Antiandrogen | |
---|---|
Drug class | |
Class identifiers | |
Synonyms | Androgen antagonists; Androgen blockers; Testosterone blockers |
Use | • Men and boys: Prostate cancer; Benign prostatic hyperplasia; Scalp hair loss; Paraphilias; Hypersexuality; Sex offenders; Precocious puberty; Priapism • Women and girls: Acne; Seborrhea; Hidradenitis suppurativa; Hirsutism; Scalp hair loss; Hyperandrogenism; Transgender hormone therapy |
ATC code | L02BB |
Biological target | Androgen receptor; Progesterone receptor; Estrogen receptor; GnRH receptor; 5α-Reductase; CYP17A1 (17α-hydroxylase/ |
Chemical class | Steroidal; Nonsteroidal; Peptide |
External links | |
MeSH | D000726 |
Legal status | |
In Wikidata |
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. [1] [2] 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. [3]
Antiandrogens are used to treat an assortment of androgen-dependent conditions. [4] In men, antiandrogens are used in the treatment of prostate cancer, enlarged prostate, scalp hair loss, overly high sex drive, unusual and problematic sexual urges, and early puberty. [4] [5] In women, antiandrogens are used to treat acne, seborrhea, excessive hair growth, scalp hair loss, and high androgen levels, such as those that occur in polycystic ovary syndrome (PCOS). [4] Antiandrogens are also used as a component of feminizing hormone therapy for transgender women and as puberty blockers in transgender girls. [4]
Side effects of antiandrogens depend on the type of antiandrogen and the specific antiandrogen in question. In any case, common side effects of antiandrogens in men include breast tenderness, breast enlargement, feminization, hot flashes, sexual dysfunction, infertility, and osteoporosis. In women, antiandrogens are much better tolerated, and antiandrogens that work only by directly blocking androgens are associated with minimal side effects. However, because estrogens are made from androgens in the body, antiandrogens that suppress androgen production can cause low estrogen levels and associated symptoms like hot flashes, menstrual irregularities, and osteoporosis in premenopausal women.
There are a few different major types of antiandrogens. [6] These include AR antagonists, androgen synthesis inhibitors, and antigonadotropins. [6] AR antagonists work by directly blocking the effects of androgens, while androgen synthesis inhibitors and antigonadotropins work by lowering androgen levels. [6] AR antagonists can be further divided into steroidal antiandrogens and nonsteroidal antiandrogens; androgen synthesis inhibitors can be further divided mostly into CYP17A1 inhibitors and 5α-reductase inhibitors; and antigonadotropins can be further divided into gonadotropin-releasing hormone modulators (GnRH modulators), progestogens, and estrogens. [6] [7] [8]
Antiandrogens are used in the treatment of an assortment of androgen-dependent conditions in both males and females. [4] [9] They are used to treat men with prostate cancer, benign prostatic hyperplasia, pattern hair loss, hypersexuality, paraphilias, and priapism, as well as boys with precocious puberty. [9] [10] [11] In women and girls, antiandrogens are used to treat acne, seborrhea, hidradenitis suppurativa, hirsutism, and hyperandrogenism. [9] [12] [13] Antiandrogens are also used in transgender women as a component of feminizing hormone therapy and as puberty blockers in transgender girls. [14] [15]
Androgens like testosterone and particularly DHT are importantly involved in the development and progression of prostate cancer. [16] They act as growth factors in the prostate gland, stimulating cell division and tissue growth. [16] In accordance, therapeutic modalities that reduce androgen signaling in the prostate gland, referred to collectively as androgen deprivation therapy, are able to significantly slow the course of prostate cancer and extend life in men with the disease. [16] Although antiandrogens are effective in slowing the progression of prostate cancer, they are not generally curative, and with time, the disease adapts and androgen deprivation therapy eventually becomes ineffective. [17] When this occurs, other treatment approaches, such as chemotherapy, may be considered. [17]
The most common methods of androgen deprivation therapy currently employed to treat prostate cancer are castration (with a GnRH modulator or orchiectomy), nonsteroidal antiandrogens, and the androgen synthesis inhibitor abiraterone acetate. [16] Castration may be used alone or in combination with one of the other two treatments. [16] [18] When castration is combined with a nonsteroidal antiandrogen like bicalutamide, this strategy is referred to as combined androgen blockade (also known as complete or maximal androgen blockade). [16] [19] Enzalutamide, apalutamide, and abiraterone acetate are specifically approved for use in combination with castration to treat castration-resistant prostate cancer. [16] [20] Monotherapy with the nonsteroidal antiandrogen bicalutamide is also used in the treatment of prostate cancer as an alternative to castration with comparable effectiveness but with a different and potentially advantageous side effect profile. [16] [21] [22]
High-dose estrogen was the first functional antiandrogen used to treat prostate cancer. It was widely used, but has largely been abandoned for this indication in favor of newer agents with improved safety profiles and fewer feminizing side effects. [23] Cyproterone acetate was developed subsequently to high-dose estrogen and is the only steroidal antiandrogen that has been widely used in the treatment of prostate cancer, [24] but it has largely been replaced by nonsteroidal antiandrogens, which are newer and have greater effectiveness, tolerability, and safety. [25] [26] Bicalutamide, as well as enzalutamide, have largely replaced the earlier nonsteroidal antiandrogens flutamide and nilutamide, which are now little used. [19] [27] [28] [29] [30] The earlier androgen synthesis inhibitors aminoglutethimide and ketoconazole have only limitedly been used in the treatment of prostate cancer due to toxicity concerns and have been replaced by abiraterone acetate. [31]
