Liqi He

Identification of a nonkinase target mediating cytotoxicity of novel kinase inhibitors.

In developing inhibitors of the LIM kinases, the initial lead molecules combined potent target inhibition with potent cytotoxic activity. However, as subsequent compounds were evaluated, the cytotoxic activity separated from inhibition of LIM kinases. A rapid determination of the cytotoxic mechanism and its molecular target was enabled by integrating data from two robust core technologies. High-content assays and gene expression profiling both indicated an effect on microtubule stability. Although the cytotoxic compounds are still kinase inhibitors, and their structures did not predict tubulin as an obvious target, these results provided the impetus to test their effects on microtubule polymerization directly. Unexpectedly, we confirmed tubulin itself as a molecular target of the cytotoxic kinase inhibitor compounds. This general approach to mechanism of action questions could be extended to larger data sets of quantified phenotypic and gene expression data. [Mol Cancer Ther 2008;7(11):3490–8]

SAR of PXR transactivation in benzimidazole-based IGF-1R kinase inhibitors

The SAR of PXR transactivation by 3-(benzimidazol-2-yl)-pyridine-2-one based ATP competitive inhibitors of Insulin-like Growth Factor 1 Receptor kinase (IGF-1R) is discussed. Compounds without PXR transactivation, with in vivo antitumor activity, reduced protein binding and improved oral exposure are presented.

Modulation of cofilin phosphorylation by inhibition of the Lim family kinases.

A series of aminothiazoles that are potent inhibitors of LIM kinases 1 and 2 is described. Appropriate choice of substituents led to molecules with good selectivity for either enzyme. An advanced member of the series was shown to effectively interfere with the phosphorylation of the LIM kinases substrate cofilin. Consistent with the important role of the LIM kinases in regulating cytoskeletal structure, treated cells displayed dramatically reduced F-actin content.

Abstract 5417: The identification of BMS-595, an orally active imidazo[1,2-b]pyridazine CK2 inhibitor with in vivo anti-tumor activity

CK2 is a highly conserved, and constitutively active family of serine/threonine kinases abnormally elevated in a wide variety of cancers and linked to poor prognosis and disease progression. The enzymes form as hetero-tetrameric complexes comprised of two highly related catalytic subunits (α or α´) with two regulatory β subunits in various combinations and distributions, depending on cell type. While CK2 plays a role in normal growth and development, deregulation of the enzymes has been shown to promote and maintain a malignant phenotype through mechanisms in both the anti-apoptotic and the pro-proliferative signaling pathways. CK2 has been reported to modulate the activity of several oncogenic transcription factors including CREB, Myc, Jun and Fos. Studies with RNAi and small molecule compounds have demonstrated tumor cell dependence on CK2. We sought to identify potent CK2 inhibitors to probe the function of CK2 in cancer-linked pathways and for evaluation in CK2 dependent tumor xenograft models. Herein we report SAR studies in the imidazo[1,2-b]pyridazine chemotype leading to the discovery of BMS-595, a highly potent and selective ATP-competitive CK2 inhibitor with a commensurate level of cellular potency. BMS-595 demonstrates strong PK/PD correlations and robust, oral anti-tumor efficacy in CK2-driven xenograft models at tolerated doses. Citation Format: Christine M. Tarby, Liqi He, Brian E. Fink, Andrew Nation, Yufen Zhao, Soong-Hoon Kim, Libing Chen, John S. Tokarski, Chiang Yu, Jonathan G. Pabalan, Urvashi V. Roongta, Jonathan Lippy, Mary Obermeier, Paul A. Elzinga, Aberra Fura, Benjamin Henley, Joseph J. Fargnoli, William R. Foster, Ashvinikumar V. Gavai, Tai W. Wong, John T. Hunt, Gregory D. Vite, Ashok V. Purandare, Brent A. Rupnow. The identification of BMS-595, an orally active imidazo[1,2-b]pyridazine CK2 inhibitor with in vivo anti-tumor activity. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5417. doi:10.1158/1538-7445.AM2015-5417