Enobosarm
[2] Known possible side effects of enobosarm include headache, fatigue, anemia, nausea, diarrhea, back pain, adverse lipid changes like decreased high-density lipoprotein (HDL) cholesterol levels, changes in sex hormone concentrations like decreased testosterone levels, elevated liver enzymes, and liver toxicity, among others.[1][2][10][17] General side effects that have been reported with enobosarm in clinical trials include headache, fatigue, anemia, nausea, diarrhea, and back pain.[17][30][28][6] In small short-term (3-month) clinical trials in healthy elderly or postmenopausal women, enobosarm at doses ranging from 0.1 to 3 mg/day had mixed effects on sebum production and did not increase body hair growth or cause hirsutism.[17][27] SARMs, particularly when used at high or excessive doses for prolonged periods of time, may result in substantial suppression of endogenous sex hormones like testosterone and estradiol, in turn producing widespread unintended deleterious effects on physiological function.[26] The United States Food and Drug Administration (FDA) has cautioned that SARMs could have serious adverse effects ranging from risk of heart attack to stroke and liver damage and has warned against their use in bodybuilding products.[5] Enobosarm sold via black-market Internet suppliers and used non-medically is often taken at much higher doses than those used widely in clinical trials (e.g., 10–30 mg/day), with unknown adverse effects and risks.[20][11][18] This receptor is the biological target of endogenous androgens like testosterone and dihydrotestosterone (DHT) and of synthetic anabolic steroids like nandrolone and oxandrolone.[49] 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.[47][49] Although enobosarm has not been specifically assessed in this area, another structurally unrelated quinolinone SARM, LGD-2226, has shown prosexual effects in male rats comparable to those of the synthetic androgen and anabolic steroid fluoxymesterone as well.[2][47][50] The molecular mechanisms underlying the tissue-selective effects of enobosarm and other SARMs compared to testosterone and other androgens and anabolic steroids remain unknown.[51][17] However, recruitment of both coactivators and corepressors instead of only coactivators and resultant differing receptor conformations, distinct tissue-specific modulation of signaling pathways mediating genomic and non-genomic effects, and differences in within-tissue ligand metabolism and modulation of ligand potency (i.e., potentiation versus lack thereof), among others, all constitute possible mechanisms.[51][48][7] Additionally, enobosarm fully maintained or restored levator ani weight at doses that did not affect LH or FSH levels in gonadally intact animals (≤0.1 mg/day).[53][17][64] The effects of higher doses of enobosarm (9–18 mg/day) on lean body mass and muscle strength are also being evaluated in women with breast cancer.[31][18] Enobosarm is not subject to this local transformation and potentiation, and so is theorized to have greatly reduced effects in these tissues relative to testosterone and certain other steroidal androgens.[17] Aside from metabolism differences related to 5α-reduction, enobosarm has also shown much greater impact in the liver, specifically on certain aspects of hepatic protein synthesis like reduction of sex hormone-binding globulin (SHBG) production, than even highly supraphysiological doses of parenteral testosterone.[74][75] One in silico study predicted that, on the basis of its overall physicochemical properties (but not considering active transport), enobosarm would be unlikely to cross the blood–brain barrier and hence would be a peripherally selective drug with reduced or no central nervous system effects.[72][73] Enobosarm and related SARMs like acetothiolutamide, andarine (acetamidoxolutamide; GTx-007; S-4), and GTx-027 were derived from structural modification of the arylpropionamide nonsteroidal antiandrogen bicalutamide.[18] By 2007, enobosarm was in a phase 2 trial, and that year GTx signed an exclusive license agreement for its SARM program with Merck & Co.[94] The companies ended the deal in 2010.[95] In August 2011, there was a 12-week double-blind, placebo controlled phase 2 trial that focused on elderly men and postmenopausal women which concluded that enobosarm showed statistically significant improvements in total lean body mass and physical function without apparent adverse effects on hair growth or sebum production.[9] In addition, they announced plans to conduct a phase 2b study of enobosarm at doses of 3 to 6 mg/day for this purpose in sarcopenic obese or overweight elderly individuals receiving GLP-1 receptor agonists.[17][25] These agents have increasingly become used by the general public as "gym supplements" such as pre-workout or lifestyle drugs, rather than as an aid to performance in athletic or bodybuilding competitions.[26] SARMs including enobosarm may be and have been used by athletes to assist in training and increase physical stamina and fitness, potentially producing effects similar to anabolic steroids.In May 2017, Dynamic Technical Formulations voluntarily recalled all lots of Tri-Ton, a dietary supplement that the FDA tested and found to contain Enobosarm and andarine.[105] In October 2018, UFC fighter Sean O'Malley tested positive for Enobosarm and was suspended by the Nevada State Athletic Commission and USADA for six months.USADA determined that none of O'Malley's positive tests were consistent with intentional use and he was allowed to compete at UFC 248 as long as he kept his levels below the threshold of 100 ng/ml.Prior to the College Football National Championship game, three Clemson players who were suspended — Dexter Lawrence, Braden Galloway and Zach Giellaall — tested positive for a substance known as enobosarm.[109] On July 6, 2021, during the 2020 Summer Olympics, Brazil women's national volleyball team player Tandara was temporarily suspended for testing positive for enobosarm.[110] On August 12, 2021, after the 2020 Summer Olympics, Chijindu "CJ" Ujah, A member of the silver medal-winning British 4×100 relay team was temporarily suspended for testing positive for both enobosarm and S-23.[115] In April 2023, British boxer Amir Khan was banned for two years after an anti-doping test revealed the presence of enobosarm following his fight against Kell Brook in February 2022.[1][8][44][45] It was also previously under development for a variety of other potential uses, including treatment of cachexia, Duchenne muscular dystrophy, muscle atrophy or sarcopenia, and stress incontinence.