Absence of QT Prolongation Associated with Relacorilant, a Selective Glucocorticoid Receptor Modulator in Development for the Treatment of Cushing Syndrome

Objective:
QT prolongation is a significant concern for patients with Cushing syndrome (CS). Approximately 26% of men with CS present with QT prolongation, and the risk of cardiac arrhythmic events correlates with the extent of QT prolongation. All currently approved CS medications are associated with QT prolongation, posing a significant risk for the management of CS. Here, we evaluate the impact relacorilant, an investigational selective glucocorticoid receptor modulator, on QT prolongation in healthy volunteers and patients with CS.

Methods:
In a 3-part, single-center, first-in-human study (NCT03508635, “phase 1 study”), 103 healthy volunteers received single or multiple ascending doses of relacorilant (up to 500 mg QD) for up to 14 days; 24 received placebo. In a randomized, partial double-blind, crossover thorough QT study (NCT04795479, “TQT study”), the effect of multiple therapeutic (400 mg QD, n=25) and supra-therapeutic (800 mg QD, n=28) doses of relacorilant on cardiac repolarization was studied in healthy volunteers. A single dose of moxifloxacin (400 mg, n=28) was used as a positive control; 29 participants received placebo. In a single-arm, open-label phase 2 study (NCT02804750, “CS study”), 17 patients with CS received low-dose relacorilant (100–200 mg QD) for 12 weeks and 18 patients received high-dose relacorilant (250–400 mg QD) for 16 weeks. In all studies, ECG data were collected, and the heart rate-corrected QT interval using Fridericia’s formula (QTcF) was assessed.

Results:
In the phase 1 study, relacorilant up to 500 mg daily did not adversely affect ECG parameters. An effect on placebo-corrected change from baseline QTcF (ΔΔQTcF) above 10 msec was excluded. In the TQT study, moxifloxacin control showed the expected QT prolongation, confirming assay sensitivity. Relacorilant had no adverse effects on ECG parameters and showed effects similar to placebo. Based on concentration-QTc analysis, an effect on ΔΔQTcF exceeding 10 msec was excluded within the full observed range of relacorilant plasma concentrations. These results constitute a negative TQT study. The CS study confirmed that these favorable findings also apply to patients with CS: Throughout the CS study, no significant changes in median QTcF were observed in either dose group.

Discussion/Conclusion:
There is an unmet need for medications to treat CS that do not cause QT prolongation and possibly fatal arrhythmias. Based on the TQT study and supported by additional data in healthy volunteers and patients with CS, relacorilant did not show an association with QT prolongation.