Amrubicin

This study is designed to compare the efficacy and safety of I-DXd with treatment of physician's choice in participants with relapsed small cell lung cancer (SCLC).

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.