A Study to Evaluate Safety, Tolerability, Pharmacokinetics, Pharmacodynamics, and Preliminary Anti-tumor Activity of RO7616789 in Advanced Small Cell Lung Cancer and Other Neuroendocrine Carcinomas

Inclusion Criteria: * Life expectancy at least 12 weeks * Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 * Adequate hematologic and end organ function * Negative serum pregnancy test. * Adequate contraception and no or interruption of breastfeeding * Histologically confirmed extensive SCLC or poorly differentiated NEC of any other origin, relapsed after at least 1 systemic therapy * Measurable disease according to Response Evaluation criteria in Solid Tumors (RECIST) Version 1.1 * Confirmed availability of representative archival tumor specimens in formalin-fixed, paraffin-embedded (FFPE) blocks or unstained slides Exclusion Criteria: * Pregnant or breastfeeding, or intending to become pregnant during the study or within 40 days after the final dose of study treatment * Poorly controlled Type 2 diabetes mellitus defined as a screening hemoglobin A1c ≥ 8% or a fasting plasma glucose ≥ 160 mg/dL (or 8.8 mmol/L) * QT interval corrected using Fridericia's formula (QTcF) \> 470 ms. Abnormal electrocardiograms (ECGs) (triplicate) should be performed \> 30 minutes apart * Current treatment with medications that are well known to prolong the QT interval * Prior treatment with anti-cluster of differentiation (CD)137 agents, anti-CD3 agents and/or delta-like ligand 3 (DLL3) targeted therapies * Any anti-cancer therapy, whether investigational or approved, including chemotherapy, hormonal therapy, or radiotherapy, within 21 days prior to initiation of study treatment * Any history of an immune-related Grade 4 adverse event (AE) attributed to prior anti-programmed death ligand-1 (PD-L1) /PD-1 or anti-cytotoxic T-lymphocyte-associated protein (CTLA-4) therapy (other than asymptomatic elevation of serum amylase or lipase) * Any history of an immune-related Grade 3 adverse event attributed to prior anti-PD-L1 /PD-1 or anti-CTLA-4 therapy (other than asymptomatic elevation of serum amylase or lipase) that resulted in permanent discontinuation of the prior immunotherapeutic agent * History or clinical evidence of primary central nervous system (CNS) malignancy, symptomatic CNS metastases, CNS metastases requiring any anti-tumor treatment, or leptomeningeal disease and current or history of CNS disease, such as stroke, epilepsy, CNS vasculitis, or neurodegenerative disease * Spinal cord compression that has not been definitively treated with surgery and/or radiation * Active or history of clinically significant autoimmune disease * Positive test for human immunodeficiency virus (HIV) infection * Positive hepatitis B surface antigen (HbsAg) test, and/or positive total hepatitis B core antibody (HbcAb) test at screening * Prior allogeneic hematopoietic stem cell transplantation or prior solid organ transplantation * Administration of a live, attenuated vaccine within 4 weeks before first RO7616789 infusion * Known allergy or hypersensitivity to any component of the RO7616789 formulation