Discovery of novel pyrido[2,3-b]pyrazine as fibroblast growth factor receptor (FGFR-1, 2, 3 & 4) kinase inhibitors with nanomolar affinity

Background: Altiratinib is a Type II switch pocket inhibitor of MET kinase as well as TIE2 and VEGFR2 kinases. This profile provides an agent that exhibits anti-tumor activity in cancers driven by MET overexpression or genomic mutation, and also blocks angiogenic and metastatic processes mediated by the tumor microenvironment. Material and Methods: Altiratinib was evaluated in MET, TIE2, and VEGFR2 biochemical studies, including evaluation in a number of MET activation mutants. Cellular activity was evaluated in tumor cell lines exhibiting MET amplification (MKN-45 gastric, EBC-1 NSCLC) or overexpression (B16/F10 melanoma; U87 glioblastoma). In vivo pharmacokinetic/pharmacodynamic studies were performed in an MKN45 xenograft model. Efficacy was demonstrated in a battery of xenograft/ allograft models including: gastric (MKN-45), melanoma (B16/F10, A375), ovarian (SKOV-3), colorectal (COLO-205), lung (EBC-1), breast (PyMT), and glioblastoma (U87). Results: Altiratinib afforded balanced inhibition of MET, TIE2, and VEGFR2 kinases in the low nM range (IC50s 2−9 nM) and blocked HGF-, ANG-, or VEGFA-induced HUVEC activation and capillary tube formation. Altiratinib retained potency versus activation loop mutant forms of MET (D1228X, Y1230X, M1250X), inhibiting all forms with IC50 24 hr after a single 10mg/kg oral dose in an MKN-45 xenograft pharmacodynamic model. Altiratinib exhibited anti-tumor activity in melanoma (B16/F10, A375), gastric (MKN-45), lung (EBC-1), colorectal (COLO-205), breast (PyMT), ovarian (SKOV-3) and GBM (U87) xenograft or allograft models. In these in vivo studies, altiratinib was shown to inhibit tumor growth, angiogenesis, invasion and/or metastasis. Altiratinib also blocked recruitment of TIE2-expressing monocytes in the PyMT breast cancer model. In some models, altiratinib was shown to increase overall survival. In particular, in the i.c.v. orthotopically implanted U87 glioblastoma model, altiratinib extended survival by 1.7-fold vs vehicle (112 days vs 66 days), while the combination of altiratinib + bevacizumab extended survival by 2.5 fold vs vehicle and by 1.9-fold vs bevacizumab single agent (166 days vs. 88 days). Conclusions: Altiratinib is a balanced inhibitor of MET, TIE2, and VEGFR2 kinases. This profile provides robust inhibition of tumors driven by MET amplification or overexpression, and also provides the potential for altiratinib to block tumor microenvironment angiogenic resistance mechanisms and pro-tumoral effects of TIE2-expressing macrophages in the clinical setting. Altiratinib is currently in Phase 1 clinical trials in patients with solid tumors.