Multi-Kinase Inhibition and MYC Depletion
Kinase inhibition of CDK9—in particular—offers an exciting therapeutic opportunity, because CDK9 inhibition results in the depletion of the key oncogenic protein MYC.

MYC is one of the first discovered oncogenes and is overexpressed in many cancers, including 80% of high-grade gliomas.1 An overexpression of MYC is associated with tumorigenesis, playing a key role in cellular proliferation, and with abnormal glucose and glutamine metabolism.2 By reducing MYC, oncogenic activity of metabolite 2-hydroxyglutarate is interrupted and tumorigenic activities of high-grade gliomas are reduced.3-5

When CDK9 is successfully inhibited, RNA polymerase II activity stalls, blocking the ability of the tumor to initiate transcription of the oncogenes MYC and MCL-1.3

Tumor Growth Is Blunted With Decreased Levels of 2-Hydroxyglutarate

MYC depletion stymies oncogenic pathways and decreases metabolic activity, reducing the activity of 2-hydroxyglutarate, an oncometabolite produced in IDH-mutated tumors.1,6,7

Multi-Kinase Inhibition Increases Cell Death via MCL-1 Depletion

MCL-1 is a member of the BCL-2 family of antiapoptotic proteins, which interfere with the process of programmed cell death that can occur if aberrant activity in a cancer cell is detected. This has been demonstrated to be an effective anticancer approach, given that cancer cells are known to be more prone to apoptosis than normal cells.8
BCL-2 antiapoptotic proteins have become established therapeutic targets, with the BCL-2 inhibitor venetoclax attaining standard-of-care status in both chronic lymphocytic leukemia and acute myeloid leukemia.
1. Annibali D, Whitfield JR, Favuzzi E, et al. Myc inhibition is effective against glioma and reveals a role for Myc in proficient mitosis. Nat Commun. 2014;5:4632. 2. Yuneva M, Zamboni N, Oefner P, Sachidanandam R, Lazebnik Y. Deficiency in glutamine but not glucose induces MYC-dependent apoptosis in human cells. J Cell Biol. 2007;178(1):93-105. 3. Tsang J, Sung S, Gosa L, Meetze K, Cloughesy T, Nathanson D. TG02, a brain-penetrant multi-CDK inhibitor, potently suppresses MYC-driven glioblastoma. Abstract EXTH-67. Neuro Oncol. 2017;19(suppl 6):vi87-vi88. 4. Le Rhun E, Von Achenbach C, Szabo E, Weller M. TG02, an oral CDK inhibitor, induces multiple cell death pathways in human glioma cell lines and glioma-initiating cells. Abstract DDIS-07. Neuro Oncol. 2017;19(suppl 6):vi60. 5. Wadhwa E, Meetze K, Nicolaides T. TG02, a novel multikinase inhibitor, is effective in pediatric brain tumors, with selective potency in those with MYC expression. Abstract PDTM-41. Neuro Oncol. 2017;19(suppl 6):vi198-vi199. 6. Chen H, Liu H, Qing G. Targeting oncogenic Myc as a strategy for cancer treatment. Signal Transduct Target Ther. 2018;3:5. doi: 10.1038/s41392-018-0008-7. 7. Huang J, Yu J, Tu L, Huang N, Li H, Luo Y. Isocitrate dehydrogenase mutations in glioma: from basic discovery to therapeutics development. Front Oncol. 2019;9:506. 8. Adams JM, Cory S. The BCL-2 arbiters of apoptosis and their growing role as cancer targets. Cell Death Differ. 2018;25(1):27-36.