A Study to Evaluate the Optimal Dose, Adverse Events and Change in Disease Activity of Intravenous ABBV-706 in Combination With Atezolizumab Versus Standard of Care as First-Line Treatment in Adult Participants With Previously Untreated Extensive Stage 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, dose, change in disease activity of ABBV-706 given with atezolizumab, compared to standard of care (SOC) treatment (etoposide, carboplatin, atezolizumab, and optional lurbinectedin). ABBV-706 is an investigational drug being developed for the treatment of SCLC. There are multiple treatment arms in this study. Participants will either receive ABBV-706 given with atezolizumab, at 1 of 2 doses, or SOC. Approximately 180 adult participants will be enrolled in the study across sites worldwide. In the safety lead-in, participants with SCLC will receive intravenous (IV) ABBV-706 in 1 of 2 doses with IV atezolizumab, or IV SOC. In the expansion portion of the study, participants with SCLC will receive IV ABBV-706 in 1 of 2 doses with atezolizumab, or IV SOC, until the optimal dose of ABBV-706 is determined. The estimated duration of the study is up to 69.5 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.

Sex

All

Minimum age

18 Years

Inclusion Criteria:

* Diagnosis of histologically or cytologically confirmed extensive stage small cell lung cancer (ES-SCLC) requiring treatment with first line therapy.
* Have an Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 to 1 during the screening period prior to the first dose of study treatment.
* Have measurable disease per Response Evaluation Criteria in Solid Tumors (RECIST v1.1).
* Suspected brain metastases at screening should have a computed tomography (CT)/ magnetic resonance imaging (MRI) of the brain prior to study entry.

Exclusion Criteria:

* Have received any kind of treatment for limited stage small cell lung cancer (LS-SCLC).
* Known active/symptomatic central nervous system (CNS) metastases should be excluded.
* History of interstitial lung disease (ILD) or pneumonitis that required treatment with systemic steroids, or any evidence of active ILD/pneumonitis on screening chest computed tomography (CT) scan should be excluded.
* Have any clinically significant conditions that would adversely affect the participant's participation in the study, and the subject should have a life expectancy of at least 3 months.