BS-181 is a small molecule inhibitor of CDK7 in a cell-free environment, which displays more potential activity than roscovitine with IC 50 of 510 nM. Among the CDKs and other 69
kinases from many different classes, BS-181 shows high inhibitory selectivity for CDK7, inhibits CDK2 at concentrations lower than 1 μM which being inhibited 35-fold less potently (IC50 with 880 nM)
than CDK7, shows slight inhibition for CDK1, CDK4, CDK5, CDK6 and CDK9 with IC50 values higher than 3.0 μM, and only shows inhibition for several kinases from other classes at high concentrations
(>10 μM).