ABBV-706 is an investigational medicine being tested in this study. It is a laboratory‑made antibody that is designed to find and attach to a protein called SEZ6 on cancer cells. By binding to this protein, the antibody may help the immune system recognize and attack the tumor. The drug is given through an IV infusion, meaning it is delivered directly into a vein over a short period. Researchers are studying whether ABBV-706 works better than usual chemotherapy for people whose small cell lung cancer has come back or did not respond to earlier treatment.

TOPOTECAN is a chemotherapy drug that is part of the standard treatment options for small cell lung cancer. It works by interfering with the DNA inside cancer cells, which stops the cells from growing and causes them to die. In this trial, topotecan may be given either as a pill you swallow (oral) or as an IV infusion, depending on the doctor’s decision. It is used as the comparison (comparator) to see if the new drug, ABBV-706, can provide better results for patients.

Small Cell Lung Cancer – Small Cell Lung Cancer is a type of lung cancer that begins in the small, round cells lining the airways. It grows quickly and can spread to other parts of the body early in its course. As the tumor expands, it may cause coughing, shortness of breath, and chest discomfort. The disease often progresses to involve nearby lymph nodes and distant organs such as the liver, brain, and bones. Its rapid growth leads to a steady increase in tumor size and spread over a relatively short period.