Abiraterone is an androgen biosynthesis inhibitor. The active substance selectively inhibits the activity of the enzyme CYP17A1. This enzyme plays a key role in androgen synthesis in the adrenal glands, testes, and prostate cancer tissues. Furthermore, CYP17 is responsible for the conversion of pregnenolone and progesterone to testosterone precursors, DHEA, and androstenedione. Abiraterone reduces plasma testosterone levels.
Abiraterone is poorly absorbed and is susceptible to hydrolysis by esterases. Therefore, it is administered as an acetate salt, which has significantly higher oral bioavailability and is resistant to the action of this group of enzymes. The active substance reaches peak plasma concentration 1.5–4 hours after administration. Food and high-fat meals increase the absorption of the compound more than 4-fold.
Abiraterone is 99.8% bound to plasma proteins.
Abiraterone acetate is hydrolysed to its active metabolite, abiraterone, by esterases. Subsequently, CYP3A4 and SULT2A1 metabolise abiraterone to two inactive metabolites known as abiraterone sulphate and abiraterone N-oxide sulphate.
Abiraterone is primarily excreted in faeces (approximately 88%) and secondarily in urine (approximately 5%). The mean plasma elimination half-life is approximately 15 hours.
⚠️ Warnings
Abiraterone may cause myopathy and anaemia. Treatment with abiraterone may lead to increased hepatic enzyme activity. Serum aminotransferase levels should be monitored regularly before and during treatment. Abiraterone should be used with caution in patients with, for example, heart failure, severe or unstable angina pectoris, ventricular arrhythmia, recent myocardial infarction, or renal impairment, as the active substance may cause hypertension, hypokalaemia, and fluid retention.
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