THZ1

THZ1 is a covalent inhibitor of CDK7 with IC50 value of 3.2nM [1].

THZ1 covalently modifies CDK7 by targeting C312 residue outside of the kinase domain, providing an unanticipated means of achieving covalent selectivity. THZ1 potently inhibits proliferation of Jurkat and Loucy T-ALL cell lines with IC50 values of 50nM and 0.55nM, respectively. In the kinase binding assay, THZ1 shows a good binding affinity with IC50 value of 3.2nM [1].

As an inhibitor of CDK7, THZ1 inhibits the phosphorylation of the C-terminal domain of RNAP polymerase II, effecting the regulation of transcription. THZ1 also inhibits the activation of the CDK proteins. It is reported to disrupt the CDK7 signalling pathways both in Jurkat cells and Loucy cells. THZ1 shows a broad-based activity with IC50 values less than 200nM in a variety of cancer cell lines. Among these cell lines, T-ALL is exceptional sensitivity to THZ1 due to the transcription effect of RUNX1 caused by THZ1 [1].

References:
[1] Nicholas Kwiatkowski, Tinghu Zhang, Peter B. Rahl et al. Targeting transcription regulation in cancer with a covalent CDK7 inhibitor. Nature, 2014.

THZ1 Reveals Roles for Cdk7 in Co-transcriptional Capping and Pausing.[Pubmed:26257281]

Mol Cell. 2015 Aug 20;59(4):576-87.

The Cdk7 subunit of TFIIH phosphorylates RNA polymerase II (Pol II) during initiation, and, while recent studies show that inhibition of human Cdk7 negatively influences transcription, the mechanisms involved are unclear. Using in vitro transcription with nuclear extract, we demonstrate that THZ1, a covalent Cdk7 inhibitor, causes defects in Pol II phosphorylation, co-transcriptional capping, promoter proximal pausing, and productive elongation. THZ1 does not affect initiation but blocks essentially all Pol II large subunit C-terminal domain (CTD) phosphorylation. We found that guanylylation of nascent RNAs is length dependent and modulated by a THZ1-sensitive factor present in nuclear extract. THZ1 impacts pausing through a capping-independent block of DSIF and NELF loading. The P-TEFb-dependent transition into productive elongation was also inhibited by THZ1, likely due to loss of DSIF. Capping and pausing were also reduced in THZ1-treated cells. Our results provide mechanistic insights into THZ1 action and how Cdk7 broadly influences transcription and capping.

THZ1 targeting CDK7 suppresses STAT transcriptional activity and sensitizes T-cell lymphomas to BCL2 inhibitors.[Pubmed:28134252]

Nat Commun. 2017 Jan 30;8:14290.

Peripheral T-cell lymphomas (PTCL) are aggressive diseases with poor response to chemotherapy and dismal survival. Identification of effective strategies to target PTCL biology represents an urgent need. Here we report that PTCL are sensitive to transcription-targeting drugs, and, in particular, to THZ1, a covalent inhibitor of cyclin-dependent kinase 7 (CDK7). The STAT-signalling pathway is highly vulnerable to THZ1 even in PTCL cells that carry the activating STAT3 mutation Y640F. In mutant cells, CDK7 inhibition decreases STAT3 chromatin binding and expression of highly transcribed target genes like MYC, PIM1, MCL1, CD30, IL2RA, CDC25A and IL4R. In surviving cells, THZ1 decreases the expression of STAT-regulated anti-apoptotic BH3 family members MCL1 and BCL-XL sensitizing PTCL cells to BH3 mimetic drugs. Accordingly, the combination of THZ1 and the BH3 mimetic obatoclax improves lymphoma growth control in a primary PTCL ex vivo culture and in two STAT3-mutant PTCL xenografts, delineating a potential targeted agent-based therapeutic option for these patients.

THZ1 is a selective and potent covalent CDK7 inhibitor with an IC50 of 3.2 nM. THZ1 also inhibits the closely related kinases CDK12 and CDK13 and downregulates MYC expression.

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