Stabilization of recombinant interferon-α by pegylation for encapsulation in PLGA microspheres

Interferon-alpha (IFN) was pegylated and encapsulated in biodegradable microspheres to achieve a long-acting formulation. IFN was pegylated with methoxy-polyethylene glycol (mPEG, MW 2000 or 5000). The conjugation procedures were optimized in terms of concentration of the reactants and the pH condition of the medium. The conjugates (IFN-mPEG(2000) and IFN-mPEG(5000)) were characterized using SDS-PAGE, size-exclusion-HPLC (SE-HPLC) and matrix-assisted laser desorption and ionization time-of-flight (MALDI-TOF) mass spectroscopy. The optimized IFN-mPEG conjugates consisted of mono- and multi-pegylated derivatives along with a small amount of native IFN (less than or equal to5%). In the simulation studies for microencapsulation, pegylated IFN showed better stability when exposed to dichloromethane as compared to native IFN. In vitro release profiles of IFN and IFN-mPEG from biodegradable poly(D,L-lactide-co-glycolide) microspheres were quite different. Native IFN was released only 16.3 +/- 0.4% after 3 weeks, but IFN-mPEG(2000) and IFN-mPEG(5000) were released 72.5 +/- 2.1 and 56.8 +/- 2.5%, respectively after the same period. It was found that in contrast to native IFN, the pegylated IFN was able to largely retain its native aqueous solubility after being exposed to detrimental conditions of microencapsulation, resulting in a continuous release in vitro. These studies show the possibility of preparation of a long-acting dosage form for IFN using a combination of pegylation and microencapsulation techniques. (C) 2002 Elsevier Science B.V. All rights reserved.