Osilodrostat maintained cortisol control in Cushing’s syndrome

Osilodrostat, a drug that normalized cortisol in 89% of patients with Cushing’s syndrome who took it during a phase II study, continued to exert a sustained benefit during a 31-month extension phase.

In an intent-to-treat analysis, all of the 16 patients who entered the LINC-2 extension study responded well to the medication, with no lapse in cortisol control, Rosario Pivonello, MD, said at the annual meeting of the Endocrine Society.

“We also saw significant improvements in systolic and diastolic blood pressure and decreases in fasting plasma glucose,” said Dr. Pivonello of the University of Naples Federico II, Italy. “Surprisingly, after 31 months, we also observed declines in body mass index and weight.”

Osilodrostat, made by Novartis, is an oral inhibitor of 11 beta–hydroxylase. The enzyme catalyzes the last step of cortisol synthesis in the adrenal cortex. The drug was granted orphan status in 2014 by the European Medicines Agency.

In the LINC-2 study, 19 patients took osilodrostat at an initial dose of either 4 mg/day or 10 mg/day, if baseline urinary-free cortisol exceeded three times the upper normal limit. The dose was escalated every 2 weeks to up to 60 mg/day, until cortisol levels were at or below the upper limit of normal. In this study, the main efficacy endpoint was normalization of cortisol, or at least a 50% decrease from baseline at weeks 10 and 22.

Overall response was 89%. Osilodrostat treatment reduced urinary-free cortisol in all patients, and 79% had normal cortisol levels at week 22. The most common adverse events were asthenia, adrenal insufficiency, diarrhea, fatigue, headache, nausea, and acne. New or worsening hirsutism and/or acne were reported among four female patients, all of whom had increased testosterone levels.

The LINC-2 extension study enrolled 16 patients from the phase II cohort, all of whom had responded to the medication. They were allowed to continue on their existing effective dose through the 31-month period.

Dr. Pivonello presented response curves that tracked cortisol levels from treatment initiation in the LINC-2 study. The median baseline cortisol level was about 1,500 nmol per 24 hours. By the fourth week of treatment, this had normalized in all of the patients who entered the extension phase. The response curve showed continued, stable cortisol suppression throughout the entire 31-month period.

Four patients dropped out during the course of the study. Dr. Pivonello didn’t discuss the reasons for these dropouts. He did break down the results by response, imputing the missing data from these four patients. In this analysis, the majority (87.5%) were fully controlled, with urinary-free cortisol in the normal range. The remainder were partially controlled, experiencing at least a 50% decrease in cortisol from their baseline levels. These responses were stable, with no patient experiencing loss of control over the follow-up period.

The 12 remaining patients are still taking the medication, and they experienced other clinical improvements as well. Systolic blood pressure decreased by a mean of 2.2% (from 130 mm Hg to 127 mm Hg). Diastolic blood pressure also improved, by 6% (from 85 mm Hg to 80 mm Hg).

Fasting plasma glucose dropped from a mean of 89 mg/dL to 82 mg/dL. Weight decreased from a mean of 84 kg to 74 kg, with a corresponding decrease in body mass index, from 29.6 kg/m2 to 26.2 kg/m2.

Serum aldosterone decreased along with cortisol, dropping from a mean of 168 pmol/L to just 19 pmol/L. Adrenocorticotropic hormone increased, as did 11-deoxycortisol, 11-deoxycorticosterone, and testosterone.

Pituitary tumor size was measured in six patients. It increased in three and decreased in three. Dr. Pivonello didn’t discuss why this might have occurred.

The most common adverse events were asthenia, adrenal insufficiency, diarrhea, fatigue, headache, nausea, and acne. These moderated over time in both number and severity.

However, there were eight serious adverse events among three patients, including prolonged Q-T interval on electrocardiogram, food poisoning, gastroenteritis, headache, noncardiac chest pain, symptoms related to pituitary tumor (two patients), and uncontrolled Cushing’s syndrome.

Two patients experienced hypokalemia. Six experienced mild events related to hypocortisolism.

Novartis is pursuing the drug with two placebo-controlled phase III studies (LINC-3 and LINC-4), Dr. Pivonello said. An additional phase II study is being conducted in Japan.

Dr. Pivonello has received consulting fees and honoraria from Novartis, which sponsored the study.

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