Formation of Human IFN-β Complex with the Soluble Type I Interferon Receptor IFNAR-2 Leads to Enhanced IFN Stability, Pharmacokinetics, and Antitumor Activity in Xenografted SCID Mice

Interferon-β (IFN-β) is biologically unstable under physiologic conditions in vitro and is cleared rapidly from the bloodstream on administration in vivo. In the present study, we demonstrate that a soluble recombinant form of the type I IFN receptor subunit, sIFNAR-2, can neutralize the bioactivity of type I IFNs at high concentrations and, at lower concentrations, causes an enhancement of IFN-β-mediated antiviral activity. The in vitro enhancement is due to the specific interaction of IFN-β with sIFNAR-2, followed by dissociation of IFN-β from the complex over time in culture. In vivo, the serum half-life of IFN-β is extended from minutes to hours when administered intravenously in mice as a sIFNAR-2-associated complex. Moreover, the antitumor effect of IFN-β is increased by between 9-fold and 27-fold when injected as an sIFNAR-2-associated complex, as demonstrated by an increase in the mean survival time of immunodeficient mice challenged with human Burkitt lymphoma cell (Daudi) xenografts (sIFNAR-2-complexed vs. free IFN-β treatment). These results show that on association with sIFNAR-2, IFN-β is more stable in vitro and exhibits increased efficacy when administered in vivo. Administration as a complex with sIFNAR-2 may, therefore, provide a method of enhancing the delivery and effectiveness of type I IFNs.