Patients With Cushing Have New Nonsurgical Treatment Option

Cushing syndrome, a rare endocrine disorder caused by abnormally excessive amounts of the hormone cortisol, has a new pharmaceutical treatment to treat cortisol overproduction.

Osilodrostat (Isturisa) is the first FDA approved drug who either can’t undergo pituitary gland surgery or have undergone the surgery but still have the disease. The oral tablet functions by blocking the enzyme responsible for cortisol synthesis, 11-beta-hydroxylase.

“Until now, patients in need of medications…have had few approved options, either with limited efficacy or with too many adverse effects. With this demonstrated effective oral treatment, we have a therapeutic option that will help address patients' needs in this underserved patient population," said Maria Fleseriu, MD, FACE, professor of medicine and neurological surgery and director of the Pituitary Center at Oregon Health Sciences University.

Cushing disease is caused by a pituitary tumor that releases too much of the hormone that stimulates cortisol production, adrenocorticotropin. This causes excessive levels of cortisol, a hormone responsible for helping to maintain blood sugar levels, regulate metabolism, help reduce inflammation, assist in memory formulation, and support fetus development during pregnancy.

The condition is most common among adults aged 30-50 and affects women 3 times more than men.

Cushing disease can lead to a number of medical issues including high blood pressure, obesity, type 2 diabetes, blood clots in the arms and legs, bone loss and fractures, a weakened immune system, and depression. Patients with Cushing disease may also have thin arms and legs, a round red full face, increased fat around the neck, easy bruising, striae (purple stretch marks), or weak muscles.

Side effects of osilodrostat occurring in more than 20% of patients are adrenal insufficiency, headache, nausea, fatigue, and edema. Other side effects can include vomiting, hypocortisolism (low cortisol levels), QTc prolongation (heart rhythm condition), elevations in adrenal hormone precursors (inactive substance converted into hormone), and androgens (hormone that regulated male characteristics).

Osilodrostat’s safety and effectiveness was evaluated in a study consisting of 137 patients, of which about 75% were women. After a 24-week period, about half of patients had achieved normal cortisol levels; 71 successful cases then entered an 8-week, double-blind, randomized withdrawal study where 86% of patients receiving osilodrostat maintained normal cortisol levels, compared with 30% who were taking a placebo.

In January 2020, the European Commission also granted marketing authorization for osilodrostat.