FIELD : medicine; pharmaceuticals.SUBSTANCE : group of inventions relates to the field of medicine, specifically to clinical pharmacology, and is intended to maintain the stability of a liquid pharmaceutical composition. Liquid pharmaceutical composition comprises a polypeptide, TRIS, phosphate, and a lyoprotectant. Said polypeptide comprises an amino acid sequence represented in SEQ ID NO : 8. Composition has pH from 5.0 to 7.5. Components are used in claimed amounts. Also provided is a solid mixture obtained by lyophilising said liquid composition. In addition, a reconstituted liquid pharmaceutical composition is provided, which is obtained by dissolving said lyophilised solid mixture in a suitable liquid medium.EFFECT : use of the group of inventions improves the stability of a liquid pharmaceutical composition by preventing the formation of undesirable polypeptide aggregates.12 cl, 22 tbl, 22 ex