Phase II Study of Platinum/Etoposide Plus Ivonescimab for Extensive-Stage Small Cell Lung Cancer

Eligible untreated participants with Extensive Stage Small Cell Lung Cancer (ES-SCLC) who are ≥ 18 years of age will be randomized to receive ivonescimab 10 milligrams per kilogram (mg/kg) or ivonescimab 20 mg/kg in combination with carboplatin and etoposide. Ivonescimab is a type of drug called a bispecific antibody. Antibodies are proteins that specifically recognize and bind to other types of proteins called antigens. Antibodies and antigens can work together to help the immune system fight cancer cells. Bispecific antibody, meaning it targets two different molecules at the same time. Ivonescimab is a new drug that may help the immune system attack cancer cells and may also block certain pathways that cancer uses to grow and spread. This dual action of ivonescimab aims to help the immune system to fight the cancer and also disrupt tumor growth by blocking blood vessel formation that tumors use to grow. Participants will receive induction with 4 cycles of ivonescimab (dose determined by randomization) with standard of care carboplatin and etoposide followed by maintenance therapy with ivonescimab at the same dose received during induction. Treatment will continue until disease progression, unacceptable toxicity or participant withdrawal. The purpose of this study is to determine what dose of ivonescimab works best in combination with carboplatin and etoposide chemotherapy in ES-SCLC. We will also examine the side effects, good and bad, associated with ivonescimab.

Selection Criteria: * Patients must have pathologically confirmed Extensive Stage Small Cell Lung Cancer (ES-SCLC). * No prior systemic therapy for the disease under study (ES-SCLC). * Patients must have measurable disease according to Response Evaluation Criteria for Solid Tumors (RECIST) v1.1. * Patient must be ≥ 18 years of age. * Patient must have an ECOG performance status of 0-1. * Patient must have the ability to understand and willingness to sign a written informed consent document. * Willing to provide archived tumor tissue (if sufficient tumor tissue available) and blood samples for research. * Patient must have adequate organ function and marrow function as defined below, obtained ≤ 14 days prior to registration/randomization. No blood transfusions or growth factor therapy allowed within 7 days of screening labs. * Absolute Neutrophil Count (ANC) ≥ 1500/microliter (mcL) * Platelets ˃100,000/mcL * Hemoglobin \>9.0 gram/deciliter (g/dL) * Prothrombin time (PT) or international normalized ratio (INR) ≤ 1.5x Upper Limit Normal (ULN), and partial prothrombin time (PTT) or activated partial thromboplastin time (aPTT) ≤ 1.5x ULN * Serum Creatinine ≤ 2x ULN * Creatinine clearance (CrCl) ≥ 50 milliliter/minute (mL/min) * Urine Protein \