Researchers are looking for new ways to treat people with extensive-stage small cell lung cancer (SCLC) that has relapsed or is refractory. Gocatamig is a new type of immunotherapy that uses a person's immune system to find and destroy cancer cells. Ifinatamab deruxtecan (also known as I-DXd) is a drug which binds to a specific target on cancer cells and delivers treatment to destroy those cells. Durvalumab is a different type of immunotherapy that also destroys cancer cells. Researchers want to know if giving gocatamig, I-DXd, and gocatamig with I-DXd or durvalumab can treat SCLC that did not respond or stopped responding to a prior treatment. The goals of this study are to learn: * If gocatamig alone, I-DXd alone, and gocatamig with I-DXd or durvalumab are safe and well tolerated * If people who receive gocatamig alone, I-DXd alone, and gocatamig with I-DXd or durvalumab have their SCLC get smaller or go away