The goal of this clinical trial is to learn if different combinations of a drug called Ivonescimab, along with chemotherapy and other investigational drugs, are safe and effective for the initial treatment of adults with extensive-stage small cell lung cancer (ES-SCLC). The main questions the study aims to answer are: * What side effects do participants experience from these combination treatments? * How well do the treatments work to shrink tumors? Researchers will compare three groups to see which combination works best. All participants will receive Ivonescimab and chemotherapy (etoposide and carboplatin). The differences are: * Group 1 will also receive an additional drug called AK117. * Group 2 will also receive a different additional drug called Cadonilimab. * Group 3 will receive Ivonescimab and chemotherapy only. Participants will: * Be assigned by chance to one of the three groups. * Undergo an initial treatment phase (about 3 months), receiving chemotherapy plus the specific study drugs for their group. * If the treatment is effective and side effects are manageable, continue with a maintenance phase using only the study drugs (without chemotherapy) for up to 2 years. * Attend regular clinic visits for check-ups, blood tests, and imaging scans (like CT scans) to see how they are responding to the treatment.