In addition to active treatment of prostate cancer, antiandrogens are effective as prophylaxis (preventatives) in reducing the risk of ever developing prostate cancer. [32] Antiandrogens have only limitedly been assessed for this purpose, but the 5α-reductase inhibitors finasteride and dutasteride and the steroidal AR antagonist spironolactone have been associated with significantly reduced risk of prostate cancer. [32] [33] In addition, it is notable that prostate cancer is extremely rare in transgender women who have been on feminizing hormone therapy for an extended period of time. [34] [35] [36]
The 5α-reductase inhibitors finasteride and dutasteride are used to treat benign prostatic hyperplasia, a condition in which the prostate becomes enlarged and this results in urinary obstruction and discomfort. [37] They are effective because androgens act as growth factors in the prostate gland. [37] The antiandrogens chlormadinone acetate and oxendolone and the functional antiandrogens allylestrenol and gestonorone caproate are also approved in some countries for the treatment of benign prostatic hyperplasia. [38] [39]
5α-Reductase inhibitors like finasteride, dutasteride, and alfatradiol and the topical nonsteroidal AR antagonist topilutamide (fluridil) are approved for the treatment of pattern hair loss, also known as scalp hair loss or baldness. [40] This condition is generally caused by androgens, so antiandrogens can slow or halt its progression. [41] Systemic antiandrogens besides 5α-reductase inhibitors are not generally used to treat scalp hair loss in males due to risks like feminization (e.g., gynecomastia) and sexual dysfunction. [42] [43] [44] [45] [46] [47] [48] However, they have been assessed and reported to be effective for this indication. [42] [43] [49]
Systemic antiandrogens are generally not used to treat acne in males due to their high risk of feminization (e.g., gynecomastia) and sexual dysfunction. [50] [51] However, they have been studied for acne in males and found to be effective. [52] [44] [45] [53] Clascoterone, a topical antiandrogen, is effective for acne in males and has been approved by the FDA in August 2020. [54] [55] [56] [57]
Androgens increase sex drive, [58] and for this reason, antiandrogens are able to reduce sex drive in men. [59] [60] In accordance, antiandrogens are used in the treatment of conditions such as hypersexuality (excessively high sex drive) and paraphilias (atypical and sometimes societally unacceptable sexual interests) like pedophilia (sexual attraction to children). [59] [60] They have been used to decrease sex drive in sex offenders so as to reduce the likelihood of recidivism (repeat offenses). [61] Antiandrogens used for these indications include cyproterone acetate, medroxyprogesterone acetate, and GnRH modulators. [62] [63]
Antiandrogens are used to treat precocious puberty in boys. [64] [65] [66] [67] They work by opposing the effects of androgens and delaying the development of secondary sexual characteristics and onset of changes in sex drive and function until a more appropriate age. [64] [65] Antiandrogens that have been used for this purpose include cyproterone acetate, medroxyprogesterone acetate, GnRH modulators, spironolactone, bicalutamide, and ketoconazole. [64] [67] [68] [69] [70] [71] Spironolactone and bicalutamide require combination with an aromatase inhibitor to prevent the effects of unopposed estrogens, while the others can be used alone. [64] [70] [71]
Antiandrogens are effective in the treatment of recurrent priapism (potentially painful penile erections that last more than four hours). [72] [73] [74] [75] [76]
Antiandrogens are used in the treatment of androgen-dependent skin and hair conditions including acne, seborrhea, hidradenitis suppurativa, hirsutism, and pattern hair loss in women. [12] All of these conditions are dependent on androgens, and for this reason, antiandrogens are effective in treating them. [12] The most commonly used antiandrogens for these indications are cyproterone acetate and spironolactone. [77] Flutamide has also been studied extensively for such uses, but has fallen out of favor due to its association with hepatotoxicity. [78] Bicalutamide, which has a relatively minimal risk of hepatotoxicity, has been evaluated for the treatment of hirsutism and found effective similarly to flutamide and may be used instead of it. [79] [80] In addition to AR antagonists, oral contraceptives containing ethinylestradiol are effective in treating these conditions, and may be combined with AR antagonists. [81] [82]
Hyperandrogenism is a condition in women in which androgen levels are excessively and abnormally high. [13] It is commonly seen in women with PCOS, and also occurs in women with intersex conditions like congenital adrenal hyperplasia. [13] Hyperandrogenism is associated with virilization – that is, the development of masculine secondary sexual characteristics like male-pattern facial and body hair growth (or hirsutism), voice deepening, increased muscle mass and strength, and broadening of the shoulders, among others. [13] Androgen-dependent skin and hair conditions like acne and pattern hair loss may also occur in hyperandrogenism, and menstrual disturbances, like amenorrhea, are commonly seen. [13] Although antiandrogens do not treat the underlying cause of hyperandrogenism (e.g., PCOS), they are able to prevent and reverse its manifestation and effects. [13] As with androgen-dependent skin and hair conditions, the most commonly used antiandrogens in the treatment of hyperandrogenism in women are cyproterone acetate and spironolactone. [13] Other antiandrogens, like bicalutamide, may be used alternatively. [13]
Antiandrogens are used to prevent or reverse masculinization and to facilitate feminization in transgender women and some nonbinary individuals who are undergoing hormone therapy and who have not undergone sex reassignment surgery or orchiectomy. [14] Besides estrogens, the main antiandrogens that have been used for this purpose are cyproterone acetate, spironolactone, and GnRH modulators. [14] Nonsteroidal antiandrogens like bicalutamide are also used for this indication. [83] [14] In addition to use in transgender women, antiandrogens, mainly GnRH modulators, are used as puberty blockers to prevent the onset of puberty in transgender girls until they are older and ready to begin hormone therapy. [15]
