BS-181 is a highly selective CDK7 inhibitor (IC50: 21 nM); >40-fold selective for CDK7 than CDK1/2/4/5/6/9.

CDK1-CyclinB:8.1 μM, CDK2-CyclinE:0.88 μM, CDK9-CyclinT:4.2 μM, CDK7:21 nM, CDK6-CyclinD1:47 μM, CDK4-CyclinD1:33 μM, CDK5-p35 NCK:3 μM

BS-181 promotes cell cycle arrest and inhibits cancer cell growth, and growth is inhibited for all cell lines tested, with IC50 values ranging from 11.5 to 37 μM. BS-181 inhibits RB phosphorylation at Ser795 and Ser821 with an apparent IC50 of 15 μM, similar to the IC50 obtained for P-Ser2 inhibition. BS-181 treatment of MCF-7 cells leads to G1 arrest at and apoptosis[1]. BS-181 inhibits GC cell and normal gastric epithelial RGM-1 cell line growth with inhibitory concentration (IC50) ranging from 17 to 22 μM and 6.5 μM, respectively. BS-181 significantly inhibits cell migration and invasion ability in a dose-dependent manner[2].

BS-181 (5 mg/kg, 10 mg/kg, i.p.) inhibits the growth of MCF-7 tumors in nude mice. Intravenous (i.v) and i.p administration of 10 mg/kg BS-181 shows rapid clearance[1]. BS-181 (10 mg/kg/d or 20 mg/kg/d, i.p.) significantly inhibits the growth of tumor in a dose-dependent manner compared to the control group[2].

In vitro kinase inhibition.: Inhibition of CDK7 activity is measured by incubation of increasing amounts of BS-181 with purified recombinant CDK7/CycH/MAT1 complex, followed by measurement of free ATP remaining in the reaction using a luciferase assay, luciferase activity therefore providing a measure of inhibition of CDK7 activity for the determination of IC50.

Cell viability is detected using Cell Counting Kit (CCK-8 kit) according to supplier's introductions. Briefly, BGC823 cells are seeded at 104?cells per well for 48 hours with or without BS-181. Then, the absorbance is detected at 450 nm (reference at 650 nm) in each well.