A Study of DS-3939a in Participants With Solid Tumors

The study includes 2 independent substudies, which have been defined by treatment combination and participant population as follows: 1. Substudy 1 will evaluate the safety and efficacy of DS-3939a in combination with immunotherapy with or without chemotherapy (carboplatin or pemetrexed) in participants with locally advanced unresectable or metastatic non-squamous (NSQ) NSCLC in the first-line setting. 2. Substudy 2 will evaluate the safety and efficacy of DS-3939a in combination with DS-1103a or as a monotherapy in participants with locally advanced unresectable or metastatic NSQ NSCLC who are pretreated. Each sub study will be conducted in 2 parts: Dose escalation (Part 1) and Dose expansion (Part 2). The allocation of participants in Part 1 will be non-randomized, and in Part 2, it will be randomized for both substudies.