Abstract 5624: Anti-c-Met Nanobody®: A potential new drug in cancer treatment.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC c-Met is the tyrosine kinase receptor of the hepatocyte growth factor (HGF). HGF-c-Met signaling is involved in a wide variety of human malignancies including colon, gastric, bladder, breast, ovarian, pancreatic, kidney, liver, lung, head and neck, thyroid, and prostate cancers, as well as sarcomas, hematological malignancies, melanoma and central nervous system tumors. In recent years, multiple agents have been developed directed to interfere at different levels in the HGF-c-Met signaling pathway, and some are currently being tested in Phase II and/or III clinical trials. Nanobodies® are therapeutic proteins based on the smallest functional fragments of heavy chain antibodies, occurring in the Camelidae family. Importantly, they retain the full antigen-binding capacity of the original heavy chain only antibodies and are highly stable. In this study, we examined the anti-cancer effects of an anti-c-Met Nanobody in vitro using human multiple myeloma as a model system. The anti-c-Met Nanobody comprises of two Nanobody moieties, one targeting c-Met and one binding to human serum albumin for half-life extension. HGF is thought to contribute to the pathogenesis of multiple myeloma in different ways, as HGF is a pivotal growth and pro-migratory factor and inhibits osteoblastogenesis in vitro suggesting that HGF may contribute to the development of myeloma bone disease. Elevated levels of HGF in serum of multiple myeloma patients are correlated with a poor prognosis. We show that the anti-c-Met Nanobody effectively inhibited the proliferation of ANBL-6 human multiple myeloma cells via inhibition of an HGF autocrine growth loop, as well as the proliferation of INA-6 cells induced by exogenously added HGF. In addition, the HGF-induced migration of INA-6 cells was completely and specifically blocked following treatment with the Nanobody at a concentration of 1 μM. The Nanobody also inhibited the HGF-induced adhesion of multiple myeloma cells to fibronectin, but did not affect stromal cell-derived factor-1 alpha-induced adhesion. Furthermore, the Nanobody abolished the inhibiting effect of HGF on bone morphogenetic protein-2-induced ALP-activity and the mineralization of human mesenchymal stem cells. Finally, we show that the Nanobody reduced the HGF mediated phosphorylation of the c-Met Tyrosine (Y) residues Y1349, Y1234/1235 and Y1003 and the phosphorylation of the downstream proteins MAPK and Akt in INA-6 cells. In conclusion, the anti-c-Met Nanobody inhibited c-Met signaling with high specificity and potency resulting in inhibition of multiple myeloma cell migration, proliferation and adhesion, and in blocking of the HGF mediated inhibition of osteoblastogenesis. Given the potential of Nanobodies to surpass drawbacks of antibodies, this anti-c-Met Nanobody might represent a potential novel therapeutic agent in the treatment of multiple myeloma and other cancers driven by HGF-c-Met signaling. Citation Format: Tobias S. Slordahl, Tinneke Denayer, Siv Helen Moen, Therese Standal, Magne Borset, Cedric Ververken, Torstein B. Ro. Anti-c-Met Nanobody®: A potential new drug in cancer treatment. [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 5624. doi:10.1158/1538-7445.AM2013-5624