The invention is related to the pharmaceutical industry and medicine, in particular, to new PEG-interferon derivatives and the discovery of a new functionally active, highly stable conjugate of interferon to polyethylene glycol with an activity of interferon alpha, with reduced immunogenicity, with prolonged biological effects and improved pharmacokinetic parameters of general formula: (I) where: n - integral values from 227 to 10 000, so that the molecular weight of PEG is about 10 000 - 40 000 Da； m - integer >； 4； IFN- natural or recombinant polypeptide having the activity of IFN-alpha. Also, the invention is related to drugs containing the declared conjugate of the formula (I), pharmaceutical compositions containing PEG-IFN conjugate and therapeutically acceptable excipients suitable for treatment of viral infections and cancer, as well as diseases associated with primary or secondary immunodeficiency. The invention is related to the use of conjugate of formula (I) in medicinal products, which have antiviral, antiproliferative and immunomodulatory activity, to approaches for prevention and / or treatment of diseases associated with primary or secondary immunodeficiency that include administration of therapeutically effective amount of conjugate of formula (I), and to the container with such pharmaceutical composition.
