Innate or acquired resistance represents a major limitation of targeted cancer therapy. The broader goal of this application is to develop drugs that prevent resistance to targeted therapy in lung cancer patients. In addition to cell-autonomous mechanisms of resistance, factors in the tumor microenvironment have been shown to block the response to therapy. The microenvironment-mediated resistance to targeted therapy is frequently mediated by Hepatocyte Growth Factor (HGF) which activates its receptor, MET, expressed on cancer cells. The rate-limiting step in HGF/MET signaling is the proteolytic activation of pro-HGF by one of the three serine proteases, matriptase, hepsin or HGFA. To mimic the activity of the endogenous HGF Activator Inhibitors, HAI- 1 and HAI-2, we developed ?triplex? inhibitors of hepsin, matriptase and HGFA from two chemical series of ketobenzothiazole (Kbts) and cyclic urea benzamidines (Cubs). We confirmed that these compounds, just like HAIs, block pro-HGF activation and thus refer to them as synthetic HAIs (sHAIs). Our strong preliminary data confirmed that sHAIs inhibit HGF/MET signaling, prevent HGF-mediated scattering, migration and survival of cancer cells. In addition, we demonstrated that sHAIs overcome therapeutic resistance to marketed drugs which target EGFR or MET in vitro. The goal of this application is to identify sHAI with optimal pharmacological properties and to provide evidence that the lead sHAI prevents/overcomes resistance to targeted therapy in animal models of lung cancer. Because murine HGF does not activate human MET expressed on human cancer cells, all in vivo experiments will be performed in human HGF knock-in mice (hHGF KI) on a SCID background.
Our specific aims are:
Specific aim 1 : To characterize lead sHAIs for their pharmacokinetic properties in vitro and in vivo, and dose- dependent toxicity mice. a) Determine metabolic stability, solubility, plasma protein binding, half-life and clearance of lead sHAIs that have the best combination of potency and target selectivity. b) Perform maximum tolerated dose (MTD) studies on selected sHAIs to prioritize two compounds for in vivo efficacy studies.
Specific aim 2 : To demonstrate that prioritized sHAIs exert anticancer activity in animal models of lung cancer and overcome resistance to targeted therapy. a) Demonstrate that two lead sHAIs inhibit HGF-dependent tumor formation, using H596 lung cancer cells that form tumors only in the presence of HGF, such as in human HGF knockin mice. b) Show that sHAI overcomes HGF-dependent resistance of lung cancer cells to EGFR inhibitors and to MET kinase inhibitors in hHGF knockin mice. Collectively, these studies will provide a rationale to include sHIAs into treatment regimens to prevent or to overcome HGF-dependent resistance to targeted therapy, and to improve the treatment outcome in lung cancer patients, who do not respond to standard therapy.
Targeted cancer therapies are a new class of anticancer drugs that inhibit targets which are specifically up-regulated or activated in tumors, thus minimizing the damage to normal cells. While cancer patients initially respond to targeted therapy, rapidly acquired resistance to kinase inhibitors remains one of the biggest challenges in the treatment of lung cancer patients. Increased production of Hepatocyte growth factor (HGF) is a common mechanism of this resistance. Accordingly, levels of HGF are elevated in the tumor microenvironment and in the sera of lung cancer patients that fail to respond to targeted therapy. Currently, there is no approved drug that would target HGF. ProteXase Therapeutics is developing the first small molecule inhibitors of HGF activation, Synthetic HGF Activator Inhibitors (sHAIs). We have shown that sHAIs have potent anticancer activity and can overcome resistance to EGFR and MET- targeted therapeutic agents in colon and lung cancer cell lines. The objective of this project is to confirm that lead sHAIs are capable of preventing resistance to these therapies in mouse models of lung cancer; a necessary step in enabling the drug development of sHAIs as a more effective treatment option for lung cancer patients.
