A Multicenter, Randomized, Open-Label, Phase 1b/2 Trial Of Valemetostat Tosylate Plus Pembrolizumab Vs Pembrolizumab Alone in Participants With Advanced or Metastatic Non-Small Cell Lung Cancer Whose Tumors Express PD-L1 With Tumor Proportion Score ≥50% Without Actionable Genomic Alterations

This trial will evaluate the safety and efficacy of valemetostat tosylate (DS-3201b) in combination with fixed-dose pembrolizumab versus pembrolizumab alone in participants with advanced or metastatic NSCLC without actionable genomic alterations, whose tumor has PD-L1 TPS ≥50%, and who have not received prior systemic therapy for advanced or metastatic NSCLC. The trial will be in 2 phases, dose escalation and dose expansion phases.