Pharmacotherapeutic group: Endocrine therapy, anti-androgens. ATC code: L02BB06.
Pharmacology: Pharmacodynamics: Mechanism of action: Darolutamide is an androgen receptor (AR) inhibitor with a flexible polar-substituted pyrazole structure that binds with high affinity directly to the receptor ligand binding domain.
Darolutamide competitively inhibits androgen binding, AR nuclear translocation, and AR mediated transcription. A major metabolite, keto-darolutamide, exhibited similar in vitro activity to darolutamide. Darolutamide treatment decreases prostate tumour cell proliferation leading to potent antitumour activity.
Pharmacodynamic effects: No prolongation of the mean QTcF interval (i.e., greater than 10 ms) was observed after oral administration of 600 mg darolutamide twice daily compared to placebo.
Clinical efficacy and safety: The efficacy and safety of darolutamide was assessed in a randomised, double-blind, placebo-controlled multicentre phase III study (ARAMIS) in patients with non-metastatic (as assessed by conventional imaging CT, bone scan, MRI) castration resistant prostate cancer with a prostate-specific antigen doubling time (PSADT) of ≤ 10 months.
Patients were included in the trial if they had 3 rising prostate-specific antigen (PSA) levels after the nadir taken at least 1 week apart during androgen deprivation therapy, PSA ≥ 2 ng/mL at screening and castrate level of serum testosterone < 1.7 nmol/L.
Patients with a medical history of seizure were allowed to enter the study. There were 12 patients (0.21%) enrolled on the darolutamide arm with a history of seizure.
Patients with uncontrolled hypertension or recent (in the past 6 months) stroke, myocardial infarction, severe/unstable angina pectoris, coronary/peripheral artery bypass graft, congestive heart failure New York Heart Association (NYHA) Class III or IV were excluded from the study.
Patients with prior treatment with second generation AR inhibitors such as enzalutamide, apalutamide and darolutamide, or CYP17 enzyme inhibitors such as abiraterone acetate as well as patients receiving systemic corticosteroid with dose greater than the equivalent 10 mg of prednisone/day within 28 days before randomisation were excluded from the study.
In total, 1509 patients were randomized 2:1 to receive either 600 mg darolutamide orally twice daily (n=955) or matching placebo (n=554).
All patients received a gonadotropin-releasing hormone (GnRH) analogue concurrently or had a bilateral orchiectomy. Patients with presence of pelvic lymph nodes < 2 cm in short axis below the aortic bifurcation were allowed to enter the study. Absence or presence of metastasis was assessed by independent central radiological review. Included in these analyses were 89 patients that were retrospectively identified with metastasis at baseline. Randomization was stratified by PSADT (≤ 6 months or > 6 months) and use of osteoclast-targeted therapy at study entry (yes or no).
The following patient demographics and disease characteristics were balanced between treatment arms. The median age was 74 years (range 48-95) and 9% of patients were 85 years of age or older. The racial distribution was 79% White, 13% Asian, and 3% Black. A majority of patients had a Gleason score of 7 or higher at diagnosis (73%). The median PSADT was 4.5 months. Nine percent (9%) of patients had prior orchiectomy, 25% of patients had prior prostatectomy and 50% of patients had at least one prior radiotherapy. Seventy-six percent (76%) of patients received more than one prior anti-hormonal treatment. Patients had an Eastern Cooperative Oncology Group Performance Status (ECOG PS) score of 0 (69%) or 1 (31%) at study entry.
Treatment with darolutamide continued until radiographic disease progression as assessed by conventional imaging (CT, bone scan, MRI) by blinded central review, unacceptable toxicity or withdrawal.
The primary efficacy endpoint was metastasis free survival (MFS). Secondary endpoints were overall survival (OS), time to pain progression, time to initiation of first cytotoxic chemotherapy for prostate cancer, and time to first symptomatic skeletal events (defined as occurrence of any of the following: external beam radiotherapy to relieve skeletal symptoms, new symptomatic pathologic bone fracture, spinal cord compression, or tumour-related orthopaedic surgical intervention).
Treatment with darolutamide resulted in an improvement in MFS compared to placebo (see Table 1 and Figure 1).
