Study of Tarlatamab in Combination With YL201 With or Without Anti-programmed Death Ligand 1 (PD-L1) in Participants With Extensive Stage (ES) Small Cell Lung Cancer (SCLC)

Inclusion criteria

• Participants ≥ 18 years of age (or legal adult age within country) at time of signing informed consent.
• Participants with histologically or cytologically confirmed ES-SCLC.
• For Parts 1 and 2, subjects must have ES-SCLC that has progressed or recurred following at least 1 prior line of platinum-based anti-cancer therapy received either for LS-SCLC or ES-SCLC.
• For Part 3, subjects must have ES-SCLC and no prior systemic treatment for ES SCLC other than 1 cycle of platinum-based chemotherapy, and etoposide, and with or without PD-(L)1 inhibitor in the first-line setting.
• At least 1 measurable lesion as defined by RECIST 1.1.
• Participants must have adequate organ function (cardiac, pulmonary, kidney, bone marrow, and liver).

Exclusion criteria

• Prior delta-like ligand 3 (DLL3) or B7 homolog 3 (B7-H3) targeted therapy.
• Prior exposure to topoisomerase I inhibitors or antibody-drug conjugate (ADC) with topoisomerase I inhibitor payload.
• Symptomatic central nervous system (CNS) metastases. Note: Participants with asymptomatic brain metastases are eligible as defined in the protocol.
• History of (non-infectious) interstitial lung disease (ILD)/pneumonitis that required corticosteroids, current ILD/pneumonitis, or suspected ILD/pneumonitis that cannot be ruled out by imaging at screening.
• Baseline requirement of supplemental oxygen.