Study Evaluating Safety, Tolerability and Pharmacokinetics (PK) of Tarlatamab in Adults With Small Cell Lung Cancer (SCLC)

• Participant has provided informed consent prior to initiation of any study-specific activities/procedures • Age greater than or equal to 18 years old at the time of signing the informed consent • Histologically or cytologically confirmed SCLC. For parts A, C, D, E, F, and G: relapsed/refractory small cell lung cancer (R/R SCLC) who progressed or recurred following platinum-based regimen • Eastern Cooperative Oncology Group (ECOG) performance status of 0-2 • Participants with treated brain metastases are eligible provided they meet defined criteria • Adequate organ function as defined in protocol

• History of other malignancy within the past 2 years prior to first dose of tarlatamab with exceptions • Major surgery within 28 days of first dose tarlatamab • Untreated (includes new lesions or progression in previously treated lesions) or symptomatic brain metastases and leptomeningeal disease (regardless of symptomatic or not). • Prior anti-cancer therapy: at least 28 days must have elapsed between any prior anti-cancer therapy and first dose of tarlatamab with the following exceptions: participants who received conventional chemotherapy are eligible if at least 14 days have elapsed and if all treatment-related toxicity has been resolved to Grade less than or equal to 1; and prior palliative radiotherapy must have been completed at least 7 days before the first dose of tarlatamab • Participants who experienced severe, life-threatening or recurrent (Grade 2 or higher) immune-mediated AEs or infusion-related reactions including those that lead to permanent discontinuation while on treatment with immune-oncology agents • Has evidence of interstitial lung disease or active, non-infectious pneumonitis • Has a diagnosis of immunodeficiency or is receiving systemic steroid therapy or any other form of immunosuppressive therapy within 7 days prior to the first dose of tarlatamab • Part C only: history of solid organ transplantation or active autoimmune disease that has required systemic treatment within the past 2 years • Participant with symptoms and/or clinical signs and/or radiographic signs that indicate an acute and/or uncontrolled active systemic infection within 7 days prior to the first dose of investigational product administration