MFS results were consistent across patient subgroups regardless of PSADT, prior use of bone-targeting agents or loco-regional disease. Additional subgroups with consistent MFS results included PSA at baseline, Gleason score at diagnosis, age, geographical region, ECOG PS at baseline, race, and number of prior hormonal therapies.
Treatment with darolutamide also resulted in a positive trend in overall survival (median was not reached in either arm at the time of the interim OS analysis) and a delay in time to pain progression compared to placebo (see Table 1 and Figure 2). Time to initiation of first cytotoxic chemotherapy and time to first symptomatic skeletal event were not mature at the time of primary analyses (see Table 1).
Click on icon to see table/diagram/image
Treatment with darolutamide also resulted in a longer progression free survival (PFS, median 36.8 vs 14.8 months, HR=0.380, nominal p<0.000001) and time to PSA progression (median 33.2 vs 7.3 months, HR=0.130, nominal p<0.000001). Consistency of effect was observed across all measures of survival (MFS, OS and PFS). (See Figures 1 and 2.)
Click on icon to see table/diagram/image
Click on icon to see table/diagram/image
Patients receiving darolutamide in the ARAMIS study demonstrated a significantly higher confirmed PSA response rate (defined as a ≥ 50% reduction from baseline), compared with patients receiving placebo, 83.6% vs 7.6% (difference = 76%, p<0.000001).
Paediatric population: The European Medicines Agency has waived the obligation to submit the results of studies with darolutamide in all subsets of the paediatric population in prostate malignant neoplasms (see Dosage & Administration for information on paediatric use).
Pharmacokinetics: General introduction: Darolutamide consists of two diastereomers [(S,R)-darolutamide and (S,S)-darolutamide] which interconvert via the main circulating metabolite called keto-darolutamide. In vitro, all three substances show similar pharmacological activity. Darolutamide is poorly soluble in aqueous solvents over a large pH range and generally more soluble in organic solvents.
Absorption: Following oral administration of 600 mg (2 tablets of 300 mg), peak plasma concentrations of darolutamide of 4.79 mg/L (coefficient of variation: 30.9%) are usually reached around 4 hours after administration. The ratio of the two diastereomers, (S,R)-darolutamide to (S,S)-darolutamide, changed from a 1:1 ratio in the tablet to an approximately 1:9 ratio in plasma based on AUC0-12 data at steady-state. Following oral administration together with food, steady-state is reached after 2-5 days of repeated twice-daily dosing.
The absolute bioavailability compared to an intravenous injection is approximately 30% following oral administration of a NUBEQA tablet containing 300 mg darolutamide under fasted conditions. Bioavailability of darolutamide was enhanced by 2.0- to 2.5-fold when administered with food. A similar increase of exposure was observed for the major metabolite keto-darolutamide.
Distribution: The apparent volume of distribution of darolutamide after intravenous administration is 119 L indicating that darolutamide is widely distributed throughout the body to both intracellular and extracellular fluid spaces.
Darolutamide is moderately (92%) bound to human plasma proteins without any difference between the two diastereomers. The major metabolite of darolutamide, keto-darolutamide, is highly (99.8%) bound to plasma proteins.
Passage of darolutamide across the blood-brain barrier has not been studied clinically. However, brain exposures to darolutamide in terms of AUC0-24 are very low with 4.5% of plasma exposure after single dose in rats and 1.9-3.9% after repeated dose in mice. This indicates low passage of darolutamide across the intact blood-brain barrier in rats and mice and a low likelihood that darolutamide crosses the intact blood-brain barrier in humans to a clinically relevant extent.
Biotransformation: The diastereomers (S,R)-darolutamide and (S,S)-darolutamide are able to interconvert via the metabolite keto-darolutamide with a preference for (S,S)-darolutamide.
Following single oral administration of 300 mg 14C-darolutamide given as an oral solution, keto-darolutamide is the only major metabolite with about 2-fold higher total exposure in plasma compared to darolutamide. Darolutamide and keto-darolutamide accounted together for 87.4% of the 14C-radioactivity in plasma indicating that all other metabolites are of minor importance.
Darolutamide is metabolised primarily by oxidative metabolism mediated mainly by CYP3A4, as well as by direct glucuronidation mediated preferentially by UGT1A9 and UGT1A1. In addition, mainly the AKR1C isoforms were shown to catalyse the reduction of keto-darolutamide to the substance diastereomers.
