Phase 2 Study of Carboplatin, Etoposide, and Atezolizumab With or Without Trilaciclib in Patients With Untreated Extensive-Stage Small Cell Lung Cancer (SCLC)

Experimental: trilaciclib+etoposide/carboplatin/atezolizumab

Induction: Patients received trilaciclib 240 mg/m² administered intravenously (IV) once daily prior to E/P/A on Days 1, 2 and 3 of each 21-day E/P/A therapy cycle (up to 4 cycles in total). Etoposide 100 mg/m² was administered IV daily on Days 1, 2, and 3 of each 21-day cycle. Carboplatin was administered on Day 1 of each 21-day cycle using the Calvert formula with a target area under the concentration-time curve (AUC) = 5 milligrams per milliliter per minute (mg/mL/min) to calculate the dose. Atezolizumab 1200 mg was administered as an IV infusion on Day 1 of each 21-day cycle.~Maintenance: Following the induction phase, patients received maintenance atezolizumab at a dose of 1200 mg on Day 1 of every 21-day cycle until disease progression, unacceptable toxicity or discontinuation by the patient or investigator.

Experimental: placebo+etoposide/carboplatin/atezolizumab

Induction: Patients received placebo administered IV once daily prior to E/P/A on Days 1, 2 and 3 of each 21-day E/P/A therapy cycle (up to 4 cycles in total). Etoposide 100 mg/m² was administered IV daily on Days 1, 2, and 3 of each 21-day cycle. Carboplatin was be administered on Day 1 of each 21-day cycle using the Calvert formula with a target AUC = 5 mg/mL/min to calculate the dose. Atezolizumab 1200 mg was administered as an IV infusion on Day 1 of each 21-day cycle.~Maintenance: Following the induction phase, patients received maintenance atezolizumab at a dose of 1200 mg on Day 1 of every 21-day cycle until disease progression, unacceptable toxicity or discontinuation by the patient or investigator.