Overview

GTX-027 is a non-steroidal selective androgen receptor modulator (SARM) developed by GTx Inc. (now Oncternal Therapeutics) as part of their continued effort to develop tissue-selective androgen receptor agonists for muscle-wasting and oncology-related indications. It emerged from the same research program that produced Ostarine (GTX-024, Enobosarm), one of the most extensively studied SARMs in clinical history, and was designed to offer improved pharmacological properties including greater anabolic potency and enhanced tissue selectivity.

GTx Inc. developed a series of arylpropionamide-derived SARMs, with GTX-027 representing a structural optimization over the parent compound. Preclinical data indicated that GTX-027 maintained favorable selectivity for muscle and bone tissue over the prostate, with potentially enhanced efficacy in building lean mass. The compound was investigated in the context of cancer-associated cachexia and stress urinary incontinence, conditions where anabolic therapies could provide significant clinical benefit without the risks associated with traditional androgens like testosterone.

GTX-027 is part of a family of GTx-developed SARMs that also includes GTX-024 (Ostarine) and other analogs. While Ostarine advanced to Phase III clinical trials for cancer cachexia (the POWER trials), GTX-027 has had a more limited public clinical profile. The SARM class continues to attract research interest for conditions where preservation of lean mass is critical, and compounds like GTX-027 contribute to the evolving understanding of how structural modifications affect tissue selectivity and clinical outcomes.

Mechanism of Action

Selective Androgen Receptor Modulation

GTX-027 is a non-steroidal selective androgen receptor modulator (SARM) developed by GTx, Inc. It binds the androgen receptor (AR) with high affinity and selectivity, inducing a distinct conformational change in the receptor's ligand-binding domain that differs from classical steroidal androgens. This unique conformation drives differential co-regulator recruitment — preferentially engaging anabolic co-activators (e.g., SRC-1, SRC-3) in muscle tissue while showing reduced interaction with co-activators in androgen-sensitive tissues like prostate (PMID: 22498816).

Tissue-Selective Genomic Signaling

The AR-GTX-027 complex translocates to the nucleus and binds androgen response elements (AREs), activating transcription of genes involved in myogenesis and muscle maintenance. In skeletal muscle, this includes upregulation of IGF-1 signaling, satellite cell activation markers, and myosin heavy chain genes. The tissue selectivity arises from both the differential co-regulator landscape across tissues and the compound's intrinsic partial agonist activity, which produces full agonism in muscle but attenuated activity in prostate and seminal vesicles.

Antiproliferative Activity in Cancer

GTX-027 demonstrates AR-mediated antiproliferative effects in androgen receptor-positive triple-negative breast cancer (AR+ TNBC) cell lines. Activation of the AR by GTX-027 suppresses the MYC and E2F proliferative transcriptional programs while upregulating tumor suppressor gene expression, including p21/CDKN1A. This leads to G1 cell cycle arrest and growth inhibition, positioning SARMs as potential therapeutic agents in AR+ breast malignancies (PMID: 26315559).

Musculoskeletal Anabolic Effects

In preclinical models, GTX-027 promotes muscle hypertrophy via activation of the mTOR/p70S6K pathway and increases pelvic floor muscle mass, with potential applications in stress urinary incontinence, sarcopenia, and muscle wasting conditions while maintaining a favorable androgenic safety profile compared to exogenous testosterone.

Reconstitution Calculator

Research

Safety Profile

Safety Profile: GTX-027 (Selective Androgen Receptor Modulator)

Common Side Effects

• GTX-027 is an investigational SARM from GTx, Inc. (now Oncternal Therapeutics); limited published clinical data
• Based on SARM class effects and available data: headache, fatigue, nausea
• Mild-to-moderate HDL cholesterol suppression (dose-dependent; consistent SARM class effect)
• Transient liver enzyme elevations (ALT/AST)
• Decreased SHBG levels
• Mild acne and skin oiliness

Serious Adverse Effects

• Hormonal axis suppression: Suppression of endogenous testosterone, LH, and FSH in a dose-dependent manner; recovery kinetics not fully characterized
• Hepatotoxicity: Potential for significant transaminase elevations; hepatic injury risk inherent to SARM class
• Cardiovascular risk: HDL reduction raises long-term cardiovascular concern; lipid profile changes may not fully reverse after short-term use
• Virilization in women: Androgenic side effects including voice changes, hirsutism, and acne
• Unknown carcinogenic potential: AR modulation may theoretically affect hormone-sensitive tumor biology

Contraindications

• Known or suspected androgen-sensitive cancers (prostate, breast)
• Severe hepatic dysfunction or elevated transaminases at baseline
• Pregnancy and breastfeeding (androgenic compounds are teratogenic)
• Women of childbearing age not on reliable contraception
• History of thromboembolic disease
• Concurrent use of exogenous androgens, anabolic steroids, or other SARMs
• Severe untreated cardiovascular disease

Drug Interactions

• Warfarin and anticoagulants: SARMs may enhance anticoagulant effects; monitor INR closely
• CYP3A4 inhibitors/inducers: May affect GTX-027 exposure; specific CYP profile not fully published
• Insulin and oral hypoglycemics: SARMs may modulate glucose handling; monitor blood glucose
• Lipid-lowering agents: Unpredictable effects on lipid panel; monitor closely
• Corticosteroids: Combined metabolic side effects; may increase risk of glucose dysregulation and muscle protein catabolism

Population-Specific Considerations

• Women: Virilization risk at any dose; use only in controlled clinical settings with appropriate monitoring
• Elderly: Potential benefit for sarcopenia and muscle wasting, but requires careful cardiovascular and hepatic risk assessment
• Adolescents/Children: Strictly contraindicated; risk of growth plate fusion and permanent endocrine disruption
• Hepatic impairment: Avoid or use with extreme caution; dose reduction and close LFT monitoring required
• Athletes: GTX-027, like all SARMs, is prohibited by WADA under the S1 Anabolic Agents category
• Note: GTX-027 is an investigational compound. Safety data are incomplete and may be revised as further clinical studies are conducted

Pharmacokinetic Profile