Blocking Activity Of A Novel Anti-Met Humanized Monoclonal Antibody, Ktn0216, Is Enhanced By Igg2 Isotype In Hgf-Dependent And Met-Amplified Tumors

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PAAberrant 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