Elimination: The effective half-life of darolutamide and keto-darolutamide in plasma of patients is approximately 20 hours. Of the two diastereomers comprising darolutamide, (S,R)-darolutamide has a shorter effective half-life of 9 hours compared to (S,S)-darolutamide with an effective half-life of 22 hours. The clearance of darolutamide following intravenous administration was 116 mL/min (CV: 39.7%). A total of 63.4% of substance-related material is excreted in the urine (approximately 7% unchanged), 32.4% is excreted in the faeces. More than 95% of the dose was recovered within 7 days after administration.
Linearity / Non-linearity: In the dose range of 100 to 700 mg (after single dose and at steady state), the exposure to the two diastereomers and the major metabolite keto-darolutamide increases linearly in a nearly dose-related manner. Based on a saturated absorption, no further increase in exposure to darolutamide was observed at 900 mg twice daily.
Special populations: Elderly: No clinically relevant differences in the pharmacokinetics of darolutamide were observed (65-95 years).
Renal impairment: In a clinical pharmacokinetic study, AUC and Cmax for darolutamide were 2.5- and 1.6-fold higher in patients with severe renal impairment (estimated Glomerular Filtration Rate [eGFR] 15 to 29 mL/min/1.73 m2) compared to healthy volunteers.
A population pharmacokinetic analysis indicates a 1.1-, 1.3- and an approximately 1.5-fold higher exposure (AUC) of darolutamide in patients with mild, moderate and severe renal impairment (eGFR 15 to 89 mL/min/1.73 m2) compared to patients with normal renal function.
The pharmacokinetics of darolutamide has not been studied in patients with end-stage renal disease receiving dialysis (eGFR < 15 mL/min/1.73 m2).
Hepatic impairment: In a clinical pharmacokinetic study, Cmax and AUC for darolutamide were 1.5 and 1.9-fold higher in patients with moderate hepatic impairment (Child-Pugh B) compared to healthy volunteers. There are no data for patients with severe hepatic impairment (Child-Pugh C).
Ethnic differences: No clinically relevant differences in the pharmacokinetics of darolutamide were observed based on ethnicity (White, Japanese, non-Japanese Asian, Black or African American). A population pharmacokinetic analysis indicated a 1.4-fold increase in exposure (AUC) in Japanese patients compared to patients from all other regions.
Toxicology: Preclinical safety data: Systemic toxicity: In repeated dose toxicity studies in rats and dogs, the main findings were changes in the male reproductive organs (decreases in organ weight with atrophy of the prostate and epididymides). These effects occurred at systemic exposures in the range of or below the anticipated human exposure (based on AUC comparison). Additional changes to reproductive tissues included minimal increase in vacuolation of the pituitary gland, atrophy and secretory reduction in seminal vesicles and mammary glands in rats as well as testicular hypospermia, seminiferous tubule dilatation and degeneration in dogs. Changes in the male reproductive organs in both species were consistent with the pharmacological activity of darolutamide and reversed or partially resolved after 4- to 8-week recovery periods.
Embryotoxicity / teratogenicity: Studies on developmental toxicity have not been performed.
Reproduction toxicity: Studies on reproductive toxicity have not been performed. However, male fertility is likely to be impaired based on the findings in repeat-dose toxicity studies in rats and dogs, which are consistent with the pharmacological activity of darolutamide.
Genotoxicity and carcinogenicity: Darolutamide did not induce mutations in the microbial mutagenesis (Ames) assay. At high concentrations, darolutamide did induce structural chromosome aberrations in vitro in cultured human lymphocytes. However, in the in vivo combined bone marrow micronucleus test and the Comet assay in the liver and duodenum of the rat, no genotoxicity was observed at exposures in excess of the maximum human exposure. Long-term animal studies to evaluate the carcinogenic potential of darolutamide have not been conducted.
Safety pharmacology: In vitro, darolutamide weakly inhibited the hERG potassium current and the L-type calcium channel. In vivo, in anaesthetised dogs, darolutamide slightly decreased the QT interval duration, but this effect was not found in conscious dogs.