Roniciclib inhibits the kinase activity of the cell-cycle CDKs CDK1/cyclin B, CDK2/cyclin E, and CDK4/cyclinD (IC50: 7, 9, and 11 nM, respectively). Roniciclibeffectively inhibits the proliferation of various human and murine tumor cell lines with a very balanced profile (mean IC50 on human tumor cells: 16 nM). The transcriptional CDKs CDK9/cyclin T1 and CDK7/cyclin H/MAT1 are inhibited in a similar range (5 and 25 nM) [1][2].

Roniciclib has low blood clearance rates in mouse, rat, and dog (0.51, 0.78, and 0.50 Lh-1kg-1, respectively). Roniciclib strongly inhibits the growth of HeLa-MaTu tumors that have been grown to a size of approximately 50mm2 before the start of treatment. Roniciclib (1.5 and 1 mg/kg) treatment slow tumor growth to T/C values of 0.15 and 0.62, respectively. The addition of Roniciclib to cisplatin causes a strong tumor growth inhibition with T/C values of 0.01 (1.0 mg/kg Roniciclib) and -0.02 (1.5 mg/kg Roniciclib) [1][2].