Long-Term Control of Urinary Free Cortisol With Osilodrostat in Patients With Cushing’s Disease: Final Results From the LINC 2 Study

Introduction: During the 22-week core LINC 2 study, the oral 11β-hydroxylase inhibitor osilodrostat normalized mean urinary free cortisol (mUFC) in 79% (15/19) of patients with Cushing’s disease. This report describes long-term LINC 2 efficacy and safety results following an optional extension. Methods: Patients receiving clinical benefit at week 22 could enter the extension (that ran until Oct 22, 2019), continuing the same osilodrostat dose; dose adjustments were permitted based on efficacy and safety. Response rate (mUFC ≤ULN [controlled] or mUFC >ULN but ≥50% decrease from baseline [BL; partially controlled]) was assessed over time. Efficacy/safety were assessed for all patients from core BL until study end. Results: Of 19 enrolled patients (female:male 14:5; mean [SD] age 36.8 years [8.4]), 16 entered the optional extension and 8 of them remained on treatment until study end. Median (range) osilodrostat exposure was 282 weeks (2-351). Mean mUFC decreased from BL (9.9 x ULN) to ≤ULN by week 4 and remained stable throughout the study. All 19 patients achieved mUFC ≤ULN at least once during the study. At each assessment up to month 70 of the extension phase, 50-88% of ongoing patients were controlled, and up to 18% were partially controlled. Mean percentage change in clinical signs from BL (mean [SD]) to last assessment were: fasting plasma glucose, -10.8% (22.1) (from BL: 105.6 mg/dL [49.2]); HbA(1c), -2.1% (9.0) (from BL: 5.7% [0.7]); systolic BP, -3.3% (12.6) (from BL: 132.6 mmHg [11.6]); diastolic BP, -2.0% (10.4) (from BL: 85.0 mmHg [6.5]); BMI, -5.9% (8.8) (from BL: 30.7 kg/m(2) [7.0]). Overall, 9 patients discontinued treatment (n=2 core and n=7 extension), mostly because of AEs or no longer requiring treatment (n=3 each). The most common AEs during the entire treatment period were nausea (n=10), adrenal insufficiency, and headache (both n=9). AEs related to hypocortisolism and adrenal hormone precursor accumulation occurred in 11 (mostly adrenal insufficiency, n=9) and 12 patients (mostly hypertension, n=4), respectively; most were grade 1/2 and managed with dose adjustment/interruption and/or concomitant medication. Mean (SD) plasma ACTH increased from 1.8 x ULN (0.9) at BL to 7.1 x ULN (12.3) at week 22 and 6.9 x ULN (12.6) at last assessment. Mean (SD) 11-deoxycortisol increased from 1.2 x ULN (1.3) at BL to 13.6 x ULN (12.2) at week 22 and 3.6 x ULN (4.2) at last assessment. In females, mean (SD) testosterone increased from 0.8 x ULN (0.4) at BL to 2.4 x ULN (2.1) at week 22 and 1.0 x ULN (0.9) at last assessment. Two patients, both female, reported an AE of hirsutism. Conclusions: Rapid reductions in mUFC were sustained for up to 6 years of osilodrostat treatment and were accompanied by improvements in clinical signs of hypercortisolism. Osilodrostat was well tolerated, with no new safety signals during long-term treatment.