This study focuses on patients with Small Cell Lung Cancer (SCLC) that has returned after previous treatment. The study will compare two different treatments: a new experimental medication called GSK5764227, which is a type of drug known as a B7-H3 Antibody Drug Conjugate, and an established cancer medication called topotecan. The purpose is to determine how well the new treatment works compared to the standard treatment in fighting the cancer.

The study involves patients whose lung cancer has already been treated with platinum-based chemotherapy combined with immunotherapy but has since returned. Both medications in this study will be given through intravenous infusion (delivered directly into a vein). GSK5764227 will be given at doses up to 8 milligrams per kilogram of body weight, while topotecan will be given at doses up to 1.5 milligrams per square meter of body surface area.

This is an open-label study, which means both the doctors and patients will know which treatment is being given. The treatment period may last up to 24 months, during which time doctors will monitor how well the cancer responds to the treatment and track the overall survival of patients. Throughout the study, patients will have regular check-ups to monitor their health and assess how well the treatment is working.