N-Terminally PEGylated Human Interferon-β-1a with Improved Pharmacokinetic Properties and in Vivo Efficacy in a Melanoma Angiogenesis Model

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Abstract
PEGylation of IFN-α has been used successfully to improve the pharmacokinetic properties and efficacy of the drug. To prepare a PEGylated form of human interferon-β-1a (IFN-β-1a) suitable for testing in vivo, we have synthesized 20 kDa mPEG-O-2-methylpropionaldehyde and used it to modify the N-terminal α-amino group of the cytokine. The PEGylated protein retained ∼50% of the activity of the unmodified protein and had significantly improved pharmacokinetic properties following intravenous administration in rats. The clearance and volume of distribution at steady state were reduced ∼30-fold and ∼4-fold, respectively, resulting in a significant increase in systemic exposure as determined by the area under the curve. The elimination half-life of the PEGylated protein was ∼13-fold greater than for the unmodified protein. The unmodified and PEGylated proteins were tested for their ability to inhibit the formation of radially oriented blood vessels entering the periphery of human SK-MEL-1 melanoma tumors in athymic nude homozygous (nu/nu) mice. In a single dose comparison study, administration of 1 × 106 units of unmodified IFN-β-1a resulted in a 29% reduction in vessel number, while 1 × 106 units of PEGylated IFN-β-1a resulted in a 58% reduction. Both treatments resulted in statistically significant reductions in mean vessel number as compared to the vehicle (control)-treated mice, with the PEGylated IFN-β-1a-treated mice showing a statistically significantly greater reduction in mean vessel number as compared to the unmodified IFN-β-1a-treated mice. In a multiple versus single dose comparison study, daily administration of 1 × 106 units of unmodified IFN-β-1a for 9 days resulted in a 51% reduction in vessel number, while a single dose of 1 × 106 units of the PEGylated protein resulted in a 66% reduction. Both treatments resulted in statistically significant reductions in mean vessel number as compared to the vehicle-treated mice, with the PEGylated IFN-β-1a-treated mice showing a statistically significantly greater reduction in mean vessel number as compared to the unmodified IFN-β-1a-treated mice. Therefore, the improved pharmacokinetic properties of the modified protein translated into improved efficacy. Since unmodified IFN-β is used for the treatment of multiple sclerosis and hepatitis C virus infection, a PEGylated form of the protein such as 20 kDa mPEG-O-2-methylpropionaldehyde-modified IFN-β-1a may serve as a useful adjunct for the treatment of these diseases. In addition, the antiangiogenic effects of PEGylated IFN-β-1a may be harnessed for the treatment of certain cancers, either as a sole agent or in combination with other antitumor drugs.