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. In addition, 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 the acetate salt, which has significantly higher oral bioavailability and is also resistant to the action of this group of enzymes. The active substance reaches maximum plasma concentration 1.5–4 hours after administration. Food and high-fat meals increase absorption of the compound more than 4-fold.
Abiraterone is 99.8% bound to plasma proteins.
Abiraterone acetate is hydrolysed to the 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 excreted mainly in faeces (approximately 88%) and secondarily in urine (approximately 5%). The mean plasma half-life is approximately 15 hours.
⚠️ Warnings
Abiraterone may cause myopathy and anaemia. Treatment with abiraterone may lead to increases in hepatic enzyme levels. Serum aminotransferase activity 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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