Abstract 4855: AMC303 inhibits tumor growth and metastasis in animal models by targeting CD44v6, a co-receptor of multiple oncogenic receptor tyrosine kinases
Authors: Heumann Tina , Al-Rawi Vanessa , Läufer Thorsten , Augsten Martin , Matzke-Ogi Alexandra , Coutelle Oliver 
Published: August 2019

Introduction: CD44v6, a member of the CD44 family, is an essential co-receptor for c-MET, RON and VEGFR-2. The receptor tyrosine kinases (RTKs) c-MET and RON, are key players in tumorigenic pathways, are activated by the ligands HGF and MSP, respectively and homo- or heterodimerize with each other or can be autoactivated due to amplification. The RTK VEGFR-2 is critical for angiogenesis in solid epithelial tumors. The peptidergic inhibitor AMC303, which allosterically and selectively binds to CD44v6, was investigated for its inhibitory effects on ligand-induced and autophosphorylated c-MET activation, and its impact on tumor growth and metastases in vivo.

Methods: In vitro, tumor cells were incubated with AMC303 for 30 min prior to induction with an RTK-ligand. Analysis of RTK activation was carried out by Western blotting. For in vivo xenotransplantation human pancreatic tumor cells (L3.6pl) were orthotopically injected. Animals were treated with AMC303 i.p. at 0.1, 1, 10 mg/kg QOD or QWK for 3 weeks to address dose-dependency, the optimal treatment schedule was investigated with one, three or five times weekly administrations. Regression of metastases was investigated at 1 mg/kg QOD. Survival was evaluated with a dose of 1 mg/kg QOD. Immunohistochemical (IHC) analysis was performed for cleaved caspase 6, smooth muscle actin and CD31. Reduction of vessel permeability was assessed in Balb/C mice with the Miles assay and quantification of intra-tumoral FITC dextran after i.v. injection.

Results: In vitro, AMC303 inhibited c-MET, VEGFR2 and RON phosphorylation induced by their respective ligands. Notably, AMC303 inhibited c-MET activation in cells with enhanced c-MET signaling caused by the exon 14 skipping mutation, but not c-MET auto-phosphorylation due to gene amplification. In vivo, AMC303 treatment attenuated primary xenograft tumor growth and metastasis and significantly prolonged survival. IHC on treated xenograft-tumors revealed an increase in apoptosis and necrosis along with a reduction in myofibroblast infiltration, angiogenesis and vessel permeability. Pharmacokinetic properties after i.p. administration of AMC303 revealed an terminal half-life of 6h. Administration schedules of AMC303 (1mg/kg) given one, three or five times per week had no significant impact on tumor growth attenuation. AMC303 treatment could be paused for 10 days without incurring significant tumor regrowth.

Conclusions: AMC303 inhibits c-MET in vitro in a ligand-dependent fashion and in vivo significantly improved overall survival in an orthotopic pancreatic xenograft mouse tumor model. AMC303 effectively attenuated both primary and metastatic tumor growth by increasing apoptosis, reduction of angiogenesis and vascular normalization. These findings demonstrate the benefit of targeting multiple oncogenic RTK signaling pathways by AMC303.

Citation Format: Tina Heumann, Vanessa Al-Rawi, Thorsten Läufer, Martin Augsten, Alexandra Matzke-Ogi, Oliver Coutelle. AMC303 inhibits tumor growth and metastasis in animal models by targeting CD44v6, a co-receptor of multiple oncogenic receptor tyrosine kinases [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4855.