CDK6 and mantle cell lymphoma: Of note, in two patients with relapsed MCL following midostaurin treatment (patient #4.3 and #15; Table 1), all CDK4/CDK6 inhibitors tested also produced growth inhibition in neoplastic cells (IC50-values: palbociclib 12 nM and 43.9 nM; ribociclib 252.6 nM and 65.5 nM; abemaciclib 13.8 nM and 98.4 nM).