PEGylated DX-1000: Pharmacokinetics and Antineoplastic Activity of a Specific Plasmin Inhibitor

• Main Authors: Laetitia Devy, Shafaat A. Rabbani, Mark Stochl, Mary Ruskowski, Ian Mackie, Laurent Naa, Mark Toews, Reinoud van Gool, Jie Chen, Art Ley, Robert C. Ladner, Daniel T. Dransfield, Paula Henderikx
• Format: Article
• Language: English
• Published: Elsevier 2007-11-01
• Series: Neoplasia: An International Journal for Oncology Research
• Subjects: Plasmin inhibitor; matrix metal lop roteinases; PEGylation; plasma clearance; antineoplastic agent
• Online Access: http://www.sciencedirect.com/science/article/pii/S1476558607800212

Novel inhibitors of the urokinase-mediated plasminogen (plg) activation system are potentially of great clinical benefit as anticancer treatments. Using phage display, we identified DX-1000 a tissue factor pathway inhibitor-derived Kunitz domain protein which is a specific high-affinity inhibitor of plasmin (pin) (Ki = 99 pM). When tested in vitro, DX-1000 blocks plasminmediated pro-matrix metal loproteinase-9 (proMMP-9) activation on cells and dose-dependently inhibits tube formation, while not significantly affecting hemostasis and coagulation. However, this low-molecular weight protein inhibitor (~ 7 kDa) exhibits rapid plasma clearance in mice and rabbits, limiting its potential clinical use in chronic diseases. After site-specific PEGylation, DX-1000 retains its activity and exhibits a decreased plasma clearance. This PEGylated derivative is effective in vitro, as well as potent in inhibiting tumor growth of green fluorescent protein (GFP)-labeled MDA-MB-231 cells. 4PEG-DX-1000 treatment causes a significant reduction of urokinase-type plasminogen activator (uPA) and plasminogen expressions, a reduction of tumor proliferation, and vascularization. 4PEG-DX-1000 treatment significantly decreases the level of active mitogenactivated protein kinase (MAPK) in the primary tumors and reduces metastasis incidence. Together, our results demonstrate the potential value of plasmin inhibitors as therapeutic agents for blocking breast cancer growth and metastasis.