Ultra-rapid cardiotoxicity of the hepatitis C virus protease inhibitor BILN 2061 in the urokinase-type plasminogen activator mouse.

BACKGROUND & AIMS: Because current therapies for chronic hepatitis C virus (HCV) infections are suboptimal and associated with severe side effects, novel treatment options are needed. A small animal model has recently been developed to study HCV infections. To examine the usefulness of this human liver-urokinase-type plasminogen activator (uPA)(+/+) severe combined immune deficient (SCID) mouse for the development of HCV-targeted drugs, we evaluated the antiviral efficacy and safety of an HCV NS3-protease inhibitor, BILN 2061.

METHODS: BILN 2061 was orally administered at clinical range doses for 4 days to SCID mice that differed in the presence of HCV infection, human hepatocyte grafts, and uPA zygosity. Treatment outcome was evaluated clinically, virologically, and morphologically. Using standard high-performance liquid chromatography-ultraviolet (HPLC-UV) methods and mass spectrometry, single-dose pharmacokinetics and multiple-dose drug exposures were analyzed. The (13)C-aminopyrine breath test was applied to compare in vivo liver function.

RESULTS: A 4-day treatment with BILN 2061 of HCV genotype-1b infected chimeric animals reduced the viral load by >100-fold, but concomitant clinical and ultrastructural signs of cardiotoxicity appeared. BILN 2061 administration to uPA-transgenic mice induced mitochondrial swelling with aberrant cristae in cardiomyocytes, but not in skeletal muscle. Because both drug accumulation and liver function were identical in affected uPA-transgenic and nontransgenic SCID mice without cardiac involvement, the urokinase plasminogen activator transgene itself appears to be implicated.

CONCLUSIONS: The human liver-uPA(+/+)SCID mouse is an interesting small animal model to evaluate the preclinical safety and efficacy of new antiviral compounds against HCV. The uPA-transgene increases the susceptibility of mice to BILN 2061-induced cardiotoxicity.