A First-in-human Study to Evaluate the Safety, Tolerability and Pharmacokinetics of DS-6051b

The Dose Escalation part (Part 1) of this study will evaluate safety and tolerability, and determine the tentative RP2D. Plasma exposure of DS-6051a and the exposure - QT interval prolongation relationship will also be assessed. Approximately 30 subjects with advanced solid tumors harboring ROS1 or NTRK1, NTRK2, or NTRK3 rearrangement, neuroendocrine carcinoma, or with advanced solid tumors and tumor-induced pain will be enrolled. The Food Effect (FE) part of this study is to determine the effect of food on the PK of DS-6051a following administration of a single oral dose of DS-6051b. The safety and tolerability of DS-6051b administered with or without food will also be assessed. After the safety profile of DS-6051b is adequately evaluated, the Dose Expansion part (Part 2) will be initiated to further assess the safety and tolerability, and preliminarily evaluate the efficacy of DS-6051b at the tentative RP2D. Approximately 40 cancer subjects carrying a ROS1 or NTRK1, NTRK2, or NTRK3 rearrangement will be enrolled.