Phase 1 Concentration‐QTc and Cardiac Safety Analysis of the MDM2 Antagonist KRT‐232 in Patients With Advanced Solid Tumors, Multiple Myeloma, or Acute Myeloid Leukemia

Cardiac safety and plasma concentration‐QTc interval analyses were completed using data from 2 phase 1 studies of the selective mouse double minute chromosome 2 antagonist, KRT‐232, in patients with solid tumors or multiple myeloma and acute myeloid leukemia (AML) who received KRT‐232 doses of 15 to 480 mg once daily (QD; N = 130). A linear mixed‐effects model related change from baseline Fridericia‐corrected QT interval (ΔQTcF) to KRT‐232 plasma concentrations. The final model included parameters for the intercept (with between‐subject variability), KRT‐232 concentration–ΔQTcF slope, and baseline QTcF effect on the intercept. Diagnostic plots indicated an adequate model fit. Mean (90% confidence interval) predicted ΔQTcF values at the maximum clinical dose (480 mg QD) were 2.04 (0.49‐3.60) milliseconds for patients with solid tumors and 4.52 (2.35‐6.69) milliseconds for patients with AML. Because the 90% confidence interval upper bound of the mean ΔQTcF was predicted to be below 10 milliseconds at doses up to 480 mg QD in patients with solid tumors, multiple myeloma, or AML, KRT‐232 does not result in clinically meaningful QT prolongation at the doses currently under investigation in clinical trials. No significant cardiac safety concerns were identified at these doses.