There are several different types of antiandrogens, including the following: [6]
Certain antiandrogens combine multiple of the above mechanisms. [6] [95] An example is the steroidal antiandrogen cyproterone acetate, which is a potent AR antagonist, a potent progestogen and hence antigonadotropin, a weak glucocorticoid and hence anticorticotropin, and a weak androgen synthesis inhibitor. [6] [95] [96] [97]
Generic name | Class | Type | Brand name(s) | Route(s) | Launch | Status | Hitsa |
---|---|---|---|---|---|---|---|
Abiraterone acetate | Steroidal | Androgen synthesis inhibitor | Zytiga | Oral | 2011 | Available | 523,000 |
Allylestrenol | Steroidal | Progestin | Gestanin, Perselin | Oral | 1961 | Availableb | 61,800 |
Aminoglutethimide | Nonsteroidal | Androgen synthesis inhibitor | Cytadren, Orimeten | Oral | 1960 | Availableb | 222,000 |
Apalutamide | Nonsteroidal | AR antagonist | Erleada | Oral | 2018 | Available | 50,400 |
Bicalutamide | Nonsteroidal | AR antagonist | Casodex | Oral | 1995 | Available | 754,000 |
Chlormadinone acetate | Steroidal | Progestin; AR antagonist | Belara, Prostal | Oral | 1965 | Available | 220,000 |
Cyproterone acetate | Steroidal | Progestin; AR antagonist | Androcur, Diane | Oral, IM | 1973 | Available | 461,000 |
Delmadinone acetate | Steroidal | Progestin; AR antagonist | Tardak | Veterinary | 1972 | Veterinary | 42,600 |
Enzalutamide | Nonsteroidal | AR antagonist | Xtandi | Oral | 2012 | Available | 328,000 |
Flutamide | Nonsteroidal | AR antagonist | Eulexin | Oral | 1983 | Available | 712,000 |
Gestonorone caproate | Steroidal | Progestin | Depostat, Primostat | IM | 1973 | Availableb | 119,000 |
Hydroxyprogesterone caproate | Steroidal | Progestin | Delalutin, Proluton | IM | 1954 | Available | 108,000 |
Ketoconazole | Nonsteroidal | Androgen synthesis inhibitor | Nizoral, others | Oral, topical | 1981 | Available | 3,650,000 |
Medroxyprogesterone acetate | Steroidal | Progestin | Provera, Depo-Provera | Oral, IM, SC | 1958 | Available | 1,250,000 |
Megestrol acetate | Steroidal | Progestin; AR antagonist | Megace | Oral | 1963 | Available | 253,000 |
Nilutamide | Nonsteroidal | AR antagonist | Anandron, Nilandron | Oral | 1987 | Available | 132,000 |
Osaterone acetate | Steroidal | Progestin; AR antagonist | Ypozane | Veterinary | 2007 | Veterinary | 87,600 |
Oxendolone | Steroidal | Progestin; AR antagonist | Prostetin, Roxenone | IM | 1981 | Availableb | 36,100 |
Spironolactone | Steroidal | AR antagonist | Aldactone | Oral, topical | 1959 | Available | 3,010,000 |
Topilutamide | Nonsteroidal | AR antagonist | Eucapil | Topical | 2003 | Availableb | 36,300 |
Footnotes:a = Hits = Google Search hits (as of February 2018). b = Availability limited / mostly discontinued. Class: Steroidal = Steroidal antiandrogen. Nonsteroidal = Nonsteroidal antiandrogen. Sources: See individual articles. |
The side effects of antiandrogens vary depending on the type of antiandrogen – namely whether it is a selective AR antagonist or lowers androgen levels – as well as the presence of off-target activity in the antiandrogen in question. [21] [98] For instance, whereas antigonadotropic antiandrogens like GnRH modulators and cyproterone acetate are associated with pronounced sexual dysfunction and osteoporosis in men, selective AR antagonists like bicalutamide are not associated with osteoporosis and have been associated with only minimal sexual dysfunction. [21] [99] [100] These differences are thought related to the fact that antigonadotropins suppress androgen levels and by extension levels of bioactive metabolites of androgens like estrogens and neurosteroids whereas selective AR antagonists similarly neutralize the effects of androgens but leave levels of androgens and hence their metabolites intact (and in fact can even increase them as a result of their progonadotropic effects). [21] As another example, the steroidal antiandrogens cyproterone acetate and spironolactone possess off-target actions including progestogenic, antimineralocorticoid, and/or glucocorticoid activity in addition to their antiandrogen activity, and these off-target activities can result in additional side effects. [98]
In males, the major side effects of antiandrogens are demasculinization and feminization. [101] These side effects include breast pain/tenderness and gynecomastia (breast development/enlargement), reduced body hair growth/density, decreased muscle mass and strength, feminine changes in fat mass and distribution, and reduced penile length and testicular size. [101] The rates of gynecomastia in men with selective AR antagonist monotherapy have been found to range from 30 to 85%. [102] In addition, antiandrogens can cause infertility, osteoporosis, hot flashes, sexual dysfunction (including loss of libido and erectile dysfunction), depression, fatigue, anemia, and decreased semen/ejaculate volume in males.[ failed verification ] [101] Conversely, the side effects of selective AR antagonists in women are minimal. [80] [103] However, antigonadotropic antiandrogens like cyproterone acetate can produce hypoestrogenism, amenorrhea, and osteoporosis in premenopausal women, among other side effects. [81] [104] [105] In addition, androgen receptor antagonists can produce unfavorable effects on cholesterol levels, which long-term may increase the risk of cardiovascular disease. [106] [107] [108] [109] [110] [111] [112]
A number of antiandrogens have been associated with hepatotoxicity. [113] These include, to varying extents, cyproterone acetate, flutamide, nilutamide, bicalutamide, aminoglutethimide, and ketoconazole. [113] In contrast, spironolactone, enzalutamide, [114] and other antiandrogens are not associated with significant rates of hepatotoxicity. However, although they do not pose a risk of hepatotoxicity, spironolactone has a risk of hyperkalemia and enzalutamide has a risk of seizures.[ citation needed ]
