacked alongside peptides in the fitness and "research chemical" community — not because it is one.

Chemistry and structure

GSK2881078 is a nonsteroidal small molecule — an amino-acid chain it is not.

Mechanism of action

• Androgen receptor (AR) agonism — tissue-selective by design. GSK2881078 is a nonsteroidal small-molecule ligand of the androgen receptor that acts as a tissue-selective modulator: it is designed to drive anabolic (muscle-building) signaling while sparing the androgenic effects on other tissues typical of testosterone and anabolic steroids. It has been reported to show greater than 100-fold selectivity for the androgen receptor over the glucocorticoid, mineralocorticoid, and progesterone receptors. As a nonsteroidal small molecule it is fundamentally NOT a peptide. [In vitro] / [Human]
• Anabolic effect in muscle (human). AR agonism in muscle is reflected by increased lean body mass (~2 kg over 13 weeks) and a strength signal in the quadriceps in the Phase 2 COPD trial (Thorax 2022, PMID 36283827; NCT03359473). [Human]
• Systemic androgenic / anti-gonadotropic activity (human). Evidenced by dose-dependent suppression of endogenous testosterone in men and reductions in sex-hormone-binding globulin (SHBG) — consistent with suppression of the hypothalamic-pituitary-testicular (HPTA) axis. This is an on-target androgenic effect, not a benign one (Clark et al., Br J Clin Pharmacol 2017, PMID 28449232). [Human]
• Lipid effect (human). A dose-dependent lowering of HDL ("good") cholesterol was observed — a metabolic/lipid change characteristic of androgenic compounds, seen in both the Phase 1 and Phase 2 trials (PMID 28449232, PMID 36283827). [Human]

Research and evidence

GSK2881078 has real, though limited, human data. It reached Phase 2 and there are no Phase 3 trials and no regulatory approval.

Human evidence in context. The efficacy signal is real but modest: about 2 kg of lean mass over 13 weeks and a strength signal in men only, with no improvement in how patients actually felt or functioned (patient-reported outcomes). There are no Phase 3 trials, no approval, and no long-term (beyond 13 weeks) safety data. Full reversibility and the time-course of testosterone/HPTA suppression after stopping are not fully characterized in the published trials.

Status and regulation

• Regulatory approval: None. GSK2881078 is not approved by the FDA, the EMA, or any other regulator for any indication. It is investigational — it reached Phase 2 and appears to have gone no further; GSK appears to have discontinued active development after Phase 2 (current development status not confirmed in sources reviewed).
• Anti-doping: Prohibited by the World Anti-Doping Agency (WADA) at all times (in- and out-of-competition), listed under S1.2 (Anabolic Agents — Other Anabolic Agents, SARMs). Validated urine and hair detection methods exist (PMID 33037775). The precise sub-code should be confirmed against the current-year WADA Prohibited List, which is revised annually. WADA is a sport-eligibility axis and is separate from any question of legality.
• Market reality: Outside clinical research it is sold only as an unregulated "research chemical" of unknown identity, purity, and potency.

Safety

Documented and expected safety signals (tagged by evidence type):

• Hepatotoxicity / transient transaminase elevation [Human]. Transient liver-enzyme (transaminase) elevations were a main treatment-related finding in the Phase 2 COPD trial, including ALT >3x the upper limit of normal that resolved after stopping. This reflects the class-wide DILI concern; the mechanism and predictors of these elevations, and long-term hepatic safety, are not established. Sources: Thorax 2022 (PMID 36283827); FDA SARM safety communications; NIH LiverTox.
• Testosterone / HPTA suppression [Human]. Dose-dependent reductions in endogenous testosterone in men, with reduced SHBG — indicating suppression of the hypothalamic-pituitary-testicular axis. This is an on-target androgenic effect, not a benign one. No dosing, "cycle," or post-cycle guidance is given here. Source: Br J Clin Pharmacol 2017 (PMID 28449232).
• HDL-cholesterol reduction [Human]. Dose-dependent, reversible lowering of HDL ("good") cholesterol in both the Phase 1 and Phase 2 trials — a cardiovascular-relevant lipid change; the consequences of chronic HDL lowering with this compound are not established. Sources: PMID 28449232, PMID 36283827.
• Not an approved medicine; very long half-life [Human]. GSK2881078 is investigational only, approved by no regulator for any indication, and its very long half-life (>100 h) means exposure and any adverse effects persist for weeks after dosing stops. It must not be framed as a milder, safer, or legal alternative to anabolic steroids.

Legal status

How it compares

GSK2881078 is often grouped with other SARMs and with non-SARM "research chemicals." The honest framing:

• Ostarine, ligandrol (LGD-4033), andarine, testolone (RAD-140) — other nonsteroidal SARMs that share GSK2881078's mechanism (AR agonism), testosterone- suppression risk, WADA S1.2 status, and lack of approval. GSK2881078 stands out for having a published, GSK-run Phase 1 and Phase 2 program, whereas most grey-market SARMs never had a sponsor take them through controlled human trials.
• Cardarine (GW-501516) and stenabolic (SR9009) — frequently sold alongside SARMs but are NOT SARMs; cardarine is a PPARδ agonist and stenabolic is a Rev-ErbA agonist, with different mechanisms and their own risks.
• MK-677 (ibutamoren) — frequently grouped with SARMs but is a growth-hormone secretagogue / ghrelin agonist, not a SARM.

The decisive point: GSK2881078 is investigational, reached only Phase 2, is not approved for anything, and its efficacy signal (~2 kg lean mass, strength in men only, no patient-reported-outcome benefit) came hand in hand with liver-enzyme, hormonal, and lipid risks. See the Muscle, growth & hormones overview.

Common misconceptions

• "GSK2881078 is a peptide." No. It is a nonsteroidal small molecule (C14H13F3N2O2S, ~330.33 g/mol). It is covered here only because it is discussed and stacked with peptides.
• "A big pharma company developed it, so it must be safe/effective for muscle." No. GSK took it to Phase 2 and no further; it is not approved, showed only a modest lean-mass gain with no patient-reported-outcome benefit, and the same trials documented liver-enzyme, testosterone, and HDL risks.
• "It's a milder, safer, legal alternative to steroids." No. It suppresses natural testosterone, lowers HDL, caused transient liver-enzyme elevations, and is not approved. "SARM" does not mean "safe."
• "Buying it as a 'research chemical' means it's clean and correctly dosed." No. Independent testing (JAMA 2017) found most products sold as SARMs were mislabeled, contained a different drug, or contained nothing.

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This entry is educational and summarizes published research and public regulatory information as of the "updated" date above. It is not medical advice, not legal advice, a recommendation, or a guide to obtaining or using any substance.