This is a first-time-in-human (FTIH), open-label, multicenter, multi-part, dose-escalation and dose-expansion study to evaluate the safety, pharmacokinetics (PK), pharmacodynamics, and efficacy of rilvegostomig (AZD2936) in adult participants with stage III unresectable or stage IV NSCLC. The study includes 4 parts: Part A (dose escalation) and Parts B-E (dose expansion).