Study of Tarlatamab + ZL-1310 +/- Anti-programmed Death Ligand 1 (Anti-PD-L1) in Small Cell Lung Cancer (SCLC)DeLLphi-313

-Age ≥ 18 years (or ≥ legal age within the country if it is older than 18 years) at the time of signing the informed consent. -Participants with Histologically or cytologically confirmed SCLC: -For Part 1, participants must have SCLC that has progressed or recurred following at least 1 line of platinum-based anti-cancer therapy. - For Parts 1 and 2, participants must have progressed or recurred following at least 1 line of platinum-based therapy. No prior tarlatamab is allowed in Cohort 2-1. -For Part 3, participants must have extensive-stage SCLC (ES-SCLC) with no prior systemic treatment other than 1 cycle of platinum-based chemotherapy. Note: Participants with prior treatment for limited-stage SCLC (LS-SCLC) before diagnosis of ES SCLC are permitted. -Eastern Cooperative Oncology Group (ECOG) performance status of 0-1. - At least 1 measurable lesion as defined per RECIST v1.1 within 21-day screening period, not previously irradiated. -Adequate organ function (hematological, coagulation, renal, hepatic, pulmonary, and cardiac function).

-Symptomatic CNS metastases. Participants with treated brain metastases are eligible provided they meet the criteria specified in the protocol. -History of interstitial lung disease (ILD)/pneumonitis. -Received thoracic radiation therapy within 90 days prior to first dose of trial intervention. -Prior therapy with any delta-like ligand 3 (DLL3)-directed therapy. -Prior exposure to topoisomerase I inhibitors or antibody-drug conjugate (ADC) with topoisomerase I inhibitor payload. -Receiving strong CYP3A4 or CPY2D6 inhibitors within 14 days or 5 half-lives (whichever is longer) before the first dose of trial treatment. -Enrollment in any tarlatamab clinical trial.