Discovery of MFH290: A Potent and Highly Selective Covalent Inhibitor for Cyclin-Dependent Kinase 12/13

Genetic
depletion of cyclin-dependent kinase 12 (CDK12) or selective
inhibition of an analog-sensitive CDK12 reduces DNA damage repair
gene expression, but selective inhibition of endogenous CDK12 is difficult.
Here, we report the development of MFH290, a novel cysteine (Cys)-directed
covalent inhibitor of CDK12/13. MFH290 forms a covalent bond with
Cys-1039 of CDK12, exhibits excellent kinome selectivity, inhibits
the phosphorylation of serine-2 in the C-terminal domain (CTD) of
RNA-polymerase II (Pol II), and reduces the expression of key DNA
damage repair genes. Importantly, these effects were demonstrated
to be CDK12-dependent as mutation of Cys-1039 rendered the kinase
refractory to MFH290 and restored Pol II CTD phosphorylation and DNA
damage repair gene expression. Consistent with its effect on DNA damage
repair gene expression, MFH290 augments the antiproliferative effect
of the PARP inhibitor olaparib.