Cushing’s disease is a progressive pituitary disorder in which there is an excess of cortisol in the body. While the disease can be treated surgically, this option is not possible for all patients. This is one of the approved medications that assist in controlling cortisol levels in people with Cushing’s disease.

sturisa was approved in 2020 to treat adults with Cushing’s disease for whom pituitary surgery is ineffective or not an option. The oral medication works by inhibiting an enzyme called 11-beta-hydroxylase, which is involved in cortisol production.

Isturisa, also known as osilodrostat or LCI699, is an approved treatment originally developed by Novartis, but now acquired by Recordati to treat people with Cushing’s disease, a condition in which a pituitary tumor causes the body to produce excessive levels of the stress hormone cortisol.

In 2020, the U.S. Food and Drug Administration (FDA) approved Isturisa to treat adults with Cushing’s disease for whom pituitary surgery was not an option, or ineffective.

Earlier that same year, the European Commission (EC) approved Isturisa to treat people with endogenous Cushing’s syndrome. The medication also was approved for the same indication in Japan in 2021.

How does Isturisa work?

Isturisa is an oral medicine that inhibits an enzyme called 11-beta-hydroxylase, which is involved in cortisol production. Blocking the activity of this enzyme prevents excessive cortisol production, normalizing the levels of the hormone in the body and easing the symptoms of Cushing’s disease.

Isturisa in clinical trials

A Phase 2 clinical trial (NCT01331239) investigated the safety and efficacy of Isturisa as a Cushing’s disease treatment. The trial that concluded in October 2019 initially was named LINC-1, but, through a study protocol amendment, patients who completed the study could continue into a second phase called LINC-2.

The company published findings that covered both patient groups in the journal Pituitary. Data showed that Isturisa reduced cortisol levels in the urine of all patients by week 22. Urine cortisol levels reached and remained within a normal range in 79% of the patients by then. Common adverse effects included nausea, diarrhea, lack of energy, and adrenal insufficiency — a condition in which the adrenal glands are unable to produce enough hormones.

A Phase 3 clinical trial (NCT02180217) called LINC-3 also assessed the safety and efficacy of Isturisa in 137 patients with Cushing’s disease (77% female, median age 40 years). Participants were given Isturisa for 26 weeks, with efficacy-based dose adjustments during the first 12 weeks.

Then, the 71 participants with a complete response (those whose urine cortisol levels were within normal limits) at week 26 and who did not require a dose increase after week 12, were assigned randomly to either continue treatment with Isturisa or switch to a placebo.

After this 34-week period, 86% of Isturisa-treated patients had normal urinary cortisol levels, as compared to 29% of participants given placebo. All participants then were given Isturisa for an additional 12 weeks. At the end of the 48-week study, 66% of participants had normal urine cortisol levels.

Results from LINC-3 formed the basis for regulatory approvals of Isturisa. Common adverse side effects in the trial included nausea, headache, fatigue, and adrenal insufficiency.

A multi-center, randomized, double-blind, placebo-controlled Phase 3 trial (NCT02697734) called LINC-4 further confirmed the safety and efficacy of Isturisa as a Cushing’s disease therapy. During the trial, patients received Isturisa or a placebo through a 12-week period followed by treatment with Isturisa until week 48.

Top-line results showed that 77% of patients on Isturisa experienced a complete response after the 12-week randomized period, as compared to 8% of those on placebo. No new safety data were noted.

A roll-over, worldwide Phase 2 study (NCT03606408) is recruiting patients who have successfully completed any of the previous clinical trials. Patients can continue to take the dosage they received during the initial trial. The aim of this study is to assess the long-term effects of Isturisa for up to five years.