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.
Flutamide, sold under the brand name Eulexin among others, is a nonsteroidal antiandrogen (NSAA) which is used primarily to treat prostate cancer. It is also used in the treatment of androgen-dependent conditions like acne, excessive hair growth, and high androgen levels in women. It is taken by mouth, usually three times per day.
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.
Metribolone is a synthetic and orally active anabolic–androgenic steroid (AAS) and a 17α-alkylated nandrolone (19-nortestosterone) derivative which was never marketed for medical use but has been widely used in scientific research as a hot ligand in androgen receptor (AR) ligand binding assays (LBAs) and as a photoaffinity label for the AR. More precisely, metribolone is the 17α-methylated derivative of trenbolone. It was investigated briefly for the treatment of advanced breast cancer in women in the late 1960s and early 1970s, but was found to produce signs of severe hepatotoxicity at very low dosages, and its development was subsequently discontinued.
Andarine is a selective androgen receptor modulator (SARM) which was developed by GTX, Inc for the treatment of conditions such as muscle wasting, osteoporosis, and benign prostatic hypertrophy (BPH), using the nonsteroidal antiandrogen bicalutamide as a lead compound. Development of andarine for all indications has been discontinued, in favor of the structurally related and improved compound enobosarm.
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.
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.
Oxendolone, sold under the brand names Prostetin and Roxenone, is an antiandrogen and progestin medication which is used in Japan in the treatment of enlarged prostate. However, this use is controversial due to concerns about its clinical efficacy. Oxendolone is not effective by mouth and must be given by injection into muscle.
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.
BOMT, also known by its developmental code name Ro 7-2340 and as 6α-bromo-4-oxa-17α-methyl-5α-dihydrotestosterone, is a synthetic steroidal antiandrogen which was first produced in 1970 and was never marketed for medical use. It is the 6α-brominated, 4-oxygenated, and 17α-methylated derivative of the androgen dihydrotestosterone (DHT). Along with benorterone, cyproterone, and flutamide, BOMT was among the earliest antiandrogens to be developed and extensively studied, although it is less well-documented in comparison to the others. BOMT has been investigated clinically in the treatment of benign prostatic hyperplasia, though development for this use did not continue. There was also interest in BOMT for the potential applications of acne, pattern hair loss, and possibly prostate cancer, but it was not developed for these indications either.
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.
A steroidal antiandrogen (SAA) is an antiandrogen with a steroidal chemical structure. They are typically antagonists of the androgen receptor (AR) and act both by blocking the effects of androgens like testosterone and dihydrotestosterone (DHT) and by suppressing gonadal androgen production. SAAs lower concentrations of testosterone through simulation of the negative feedback inhibition of the hypothalamus. SAAs are used in the treatment of androgen-dependent conditions in men and women, and are also used in veterinary medicine for the same purpose. They are the converse of nonsteroidal antiandrogens (NSAAs), which are antiandrogens that are not steroids and are structurally unrelated to testosterone.
AA560 is an orally active nonsteroidal antiandrogen (NSAA) that was developed in Japan and was first described in the literature in 1977 but was never marketed. It is an anilide derivative and analogue of the NSAA flutamide, and shows greater in vivo antiandrogenic potency than does flutamide. Similarly to flutamide, AA560 is a selective antagonist of the androgen receptor (AR) and consequently shows progonadotropic effects by increasing levels of gonadotropins and testosterone via disinhibition of the hypothalamic-pituitary-gonadal axis.
LG-120907 is a nonsteroidal antiandrogen (NSAA) of the quinoline group which was developed by Ligand Pharmaceuticals along with selective androgen receptor modulators (SARMs) like LG-121071 and was never marketed. The drug is a high-affinity antagonist of the androgen receptor (AR) with a Ki value of 26 nM and has been found to inhibit growth of the ventral prostate and seminal vesicles in male rats without increasing circulating levels of luteinizing hormone or testosterone. However, this tissue selectivity has not been assessed in humans. LG-120907 is orally active and shows greater oral potency than the arylpropionamide NSAA flutamide.
Comparison of the nonsteroidal antiandrogen (NSAA) bicalutamide with other antiandrogens reveals differences between the medications in terms of efficacy, tolerability, safety, and other parameters. Relative to the other first-generation NSAAs, flutamide and nilutamide, bicalutamide shows improved potency, efficacy, tolerability, and safety, and has largely replaced these medications in clinical practice. Compared to the second-generation NSAAs, enzalutamide and apalutamide, bicalutamide has inferior potency and efficacy but similar tolerability and safety and a lower propensity for drug interactions.
The pharmacology of bicalutamide is the study of the pharmacodynamic and pharmacokinetic properties of the nonsteroidal antiandrogen (NSAA) bicalutamide. In terms of pharmacodynamics, bicalutamide acts as a selective antagonist of the androgen receptor (AR), the biological target of androgens like testosterone and dihydrotestosterone (DHT). It has no capacity to activate the AR. It does not decrease androgen levels and has no other important hormonal activity. The medication has progonadotropic effects due to its AR antagonist activity and can increase androgen, estrogen, and neurosteroid production and levels. This results in a variety of differences of bicalutamide monotherapy compared to surgical and medical castration, such as indirect estrogenic effects and associated benefits like preservation of sexual function and drawbacks like gynecomastia. Bicalutamide can paradoxically stimulate late-stage prostate cancer due to accumulated mutations in the cancer. When used as a monotherapy, bicalutamide can induce breast development in males due to its estrogenic effects. Unlike other kinds of antiandrogens, it may have less adverse effect on the testes and fertility.
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-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.
