Enobosarm: Research & Studies

Research Overview#

Enobosarm (Ostarine, GTx-024) has one of the most extensive clinical datasets of any SARM, spanning over 15 years of clinical development across multiple indications. The research program has evolved from cancer-associated muscle wasting (where Phase 3 trials did not meet co-primary endpoints) to a promising new application: muscle preservation during GLP-1 receptor agonist-induced weight loss.

The evidence level is classified as moderate based on published Phase 2 data in two peer-reviewed journals (JCSM 2011, Lancet Oncology 2013), positive Phase 2b QUALITY topline results (press release), and FDA regulatory feedback confirming an acceptable approval pathway. Full peer-reviewed publication of the QUALITY data and Phase 3 PLATEAU results are needed for definitive evidence classification.

Phase 2 -- Healthy Elderly (JCSM 2011)#

Dalton et al., J Cachexia Sarcopenia Muscle 2011 (PMID: 22031847)#

The foundational Phase 2 trial enrolled 120 healthy elderly men (>60 years) and postmenopausal women in a 12-week, double-blind, placebo-controlled study.

Study Design:

• 120 participants randomized to enobosarm 1 mg, 3 mg, or placebo
• 12 weeks of oral daily dosing
• Primary endpoint: total lean body mass (DXA)
• Secondary endpoints: physical function (stair climb), insulin resistance, lipids

Key Results:

• Dose-dependent increase in total lean body mass at both 1 mg and 3 mg
• Clinically meaningful improvement in stair climb test
• No evidence of androgenic side effects (prostate-specific antigen, sebum, hair)
• Reduction in total cholesterol and triglycerides
• SHBG significantly reduced at both doses (P<0.001)

Safety:

• Transient ALT elevations in 8 subjects (6.7%)
• 7 of 8 resolved while continuing treatment
• 1 subject discontinued for ALT 4.2x upper limit of normal (resolved after discontinuation)
• No clinically significant abnormalities in AST

Phase 2 -- Cancer Cachexia (Lancet Oncology 2013)#

Dobs et al., Lancet Oncology 2013 (PMID: 23499390)#

Phase 2 trial evaluating enobosarm in patients with cancer-associated muscle wasting.

Key Results:

• Significant lean body mass gain: median 1.5 kg (1 mg) and 1.0 kg (3 mg) compared with baseline by day 113
• Improvements in stair climb power
• Quality of life improvements on FAACT-A and FACIT-F scales

Safety:

• ALT elevations in 20.8% at 3 mg dose
• Generally well tolerated
• No virilizing effects reported

Phase 3 -- POWER Trials (Cancer Cachexia)#

Crawford et al., Curr Oncol Rep 2016 (PMID: 27138015)#

Two identically designed Phase 3 trials (POWER 1 and POWER 2) evaluated enobosarm 3 mg in NSCLC patients initiating first-line chemotherapy.

Outcome:

• Lean body mass primary endpoint: MET in both trials
• Physical function (stair climb) co-primary endpoint: NOT MET
• Because the design required both co-primary endpoints, the program was considered unsuccessful

Interpretation: The failure to meet the physical function endpoint in advanced cancer patients receiving chemotherapy may reflect the difficulty of demonstrating functional improvement in a population with progressive disease and multiple confounding factors, rather than inadequate pharmacological activity of enobosarm.

Phase 2b -- QUALITY Trial (Obesity + GLP-1)#

Veru Inc. Press Releases (January and June 2025)#

The QUALITY trial represents the pivotal repositioning of enobosarm for obesity-related muscle preservation.

Study Design:

• 168 patients aged >60 years with overweight or obesity
• Randomized to enobosarm 3 mg, 6 mg, or placebo, all receiving semaglutide (Wegovy)
• 16-week treatment period + 12-week maintenance extension
• Primary endpoint: lean body mass change

Key Results (Treatment Period, 16 weeks):

• 71% reduction in lean mass loss with enobosarm vs placebo (all doses)
• Enobosarm 3 mg + semaglutide: 0% lean mass loss, 100% fat mass loss
• Physical function preserved (44.8% of semaglutide-only group had >10% stair climb decline)
• Enobosarm did not increase GI adverse events above semaglutide alone

Key Results (Maintenance Extension, 12 weeks post-semaglutide):

• Placebo group regained 43% of previously lost body weight
• Enobosarm 3 mg reduced weight regain by 46%
• Enobosarm completely prevented fat regain
• Lean mass preserved during maintenance period

FDA Regulatory Pathway (September 2025)#

Following a successful FDA meeting, Veru received key regulatory guidance:

• Enobosarm 3 mg confirmed as an acceptable dosage
• Incremental weight loss over GLP-1 alone is an acceptable primary endpoint for approval
• FDA encouraged expansion to include younger patients with obesity
• Phase 2b PLATEAU trial with tirzepatide planned for Q1 2026

Evidence Quality Assessment#

Key Research Gaps#

1. Peer-reviewed QUALITY publication: The pivotal obesity data are currently available only as press releases, limiting independent evaluation.

2. Long-term safety in obesity: The QUALITY trial was 16 weeks; the PLATEAU trial (72 weeks) will provide longer-term data on liver enzymes, hormone levels, and cardiovascular markers.

3. Younger population: The QUALITY trial enrolled patients >60 years. The FDA has encouraged expansion to younger adults with obesity.

4. Comparison with other approaches: No head-to-head trial vs bimagrumab, trevogrumab, or apitegromab in the GLP-1 combination setting.

5. Bone mineral density: The effect on BMD during GLP-1-induced weight loss has not been specifically studied.

6. Liver safety with chronic use: ALT elevations have been observed at 3 mg; long-term hepatic safety data are needed.

Related Reading#

• Enobosarm overview and research guide
• Enobosarm dosing protocols
• Enobosarm molecular structure
• Bimagrumab research guide