Trilaciclib (G1T28): A cyclin dependent kinase 4/6 inhibitor, in combination with etoposide and carboplatin (EP) for extensive stage small cell lung cancer (ES-SCLC)—Phase 1b results.

8568Background: Chemotherapy (chemo) has significant clinical utility, however consequent damage to hematopoietic stem and progenitor cells (HSPCs) and the immune system may limit activity. If chemo-mediated anti-tumor activity was maximized, while minimizing myelosuppression and immunosuppression, patient outcomes would be improved. Trilaciclib (T) is an intravenous CDK4/6 inhibitor in development to reduce myelosuppression and preserve immune system function during chemo. HSPCs are dependent on CDK4/6 for proliferation. Preclinical data demonstrated that transient T-induced G1 cell cycle arrest renders HSPCs resistant to chemo cytotoxicity, allowing faster hematopoietic recovery, preservation of long-term function, and enhancement of anti-tumor immunity and activity. Methods: Objectives of this ongoing multicenter Phase 1b/2a study are to assess dose limiting toxicities (DLTs), safety, tolerability, hematological profile, PK, and anti-tumor activity of T administered prior to EP. Phase 1b was open-label...