Antiandrogens, also known as androgen antagonists or testosterone blockers, are a class of drugs that prevent androgens like testosterone and dihydrotestosterone (DHT) from mediating their biological effects in the body. They act by blocking the androgen receptor (AR) and/or inhibiting or suppressing androgen production. They can be thought of as the functional opposites of AR agonists, for instance androgens and anabolic steroids (AAS) like testosterone, DHT, and nandrolone and selective androgen receptor modulators (SARMs) like enobosarm. Antiandrogens are one of three types of sex hormone antagonists, the others being antiestrogens and antiprogestogens.
Nilutamide, sold under the brand names Nilandron and Anandron, is a nonsteroidal antiandrogen (NSAA) which is used in the treatment of prostate cancer. It has also been studied as a component of feminizing hormone therapy for transgender women and to treat acne and seborrhea in women. It is taken by mouth.
A nonsteroidal compound is a drug that is not a steroid nor a steroid derivative. Nonsteroidal anti-inflammatory drugs (NSAIDs) are distinguished from corticosteroids as a class of anti-inflammatory agents.
Epitestosterone, or isotestosterone, also known as 17α-testosterone or as androst-4-en-17α-ol-3-one, is an endogenous steroid and an epimer of the androgen sex hormone testosterone. It is a weak competitive antagonist of the androgen receptor (AR) and a potent 5α-reductase inhibitor.
Trestolone, also known as 7α-methyl-19-nortestosterone (MENT), is an experimental androgen/anabolic steroid (AAS) and progestogen medication which has been under development for potential use as a form of hormonal birth control for men and in androgen replacement therapy for low testosterone levels in men but has never been marketed for medical use. It is given as an implant that is placed into fat. As trestolone acetate, an androgen ester and prodrug of trestolone, the medication can also be given by injection into muscle.
Acyl-CoA-binding protein in humans belongs to the family of Acyl-CoA-binding proteins.
The first antiandrogen was discovered in the 1960s. Antiandrogens antagonise the androgen receptor (AR) and thereby block the biological effects of testosterone and dihydrotestosterone (DHT). Antiandrogens are important for men with hormonally responsive diseases like prostate cancer, benign prostatic hyperplasia (BHP), acne, seborrhea, hirsutism and androgen alopecia. Antiandrogens are mainly used for the treatment of prostate diseases. Research from 2010 suggests that ARs could be linked to the disease progression of triple-negative breast cancer and salivary duct carcinoma and that antiandrogens can potentially be used to treat it.
RU-58642 is a nonsteroidal antiandrogen (NSAA) derived from nilutamide with very high affinity and selectivity for the androgen receptor (AR), which made it among the most potent and efficacious antiandrogens known at the time of its discovery. It was investigated for topical application for the treatment of androgenetic alopecia, but development did not proceed past initial trial stages, and it is now only used for scientific research into the AR.
Hydroxyflutamide (HF, OHF) (developmental code name SCH-16423), or 2-hydroxyflutamide, is a nonsteroidal antiandrogen (NSAA) and the major active metabolite of flutamide, which is considered to be a prodrug of hydroxyflutamide as the active form. It has been reported to possess an IC50 of 700 nM for the androgen receptor (AR), which is about 4-fold less than that of bicalutamide.
RU-58841, also known as PSK-3841 or HMR-3841, is a nonsteroidal antiandrogen (NSAA) which was initially developed in the 1980s by Roussel Uclaf, the French pharmaceutical company from which it received its name. It was formerly under investigation by ProStrakan for potential use as a topical treatment for androgen-dependent conditions including acne, pattern hair loss, and excessive hair growth. The compound is similar in structure to the NSAA RU-58642 but contains a different side-chain. These compounds are similar in chemical structure to nilutamide, which is related to flutamide, bicalutamide, and enzalutamide, all of which are NSAAs similarly. RU-58841 can be synthesized either by building the hydantoin moiety or by aryl coupling to 5,5-dimethylhydantoin.
A nonsteroidal antiandrogen (NSAA) is an antiandrogen with a nonsteroidal chemical structure. They are typically selective and full or silent antagonists of the androgen receptor (AR) and act by directly blocking the effects of androgens like testosterone and dihydrotestosterone (DHT). NSAAs are used in the treatment of androgen-dependent conditions in men and women. They are the converse of steroidal antiandrogens (SAAs), which are antiandrogens that are steroids and are structurally related to testosterone.