In women who are pregnant, antiandrogens can interfere with the androgen-mediated sexual differentiation of the genitalia and brain of male fetuses. [115] This manifests primarily as ambiguous genitalia – that is, undervirilized or feminized genitalia, which, anatomically, are a cross between a penis and a vagina – and theoretically also as femininity. [115] [116] As such, antiandrogens are teratogens, and women who are pregnant should not be treated with an antiandrogen. [82] Moreover, women who can or may become pregnant are strongly recommended to take an antiandrogen only in combination with proper contraception. [82]
Antiandrogens are relatively safe in acute overdose.[ citation needed ]
Inhibitors and inducers of cytochrome P450 enzymes may interact with various antiandrogens.[ citation needed ]
Antiandrogen | Relative binding affinities | ||||
---|---|---|---|---|---|
AR | PR | ER | GR | MR | |
Cyproterone acetate | 8–10 | 60 | <0.1 | 5 | 1 |
Chlormadinone acetate | 5 | 175 | <0.1 | 38 | 1 |
Megestrol acetate | 5 | 152 | <0.1 | 50 | 3 |
Spironolactone | 7 | 0.4a | <0.1 | 2a | 182 |
Trimethyltrienolone | 3.6 | <1 | <1 | <1 | <1 |
Inocoterone | 0.8 | <0.1 | <0.1 | <0.1 | <0.1 |
Inocoterone acetate | <0.1 | <0.1 | <0.1 | <0.1 | <0.1 |
Flutamide | <0.1 | <0.1 | <0.1 | <0.1 | <0.1 |
Hydroxyflutamide | 0.5–0.8 | <0.1 | <0.1 | <0.1 | <0.1 |
Nilutamide | 0.5–0.8 | <0.1 | <0.1 | <0.1 | <0.1 |
Bicalutamide | 1.8 | <0.1 | <0.1 | <0.1 | <0.1 |
Notes: (1): Reference ligands (100%) were testosterone for the AR , progesterone for the PR , estradiol for the ER , dexamethasone for the GR , and aldosterone for the MR . (2): Tissues were rat prostate (AR), rabbit uterus (PR), mouse uterus (ER), rat thymus (GR), and rat kidney (MR). (3): Incubation times (0 °C) were 24 hours (AR, a), 2 hours (PR, ER), 4 hours (GR), and 1 hour (MR). (4): Assay methods were different for bicalutamide for receptors besides the AR. Sources: [117] [118] [119] [120] [121] [122] [123] [124] [125] [126] |
Antiandrogen | Relative potency |
---|---|
Bicalutamide | 4.3 |
Hydroxyflutamide | 3.5 |
Flutamide | 3.3 |
Cyproterone acetate | 1.0 |
Zanoterone | 0.4 |
Description: Relative potencies of orally administered antiandrogens in antagonizing 0.8 to 1.0 mg/kg s.c. testosterone propionate-induced ventral prostate weight increase in castrated immature male rats. Higher values mean greater potency. Sources: See template. |
AR antagonists act by directly binding to and competitively displacing androgens like testosterone and DHT from the AR, thereby preventing them from activating the receptor and mediating their biological effects. [84] [85] AR antagonists are classified into two types, based on chemical structure: steroidal and nonsteroidal. [7] [8] [84] [85] [92] Steroidal AR antagonists are structurally related to steroid hormones like testosterone and progesterone, whereas nonsteroidal AR antagonists are not steroids and are structurally distinct. Steroidal AR antagonists tend to have off-target hormonal actions due to their structural similarity to other steroid hormones. [92] In contrast, nonsteroidal AR antagonists are selective for the AR and have no off-target hormonal activity. [92] For this reason, they are sometimes described as "pure" antiandrogens. [92]
Although they are described as antiandrogens and indeed show only such effects generally, most or all steroidal AR antagonists are actually not silent antagonists of the AR but rather are weak partial agonists and are able to activate the receptor in the absence of more potent AR agonists like testosterone and DHT. [84] [31] [127] [128] This may have clinical implications in the specific context of prostate cancer treatment. [84] [127] As an example, steroidal AR antagonists are able to increase prostate weight and accelerate prostate cancer cell growth in the absence of more potent AR agonists, [84] [127] and spironolactone has been found to accelerate progression of prostate cancer in case reports. [129] [130] In addition, whereas cyproterone acetate produces ambiguous genitalia via feminization in male fetuses when administered to pregnant animals, [131] it has been found to produce masculinization of the genitalia of female fetuses of pregnant animals. [84] In contrast to steroidal AR antagonists, nonsteroidal AR antagonists are silent antagonists of the AR and do not activate the receptor. [132] [31] [133] [127] This may be why they have greater efficacy than steroidal AR antagonists in the treatment of prostate cancer and is an important reason as to why they have largely replaced them for this indication in medicine. [132] [31] [133] [127]
Nonsteroidal antiandrogens have relatively low affinity for the AR compared to steroidal AR ligands. [31] [133] [134] For example, bicalutamide has around 2% of the affinity of DHT for the AR and around 20% of the affinity of CPA for the AR. [134] Despite their low affinity for the AR however, the lack of weak partial agonist activity of NSAAs appears to improve their potency relative to steroidal antiandrogens. [134] [135] For example, although flutamide has about 10-fold lower affinity for the AR than CPA, it shows equal or slightly greater potency to CPA as an antiandrogen in bioassays. [134] [135] In addition, circulating therapeutic concentrations of nonsteroidal antiandrogens are very high, on the order of thousands of times higher than those of testosterone and DHT, and this allows them to efficaciously compete and block AR signaling. [136]
AR antagonists may not bind to or block membrane androgen receptors (mARs), which are distinct from the classical nuclear AR. [137] [138] [139] However, the mARs do not appear to be involved in masculinization. This is evidenced by the perfectly female phenotype of women with complete androgen insensitivity syndrome. [140] [141] These women have a 46,XY karyotype (i.e., are genetically "male") and high levels of androgens but possess a defective AR and for this reason never masculinize. [140] [141] They are described as highly feminine, both physically as well as mentally and behaviorally. [142] [143] [144]
