Rational design of a potent, long-lasting form of interferon: A 40 kDa branched polyethylene glycol-conjugated interferon alpha-2a for the treatment of hepatitis C

A potent, long-lasting form of interferon alpha -2a mono-pegylated with a 4 0 kilodalton branched poly(ethylene glycol) was designed, synthesized, and characterized. Mono-pegylated interferon a-2a was comprised of four major p ositional isomers involving Lys(31), Lys(121), Lys(131), and Lys(134) of in terferon. The in vitro anti-viral activity of pegylated interferon alpha -2 a was found to be only 7% of the original activity. In contrast, the in viv o antitumor activity was severalfold enhanced compared to interferon alpha -2a. Pegylated interferon alpha -2a showed no immunogenicity in mice. After subcutaneous injection of pegylated interferon alpha -2a, a 70-fold increa se in serum half-life and a 50-fold increase in mean plasma residence time concomitant with sustained serum concentrations were observed relative to i nterferon alpha -2a. These preclinical results suggest a significantly enha nced human pharmacological profile for pegylated interferon alpha -2a. Resu lts of Phase II/III hepatitis C clinical trials in humans confirmed the sup erior efficacy of pegylated interferon alpha -2a compared to unmodified int erferon alpha -2a.