Study Populations
Pharmacokinetic results from three phase I clinical trials are reported (Table 1): a trial in healthy male subjects (ARIADME, NCT02418650), a trial evaluating the effect of impaired hepatic or renal function in male patients without cancer (Study 17721, NCT02894385), and a drug–drug interaction trial that included single-dose and multiple-dose pharmacokinetic analyses (Study 17723, NCT02671097 [11]). All studies were conducted in accordance with the International Council for Harmonization Good Clinical Practice, the principles of the Declaration of Helsinki, and all applicable national regulations. An independent ethics committee at each study site approved each study protocol, and all participants provided written informed consent.
Table 1 Overview of darolutamide clinical studies with pharmacokinetic evaluations in healthy subjects and in patients without cancer with severe renal or moderate hepatic impairment Pharmacokinetic and Analytical Methods
Pharmacokinetic blood samples were collected according to schedules defined for each trial, using K2-EDTA as the anticoagulant. The bioanalytical methods used for pharmacokinetic sampling are summarized in the ESM.
The plasma concentrations of darolutamide (sum of concentrations of (S,R)-darolutamide and (S,S)-darolutamide) and keto-darolutamide were used to calculate pharmacokinetic parameters in non-compartmental analyses using WinNonlin version 5.3 (Pharsight Corporation, Mountain View, CA, USA) and applicable complementary software. The following pharmacokinetic parameters were estimated: maximum observed plasma concentration (Cmax); time to Cmax (tmax); area under the concentration–time curve (AUC) from time 0 to the time of the last measurable concentration (AUC0−tlast), to infinity (AUC0−inf), and to 12 or 48 h after darolutamide administration (AUC0–12 and AUC0–48, respectively); terminal half-life (t½) and effective t½; clearance following intravenous (IV) administration; and volume of distribution. Diastereomer ratios in plasma based on AUC0–inf and keto-darolutamide:darolutamide ratios based on AUC0–inf were calculated after oral and IV administration. Accumulation ratios based on AUC0–12 and Cmax for single vs multiple dosing were calculated for darolutamide, both diastereomers, and keto-darolutamide. The linearity factor (RLIN; the ratio of multiple-dose AUC0–12 to single-dose AUC0−inf) was also calculated. Effective t½ was based on the mean accumulation ratio of AUC0–12 at steady state divided by AUC0–12 after single administration.
Protein binding of darolutamide, (S,R)-darolutamide, (S,S)-darolutamide, and keto-darolutamide, and blood partitioning of darolutamide and keto-darolutamide were investigated in vitro using blood and plasma from healthy male subjects and patients without cancer with moderate hepatic impairment or severe renal impairment. Unbound fractions were determined by equilibrium dialysis (see ESM).
Study Designs
Pharmacokinetics and Bioavailability Study
The ARIADME study was a phase I, single-center, open-label, non-randomized, two-part trial to determine the absolute bioavailability and pharmacokinetics of darolutamide, its diastereomers, and keto-darolutamide, as well as evaluations of mass balance, metabolism, and excretion routes of darolutamide, which are reported elsewhere [6]. In Part 1, six healthy male subjects received a single oral dose of darolutamide 300 mg as a tablet, followed by a single IV microtracer dose administered as a 15-min infusion ending at the expected tmax for the oral tablet (3 h post-dose) to assess absolute bioavailability. The microtracer dose did not exceed 100 μg of 14C-darolutamide and contained ≤37 kBq (1000 nCi) 14C. In Part 2, six healthy male subjects received a single oral dose of 14C-darolutamide 300 mg as an aqueous propylene glycol solution containing ≤ 6.3 MBq (171 μCi) 14C. All doses were administered after overnight fasting.