N-Terminal domain AR antagonists are a new type of AR antagonist that, unlike all currently marketed AR antagonists, bind to the N-terminal domain (NTD) of the AR rather than the ligand-binding domain (LBD). [145] Whereas conventional AR antagonists bind to the LBD of the AR and competitively displace androgens, thereby preventing them from activating the receptor, AR NTD antagonists bind covalently to the NTD of the AR and prevent protein–protein interactions subsequent to activation that are required for transcriptional activity. [145] As such, they are non-competitive and irreversible antagonists of the AR. [146] Examples of AR NTD antagonists include bisphenol A diglycidyl ether (BADGE) and its derivatives EPI-001, ralaniten (EPI-002), and ralaniten acetate (EPI-506). [145] [147] AR NTD antagonists are under investigation for the potential treatment of prostate cancer, and it is thought that they may have greater efficacy as antiandrogens relative to conventional AR antagonists. [145] In accordance with this notion, AR NTD antagonists are active against splice variants of the AR, which conventional AR antagonists are not, and AR NTD antagonists are immune to gain-of-function mutations in the AR LBD that convert AR antagonists into AR agonists and commonly occur in prostate cancer. [145]
Selective androgen receptor degraders (SARDs) are another new type of antiandrogen that has recently been developed. [148] They work by enhancing the degradation of the AR, and are analogous to selective estrogen receptor degraders (SERDs) like fulvestrant (a drug used to treat estrogen receptor-positive breast cancer). [148] Similarly to AR NTD antagonists, it is thought that SARDs may have greater efficacy than conventional AR antagonists, and for this reason, they are under investigation for the treatment of prostate cancer. [149] An example of a SARD is dimethylcurcumin (ASC-J9), which is under development as a topical medication for the potential treatment of acne. [150] SARDs like dimethylcurcumin differ from conventional AR antagonists and AR NTD antagonists in that they may not necessarily bind directly to the AR. [149]
Androgen synthesis inhibitors are enzyme inhibitors that prevent the biosynthesis of androgens. [31] This process occurs mainly in the gonads and adrenal glands, but also occurs in other tissues like the prostate gland, skin, and hair follicles. These drugs include aminoglutethimide, ketoconazole, [151] and abiraterone acetate. [89] [31] [152] Aminoglutethimide inhibits cholesterol side-chain cleavage enzyme, also known as P450scc or CYP11A1, which is responsible for the conversion of cholesterol into pregnenolone and by extension the production of all steroid hormones, including the androgens. [89] Ketoconazole and abiraterone acetate are inhibitors of the enzyme CYP17A1, also known as 17α-hydroxylase/17,20-lyase, which is responsible for the conversion of pregnane steroids into androgens, as well as the conversion of mineralocorticoids into glucocorticoids. [89] [31] Because these drugs all prevent the formation of glucocorticoids in addition to androgens, they must be combined with a glucocorticoid like prednisone to avoid adrenal insufficiency. [152] A newer drug currently under development for treatment of prostate cancer, seviteronel, is selective for inhibition of the 17,20-lyase functionality of CYP17A1, and for this reason, unlike earlier drugs, does not require concomitant treatment with a glucocorticoid. [153]
5α-Reductase inhibitors such as finasteride and dutasteride are inhibitors of 5α-reductase, an enzyme that is responsible for the formation of DHT from testosterone. [154] DHT is between 2.5- and 10-fold more potent than testosterone as an androgen [155] and is produced in a tissue-selective manner based on expression of 5α-reductase. [156] Tissues in which DHT forms at a high rate include the prostate gland, skin, and hair follicles. [41] [156] In accordance, DHT is involved in the pathophysiology of benign prostatic hyperplasia, pattern hair loss, and hirsutism, and 5α-reductase inhibitors are used to treat these conditions. [41] [156] [157]
Antigonadotropins are drugs that suppress the GnRH-mediated secretion of gonadotropins from the pituitary gland. [91] Gonadotropins include luteinizing hormone (LH) and follicle-stimulating hormone (FSH) and are peptide hormones that signal the gonads to produce sex hormones. By suppressing gonadotropin secretion, antigonadotropins suppress gonadal sex hormone production and by extension circulating androgen levels. [91] GnRH modulators, including both GnRH agonists and GnRH antagonists, are powerful antigonadotropins that are able to suppress androgen levels by 95% in men. [160] In addition, estrogens and progestogens are antigonadotropins via exertion of negative feedback on the hypothalamic–pituitary–gonadal axis (HPG axis). [2] [93] [161] High-dose estrogens are able to suppress androgen levels to castrate levels in men similarly to GnRH modulators, [162] while high-dose progestogens are able to suppress androgen levels by up to approximately 70 to 80% in men. [163] [164]
Examples of GnRH agonists include leuprorelin (leuprolide) and goserelin, while an example of a GnRH antagonist is cetrorelix. [92] Estrogens that are or that have been used as antigonadotropins include estradiol, estradiol esters like estradiol valerate, estradiol undecylate, and polyestradiol phosphate, conjugated estrogens, ethinylestradiol, diethylstilbestrol (no longer widely used), and bifluranol. [165] [166] Progestogens that are used as antigonadotropins include chlormadinone acetate, cyproterone acetate, gestonorone caproate, [167] hydroxyprogesterone caproate, medroxyprogesterone acetate, megestrol acetate, and oxendolone. [2] [168] [169]
