Effective as of Amendment 5, Participants receiving coformulation of pembrolizumab/vibostolimab plus chemotherapy will be transitioned to standard of care (SOC, pembrolizumab plus chemotherapy). Participants with access to approved standard of care (SOC) should be considered for discontinuation from the study. Those benefiting from pembrolizumab plus chemotherapy, but unable to access it as SOC outside the study, may continue on study and receive treatment with pembrolizumab plus chemotherapy until discontinuation criteria are met.