Controlled release interferon drug products and treatment of HCV infections using same

A method of treating acute or chronic hepatitis C comprising administering to treatment naive subjects in need thereof a controlled release formulation comprising a microsphere comprising a biodegradable polymer and interferon-α2b encapsulated by or dispersed in the biodegradable polymer, wherein the Cmax of said interferon-α2b in the blood plasma is reached after about 48 hours after initial administration of the formulation and said formulation is administered no more than once every two weeks, wherein the interferon-α2b is present in an amount of about 0.2 wt % to about 10 wt % of the microsphere and at least about 100 MIU per dose, wherein said formulation is administered in combination therapy with ribavirin, wherein at least 80% of the subjects exhibit more than two log reduction in HCV RNA 12 weeks after initial administration of the formulation, and wherein greater than 80% of the flu-like symptoms that occur in the subjects are mild.