In addition to their antigonadotropic effects, estrogens are also functional antiandrogens by decreasing free concentrations of androgens via increasing the hepatic production of sex hormone-binding globulin (SHBG) and by extension circulating SHBG levels. [170] [171] [172] Combined oral contraceptives containing ethinylestradiol have been found to increase circulating SHBG levels by 2- to 4-fold in women and to reduce free testosterone concentrations by 40 to 80%. [171] However, combined oral contraceptives that contain the particularly androgenic progestin levonorgestrel have been found to increase SHBG levels by only 50 to 100%, [171] which is likely because activation of the AR in the liver has the opposite effect of estrogen and suppresses production of SHBG. [173] Levonorgestrel and certain other 19-nortestosterone progestins used in combined oral contraceptives like norethisterone also directly bind to and displace androgens from SHBG, which may additionally antagonize the functional antiandrogenic effects of ethinylestradiol. [173] [174] In men, a study found that treatment with a relatively low dosage of 20 μg/day ethinylestradiol for 5 weeks increased circulating SHBG levels by 150% and, due to the accompanying decrease free testosterone levels, increased total circulating levels of testosterone by 50% (via reduced negative feedback by androgens on the HPG axis). [170]
Estrogens at high doses can partially suppress adrenal androgen production. [175] [176] [177] [178] [179] [180] A study found that treatment with a high-dose ethinylestradiol (100 μg/day) reduced levels of major circulating adrenal androgens by 27 to 48% in transgender women. [175] [176] [177] Decreased adrenal androgens with estrogens is apparent with oral and synthetic estrogens like ethinylestradiol and estramustine phosphate but is minimal with parenteral bioidentical estradiol forms like polyestradiol phosphate. [179] It is thought to be mediated via a hepatic mechanism, probably increased corticosteroid-binding globulin (CBG) production and levels and compensatory changes in adrenal steroid production (e.g., shunting of adrenal androgen synthesis to cortisol production). [179] [180] It is notable in this regard that oral and synthetic estrogens, due to the oral first pass and resistance to hepatic metabolism, have much stronger influences on liver protein synthesis than parenteral estradiol. [181] The decrease in adrenal androgen levels with high-dose estrogen therapy may be beneficial in the treatment of prostate cancer. [177] [180]
Anticorticotropins such as glucocorticoids and mineralocorticoids work by exerting negative feedback on the hypothalamic–pituitary–adrenal axis (HPA axis), thereby inhibiting the secretion of corticotropin-releasing hormone (CRH) and hence adrenocorticotropic hormone (ACTH; corticotropin) and consequently suppressing the production of androgen prohormones like dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEA-S), and androstenedione in the adrenal gland. [182] [183] They are rarely used clinically as functional antiandrogens, but are used as such in the case of congenital adrenal hyperplasia in girls and women, in which there are excessive production and levels of adrenal androgens due to glucocorticoid deficiency and hence HPA axis overactivity. [182] [183]
In women with insulin resistance, such as those with polycystic ovary syndrome, androgen levels are often elevated. [184] Metformin, an insulin-sensitizing medication, has indirect antiandrogenic effects in such women, decreasing testosterone levels by as much as 50% secondary to its beneficial effects on insulin sensitivity. [184] [185] [186]
Ovandrotone albumin (Fecundin, Ovastim) and Androvax (androstenedione albumin) are immunogens and vaccines against androstenedione that are used in veterinary medicine to improve fecundity (reproductive rate) in ewes (adult female sheep). [187] [188] The generation of antibodies against androstenedione by these agents is thought to decrease circulating levels of androstenedione and its metabolites (e.g., testosterone and estrogens), which in turn increases the activity of the HPG axis via reduced negative feedback and increases the rate of ovulation, resulting in greater fertility and fecundity. [187] [188]
Antiandrogens can be divided into several different types based on chemical structure, including steroidal antiandrogens, nonsteroidal antiandrogens, and peptides. Steroidal antiandrogens include compounds like cyproterone acetate, spironolactone, estradiol, abiraterone acetate, and finasteride; nonsteroidal antiandrogens include compounds like bicalutamide, elagolix, diethylstilbestrol, aminoglutethimide, and ketoconazole; and peptides include GnRH analogues like leuprorelin and cetrorelix.[ citation needed ]
Antigonadotropins like estrogens and progestogens were both first introduced in the 1930s. [189] The beneficial effects of androgen deprivation via surgical castration or high-dose estrogen therapy on prostate cancer were discovered in 1941. [31] : 56 [190] AR antagonists were first discovered in the early 1960s. [96] The steroidal antiandrogen cyproterone acetate was discovered in 1961. and introduced in 1973. and is often described as the first antiandrogen to have been marketed. [191] [62] However, spironolactone was introduced in 1959., [192] [193] although its antiandrogen effects were not recognized or taken advantage of until later and were originally an unintended off-target action of the drug. [194] In addition to spironolactone, chlormadinone acetate and megestrol acetate are steroidal antiandrogens that are weaker than cyproterone acetate but were also introduced earlier, in the 1960s. [195] [196] [197] Other early steroidal antiandrogens that were developed around this time but were never marketed include benorterone (SKF-7690; 17α-methyl-B-nortestosterone), BOMT (Ro 7–2340), cyproterone (SH-80881), and trimethyltrienolone (R-2956). [198] [199]
The nonsteroidal antiandrogen flutamide was first reported in 1967. [24] It was introduced in 1983 and was the first nonsteroidal antiandrogen marketed. [200] [201] Another early nonsteroidal antiandrogen, [202] DIMP (Ro 7–8117), which is structurally related to thalidomide [203] and is a relatively weak antiandrogen, [204] [205] was first described in 1973 and was never marketed. [206] Flutamide was followed by nilutamide in 1989. and bicalutamide in 1995. [207] In addition to these three drugs, which have been regarded as first-generation nonsteroidal antiandrogens, the second-generation nonsteroidal antiandrogens enzalutamide and apalutamide were introduced in 2012. and 2018. [208] [209] [210] They differ from the earlier nonsteroidal antiandrogens namely in that they are much more efficacious in comparison. [209]
