No QTc Prolongation With Zanubrutinib: Results of Concentration-QTc Analysis From a Thorough QT Study in Healthy Subjects

This thorough QT (TQT) study evaluated the effect of zanubrutinib on electrocardiogram (ECG) parameters by using concentration-QTc (C-QTc) analysis as the primary analysis for this study. Part A of the study determined the safety and tolerability of a single supratherapeutic dose of zanubrutinib (480 mg) in healthy volunteers. Part B was a randomized, blinded, placebo-controlled and positive-controlled, four-way crossover, TQT study of single therapeutic (160 mg) and supratherapeutic (480 mg) doses of zanubrutinib, placebo, and open-label moxifloxacin 400 mg. Thirty-two participants received at least 1 dose of zanubrutinib, and 26 participants completed all 4 periods. Zanubrutinib did not have any effect on heart rate or cardiac conduction (pulse rate, QRS interval, or T-wave morphology) and was generally well-tolerated. Using C-QTc analysis, the predicted placebo-corrected change-from-baseline QT interval using Fridericia's formula (Delta Delta QTcF) was -3.4 msec (90% confidence interval: -4.9 to -1.9 msec) at peak concentrations of the 480 mg dose. A QT effect (Delta Delta QTcF) exceeding 10 msec could be excluded within the observed concentration range at 160 and 480 mg doses. Assay sensitivity was established by moxifloxacin with 90% lower bound exceeding 5 msec. Implementing a C-QTc analysis prospectively in this TQT study resulted in a substantially smaller sample size to maintain a similar study power as shown in the traditional time-point analysis. A single 160-mg or 480-mg zanubrutinib dose did not prolong the QTc interval or have any other clinically relevant effects on ECG parameters.