Selective inhibition of CDK9 in triple negative breast cancer.

Targeted therapy for triple-negative breast cancers (TNBC) remains a clinical challenge due to tumour heterogeneity. Since TNBC have key features of transcriptionally addicted cancers, targeting transcription via regulators such as cyclin-dependent kinase 9 (CDK9) has potential as a therapeutic strategy. Herein, we preclinically tested a new selective CDK9 inhibitor (CDDD11-8) in TNBC using cell line, patient-derived organoid, and patient-derived explant models. In vitro, CDDD11-8 dose-dependently inhibited proliferation (IC50 range: 281-734 nM), induced cell cycle arrest, and increased apoptosis of cell lines, which encompassed the three major molecular subtypes of TNBC. On target inhibition of CDK9 activity was demonstrated by reduced RNAPII phosphorylation at a CDK9 target peptide and down-regulation of the MYC and MCL1 oncogenes at the mRNA and protein levels in all cell line models. Drug induced RNAPII pausing was evident at gene promoters, with strongest pausing at MYC target genes. Growth of five distinct patient-derived organoid models was dose-dependently inhibited by CDDD11-8 (IC50 range: 272-771 nM), including three derived from MYC amplified, chemo-resistant TNBC metastatic lesions. Orally administered CDDD11-8 also inhibited growth of mammary intraductal TNBC xenograft tumours with no overt toxicity in vivo (mice) or ex vivo (human breast tissues). In conclusion, our studies indicate that CDK9 is a viable therapeutic target in TNBC and that CDDD11-8, a novel selective CDK9 inhibitor, has efficacy in TNBC without apparent toxicity to normal tissues.

CDKI-73: an orally bioavailable and highly efficacious CDK9 inhibitor against acute myeloid leukemia.

Acute myeloid leukemia (AML) is the most common form of acute leukemia with dismal long-term prognosis with age. The most aggressive subtype of AML is MLL-AML that is characterized by translocations of the mixed-lineage leukemia gene (MLL) and resistance to conventional chemotherapy. Cyclin dependent kinase 9 (CDK9) plays a crucial role in the MLL-driven oncogenic transcription, and hence, inhibiting activity of CDK9 has been proposed as a promising strategy for treatment of AML. We investigated the therapeutic potential of CDKI-73, one of the most potent CDK9 inhibitors, against a panel of AML cell lines and samples derived from 97 patients. CDKI-73 induced cancer cells undergoing apoptosis through transcriptional downregulation of anti-apoptotic proteins Bcl-2, Mcl-1 and XIAP by majorly targeting CDK9. Contrastively, it was relatively low toxic to the bone marrow cells of healthy donors. In MV4-11 xenograft mouse models, oral administration of CDKI-73 resulted in a marked inhibition of tumor growth (p < 0.0001) and prolongation of animal life span (P < 0.001) without causing body weight loss and other overt toxicities. The study suggests that CDKI-73 can be developed as a highly efficacious and orally deliverable therapeutic agent for treatment of AML.

Dual Inhibition of Mnk2 and FLT3 for potential treatment of acute myeloid leukaemia.

The discovery of novel anti-AML therapeutic agents is urgently needed, but the complex heterogeneity of the disease has so far hampered the development of a curative treatment. FLT3 inhibitors have shown therapeutic potential in clinical trials; but a monotherapy regimen has been associated with resistance mediated by the activation of parallel signalling circuitry, including MAPK and mTOR. Therefore, inhibiting a nexus of the two signalling pathways along with inhibition of FLT3 might be advantageous. Herein, we propose that a dual inhibition of FLT3 and Mnk would provide a better clinical option for AML patients compared to targeting FLT3 alone. Thus, a series of N-phenyl-4-(thiazol-5-yl)pyrimidin-2-amines and 4-(indol-3-yl)-N-phenylpyrimidin-2-amines were prepared. Potent Mnk2 inhibitors, FLT3 inhibitors, and dual inhibitors of Mnk2 and FLT3 were identified and their anti-proliferative activities assessed against MV4-11 AML cell lines. Dual inhibition of FLT3 and Mnk2 caused the increased apoptotic cell death of MV4-11 cells compared to inhibition of FLT3 or Mnk2 alone.

Discovery of (E)-3-((styrylsulfonyl)methyl)pyridine and (E)-2-((styrylsulfonyl)methyl)pyridine derivatives as anticancer agents: synthesis, structure-activity relationships, and biological activities.

ON01910.Na is a highly effective anticancer agent that induces mitotic arrest and apoptosis. Clinical studies with ON01910 in cancer patients have shown efficacy along with an impressive safety profile. While ON01910 is highly active against cancer cells, it has a low oral availability and requires continuous intravenous infusion or multiple gram doses to ensure sufficient drug exposure for biological activity in patients. We have identified two novel series of styrylsulfonyl-methylpyridines. Lead compounds 8, 9a, 18 and 19a are highly potent mitotic inhibitors and selectively cytotoxic to cancer cells. Impressively, these compounds possess excellent pharmaceutical properties and two lead drug candidates 9a and 18 demonstrated antitumor activities in animal models.