Enobosarm: Side Effects
Known side effects, contraindications, and interactions
📌TL;DR
- •6 known side effects documented
- •3 mild, 3 moderate, 0 severe
- •4 contraindications listed
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Side Effects Severity Chart
Transient ALT elevations observed in 6.7% overall in Phase 2 elderly study and 20.8% at 3 mg in cancer cachexia trial. Most elevations resolved while continuing treatment. One discontinuation for ALT 4.2x upper limit of normal. Periodic liver monitoring recommended.
Decreases in total testosterone, sex hormone-binding globulin (SHBG), LH, and FSH have been observed in clinical trials. SHBG reduction was statistically significant at both 1 mg and 3 mg. Effects may be reversible upon discontinuation.
Decreases in HDL cholesterol have been observed in clinical trials. The clinical significance of this finding with chronic use is uncertain and requires monitoring in longer-term studies.
Reported as a common adverse event in Phase 1 and Phase 2 studies. Generally mild and transient.
Reported in clinical trials. Generally mild. May be related to hormonal changes or concurrent GLP-1 therapy in the obesity setting.
Reported in clinical trials, though in the QUALITY trial enobosarm did not increase the rate of GI adverse events above semaglutide alone.
⛔Contraindications
- •Known hypersensitivity to enobosarm or any excipient
- •Pregnancy and breastfeeding (androgen receptor modulation may cause fetal harm)
- •Hormone-sensitive cancers (androgen receptor activation may stimulate tumor growth in certain contexts)
- •Active liver disease or significantly elevated liver enzymes
⚠️Drug Interactions
- •CYP enzyme substrates: As a hepatically metabolized compound, enobosarm may interact with drugs metabolized by cytochrome P450 enzymes. Specific interaction data are limited.
- •GLP-1 receptor agonists: QUALITY trial showed no increased GI adverse events when combined with semaglutide. Formal PK interaction data with tirzepatide pending from PLATEAU trial.
- •Anticoagulants: Androgen receptor modulators may potentiate anticoagulant effects. Monitor INR if co-administered with warfarin or similar agents.
Community-Reported Side Effects
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Based on 500+ community reports
View community protocolsSafety Overview#
Enobosarm has been evaluated in over 1,000 patients across its clinical development program, including Phase 1 studies, Phase 2 trials in healthy elderly and cancer patients, Phase 3 POWER trials in NSCLC, and the Phase 2b QUALITY trial with semaglutide. The safety profile is characterized by dose-dependent liver enzyme elevations, mild hormonal suppression, and lipid changes, with no virilizing effects or serious safety signals at therapeutic doses.
Notably, the QUALITY trial reported that enobosarm did not increase the rate of gastrointestinal adverse events when added to semaglutide therapy, addressing a key concern about combination tolerability.
Liver Enzyme Effects#
Liver enzyme (ALT) elevation is the most clinically important adverse effect:
Clinical Trial Data#
| Study | Dose | ALT Elevation Rate | Severity |
|---|---|---|---|
| Dalton et al. (elderly) | 1-3 mg | 6.7% overall | Mostly transient; 1 discontinuation |
| Dobs et al. (cancer) | 3 mg | 20.8% | Mostly transient |
| QUALITY trial | 3-6 mg | Not publicly detailed | No reported discontinuations |
Characteristics#
- ALT elevations are typically transient, with 7 of 8 cases in the Phase 2 elderly trial resolving while continuing enobosarm
- One patient was discontinued for ALT 4.2x the upper limit of normal; levels normalized after stopping
- ALT monitoring is recommended at baseline and periodically during treatment
Context#
- Published case reports of "Ostarine"-associated liver injury exist, but these involve non-pharmaceutical products from the supplement/research chemical market that may be contaminated, mislabeled, or contain incorrect doses
- The pharmaceutical-grade enobosarm used in clinical trials has a more controlled hepatic risk profile
Hormonal Effects#
Enobosarm modulates the hypothalamic-pituitary-gonadal axis:
Documented Changes#
- SHBG: Significantly reduced at both 1 mg (P<0.001) and 3 mg (P<0.001) vs placebo
- Total testosterone: Decreased in male participants
- LH and FSH: Statistically significant decreases in postmenopausal women at 3 mg
- Estradiol: No significant changes reported
Clinical Significance#
- Hormonal suppression is milder than that seen with anabolic steroids or full androgen agonists
- Reversibility upon discontinuation has been suggested but not systematically studied in long-term trials
- The clinical impact in the context of short-term (16-72 week) obesity treatment is uncertain
Lipid Effects#
- HDL cholesterol decreases observed in clinical trials
- Total cholesterol and triglycerides showed reductions (which may be beneficial)
- Long-term cardiovascular implications of HDL reduction are unknown
- Lipid monitoring recommended during treatment
No Androgenic Side Effects#
In published clinical trials at therapeutic doses (1-3 mg):
- No prostate stimulation (PSA unchanged)
- No changes in sebum production
- No hair growth changes
- No voice deepening
- No virilizing effects in women
This confirms the tissue-selective activity that distinguishes SARMs from traditional androgens.
Adverse Event Summary#
| Adverse Event | Frequency | Clinical Significance |
|---|---|---|
| ALT elevation | 6.7-20.8% (dose-dependent) | Monitor; mostly transient |
| SHBG suppression | Common | Hormonal monitoring advised |
| Testosterone decrease | Common (men) | Reversibility expected but not confirmed |
| HDL reduction | Common | Cardiovascular significance uncertain |
| Headache | Common | Mild, transient |
| Fatigue | Common | Mild |
| GI events with GLP-1 | Not increased | Favorable combination tolerability |
| Virilizing effects | None reported | Tissue selectivity confirmed |
Contraindications#
- Active liver disease: Given ALT elevation risk
- Pregnancy: Androgen receptor modulation may cause fetal harm
- Hormone-sensitive malignancies: AR activation could stimulate certain tumors
- Hypersensitivity: To enobosarm or excipients
Drug Interactions#
Limited formal drug interaction data are available:
- GLP-1 agonists: No increased GI adverse events with semaglutide in QUALITY
- CYP substrates: Potential hepatic CYP interactions (not fully characterized)
- Anticoagulants: AR modulators may potentiate anticoagulant effects
Related Reading#
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