A Study to Evaluate Adverse Events and Change in Disease Activity of Intravenous ABBV-706 Versus Standard of Care in Adult Participants With Relapsed/Refractory Small Cell Lung Cancer

Small cell lung cancer (SCLC) is characterized by aggressive and rapid growth and a tendency to develop early spread to distant sites including mediastinal lymph nodes, liver, bones, adrenal glands, and brain. The purpose of this study is to assess safety, tolerability, and change in disease activity of ABBV-706 compared to standard of care (SOC) treatment (topotecan, lurbinectedin, or amrubicin). ABBV-706 is an investigational drug being developed for the treatment of SCLC. There are two treatment arms in this study. Participants will either receive ABBV-706 or SOC. Approximately 531 adult participants will be enrolled in the study across 175 sites worldwide. Participants with SCLC will receive intravenous (IV) ABBV-706 or SOC \[topotecan (IV or orally), or lubinectedin (IV), or amrubicin (IV)\]. The estimated duration of the study is approximately 53 months. There may be higher treatment burden for participants in this trial compared to their standard of care. Participants will attend regular visits during the study at a hospital or clinic and may require frequent medical assessments, blood tests, questionnaires, and scans.