Cytochrome P450 inhibition
Nilutamide is known to inhibit several cytochrome P450 enzymes, including CYP1A2, CYP2C9, and CYP3A4, and can result in increased levels of medications that are metabolized by these enzymes. It has also been found to inhibit the enzyme CYP17A1 (17α-hydroxylase/17,20-lyase) in vitro and thus the biosynthesis of androgens. However, nilutamide monotherapy significantly increases testosterone levels in vivo, so the clinical significance of this finding is uncertain. Pharmacokinetics
Nilutamide has an elimination half-life of 23 to 87 hours, with a mean of 56 hours, or about two days; this allows for once-daily administration. Steady state (plateau) levels of the drug are attained after two weeks of administration with a dosage of 150 mg twice daily (300 mg/day total). It is metabolized by CYP2C19, with at least five metabolites. Virtually all of the antiandrogenic activity of nilutamide comes from the parent drug (as opposed to metabolites). Chemistry
Nilutamide is structurally related to the first-generation NSAAs flutamide and bicalutamide as well as to the second-generation NSAAs enzalutamide and apalutamide. History
Nilutamide was developed by Roussel and was first described in 1977. It was first introduced for medical use in 1987 in France and was the second NSAA to be marketed, with flutamide preceding it and bicalutamide following it in 1995. It was not introduced until 1996 in the United States. Society and culture
Generic names
Nilutamide is the generic name of the drug and its INN, USAN, BAN, and DCF.
Similarly to flutamide, nilutamide exhibits mitochondrial toxicity in hepatocytes by inhibiting respiratory complex I (NADH ubiquinone oxidoreductase) (though not respiratory complexes II, III, or IV) in the electron transport chain, resulting in reduced ATP and glutathione production and thus decreased hepatocyte survival. The nitro group of nilutamide has been theorized to be involved in both its hepatotoxicity and its pulmonary toxicity. Pharmacology
Pharmacodynamics
Antiandrogenic activity
Nilutamide acts as a selective competitive silent antagonist of the AR (IC50 = 412 nM), which prevents androgens like testosterone and DHT from activating the receptor. The affinity of nilutamide for the AR is about 1 to 4% of that of testosterone and is similar to that of bicalutamide and 2-hydroxyflutamide. Similarly to 2-hydroxyflutamide, but unlike bicalutamide, nilutamide is able to weakly activate the AR at high concentrations. It does not inhibit 5α-reductase.Like other NSAAs such as flutamide and bicalutamide, nilutamide, without concomitant GnRH analogue therapy, increases serum androgen (by two-fold in the case of testosterone), estrogen, and prolactin levels due to inhibition of AR-mediated suppression of steroidogenesis via negative feedback on the hypothalamic–pituitary–gonadal axis. As such, though nilutamide is still effective as an antiandrogen as a monotherapy, it is given in combination with a GnRH analogue such as leuprorelin in prostate cancer to suppress androgen concentrations to castrate levels in order to attain maximal androgen blockade (MAB).Like flutamide and bicalutamide, nilutamide is able to cross the blood–brain barrier and has central antiandrogen actions.