Trimethyltrienolone (TMT), also known by its developmental code name R-2956 or RU-2956, is an antiandrogen medication which was never introduced for medical use but has been used in scientific research.
Cl-4AS-1 is a dual anabolic–androgenic steroid (AAS) and 5α-reductase inhibitor. It is a potent and selective full agonist of the androgen receptor (IC50 = 12 nM) and inhibitor of 5α-reductase types I and II (IC50 = 6 and 10 nM, respectively). Structurally, Cl-4AS-1 is a 4-azasteroid.
TFM-4AS-1 is a dual selective androgen receptor modulator (SARM) and 5α-reductase inhibitor. It is a potent and selective partial agonist (Emax = 55%) of the androgen receptor (IC50 = 30 nM) and inhibitor of 5α-reductase types I and II (IC50 = 2 and 3 nM, respectively). TFM-4AS-1 shows tissue-selective androgenic effects; it promotes the accumulation of bone and muscle mass and has reduced effects in reproductive tissues and sebaceous glands. In an animal study, TFM-4AS-1 stimulated sebaceous gland formation only 31% as much as dihydrotestosterone (DHT) at doses that were as anabolic or more so than DHT. In addition, TFM-4AS-1 only weakly promoted growth of the prostate gland and it partially antagonized the actions of DHT in the seminal vesicles and endogenous androgens in the prostate gland. Structurally, TFM-4AS-1 is a 4-azasteroid. A structurally related and more advanced version of TFM-4AS-1, MK-0773, was developed and pursued for potential pharmaceutical use.
RU-59063 is a nonsteroidal androgen or selective androgen receptor modulator (SARM) which was first described in 1994 and was never marketed. It was originally thought to be a potent antiandrogen, but subsequent research found that it actually possesses dose-dependent androgenic activity, albeit with lower efficacy than dihydrotestosterone (DHT). The drug is an N-substituted arylthiohydantoin and was derived from the first-generation nonsteroidal antiandrogen (NSAA) nilutamide. The second-generation NSAAs enzalutamide, RD-162, and apalutamide were derived from RU-59063.
5α-Dihydrolevonorgestrel (5α-DHLNG) is an active metabolite of the progestin levonorgestrel which is formed by 5α-reductase. It has about one-third of the affinity of levonorgestrel for the progesterone receptor. In contrast to levonorgestrel, the compound has both progestogenic and antiprogestogenic activity, and hence has a selective progesterone receptor modulator-like profile of activity. This is analogous to the case of norethisterone and 5α-dihydronorethisterone. In addition to the progesterone receptor, 5α-DHLNG interacts with the androgen receptor. It has similar affinity for the androgen receptor relative to levonorgestrel, and has androgenic effects similarly to levonorgestrel and testosterone. 5α-DHLNG is further transformed into 3α,5α- and 3β,5α-THLNG, which bind weakly to the estrogen receptor and have weak estrogenic activity. These metabolites are considered to be responsible for the weak estrogenic activity of high doses of levonorgestrel.
EM-5854 is a steroidal antiandrogen which was under development by Endoceutics, Inc. for the treatment of prostate cancer. It was first described in a patent in 2008, and was further characterized in 2012. EM-5854 reached phase I/II clinical trials for the treatment of prostate cancer but development was discontinued in March 2019.
5α-Dihydroethisterone is an active metabolite of the formerly clinically used but now-discontinued progestin ethisterone and the experimental and never-marketed hormonal antineoplastic agent ethynylandrostanediol (HE-3235). Its formation from its parent drugs is catalyzed by 5α-reductase in tissues that express the enzyme in high amounts like the liver, skin, hair follicles, and prostate gland. 5α-DHET has significant affinity for steroid hormone receptors and may contribute importantly to the activities of its parent drugs.
RU-57073 is a nonsteroidal antiandrogen which was never marketed. It shows 163% of the affinity of testosterone for the androgen receptor and negligible affinity for other steroid hormone receptors.
Cyanonilutamide is a nonsteroidal antiandrogen which was never marketed. Both RU-56187 and RU-58841 appear to be prodrugs of cyanonilutamide in vivo in animals. It has relatively low affinity for the androgen receptor but nonetheless shows significant antiandrogenic activity in animals.
