Apalutamide

Pharmaceuticals -> Antineoplastic and immunomodulating agents -> Antineoplastic agents

Pharmaceuticals -> Listed in ZINC15

FDA approved drugs -> Active ingredient

EMA approved medicines: Human medicine

FDA approved drugs -> Active ingredient

Danger

H360 (94.6%): May damage fertility or the unborn child [Danger Reproductive toxicity]

P203, P280, P318, P405, and P501 (click each P-code to see the statement)

Aggregated GHS information provided per 56 reports by companies from 4 notifications to the ECHA C&L Inventory.

In prelicensure controlled trials of apalutamide, serum aminotransferase elevations were uncommon and generally transient and mild, not requiring dose modification. Clinically apparent liver injury with jaundice attributable to apalutamide was not reported in the preregistration trials and is not mentioned as an adverse event in the product label. Since the approval and general clinical use of apalutamide, there have been no publications or descriptions of the clinical features of hepatotoxicity with jaundice associated with its use. The first and second generation androgen receptor blockers, flutamide, nilutamide, and bicalutamide, have all been linked to instances of hepatitis-like liver injury with jaundice that can be severe and even fatal. However, such cases have not been described with apalutamide and other third generation androgen receptor antagonists. Thus, clinically apparent liver injury due to apalutamide must be rare, if it occurs at all.

Drug Induced Liver Injury Rank (DILIrank 2.0)

Apalutamide

vNo-DILI-concern

0

No match

DOI:10.1016/j.drudis.2016.02.015

L - Antineoplastic and immunomodulating agents

QL - Antineoplastic and immunomodulating agents

In androgen receptors (AR)-overexpressing LNCaP cells, apaludatamide was reported to have a 7 to 10-fold greater affinity to the AR than bicalutamide. Additionally, apalutamide still possesses total antagonistic activity in AR-overexpressing cell lines with bicalutamide-resistance mutations such as T878A and W741C. In castrate mice with LNCaP/AR(cs) tumors, apalutamide produced tumor regression (defined by >50% regression in tumor volume) in 8 mice compared to only 1 for bicalutamide. The apalutamide-treated tumors also have a 60% decrease in proliferative index and a 10-fold increase in apoptotic rate compared with vehicle. In an open-label, uncontrolled, multicenter, single-arm dedicated QT study in 45 patients with CRPC, an exposure-QT analysis suggested a concentration-dependent increase in QTcF for apalutamide and its active metabolite. Apalutamide demonstrated antitumor activity in the mouse xenograft models of prostate cancer, where it decreased tumor cell proliferation and reduced tumor volume.

Persistent androgen receptor (AR) signaling is a common feature of castration-resistant prostate cancer (CRPC), attributed to AR gene amplification, AR gene mutation, increased AR expression, or increased androgen biosynthesis in prostate tumors. Apalutamide is an antagonist of AR that binds directly to the ligand-binding domain of the AR with the IC50 of 16 nM. Upon binding, apalutamide disrupts AR signalling, inhibits DNA binding, and impedes AR-mediated gene transcription. Apalutamide impairs the translocation of AR from the cytoplasm to the nucleus thus reducing the concentrations of AR available to interact with the androgen response elements (AREs). Upon treatment with apalutamide, AR was not recruited to the DNA promoter regions. Its main metabolite, N-desmethyl apalutamide, is a less potent inhibitor of AR, and exhibited one-third of the activity of apalutamide in an in vitro transcriptional reporter assay.

Metabolism is the main route of elimination of apalutamide. Apalutamide is primarily metabolized by CYP2C8 and CYP3A4 to form active metabolite, N-desmethyl apalutamide. The contribution of CYP2C8 and CYP3A4 in the metabolism of apalutamide is estimated to be 58% and 13% following single dose but changes to 40% and 37%, respectively at steady-state. The auto-induction of CYP3A4-mediated metabolism by apalutamide may explain the increase in CYP3A4 enzymatic activity at steady-state.

Mean absolute oral bioavailability was approximately 100%. The median time to achieve peak plasma concentration (tmax) was 2 hours (range: 1 to 5 hours). The major active metabolite N-desmethyl apalutamide Cmax was 5.9 mcg/mL (1.0) and AUC was 124 mcg·h/mL (23) at steady-state after the recommended dosage. Administration of apalutamide to healthy subjects under fasting conditions and with a high-fat meal (approximately 500 to 600 fat calories, 250 carbohydrate calories, and 150 protein calories) resulted in no clinically relevant changes in Cmax and AUC. The median time to reach tmax was delayed approximately 2 hours with food. Following administration of the recommended dosage, apalutamide steady-state was achieved after 4 weeks and the mean accumulation ratio was approximately 5-fold. Apalutamide Cmax was 6.0 mcg/mL (1.7) and AUC was 100 mcg·h/mL (32) at steady-state. Daily fluctuations in apalutamide plasma concentrations were low, with the mean peak-to-trough ratio of 1.63. Oral administration of four 60 mg apalutamide tablets dispersed in applesauce resulted in no clinically relevant changes in Cmax and AUC compared to the administration of four intact 60 mg tablets under fasting conditions.

Apalutamide and its main active metabolite are subject to both renal and focal elimination. Up to 70 days following a single oral administration of radiolabeled apalutamide, 65% of the dose was recovered in urine (1.2% of dose as unchanged apalutamide and 2.7% as N-desmethyl apalutamide) and 24% was recovered in feces (1.5% of dose as unchanged apalutamide and 2% as N-desmethyl apalutamide).

The mean apparent volume of distribution at steady state of apalutamide was approximately 276 L.

The CL/F of apalutamide was 1.3 L/h after single dosing and increased to 2.0 L/h at steady-state after once-daily dosing likely due to CYP3A4 auto-induction. The auto-induction effect likely reached its maximum at the recommended dosage because exposure to apalutamide across the dose range of 30 to 480 mg is dose-proportional.