[4][5][6][7] It is specifically under development for the treatment of androgen receptor-positive, estrogen receptor-negative, HER2-negative advanced breast cancer.

[4][18] Aside from its development as a potential pharmaceutical drug, vosilasarm is on the World Anti-Doping Agency list of prohibited substances[19] and is sold for physique- and performance-enhancing purposes by black-market Internet suppliers.

[4] Side effects of vosilasarm in preliminary clinical studies in women with metastatic breast cancer have included vomiting (27%), dehydration (27%), constipation, decreased appetite and weight loss (27%), hypophosphatemia, decreased sex hormone-binding globulin (SHBG) levels (100%), increased prostate-specific antigen (PSA) levels (80%), and abnormal liver function tests, including elevated aspartate aminotransferase (59%), elevated alanine aminotransferase (46%), and elevated total blood bilirubin (27%).

[10][3][2] The drug sold via black-market Internet suppliers and used non-medically has been reported to be taken at doses of 5 to 30 mg/day, with unknown adverse effects and risks.

[6][7] This receptor is the biological target of endogenous androgens like testosterone and dihydrotestosterone (DHT) and of synthetic anabolic steroids like nandrolone and oxandrolone.

[9] Vosilasarm also shows potent efficacy in terms of AR activation, with an EC50 value of 0.1 nM in the C2C12 osteoblast differentiation assay.

[7][9] The AR is widely expressed in tissues throughout the body, including in the prostate gland, seminal vesicles, genitals, gonads, skin, hair follicles, muscle, bone, heart, adrenal cortex, liver, kidneys, and brain, among others.

[7][6][9] Moreover, when combined with testosterone propionate, vosilasarm partially antagonized the weight increases of the prostate gland and seminal vesicles, reducing them to 84% and 78% (both from 100%), respectively.

[7][9] Conversely however, the combination of testosterone propionate and vosilasarm was additive in terms of levator ani muscle weight stimulation, increasing it to 124%.

[7][9] Conversely, a 33-fold higher dose of 10 mg/kg/day was required to stimulate prostate weight to a similar extent as that in non-castrated controls.

[9] It was stated in this paper that phase 1 clinical studies of vosilasarm for treatment of severe weight loss due to cancer cachexia were being prepared.

[21] The first-in-human study, a phase 1 trial, was initiated in October 2017 and completed in September 2020 in postmenopausal women with breast cancer.