A safety, tolerability, and pharmacokinetic analysis of two phase I studies of multitargeted small molecule tyrosine kinase inhibitor XL647 with an intermittent and continuous dosing schedule in patients with advanced solid malignancies.

Abstract

To evaluate the safety, tolerability, and pharmacokinetics of XL647 and determine the maximum tolerated dose (MTD) of oral XL647 once-daily using intermittent or continuous dosing schedules. Patients with advanced solid malignancies were enrolled in successive cohorts to receive escalating dose levels of oral once-daily XL647 using two different dosing schedules: 5 consecutive days of every 14-day cycle (study XL647-001) or continuously over 28-day cycles (study XL647-002). PK sampling was performed to determine Cmax, and AUC. Patients remained on study until progressive disease or unacceptable AEs. In XL647-001, 42 individuals were enrolled across 9 dose levels. The most frequently occurring drug-related AEs were diarrhea, nausea, rash, and fatigue. Expansion of the 4.68mg/kg cohort to 6 patients occurred without further dose-limiting toxicities (DLTs) and this was considered the MTD. In XL647-002, 31 patients were enrolled across 5 dose levels. A DLT of grade 3 pneumonitis occurred in 1/6 patients at 300mg, which was declared the MTD. The most common AEs included grade 1/2 rash, diarrhea, fatigue, dysgeusia, and QTc prolongation. Levels of pharmacodynamic plasma markers were not consistently changed after XL647 and no conclusions could be drawn with this limited data set. For oral XL647, the MTD was 4.68mg/kg or 350mg fixed dose when administered once-daily for 5 consecutive days of every 14-day cycle and was 300mg when administered once-daily continuously. XL647 was well tolerated at doses up to the MTD.