Abstract LB-316: The anti-c-Met Nanobody®, a novel and promising anti-cancer therapeutic.
Authors: Denayer Tinneke , Stöhr Thomas , Beste Gerald , Brige Ann , Ververken Cedric , Holz Josefin-Beate 
Published: August 2014

Abstract
The hepatocyte growth factor (HGF) and its receptor, c-Met, are implicated in many human cancers to promote tumor proliferation, migration, invasion and angiogenesis. Dysregulation of the HGF/c-Met pathway is known to correlate with poor prognosis. In recent years, multiple anti-cancer agents have been developed interfering at different levels in the HGF/c-Met pathway. Here, we investigated the in vitro and in vivo efficacy of a novel Nanobody effectively antagonizing c-Met. Nanobodies are therapeutic proteins based on the smallest functional fragments of heavy chain antibodies, naturally occurring in Camelidae. The Nanobody platform allows designing modular drugs, including multivalent, biparatopic and bifunctional molecules. The anti-c-Met Nanobody is a bispecific Nanobody that comprises two building blocks, one targeting c-Met and one binding human serum albumin for half-life extension purposes. In vitro characterization revealed that the Nanobody is able to specifically and completely inhibit HGF/c-Met interaction with high potency in an ELISA-based assay. In addition, the anti-c-Met Nanobody was able to completely block the HGF-dependent c-Met-phosphorylation in the A549 non-small cell lung cancer cell line. Importantly, no agonistic activity was observed in absence of HGF, as the Nanobody was designed to have a monovalent interaction with c-Met. Next, the in vivo effect was translated towards a potent in vivo effect. The anti-tumor efficacy of the anti-c-Met Nanobody was assessed in xenograft mouse models in which autocrine U87MG (HGF+, c-Met+) glioblastoma cells, or autocrine KP4 (HGF+, c-Met+) pancreatic carcinoma cells were subcutaneously injected. In the U87MG xenograft model, Nanobody treatment (10 mg/kg i.p 3x/week) resulted in significant tumor growth inhibition compared to vehicle and sustained tumor growth suppression after cessation of the treatment. Treatment with the anti-c-Met Nanobody in the KP4 xenograft model (10 mg/kg i.p 3x/week) led to a significant tumor growth inhibition and even tumor regression. In the latter model, serum levels of soluble c-Met, IL-8 and HGF were shown to be significantly reduced upon Nanobody treatment, which could make these markers attractive as potential translational pharmacodynamics biomarkers. Furthermore, the ratio of tyrosine phosphorylated c-Met over total c-Met levels was significantly lower in KP4 tumors treated with Nanobody versus vehicle. It could be postulated based on literature data that the anti-c-Met Nanobody, by possessing an anti-albumin Nanobody building block, has the potential to show superior tumor penetration than c-Met targeting antibodies. Hence, the anti-c-Met Nanobody might be a valuable novel biological for the treatment of cancer driven by HGF-c-Met signaling.
Citation Format: Tinneke Denayer, Thomas Stöhr, Gerald Beste, Ann Brige, Cedric Ververken, Josefin-Beate Holz. The anti-c-Met Nanobody®, a novel and promising anti-cancer therapeutic. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-316. doi:10.1158/1538-7445.AM2013-LB-316