The androgen synthesis inhibitors aminoglutethimide and ketoconazole were first marketed in 1960. and 1977., respectively, [211] [212] and the newer drug abiraterone acetate was introduced in 2011. [213] GnRH modulators were first introduced in the 1980s. [214] The 5α-reductase inhibitors finasteride and dutasteride were introduced in 1992. and 2002. respectively. [215] [216] Elagolix, the first orally active GnRH modulator to be marketed, was introduced in 2018. [217]
The following is a timeline of events in the history of antiandrogens: [218]
The term antiandrogen is generally used to refer specifically to AR antagonists, as described by Dorfman (1970): [247] [248]
Antiandrogens are substances which prevent androgens from expressing their activity at target sites. The inhibitory effect of these substances, therefore, should be differentiated from compounds which decrease the synthesis and/or release of hypothalamic (releasing) factors, from anterior pituitary hormones (gonadotropins, particularly luteinizing hormone) and from material which acts directly on the gonads to inhibit biosynthesis and/or secretion of androgens. [247] [248]
However, in spite of the above, the term may also be used to describe functional antiandrogens like androgen synthesis inhibitors and antigonadotropins, including even estrogens and progestogens. [2] [6] [249] For example, the progestogen and hence antigonadotropin medroxyprogesterone acetate is sometimes described as a steroidal antiandrogen, even though it is not an antagonist of the AR. [250] [249]
This section's factual accuracy may be compromised due to out-of-date information. The reason given is: Clascoterone has been approved for acne by the FDA in August 2020, and is considered to be highly effective (>= tretinoin 0.05%).(April 2024) |
There has been much interest and effort in the development of topical AR antagonists to treat androgen-dependent conditions like acne and pattern hair loss in males. [251] Unfortunately, whereas systemic administration of antiandrogens is very effective in treating these conditions, topical administration has disappointingly been found generally to possess limited and only modest effectiveness, even when high-affinity steroidal AR antagonists like cyproterone acetate and spironolactone have been employed. [251] Moreover, in the specific case of acne treatment, topical AR antagonists have been found much less effective compared to established treatments like benzoyl peroxide and antibiotics. [251]
A variety of AR antagonists have been developed for topical use but have not completed development and hence have never been marketed. These include the steroidal AR antagonists clascoterone, cyproterone, rosterolone, and topterone and the nonsteroidal AR antagonists cioteronel, inocoterone acetate, RU-22930, RU-58642, and RU-58841. However, one topical AR antagonist, topilutamide (fluridil), has been introduced in a few European countries for the treatment of pattern hair loss in men. [40] In addition, a topical 5α-reductase inhibitor and weak estrogen, alfatradiol, has also been introduced in some European countries for the same indication, although its effectiveness is controversial. [40] Spironolactone has been marketed in Italy in the form of a topical cream under the brand name Spiroderm for the treatment of acne and hirsutism, but this formulation was discontinued and hence is no longer available. [252]
Antiandrogens, such as cyproterone acetate, have been studied for potential use as male hormonal contraceptives. [253] [254] [255] [256] [65] [257] [258] [259] While effective in suppressing male fertility, their use as monotherapies is precluded by side effects, such as androgen deficiency (e.g., demasculinization, sexual dysfunction, hot flashes, osteoporosis) and feminization (e.g., gynecomastia). [65] [257] [258] [260] The combination of a primary antigonadotropin such as cyproterone acetate to prevent fertility and an androgen like testosterone to prevent systemic androgen deficiency, resulting in a selective antiandrogenic action locally in the testes, has been extensively studied and has shown promising results, but has not been approved for clinical use at this time. [258] [259] [261] [262] [260] Dimethandrolone undecanoate (developmental code name CDB-4521), an orally active dual AAS and progestogen, is under investigation as a potential male contraceptive and as the first male birth control pill. [263] [264]
Antiandrogens such as bicalutamide, enzalutamide, and abiraterone acetate are under investigation for the potential treatment of breast cancer, including AR-expressing triple-negative breast cancer and other types of AR-expressing breast cancer. [265] [266] [267] [268] [269]
Antiandrogens may be effective in the treatment of obsessive–compulsive disorder. [270]
Bicalutamide, sold under the brand name Casodex among others, is an antiandrogen medication that is primarily used to treat prostate cancer. It is typically used together with a gonadotropin-releasing hormone (GnRH) analogue or surgical removal of the testicles to treat metastatic prostate cancer (mPC). To a lesser extent, it is used at high doses for locally advanced prostate cancer (LAPC) as a monotherapy without castration. Bicalutamide was also previously used as monotherapy to treat localized prostate cancer (LPC), but authorization for this use was withdrawn following unfavorable trial findings. Besides prostate cancer, bicalutamide is limitedly used in the treatment of excessive hair growth and scalp hair loss in women, as a puberty blocker and component of feminizing hormone therapy for transgender girls and women, to treat gonadotropin-independent early puberty in boys, and to prevent overly long-lasting erections in men. It is taken by mouth.
