CDK4 and neutropenia: The rates of hematologic toxicities with culmerciclib were comparable with abemaciclib for Chinese patients.29 The rate of grade 3 or 4 neutropenia was the lowest with culmerciclib among CDK4/6 inhibitors and no febrile neutropenia occurred, likely because that culmerciclib is a potent CDK4-biased inhibitor over CDK6, thereby leading to less prominent hematologic toxicities.11 Though Asian patients were significantly more likely to have neutropenia.30,31 culmerciclib had a low rate of grade 3 or 4 neutropenia (24.7%).