FIELD: medicine, pharmaceutics.SUBSTANCE: group of inventions refers to biochemistry. What is presented is pegylated interferon-α2b (IFN-α2b) having a structure as shown in the patent claim. Pegylated interferon-α2b is prepared by combining IFN-α2b with branched Y-polyethylene glycol (YPEG), wherein YPEG is bound to IFN-α2b by an amide bond formed by ε-amino group of a side of Lys residue in IFN-α2b in the position of 134 in SEQ ID No. 1. A method for preparing and purifying pegylated IFN-α2b involves the stages as follows. In an alkaline medium at pH 9.0, branched Y-polyethylene glycol is reacted with IFN-α2b to prepare pegylated IFN-α2b. The prepared reaction products are recovered by an anion exchange resin, and the given products are eluted by an anion gradient to prepare modified products. The anion exchange resin is Q Sepharose FF, and the anion gradient is a chloride ion gradient. Further, the modified products are eluted by a cation exchange resin with a cation gradient. The cation exchange resin is SP Sepharose FF, and the cation gradient is a sodium ion gradient. Thereafter, each peak is collected separately. The product activity of each peak is determined to choose a peak corresponding to the reaction product having the highest activity. What is also presented is a formulation for treating a disease requiring IFN-α2b to be used, which consists of a pharmaceutically effective amount of said pegylated IFN-α2b and a pharmaceutically acceptable carrier, or an inactive substance. Pegylated IFN-α2b or the above formulation is also used for preparing a medicine for treating various diseases requiring IFN-α2b to be used.EFFECT: presented pegylated IFN-α2b has a higher specific activity of 2,65±0,185×106 IU/mg and a prolonged serum half-life.26 cl, 11 dwg, 5 tbl, 3 exГруппа изобретений относится к области биохимии. Предложен пегилированный интерферон-α2b (IFN-α2b), имеющий структуру, как указано в формуле изобретения. Пегилированный интерферон-α2b получают соеди
