Nonsteroidal antiandrogen

Nonsteroidal antiandrogen
	Drug class
	Bicalutamide, the most widely used nonsteroidal antiandrogen and the most widely used antiandrogen in prostate cancer.
Class identifiers
Synonyms	Nonsteroidal androgen receptor antagonists
Use	Prostate cancer; Acne; Hirsutism; Seborrhea; Pattern hair loss; Hyperandrogenism; Transgender hormone therapy; Male precocious puberty; Priapism
ATC code	L02BB
Biological target	Androgen receptor
Chemical class	Nonsteroidal
	In Wikidata

A nonsteroidal antiandrogen (NSAA) is an antiandrogen with a nonsteroidal chemical structure.[1][2][3] 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).[2][3] NSAAs are used in the treatment of androgen-dependent conditions in men and women.[2] They are the converse of steroidal antiandrogens (SAAs), which are antiandrogens that are steroids and are structurally related to testosterone.[2][3]

Medical uses

NSAAs are used in clinical medicine for the following indications:[2]

Prostate cancer in men
Androgen-dependent skin and hair conditions like acne, hirsutism,[4] seborrhea, and pattern hair loss (androgenic alopecia) in women
Hyperandrogenism, such as due to polycystic ovary syndrome or congenital adrenal hyperplasia, in women
As a component of hormone therapy for transgender women[5]
Precocious puberty in boys
Priapism in men

Available forms

Antiandrogens marketed for clinical or veterinary use
Generic name	Class	Type	Brand name(s)	Route(s)	Launch	Status	Hits^a
Abiraterone acetate	Steroidal	Androgen synthesis inhibitor	Zytiga	Oral	2011	Available	523,000
Allylestrenol	Steroidal	Progestin	Gestanin, Perselin	Oral	1961	Available^b	61,800
Aminoglutethimide	Nonsteroidal	Androgen synthesis inhibitor	Cytadren, Orimeten	Oral	1960	Available^b	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	Available^b	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	Available^b	36,100
Spironolactone	Steroidal	AR antagonist	Aldactone	Oral, topical	1959	Available	3,010,000
Topilutamide	Nonsteroidal	AR antagonist	Eucapil	Topical	2003	Available^b	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.

Pharmacology

Unlike SAAs, NSAAs have little or no capacity to activate the AR, show no off-target hormonal activity such as progestogenic, glucocorticoid, or antimineralocorticoid activity, and lack antigonadotropic effects.[2] For these reasons, they have improved efficacy and selectivity as antiandrogens and do not lower androgen levels, instead acting solely by directly blocking the actions of androgens at the level of their biological target, the AR.[2]

List of NSAAs

Marketed

First-generation

Flutamide (Eulexin): Marketed for the treatment of prostate cancer and also used in the treatment of acne, hirsutism, and hyperandrogenism in women.[3][4] It has also been studied in the treatment of benign prostatic hyperplasia.[6] Now little-used due to high incidences of elevated liver enzymes and hepatotoxicity and the availability of safer agents.
Nilutamide (Anandron, Nilandron): Marketed for the treatment of prostate cancer.[3] Very little-used due to a high incidence of interstitial pneumonitis and high rates of several unique and unfavorable side effects such as nausea and vomiting, visual disturbances, and alcohol intolerance.
Bicalutamide (Casodex): Marketed for the treatment of prostate cancer and also used in the treatment of hirsutism in women,[4] as a component of hormone therapy for transgender women,[5] to delay precocious puberty in boys,[7] to prevent or alleviate priapism,[8] and for other indications. It has also been studied in the treatment of benign prostatic hyperplasia.[6] By far the most widely used NSAA, due to its favorable profile of efficacy, tolerability, and safety.
Topilutamide (Eucapil): Also known as fluridil. Marketed as a topical medication for the treatment of pattern hair loss (androgenic alopecia) in the Czech Republic and Slovakia. Limited availability and lack of an oral formulation for systemic use make it a very little-known drug.