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.
Feminizing hormone therapy, also known as transfeminine hormone therapy, is hormone therapy and sex reassignment therapy to change the secondary sex characteristics of transgender people from masculine or androgynous to feminine. It is a common type of transgender hormone therapy and is used to treat transgender women and non-binary transfeminine individuals. Some, in particular intersex people, but also some non-transgender people, take this form of therapy according to their personal needs and preferences.
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.
Cyproterone acetate (CPA), sold alone under the brand name Androcur or with ethinylestradiol under the brand names Diane or Diane-35 among others, is an antiandrogen and progestin medication used in the treatment of androgen-dependent conditions such as acne, excessive body hair growth, early puberty, and prostate cancer, as a component of feminizing hormone therapy for transgender individuals, and in birth control pills. It is formulated and used both alone and in combination with an estrogen. CPA is taken by mouth one to three times per day.
Benorterone, also known by its developmental code name SKF-7690 and as 17α-methyl-B-nortestosterone, is a steroidal antiandrogen which was studied for potential medical use but was never marketed. It was the first known antiandrogen to be studied in humans. It is taken by mouth or by application to skin.
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.
The medical uses of bicalutamide, a nonsteroidal antiandrogen (NSAA), include the treatment of androgen-dependent conditions and hormone therapy to block the effects of androgens. Indications for bicalutamide include the treatment of prostate cancer in men, skin and hair conditions such as acne, seborrhea, hirsutism, and pattern hair loss in women, high testosterone levels in women, hormone therapy in transgender women, as a puberty blocker to prevent puberty in transgender girls and to treat early puberty in boys, and the treatment of long-lasting erections in men. It may also have some value in the treatment of paraphilias and hypersexuality in men.
The side effects of bicalutamide, a nonsteroidal antiandrogen (NSAA), including its frequent and rare side effects, have been well-studied and characterized. The most common side effects of bicalutamide monotherapy in men include breast tenderness, breast growth, feminization, demasculinization, and hot flashes. Less common side effects of bicalutamide monotherapy in men include sexual dysfunction, depression, fatigue, weakness, and anemia. Bicalutamide is well tolerated and has few side effects in women. General side effects of bicalutamide that may occur in either sex include diarrhea, constipation, abdominal pain, nausea, dry skin, itching, and rash.
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.
A sex-hormonal agent, also known as a sex-hormone receptor modulator, is a type of hormonal agent which specifically modulates the effects of sex hormones and of their biological targets, the sex hormone receptors. The sex hormones include androgens such as testosterone, estrogens such as estradiol, and progestogens such as progesterone. Sex-hormonal agents may be either steroidal or nonsteroidal in chemical structure and may serve to either enhance, inhibit, or have mixed effects on the function of the sex hormone systems.
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.
The pharmacodynamics of spironolactone, an antimineralocorticoid and antiandrogen medication, concern its mechanisms of action, including its biological targets and activities, as well as its physiological effects. The pharmacodynamics of spironolactone are characterized by high antimineralocorticoid activity, moderate antiandrogenic activity, and weak steroidogenesis inhibition. In addition, spironolactone has sometimes been found to increase estradiol and cortisol levels and hence could have slight indirect estrogenic and glucocorticoid effects. The medication has also been found to interact very weakly with the estrogen and progesterone receptors, and to act as an agonist of the pregnane X receptor. Likely due to increased activation of the estrogen and/or progesterone receptors, spironolactone has very weak but significant antigonadotropic effects.
The pharmacology of cyproterone acetate (CPA) concerns the pharmacology of the steroidal antiandrogen and progestin medication cyproterone acetate.
There are several classes of antiandrogens including (1) antigonadotropins (eg, LHRH agonists/antagonists, synthetic estrogens [diethylstilbestrol]); (2) nonsteroidal androgen-receptor antagonists (eg, flutamide, bicalutamide, nilutamide); (3) steroidal agents with mixed actions (eg, cyproterone acetate); (4) adrenal androgen inhibitors (eg, ketoconazole, hydrocortisone); (5) steroidal agents that inhibit androgen biosynthesis (eg, 5α-reductase inhibitors (type II) and dual-acting 5α-reductase inhibitors); [...]
From a structural standpoint, antiandrogens are classified as steroidal, including cyproterone [acetate] (Androcur) and megestrol [acetate], or nonsteroidal, including flutamide (Eulexin, others), bicalutamide (Casodex), and nilutamide (Nilandron). The steroidal antiandrogens are rarely used.
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: CS1 maint: DOI inactive as of November 2024 (link)Because steroidal antiandrogens such as cyproterone acetate have intrinsic androgenic activity and lower antiandrogenic activity than the NSAAs such as flutamide and nilutamide,39–43 it is not surprising that the two classes of antiandrogens may have different efficacies.
In patients receiving flutamide at the usual dosage of 250 mg every 8 hours, the minimal plasma concentration of hydroxyflutamide is about 5 uM, which is 5,000 times the plasma concentration of testosterone (1 nM) in patients treated with an LHRH agonist.127 As hydroxyflutamide is only one percent as potent as testosterone in competing for binding to the androgen receptor,126 a plasma level of 5 uM hydroxyflutamide is required to ensure effective competition.127 [...] Both cyproterone acetate and flutamide have been demonstrated to be effective therapy (roughly equivalent to an estrogen) when used alone in the treatment of carcinoma of the prostate.123