Background:

IC50: 21 nm (CDK7)

Normal progression through the cell cycle requires the sequential action of cyclin-dependent kinases CDK1, CDK2, CDK4, and CDK6. Direct or indirect deregulation of CDK activity is a feature of almost all cancers and has led to the development of CDK inhibitors as anticancer agents.BS-181 is a highly selective CDK7 inhibitor with IC50 of 21 nM. ; >40-fold selective for CDK7 than CDK1, 2, 4, 5, 6, or 9.

In vitro: BS-181, inhibited CAK activity with an IC50 of 21 nmol/L. Testing of other CDKs as well as another 69 kinases showed that BS-181 only inhibited CDK2 at concentrations lower than 1 μmol/L, with CDK2 being inhibited 35-fold less potently (IC50 880 nmol/L) than CDK7. In MCF-7 cells, BS-181 inhibited the phosphorylation of CDK7 substrates, promoted cell cycle arrest and apoptosis to inhibit the growth of cancer cell lines [1].

In vivo: BS-181 was stable in vivo with a plasma elimination half-life in mice of 405 minutes after i.p. administration of 10 mg/kg. The same dose of drug inhibited the growth of MCF-7 human xenografts in nude mice. BS-181 therefore provides the first example of a potent and selective CDK7 inhibitor with potential as an anticancer agent [1].

Clinical trial: BS-181 is currently in the preclinical development and non clinical trial is ongoing.

Reference:
[1] Ali S, Heathcote DA, Kroll SH, Jogalekar AS, Scheiper B, Patel H, Brackow J, Siwicka A, Fuchter MJ, Periyasamy M, Tolhurst RS, Kanneganti SK, Snyder JP, Liotta DC, Aboagye EO, Barrett AG, Coombes RC.  The development of a selective cyclin-dependent kinase inhibitor that shows antitumor activity. Cancer Res. 2009;69(15):6208-15.
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