QT Interval Shortening With Isavuconazole: In Vitro and In Vivo Effects on Cardiac Repolarization

The effects of isavuconazole (active moiety of isavuconazonium sulfate) on cardiac ion channels in vitro and cardiac repolarization clinically were assessed in a phase I, randomized, double‐blind study in healthy individuals who received isavuconazole (after 2‐day loading dose), at therapeutic or supratherapeutic doses daily for 11 days, moxifloxacin (400 mg q.d.), or placebo. A post‐hoc analysis of the phase III SECURE trial assessed effects on cardiac safety. L‐type Ca2+ channels were most sensitive to inhibition by isavuconazole. The 50% inhibitory concentrations for ion channels were higher than maximum serum concentrations of nonprotein‐bound isavuconazole in vivo. In the phase I study (n = 161), isavuconazole shortened the QT interval in a dose‐ and plasma concentration‐related manner. There were no serious treatment‐emergent adverse events; palpitations and tachycardia were observed in placebo and supratherapeutic isavuconazole groups; no cardiac safety signals were detected in the SECURE study (n = 257). Isavuconazole was associated with a shortened cardiac QT interval.