Abiraterone

Pharmaceuticals -> Listed in ZINC15

Pharmaceuticals -> Metabolite of Abiraterone acetate

Danger

H360 (57.1%): May damage fertility or the unborn child [Danger Reproductive toxicity]

P203, P260, P273, P280, P318, P319, P391, P405, and P501 (click each P-code to see the statement)

Aggregated GHS information provided per 7 reports by companies from 4 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.

Serum aminotransferase elevations occur in up to 13% of patients treated with abiraterone compared with 1% to 8% receiving placebo or a comparator drug, but the abnormalities are generally mild, transient and not associated with symptoms or jaundice. ALT elevations above 5 times the upper limit of normal (ULN) occur in 6% of abiraterone treated vs

Drug-Induced Liver Injury Severity and Toxicity (DILIst)

Abiraterone

DILI Positive

DOI:10.1016/j.drudis.2019.09.022

L02BX03

L - Antineoplastic and immunomodulating agents

QL - Antineoplastic and immunomodulating agents

L02BX03

_In vivo_, abiraterone acetate is rapidly hydrolyzed to abiraterone, which mediates its pharmacological actions. Abiraterone decreases serum testosterone and other androgens. A change in serum prostate-specific antigen (PSA) levels may be observed.

17α-hydroxylase/C17,20-lyase (CYP17) is a key enzyme in androgen biosynthesis. It is primarily expressed in testicular, adrenal, and prostatic tumours. CYP17 catalyzes the 17α-hydroxylation of pregnenolone and progesterone to their 17α-hydroxy derivative, followed by subsequent cleavage of the C 20,21-acetyl group to yield dehydroepiandrosterone (DHEA) and androstenedione. DHEA and androstenedione are precursors of testosterone. Aberrant androgen levels and unregulated androgen receptor signalling have been implicated in the development and progression of various prostate cancers. Androgen-sensitive prostatic carcinoma responds to treatment that decreases androgen levels. Androgen deprivation therapies, such as treatment with GnRH agonists or orchiectomy, decrease androgen production in the testes but do not affect androgen production by the adrenals or in the tumour. Abiraterone inhibits CYP17 to block androgen production. Inhibition of CYP17 can also result in increased mineralocorticoid production by the adrenals.

The conversion of abiraterone acetate to abiraterone, the active metabolite, is likely to be mediated by esterases, although specific esterases have not been identified. In human plasma, the two main circulating metabolites are abiraterone sulfate, which is formed by CYP3A4 and SULT2A1, and N-oxide abiraterone sulfate, which is formed by SULT2A1. These metabolites each account for about 43% of abiraterone exposure and are pharmacologically inactive.

Abiraterone has known human metabolites that include abiraterone sulfate.

G819A456D0

ABIRATERONE

Mechanisms of Action [MoA] - Cytochrome P450 17A1 Inhibitors

Established Pharmacologic Class [EPC] - Cytochrome P450 17A1 Inhibitor

Mechanisms of Action [MoA] - Cytochrome P450 2D6 Inhibitors

Mechanisms of Action [MoA] - Cytochrome P450 2C8 Inhibitors

Geometric mean (± SD) Cmax was 73 (± 44) ng/mL and AUC0-∞ was 373 (± 249) ng x hr/mL following a single dose of 500 mg abiraterone acetate in overnight-fasted healthy subjects. Dose proportionality was observed in single doses of abiraterone acetate ranging from 125 mg to 625 mg. A group of patients with mCRPC received a daily dose of 1,000 mg: at steady-state, the mean (± SD) Cmax was 226 (± 178) ng/mL and AUC was 993 (± 639) ng x hr/mL. Following oral administration of abiraterone acetate to patients with metastatic castration-resistant prostate cancer, the median Tmax was two hours. _In vivo_, abiraterone acetate is converted to abiraterone. In clinical studies of other abiraterone acetate formulations, abiraterone acetate plasma concentrations were below detectable levels (< 0.2 ng/mL) in > 99% of the analyzed samples. Systemic exposure to abiraterone is increased when abiraterone acetate is administered with food. Abiraterone Cmax was approximately 6.5-fold higher, and AUC0-∞ was 4.4-fold higher when a single dose of abiraterone acetate 500 mg was administered with a high-fat meal (56-60% fat, 900-1,000 calories) compared to overnight fasting in healthy subjects. Given the normal variation in the content and composition of meals, taking abiraterone with meals has the potential to result in increased and highly variable exposures.

Following oral administration of ¹⁴C-abiraterone acetate, approximately 88% of the radioactive dose is recovered in feces: the major compounds present in feces are unchanged abiraterone acetate and abiraterone, accounting for approximately 55% and 22% of the administered dose, respectively. Approximately 5% of the dose is recovered in urine.

The mean (± SD) apparent steady-state volume of distribution is 19,669 (± 13,358) L.