1521-009X/47/5/453–464$35.00 https://doi.org/10.1124/dmd.118.084517 DRUG METABOLISM AND DISPOSITION Drug Metab Dispos 47:453–464, May 2019 Copyright ª 2019 by The American Society for Pharmacology and Experimental Therapeutics Apalutamide Absorption, Metabolism, and Excretion in Healthy Men, and Enzyme Reaction in Human Hepatocytes s Ronald de Vries, Frank Jacobs, Geert Mannens, Jan Snoeys, Filip Cuyckens, Caly Chien, and Peter Ward Janssen Research & Development, Beerse, Belgium (R.d.V., F.J., G.M., J.S., F.C.); Janssen Research & Development, Spring House, Pennsylvania (C.C.); and Janssen Research & Development, San Diego, California (P.W.) Received October 2, 2018; accepted February 4, 2019 ABSTRACT In this phase 1 study, the absolute bioavailability and absorption, metabolism, and excretion (AME) of apalutamide, a competitive inhib- itor of the androgen receptor, were evaluated in 12 healthy men. Subjects received 240 mg of apalutamide orally plus a 15-minute intravenous infusion of 100 mg of apalutamide containing 9.25 kBq (250 nCi) of 14 C-apalutamide (2 hours postdose) for absolute bioavail- ability assessment or plus one 400-mg capsule containing 37 kBq (1000 nCi) of 14 C-apalutamide for AME assessment. Content of 14 C and metabolite profiling for whole blood, plasma, urine, feces, and expired air samples were analyzed using accelerator mass spectrometry. Apalutamide absolute oral bioavailability was 100%. After oral administration, apalutamide, its N-desmethyl metabolite (M3), and an inactive carboxylic acid metabolite (M4) accounted for most 14 C in plasma (45%, 44%, and 3%, respectively). Apalutamide elimination was slow, with a mean plasma half-life of 151–178 hours. The mean cumulative recovery of total 14 C over 70 days postdose was 64.6% in urine and 24.3% in feces. The urinary excretion of apalutamide, M3, and M4 was 1.2%, 2.7%, and 31.1% of dose, respectively. Fecal excretion of apalutamide, M3, and M4 was 1.5%, 2.0%, and 2.4% of dose, respectively. Seventeen apalutamide metabolites and six main meta- bolic clearance pathways were identified. In vitro studies confirmed CYP2C8 and CYP3A4 roles in apalutamide metabolism. Introduction Apalutamide is a potent, specific, orally administered competitive inhibitor of the androgen receptor. Apalutamide has been studied in the treatment of men with nonmetastatic castration-resistant prostate cancer (CRPC) who are at high risk for the development of metastatic disease (Smith et al., 2005; Lin et al., 2017). Its mechanism of action involves the blockade of androgen receptor nuclear translocation, DNA binding to androgen response elements, and transcription of androgen target genes (Clegg et al., 2012). On the basis of the phase 3 SPARTAN trial, which demonstrated that metastasis-free survival was more than 2 years longer with apalutamide 240 mg/day compared with placebo in men with nonmetastatic CRPC (Smith et al., 2018), apalutamide received US Food and Drug Administration approval (ERLEADA, 2018). In a phase 1 study conducted in men with CRPC, apalutamide was safe and well tolerated across the dose range of 30–480 mg (Rathkopf et al., 2013). The C max of apalutamide and the area under the plasma concentration-time curve (AUC) increased proportionally after repeated once-daily dosing of 30–480 mg. Apalutamide steady state was achieved after 4 weeks, and the mean accumulation ratio was approximately 5-fold. Apalutamide declined slowly in plasma, and the mean effective half-life was about 3–4 days at steady state. An increase in apparent clearance was observed with repeat dosing of apalutamide, likely due to metabolic autoinduction (ERLEADA, 2018). The major active metab- olite of apalutamide, N-desmethyl apalutamide (M3), which exhibited one-third the activity of apalutamide in an in vitro transcriptional reporter assay, was detected in plasma as early as 1 hour after ingestion of the first apalutamide dose, with concentrations increasing steadily during the first 24 hours after single-dose administration. M3 plasma levels approached steady state after 6–8 weeks and were comparable to its parent with minimal fluctuation. A minor, inactive carboxylic acid metabolite of apalutamide (M4) was also detected in plasma, with systemic exposure below 10% of the parent compound apalutamide plus metabolites (M3 and M4) combined at steady state. The recommended phase 2 dose of apalutamide, 240 mg/day, showed robust activity based on durable prostate-specific antigen responses and disease control in a phase 2 study of patients with nonmetastatic CRPC (Smith et al., 2016), findings that have since been confirmed in the phase 3 SPARTAN trial (Smith et al., 2018). Though previous studies that supported the clinical development of apalutamide have evaluated the efficacy and pharmacodynamic profile of this agent, the absolute bioavailability, absorption, metabolism, and excretion (AME) profile of apalutamide in humans has not been completely characterized. The present study was therefore conducted with the primary objective of determining the absolute bioavailabil- ity, and absorption, metabolic pathways, and excretion routes of This study was funded by Janssen Research & Development. https://doi.org/10.1124/dmd.118.084517. s This article has supplemental material available at dmd.aspetjournals.org. ABBREVIATIONS: ABT, aminobenzotriazole; AE, adverse event; AME, absorption, metabolism, and excretion; AMS, accelerator mass spectrometry; AUC, area under the plasma concentration-time curve; AUC 0–inf , area under the plasma concentration-time curve from time zero to infinity; AUC 0–t , area under the plasma concentration-time curve from time zero to the last time point with a measurable concentration; BNPP, bis-nitrophenol phosphate; CRPC, castration-resistant prostate cancer; HPLC, high-performance liquid chromatography; LC, liquid chromatog- raphy; M, metabolite; M3, N-desmethyl metabolite; M4, carboxylic acid metabolite of apalutamide; MS, mass spectrometry; MS/MS, tandem mass spectrometry; m/z, mass/charge ratio; NMR, nuclear magnetic resonance; T max , time to C max . 453 http://dmd.aspetjournals.org/content/suppl/2019/02/20/dmd.118.084517.DC1 Supplemental material to this article can be found at: at ASPET Journals on July 4, 2020 dmd.aspetjournals.org Downloaded from