Halotestin (Fluoxymesterone)

Yes. ChEMBL lists fluoxymesterone with phase 4 as the highest phase and first approval in 1956. ClinicalTrials.gov lists only one trial, a phase 2 trial in breast cancer with 5 participants that was terminated early (as of 26 October 2026).⁹⁸

According to ChEMBL it binds directly to the androgen receptor and activates it. The 17-alpha alkylation makes it work as a tablet. Reviews describe a partial separation of muscle and androgenic effects in anabolic steroids via the receptor and metabolism inside the cell.⁹⁶

In metastatic breast cancer 53 percent responded to tamoxifen plus fluoxymesterone, 42 percent to tamoxifen alone. Median time to progression was 350 instead of 199 days, survival was the same. After tamoxifen failed, 40 percent responded to fluoxymesterone. After surgery it gave no significant benefit.¹²

In a three-arm trial fluoxymesterone stimulated appetite clearly less than megestrol acetate and dexamethasone. Tolerability was also worse. The authors rate it as the inferior choice there.⁴

In the breast cancer trials androgenic side effects and virilisation were more common than without fluoxymesterone. For anabolic steroids in general a review names falling HDL cholesterol, rising blood pressure, acne, more aggression and suppressed own testosterone production.¹²³⁷

Not for fluoxymesterone itself. The review of anabolic steroids in athletes names 5 to 20 percent more strength and 2 to 5 kg more body weight for short-term use in general, without separating single compounds.⁷