Osilodrostat on the PBS

Osilodrostat has been added to the Pharmaceutical Benefits Scheme (PBS) for the treatment of endogenous Cushing’s syndrome. This is a rare condition caused by glucocorticoid overproduction, often due to a pituitary tumour. Excess cortisol is associated with significant morbidity and mortality, largely related to cardiovascular disease and infections.

Osilodrostat inhibits 11β-hydroxylase (CYP11B1) and aldosterone synthase (CYP11B2), enzymes responsible for the final step of cortisol and aldosterone production in the adrenal gland. Cortisol levels must be regularly monitored throughout therapy. Adverse effects related to low cortisol levels can occur, including dizziness, nausea, vomiting, fatigue, and reduced appetite. Accumulation of adrenal steroid precursors and increased testosterone levels can also occur. In female patients, elevated testosterone may be associated with hirsutism or acne.

The dose of osilodrostat is adjusted according to individual response and tolerability. The usual initial dose is 2mg twice daily. However, a lower starting dose of 1mg twice daily is recommended for patients of Asian descent as this population demonstrates higher relative bioavailability.