Lyophilized polyethylene oxide modified protein and polypeptide complexes with cyclodextrin

A process of preparing a lyophilized biologically active proteinaceous composition comprising the steps of:

• a) carboxylating polyethylene glycol containing less than 10% w/w non-monomethoxylated polyethylene glycol;
• b) activating said carboxylated polyethylene glycol to obtain an active polyethylene glycol ester;
• c) covalently attaching said active polyethylene glycol ester to a biologically active protein.
• d) solubilizing said covalently attached polyethylene glycol ester and said biologically active protein in an aqueous media;
• e) solubilizing cyclodextrin in said aqueous media to obtain a homogeneous solution;
• f) buffering said solution to a pH of from about 5.7 to about 6.5;
• and
• h) lyophillzing the solution.