FDA approves Isturisa (osilodrostat) treatment for Cushing’s disease

The US Food and Drug Administration (FDA) has approved the use of Isturisa (osilodrostat) oral tablets for adults with Cushing’s disease who either cannot undergo pituitary gland surgery or have undergone the surgery but still have the disease.

Cushing’s disease is caused by a pituitary tumour that releases too much adrenocorticotropin, a hormone that signals the adrenal glands to overproduce cortisol. This results in symptoms such as high blood pressure, type II diabetes, weakened bones and muscles, easy bruising and blood clots in the arms and legs

Isturisa prevents the overproduction of cortisol by blocking the enzyme 11-beta-hydroxylase, which is responsible for cortisol synthesis. The approval was based on trials evaluating its effectiveness in 137 adult patients, the majority of which had undergone pituitary surgery that failed to cure their disease.

In the 24-week, single-arm, open-label period, all patients received a starting dose of 2 milligrams (mg) of Isturisa twice a day that could be increased every two weeks up to 30mg twice a day. At the end of this 24-week period, approximately half of patients had cortisol levels within normal limits. At this point, 71 patients who did not need further dose increases and tolerated the drug for the last 12 weeks entered an eight-week, double-blind, randomised withdrawal study wherein they either received Isturisa or a placebo (inactive treatment). At the end of this withdrawal period, 86 percent of patients receiving Isturisa maintained cortisol levels within normal limits, compared to 30 percent of patients taking the placebo.

The most common side effects included adrenal insufficiency, nausea, fatigue and oedema.

“The FDA supports the development of safe and effective treatments for rare diseases, and this new therapy can help people with Cushing’s disease, a rare condition where excessive cortisol production puts them at risk for other medical issues,” said Dr Mary Thanh Hai, acting director of the Office of Drug Evaluation II in the FDA’s Center for Drug Evaluation and Research. “By helping patients achieve normal cortisol levels, this medication is an important treatment option for adults with Cushing’s disease.”

The FDA granted the approval of Isturisa to Novartis.