Second-generation

Apalutamide (Erleada): Marketed for the treatment of prostate cancer. Very similar to enzalutamide, but with reduced central nervous system distribution and hence is expected to have a reduced risk of seizures and other central side effects.
Enzalutamide (Xtandi): Marketed for the treatment of prostate cancer. More effective than the first-generation NSAAs due to increased efficacy and potency and shows no risk of elevated liver enzymes or hepatotoxicity. However, it has a small (1%) risk of seizures and has central nervous system side effects like anxiety and insomnia due to off-target inhibition of the GABA_A receptor that the first-generation NSAAs do not have. In addition, it has prominent drug interactions due to moderate to strong induction of multiple cytochrome P450 enzymes. Currently on-patent with no generic availability and hence is very expensive.
Darolutamide (Nubeqa): Marketed for the treatment of prostate cancer. Structurally distinct from enzalutamide, apalutamide, and other NSAAs. Relative to enzalutamide and apalutamide, shows greater efficacy as an AR antagonist, improved activity against mutated AR variants in prostate cancer, little or no inhibition or induction of cytochrome P450 enzymes, and little or no central nervous system distribution. However, has a much shorter terminal half-life and lower potency.

Miscellaneous

Cimetidine (Tagamet): An over-the-counter histamine H₂ receptor antagonist that also shows very weak activity as an AR antagonist. Also inhibits cytochrome P450 enzymes and thereby inhibits hepatic estradiol metabolism and increases circulating estradiol levels. It has been investigated in the treatment of hirsutism but showed minimal effectiveness. Sometimes causes gynecomastia as a rare side effect.

Nonsteroidal androgen synthesis inhibitors like ketoconazole can also be described as "NSAAs", although the term is usually reserved to describe AR antagonists.

Not marketed

Under development

Proxalutamide (GT-0918): A second-generation NSAA. It is under development for the treatment of prostate cancer. Similar to enzalutamide and apalutamide, but with increased efficacy as an AR antagonist, little or no central nervous system distribution, and no induction of seizures in animals.

Seviteronel (VT-464) is a nonsteroidal androgen biosynthesis inhibitor which is under development for the treatment of prostate cancer.

Development discontinued

Cioteronel (CPC-10997; Cyoctol, Ethocyn, X-Andron): A structurally unique first-generation NSAA. It was under development as an oral medication for the treatment of benign prostatic hyperplasia and as a topical medication for the treatment of acne and pattern hair loss. It reached phase II and phase III clinical trials for these indications prior to discontinuation due to insufficient effectiveness.
Inocoterone acetate (RU-38882, RU-882): A steroid-like NSAA. It was under development as a topical medication for the treatment of acne but was discontinued due to insufficient effectiveness in clinical trials.
RU-58841 (PSK-3841, HMR-3841): A first-generation NSAA related to nilutamide. It was under development as a topical medication for the treatment of acne and pattern hair loss but its development was discontinued during phase I clinical trials.

References

Kolvenbag, Geert J. C. M.; Furr, Barrington J. A. (2009). "Nonsteroidal Antiandrogens". In V. Craig Jordan; Barrington J. A. Furr (eds.). Hormone Therapy in Breast and Prostate Cancer. Humana Press. pp. 347–368. doi:10.1007/978-1-59259-152-7_16. ISBN 978-1-60761-471-5.
Singh SM, Gauthier S, Labrie F (2000). "Androgen receptor antagonists (antiandrogens): structure-activity relationships". Curr. Med. Chem. 7 (2): 211–47. doi:10.2174/0929867003375371. PMID 10637363.
Migliari R, Muscas G, Murru M, Verdacchi T, De Benedetto G, De Angelis M (1999). "Antiandrogens: a summary review of pharmacodynamic properties and tolerability in prostate cancer therapy". Arch Ital Urol Androl. 71 (5): 293–302. PMID 10673793.
Erem C (2013). "Update on idiopathic hirsutism: diagnosis and treatment". Acta Clin Belg. 68 (4): 268–74. doi:10.2143/ACB.3267. PMID 24455796.
Gooren LJ (2011). "Clinical practice. Care of transsexual persons". N. Engl. J. Med. 364 (13): 1251–7. doi:10.1056/NEJMcp1008161. PMID 21449788.
Kenny B, Ballard S, Blagg J, Fox D (1997). "Pharmacological options in the treatment of benign prostatic hyperplasia". J. Med. Chem. 40 (9): 1293–315. doi:10.1021/jm960697s. PMID 9135028.
Reiter EO, Norjavaara E (2005). "Testotoxicosis: current viewpoint". Pediatr Endocrinol Rev. 3 (2): 77–86. PMID 16361981.
Yuan J, Desouza R, Westney OL, Wang R (2008). "Insights of priapism mechanism and rationale treatment for recurrent priapism". Asian J. Androl. 10 (1): 88–101. doi:10.1111/j.1745-7262.2008.00314.x. PMID 18087648.