Pharmacokinetic samples were collected from all subjects receiving darolutamide oral tablets in Part 1 as follows: blood samples were obtained pre-dose and at 0.5, 1, 1.5, 2, 3, 4, 5, 6, 8, 12, 16, 24, 48, and 72 h post-dose; urine samples were collected from 0 to 12 h and 12 to 24 h post-dose, and then at intervals of 24 h up to 72 h post-dose. Plasma samples for the IV microtracer dose of 14C-darolutamide in Part 1 were collected at the start of the infusion, 10 min after the start of the infusion, and at the end of the infusion, then at 10, 20, and 40 min post-infusion and at 1, 1.5, 2, 3, 4, 5, 7, 9, 15, 21, 45, and 69 h post-infusion. Plasma samples for subjects receiving darolutamide oral solution in Part 2 were collected pre-dose, at 0.25, 0.5, 1, 1.5, 2, 3, 4, 5, 6, 8, 12, 16, and 24 h post-dose, then at 24-h intervals up to 168 h post-dose. Urine samples were collected from 0 to 12 h and 12 to 24 h post-dose, then at intervals of 24 h up to 72 h (tablet) or 168 h (solution) post-dose. Whole blood samples for total radioactivity after oral solution dosing were collected pre-dose and at 0.5, 1, 1.5, 3, 8, and 24 h post-dose.
After oral dosing with the solution or tablet, plasma concentrations of darolutamide, its diastereomers, and keto-darolutamide and urine concentrations of the diastereomers were determined in samples using high-performance liquid chromatography mass spectrometry methods that were validated in accordance with regulatory guidance (plasma) [12, 13] or were qualified against validated methods (urine). Plasma concentrations of IV 14C-labeled darolutamide, (S,R)-darolutamide, (S,S)-darolutamide, and keto-darolutamide were determined using a validated method consisting of liquid chromatography followed by fractionation and accelerator mass spectrometry. Plasma and whole blood concentrations of 14C-radioactivity were determined using liquid scintillation counting. Details of the bioanalytical methods are included in the ESM.
Single-Dose and Multiple-Dose Pharmacokinetics
The phase I study that included investigation of single-dose and multiple-dose pharmacokinetics of darolutamide was a prospective, open-label, non-randomized, fixed-sequence trial in healthy male subjects, with the primary objective of assessing drug–drug interactions between darolutamide and rosuvastatin [11] (Table 1). Darolutamide 600 mg was administered orally as two 300-mg tablets 30 min after the start of a standardized meal on day 1 (morning), then BID on days 4–7. Pharmacokinetic blood samples were collected pre-dose and at 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 24, 36, 38, 60, and 72 h post-dose (for single-dose pharmacokinetics), in the morning on days 4–6 (trough concentration), and pre-dose and at 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, and 12 h post-dose on day 7 (for multiple-dose pharmacokinetics). Plasma samples were extracted using a solid-phase extraction procedure, and concentrations of darolutamide, its diastereomers, and keto-darolutamide were determined using a validated liquid chromatography–tandem mass spectrometry detection assay (see ESM).
Hepatic and Renal Impairment Study
An open-label, non-randomized, parallel-group, multicenter, phase I clinical trial was conducted to evaluate the potential effects of hepatic or renal impairment on the pharmacokinetics of darolutamide, its diastereomers, and keto-darolutamide. The study population comprised male patients (aged 45–79 years) who had moderate hepatic impairment or severe renal impairment and an age-matched and weight-matched control group of healthy male subjects. Patients with moderate hepatic impairment were eligible if they had histopathologically confirmed liver cirrhosis and Child–Pugh classification B [14]. Patients with renal impairment were eligible if they had an estimated glomerular filtration rate of 15–29 mL/min/1.73 m2 according to the four-variable abbreviated ‘Modification of Diet in Renal Disease’ Study equation, were not undergoing dialysis or expected to start dialysis in the next 3 months, and had stable renal disease (serum creatinine within ± 25% of the last determination obtained ≤ 3 months before study entry).
Darolutamide 600 mg was administered orally as two 300-mg tablets 30 min after the start of a standardized breakfast. Pharmacokinetic blood samples were collected pre-dose and at 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 24, 36, and 48 h post-dose. Quantitative analysis of darolutamide, its diastereomers, and keto-darolutamide was performed using a validated liquid chromatography-tandem mass spectrometry detection assay (see ESM). Pharmacokinetic parameters were calculated based on total and unbound concentration–time data for darolutamide, its diastereomers, and keto-darolutamide in plasma.