Evaluation of Rusfertide, a Hepcidin Mimetic, on Cardiac Repolarization: A Randomized, Placebo- and Positive-Controlled Crossover Thorough QT Study in Healthy Participants.

Abstract

Purpose: Rusfertide, a hepcidin mimetic, is in clinical development for the treatment of polycythemia vera. This study evaluated the effect of rusfertide on cardiac repolarization.

Methods: A positive-controlled, randomized, double-blind, crossover study was conducted in healthy adults. Subjects received subcutaneous rusfertide 90 mg, matching subcutaneous placebo, and oral moxifloxacin. Subjects underwent continuous 12-lead Holter recording during each period. A central laboratory extracted up to 10 replicate electrocardiograms (ECGs) at each time point prior to and following treatment, paired with pharmacokinetic sampling. The primary analysis for Fridericia corrected QT interval (QTcF) was a mixed model for repeated measures with change from baseline QTcF (ΔQTcF) as the dependent variable; period, sequence, time, treatment, and time-by-treatment interaction as fixed effects; and baseline QTcF as a covariate. The relationship between rusfertide and metabolite concentrations and change-from-baseline QTcF was quantified using linear mixed-effects modeling.

Findings: Mean age and body mass index were 40.1 years and 25.4 mg/m², respectively, with a slight majority of female (57%) and White (60%) subjects. Mean rusfertide plasma concentrations increased rapidly, with median peak of 4 hours. The geometric mean rusfertide peak concentration (C_max) was 1100 ng/mL. Rusfertide did not have a clinically relevant effect on heart rate (HR) or cardiac conduction (PR and QRS interval). The least squares (LS) mean ΔQTcF on rusfertide closely followed the placebo pattern, and LS mean placebo-corrected ΔQTcF (ΔΔQTcF) varied from -2.0 to 1.8 ms. After 400 mg oral moxifloxacin, an increase of LS mean ΔΔQTcF was observed with a peak of 12.4, 12.4, and 11.2 ms at 2, 3, and 4 hours, respectively, with all three lower bounds of the 2-sided 90% confidence interval greater than 5 ms. Estimated population slope of the rusfertide concentration-QTc relationship was not statistically significant: 0.00042 ms per ng/mL (90% confidence interval [CI]: -0.001172 to 0.002013; P = 0.6624). Predicted ΔΔQTcF at the geometric mean C_max was 0.04 ms (90% CI: -1.21 to 1.29). Overall, 24 of 60 subjects (40.0%) experienced treatment-emergent adverse events (TEAEs). All TEAEs were mild. TEAEs noted in ≥5% subjects were headache, nausea, injection site erythema, injection site pain, and influenza-like illness. There were no clinically significant changes in clinical laboratory, vital signs, ECG, or physical examination findings.

Implications: Rusfertide had no clinically relevant effect on HR, cardiac conduction, or QTc. Rusfertide was well tolerated. An effect on ΔΔQTcF exceeding 10 ms could be excluded within the observed rusfertide plasma concentrations up to approximately 2130 ng/mL.