Yaron R. Hadari

Arylphthalazines as potent, and orally bioavailable inhibitors of VEGFR-2

A series of arylphthalazine derivatives were synthesized and evaluated as antagonists of VEGF receptor II (VEGFR-2). IM-094482 57, which was prepared in two steps from commercially available starting materials, was found to be a potent inhibitor of VEGFR-2 in enzymatic, cellular and mitogenic assays (comparable activity to ZD-6474). Additionally, 57 inhibited the related receptor, VEGF receptor I (VEGFR-1), and showed excellent exposure when dosed orally to female CD-1 mice.

Synthesis and evaluation of heteroaryl-ketone derivatives as a novel class of VEGFR-2 inhibitors

We have discovered novel inhibitors of VEGFR-2 kinase with low nanomolar potency in both enzymatic and cell-based assays. Active series are heteroaryl-ketone compounds containing a central aromatic ring with either an indazolyl or indolyl keto group in the ortho orientation to the benzylic amine group (Fig. 1). The best compounds were demonstrated to be inactive against a small select panel of tyrosine and serine/threonine kinases with the exception of VEGFR-1 kinase, a close family member. In addition, the lead candidate 8 displayed acceptable exposure levels when administered orally to mice.

Abstract 1696: Blocking activity of a novel anti-MET humanized monoclonal antibody, KTN0216, is enhanced by IgG2 isotype in HGF-dependent and Met-amplified tumors

Aberrant activation of MET kinase can be mediated by ligand-dependent mechanisms through paracrine or autocrine stimulation by its ligand, HGF, or by ligand-independent mechanisms through gene amplification, over-expression or mutation. Both mechanisms of activating MET have been associated with promoting tumor growth and progression. The discovery of antagonistic MET antibodies has been challenging as many anti-MET antibodies promote kinase activation that leads to cell proliferation and migration. We have systematically screened MET antibodies using cell based functional assays and identified a number of antibodies that potently block MET-dependent cell proliferation, cell scattering as well as tumor growth in vivo. One such antibody, KTN-MET-IgG1, binds to the Sema/PSI domain and prevents HGF-MET interaction; additionally it induces receptor ubiqutination and degradation. To evaluate if the IgG isotype influences activity on MET activation and tumor growth we grafted the binding domains of this antibody onto 2 other IgG backbones: KTN-MET-IgG2 and KTN-MET-IgG4. Surprisingly, grafting the antibody variable regions onto the IgG2 framework dramatically enhanced the anti-MET activity in vitro and in vivo. Comparing to KTN-MET-IgG1 and KTN-MET-IgG4 antibodies with KTN-MET-IgG2 antibody, it demonstrated significantly better inhibition of receptor phosphorylation and cell proliferation in MET amplified tumor cell lines (EBC1, SNU5) and comparable activity in HGF-dependent tumor cell lines (A549, U87MG). KTN-MET-IgG2 treatment of tumor bearing mice achieved potent and prolonged suppression of tumor growth using the U87MG glioblastoma xenograft model and tumor growth regression with tumors remaining below detection for over 90 days post last dosing using the SNU5 gastric cancer xenograft model. In summary, we have found a novel IgG2 anti-MET antibody that inhibits tumor growth driven by HGF-dependent MET activation and MET amplification. A model to help explain the contribution of IgG2 isotype to enhanced blocking activity will be presented. The humanized version of KTN-MET-IgG2, KTN0216, is currently in preclinical development to evaluate tumor types best suited for KTN0216 treatment. Citation Format: Sreekala Mandiyan, Brett S. Robinson, Lida Kimmel, Gerald McMahon, Yaron Hadari, Yan Yang. Blocking activity of a novel anti-MET humanized monoclonal antibody, KTN0216, is enhanced by IgG2 isotype in HGF-dependent and Met-amplified tumors. [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 1696. doi:10.1158/1538-7445.AM2015-1696