Trilaciclib (G-1T28; G1T28; Cosela) is a novel, first-in-class and short-acting CDK4/6 inhibitor approved in 2021 by FDA as a medication to reduce the frequency of chemotherapy-induced bone marrow suppression. It inhibts CDK4/6 with IC50s of 1 nM and 4 nM, respectively. It is under development to preserve hematopoietic stem cells and enhance immune system function during chemotherapy. Trilaciclib is administered intravenously prior to chemotherapy and has the potential to significantly improve treatment outcomes.