Abstract 1324: Dual targeting of CDK4 and ARK5 using a novel kinase inhibitor ON123300 is effective in vitro and in vivo in Multiple Myeloma
Authors: Perumal Deepak , Thirukonda Venu , Jiang Zewei , Leshchenko Violetta V. , Kuo Pei-yu , Shahnaz Samira , Rubel Jennifer , Zhang Weijia , Cho Hearn Jay , Reddy M.V. Ramana , Reddy E. Premkumar , Parekh Samir 
Published: May 2015

Multiple Myeloma (MM) is an incurable malignancy of plasma cells afflicting over 21,000 patients and accounting for over 10,000 deaths in the US each year. It is characterized by recurrent chromosomal translocations resulting in the dysregulation of cyclinD1, cyclinD3, c-Maf, MafB and MMSET. Despite cell cycle dysregulation being prominent in myeloma pathogenesis, clinical efficacy of CDK4/CDK6 inhibitors has been modest. We therefore developed ON123300, an orally available and potent small inhibitor of CDK4/CDK6 and ARK5. ARK5 is a member of the AMP-activated protein kinase (AMPK) catalytic subunit family and is associated with increased tumor cell invasiveness in MM [Suzuki et al., Mol. Cell. Bio 2004] and transcriptionally regulated by oncogenes such as MMSET, c-Maf and MafB. In this study, we evaluated the in vitro and in vivo efficacy of ON123300 in MM cell lines.

A panel of nine MM cell lines was treated with varying doses of ON123300 and cell viability assessed using the CellTitre Blue assay after 48 hours. ON123300 decreased cell viability by approximately 30 to 70% (IC50:50-200nM) in 9/9 MM cell lines examined. Based on IC50 of 50 nM, we could stratify the cell lines into two groups: 6 cell lines (MM.1R, MM.1S, KMS11, U266, RPMI-8226 and ARP1) had IC50 of 50-150 nm and three cell lines (EJM, JJN3 and NCI-H929) were very sensitive (IC50 &lt;50nM). ARK5 protein expression was confirmed by western blot in MM.1R, MM.1S, RPMI-8226, ARP1, EJM and JJN3 and was significantly higher in the more sensitive cell lines EJM and JJN3. Transcriptomic differences between more sensitive cell lines EJM, JJN3, NCI-H929 as compared to the six less sensitive cell lines were culled from RNA-seq and analyzed in different databases Genego, IPA and DAVID. Cell cycle was the top KEGG pathway identified in this analysis and included CDK6, a key target of ON123300. Simultaneously a xenograft mouse model was used to evaluate the therapeutic potential of ON123300 in vivo. ARK5 positive MM.1S myeloma cells (with pcDNA-mCh-luc constitutively expressing luciferase) were injected subcutaneously into SCID mice. Following tumor growth the mice were grouped as- control/untreated (n=5) and ON123300 treated (n = 5). ON123300 (100mg/kg) was administered by IP injection on alternative days and tumor growth monitored using highly sensitive IVIS imaging system. Mice in the treated group responded with 100 fold decrease in bioluminescence intensity (Control- 3.7xE10p/sec/cm2/sr, Treated-3.5xE08p/sec/cm2/sr) in their tumors as compared to untreated control mice.

Our results suggest that ON123300 to be a potent inhibitor of tumor growth in vitro and in vivo and could be an effective agent for myeloma treatment especially for patients with aggressive disease driven by cytogenetic changes involving the MAF/ MMSET transcription factors. We expect our studies to expand therapeutic options for patients with this challenging disease.

Citation Format: Deepak Perumal, Venu Thirukonda, Zewei Jiang, Violetta V. Leshchenko, Pei-yu Kuo, Samira Shahnaz, Jennifer Rubel, Weijia Zhang, Hearn Jay Cho, M.V. Ramana Reddy, E. Premkumar Reddy, Samir Parekh. Dual targeting of CDK4 and ARK5 using a novel kinase inhibitor ON123300 is effective in vitro and in vivo in Multiple Myeloma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1324. doi:10.1158/1538-7445.AM2014-1324