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VIP152 is a Selective CDK9 Inhibitor with Pre-Clinical In Vitro and In Vivo Efficacy in Chronic Lymphocytic Leukemia

ABSTRACT: Chronic lymphocytic leukemia (CLL) is effectively treated with targeted therapies including Bruton tyrosine kinase inhibitors (ibrutinib or acalabrutinib) and BCL2 antagonists (venetoclax). When these become ineffective, treatment options are limited. Positive transcription elongation factor complex (P-TEFb), a heterodimeric protein complex composed of cyclin dependent kinase 9 (CDK9) and cyclin T1, functions to regulate short half-life transcripts by releasing RNA Polymerase II (POLII) from proximal-promoter pause by way of phosphorylation. The transcripts regulated by P-TEFb are frequently dysregulated in solid tumors and hematologic malignancies; however, therapies targeting inhibition of P-TEFb have not yet achieved approval for cancer treatment. This is due to lack of selective inhibitors and undesirable side-effect profiles of less selective inhibitors. VIP152 kinome profiling revealed CDK9 as the main enzyme inhibited at 100nM, with over a 10-fold increase in potency compared with other inhibitors currently in development for this target. VIP152 induced cell death as measured by apoptosis in CLL cell lines and primary patient samples. Transcriptome analysis revealed compensatory upregulation in translation machinery and inhibition of RNA degradation. Mechanistically, VIP152 inhibits the assembly of P-TEFb onto the transcription machinery and disturbs CDK9 binding partners such as HEXIM1, MEPCE, and LARP7. Finally, C57BL/6J immune competent mice were engrafted with CLL-like cells of Eµ-MTCP1 over-expressing mice and treated with either VIP152 or vehicle. VIP152-treated mice had a reduction of blood disease over time and an improved overall survival. These data suggest that VIP152 is a highly selective inhibitor of CDK9 that represents an attractive new therapy for CLL.

ORGANISM(S): Homo sapiens

PROVIDER: GSE199037 | GEO | 2023/03/20

REPOSITORIES: GEO

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Project description:Transcript elongation by RNA polymerase II (RNAPII) is accompanied by conserved patterns of histone modification within transcribed regions, but it remains uncertain how these modifications influence, or are influenced by, properties of the elongation complex. Here we establish an intimate link between Cdk9, the kinase component of positive transcription elongation factor b (P-TEFb), and mono-ubiquitylation of histone H2B (H2Bub1), in the fission yeast Schizosaccharomyces pombe. Mutations that impair Cdk9 function reduce H2Bub1 levels in vivo. Conversely, mutations that prevent H2Bub1 decrease phosphorylation of elongation factor subunit Spt5, a sensitive and specific indicator of Cdk9 activity. Chromatin immunoprecipitation (ChIP) analysis suggests this is due to impaired Cdk9 recruitment to H2Bub1-deficient chromatin. P-TEFb and H2Bub1 pathways also interact genetically: mutation of the histone H2B ubiquitin-acceptor residue decreases the requirement for Cdk9 activity in vivo, and multiple cdk9 mutations suppress morphological defects of H2Bub1-deficient strains. Moreover, H2Bub1 loss causes redistribution of transcribing RNAPII on chromatin that is corrected by a hypomorphic cdk9 mutation. Therefore, whereas mutual dependence of Spt5 phosphorylation and H2Bub1 suggests positive feedback between P-TEFb and the ubiquitylation machinery, mutual suppression by cdk9 and H2Bub1-pathway mutations indicates an antagonistic relationship, whereby the activities must be balanced to properly regulate elongation. In order to study the genome-wide localization of H2Bub1 in Schizosaccharomyces pombe, H2Bub1, H2B-Flag as well as RNAPII (along with associated DNA sequences) were immunoprecipitated using repectively anti-H2Bub1, anti-Flag and anti-8WG16 antibodies. The ChIPs were performed in duplicate from WT cells as well as in the H2B-K119R mutant. The extracted DNA was hybridized to a DNA microarray containing an average of 4 probes per kilobase across the whole yeast genome. The combined datasets are available in the supplemental files of the related publication.

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VIP152 is a Selective CDK9 Inhibitor with Pre-Clinical In Vitro and In Vivo Efficacy in Chronic Lymphocytic Leukemia

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