NICE has issued an Appraisal Consultation Document on abiraterone, an oral selective inhibitor of androgen biosynthesis which irreversibly blocks cytochrome P17 (an enzyme involved in the production of testosterone), thereby stopping androgen synthesis in the adrenals, prostate and the tumour. The Institute does not recommend abiraterone in combination with prednisone or prednisolone for the treatment of castration-resistant metastatic prostate cancer that has progressed on or after a docetaxel-containing regimen.