Atuveciclib (BAY-1143572) is a potent and highly selective, oral PTEFb / CDK9 inhibitor that inhibits CDK9 / CycT1 with an IC 50 of 13 nM [1].

CDK5-p35:1600 nM, CDK9-CyclinT1:13 nM, CDK9-CyclinT1:6 nM, CDK1-CyclinB:1100 nM, CDK2-CyclinE:1000 nM, CDK3-CyclinE:890 nM

Positive transcription elongation factor b (PTEFb) is a heterodimer of CDK9 and one of four cyclin partners, cyclin T1, cyclin K, cyclin T2a or cyclin T2b. Atuveciclib (BAY-1143572) shows potent antiproliferative activity against HeLa cells (IC 50 =920 nM) and MOLM-13 cells (IC 50 =310 nM) [1].

In vivo efficacy studies in the MOLM-13 xenograft model in mice, Atuveciclib (BAY-1143572) exhibits great potency and high antitumor efficacy. Daily administration of Atuveciclib (BAY-1143572) at 6.25 or 12.5 mg/kg results in a dose-dependent antitumor efficacy with a treatment-to-control (T/C) ratio of 0.64 and 0.49, respectively (p<0.001). In a separate experiment with a higher daily dose of 20 or 25 mg/kg Atuveciclib (BAY-1143572), antitumor efficacy with a T/C ratio of 0.41 and 0.31, respectively, is observed (p<0.001). The 25 mg/kg once daily dose is the maximum tolerated dose in nude mice. Furthermore, Atuveciclib (BAY-1143572) administered at 25 or 35 mg/kg, three days on / two days off, results in a T/C ratio of 0.33 and 0.20, respectively (p<0.001). Treatment with Atuveciclib (BAY-1143572) is well-tolerated, as demonstrated by less than 10 % mean body weight reduction throughout the study. In an in vivo pharmacokinetic study in rats, Atuveciclib (BAY-1143572) shows low blood clearance (CL b 1.1 L/kg per hour) [1].