Discovery of Potent and Selective CDK4/6 Inhibitors for the Treatment of Chemotherapy-Induced Myelosuppression

Chemotherapy-induced myelosuppression (CIM) significantly
impairs
hematopoiesis. Trilaciclib (TC), originally developed for oncology
application, is the only FDA-approved CDK4/6 inhibitor for CIM, which
effectively protects bone marrow cells by inhibiting their proliferation.
In this study, a series of TC derivatives were designed and synthesized
as CDK4/6 inhibitors (CDK4/6i) for alleviating CIM. Among these, 42 displayed potent CDK4/6 inhibitory activity (IC50 = 11 nM), lower cytotoxicity (CC50 > 100 μM)
and
showed high selectivity among 86 kinases. Additionally, 42 possessed strong bone marrow penetration, favorable pharmacokinetic
properties, excellent safety profiles, and superior efficacy in mitigating
myelosuppression caused by 5-fluorouracil (5-FU) in vivo. In conclusion,
as the first oral small-molecule CDK4/6 inhibitor optimized specifically
for myelosuppression treatment, 42 expands the therapeutic
applications of CDK4/6i, optimizes the mode of administration, and
offers significant translational value and clinical potential.