New Abiraterone Formulation

Yonsa Mpred™ is now listed on the Pharmaceutical Benefits Scheme (PBS) for the treatment of castration-resistant metastatic prostate cancer. Yonsa Mpred™ is supplied as a composite pack containing abiraterone acetate 125mg tablets and methylprednisolone 4mg tablets.

Abiraterone is an inhibitor of cytochrome P450 C17 (CYP17), an enzyme involved in the synthesis of testosterone and other androgens. Studies demonstrate that blocking this enzyme can produce tumour responses in patients who no longer respond to standard hormonal therapies.

Abiraterone also reduces cortisol levels, which leads to a compensatory increase in adrenocorticotropic hormone (ACTH) release. This can result in increased production of adrenal mineralocorticoids, with adverse effects such as hypertension, oedema, and hypokalaemia. The addition of the glucocorticoid, methylprednisolone, suppresses ACTH drive and reduces the incidence and severity of mineralocorticoid excess.

This is the second abiraterone preparation available on the PBS. Zytiga® (abiraterone acetate) tablets exhibit large variations in absorption depending on the fat content of meals. Therefore, these tablets must be taken on an empty stomach. In comparison, the abiraterone in Yonsa Mpred™ was developed to have a smaller particle size, improving bioavailability and allowing tablets to be taken without regard to food. The dosing of these two products is also different. A small study demonstrated therapeutic equivalence between 500mg of fine particle abiraterone acetate (i.e. Yonsa Mpred™) and 1000mg of originator abiraterone acetate based on testosterone suppression.