Quantifying CDK inhibitor selectivity in live cells.
Wells CI., Vasta JD., Corona CR., Wilkinson J., Zimprich CA., Ingold MR., Pickett JE., Drewry DH., Pugh KM., Schwinn MK., Hwang BB., Zegzouti H., Huber KVM., Cong M., Meisenheimer PL., Willson TM., Robers MB.
Concerted multidisciplinary efforts have led to the development of Cyclin-Dependent Kinase inhibitors (CDKi's) as small molecule drugs and chemical probes of intracellular CDK function. However, conflicting data has been reported on the inhibitory potency of CDKi's and a systematic characterization of affinity and selectivity against intracellular CDKs is lacking. We have developed a panel of cell-permeable energy transfer probes to quantify target occupancy for all 21 human CDKs in live cells, and present a comprehensive evaluation of intracellular isozyme potency and selectivity for a collection of 46 clinically-advanced CDKi's and tool molecules. We observed unexpected intracellular activity profiles for a number of CDKi's, offering avenues for repurposing of highly potent molecules as probes for previously unreported targets. Overall, we provide a broadly applicable method for evaluating the selectivity of CDK inhibitors in living cells, and present a refined set of tool molecules to study CDK function.