J.W. Larrick, A. Mendelsohn, V. Sharma, J. Wang, J. Fang, M. Huang, S.C. Wright

Hepatocyte growth factor (HGF) is a pleiotropic cytokine that promotes cell proliferation, motility, survival, and morphogenesis. HGF binds to its receptor c-Met tyrosine kinase and triggers signal transduction that protects cells against apoptosis and enhances cell growth for tissue regeneration. The profound effects of HGF to prevent cell death and to promote tissue regeneration make HGF an interesting drug candidate for therapeutic use. However, the activation of c-Met by HGF also leads to enhanced tumor metastasis and invasion. This pro-invasive feature of HGF has raised concerns regarding its clinical applications. It would be ideal to separate the beneficial cell-protective signals from the pro-invasive signals of HGF. To test this possibility, Michieli et al., (Nature Biotechnology 20:488; 2002) created a recombinant single-chain chimera consisting of a truncated HGF alpha chain and a truncated MSP (macrophage-stimulating protein, a cytokine with high homology to HGF) alpha-chain linked by a short polypeptide linker, termed Metron factor-1 or MF-1. This chimeric HGF−MSP protein binds to the HGF receptor c-Met and the MSP receptor Ron independently and elicits a biological signal only through Met−Ron heterodimerization. MF-1 prevents liver or renal damage and enhances liver or kidney regeneration, without inducing tumor metastasis and growth. MF-1 has a short plasma half-life (one hour) and is not suitable for development as therapeutic agent with the common i.v. or s.c. administration routes. However, it does provide a unique approach to separate the beneficial organ-protective signaling from undesired pro-invasive signals in HGF-Met pathway. Based on this work we designed and constructed a number of novel heterodimeric Fc fusion proteins (“trophokines”) that can induce Met-Ron heterodimerization. Each of our novel trophokines contains an HGF-Fc and MSP-Fc fusion protein, which form heterodimers through the knobs-to-holes designed into the CH3 domains of their IgG1 Fc regions. Because of this unique design, each trophokine protein contains one c-Met binding site and one Ron binding site to induce c-Met and Ron heterodimerization. These newly designed molecules prevent target cell apoptosis and promote tissue regeneration. By eliminating the pro-invasive or scattering effects of HGF on cells, these novel proteins do not promote tumor metastasis or tumor growth. Most importantly, these novel trophokines have significantly improved plasma half-life and facile manufacturing, purification, and other downstream development processes. These novel proteins are likely to provide therapeutic benefit to patients in a wide range of pathological conditions, such as liver cirrhosis, liver fibrosis, renal failure, wound healing, and chemotherapy-induced liver or renal damage. We have successfully expressed four designed trophokine fusion proteins and the results of preclinical biochemical and biological studies will be presented.

Keywords (Optional):