Ostarine (MK-2866 / enobosarm)
Muscle Building · SARM
Tier C+
What this is
Most studied SARM clinically. Veru ARES Ph3 in AR+/ER+ breast cancer (2024). FDA has warned against SARMs in supplements multiple times. 2025 Grassley/Whitehouse SARMs Control Act bill introduced again; previous versions (2018, 2019) did not pass. Despite marketing, not 'side-effect-free' vs steroids.
Mechanism
Selective androgen receptor modulator; tissue-selective AR agonist (muscle/bone agonist, lesser prostate activity); developed by GTx for muscle wasting and now Veru for breast cancer (ARES trial)
Dose & route
Typical illicit: 10-25 mg/day PO for 8-12 weeks
Citations
- https://pubmed.ncbi.nlm.nih.gov/21798027/
- https://www.fda.gov/consumers/consumer-updates/fda-warns-against-using-sarms-bodybuilding-products
- https://www.supplysidesj.com/supplement-regulations/senators-introduce-bill-to-make-sarms-controlled-substances
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This is an independent synthesis of published research by a non-clinician. Scores are opinions supported by citations, not prescriptions. See the full disclaimer and methodology for how this score was produced and what it does and doesn't mean.