Ostarine (MK-2866) also known as Enobosarm, is a selective androgen receptor modulator (SARM) developed by GTX Pharmaceuticals to help prevent muscle loss in people with serious illnesses such as cancer and HIV. Clinical trials, including a Phase 2 study presented at the Endocrine Society Annual Meeting, showed that Ostarine significantly increased lean body mass and improved muscle function with good tolerability.

Benefits (from the passage)
Increases lean body mass (LBM), confirmed by DEXA scans
Improves muscle strength and performance, including faster stair-climbing time and greater power output
Effective at low doses in clinical settings (1–3 mg)
Well tolerated in both men and women in multiple Phase II trials
Supports physical function in cancer patients with muscle wasting
Associated with improved survival indicators (lower hazard ratio) in cancer populations
Recreational users report lean muscle gains of approximately 5–10 pounds over typical cycles.