Ivonescimab 10 mg/kg

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.