Phase 1b/2a Safety and Pharmacokinetic Study of G1T28 in Patients With Extensive Stage Small Cell Lung Cancer (SCLC) Receiving Etoposide and Carboplatin

This is a study to investigate the potential clinical benefit of trilaciclib (G1T28) in preserving the bone marrow and the immune system, and enhancing chemotherapy antitumor efficacy when administered prior to carboplatin and etoposide in first line treatment for patients with newly diagnosed extensive-stage SCLC. The study consists of 2 parts: a limited open-label, dose-finding portion (Part 1), and a randomized double-blind portion (Part 2). Both parts include 3 study phases: Screening Phase, Treatment Phase, and Survival Follow-up Phase. The Treatment Phase begins on the day of first dose with study treatment and completes at the Post-Treatment Visit. Approximately, 90 patients will be enrolled in the study; 20 patients in the Part 1 and 70 patients in the Part 2 portion.