| abstract |
The invention also provides a process for preparing a composition comprising: preparing a mixture of polypeptides, wherein each polypeptide in the mixture .(a) is a copolymer of the amino acids L-alanine, L-glutamic acid, L-tyrosine and L-lysine, and (b) may be present in the form of a pharmaceutically acceptable salt; and wherein in the mixture 13% to 38% of the polypeptides have a diethylamide group instead of a carboxyl group present at one end thereof; determining the average molecular weight of the polypeptides in the mixture by size exclusion chromatography on a gel permeation chromatography column calibrated using a plurality of copolymers of defined sequence and molecular weight; and including in the composition only those polypeptide mixtures determined to have an average molecular weight between 13,500 and 18,500 Daltons, wherein each of the copolymers is a polypeptide consisting of L-alanine, L- glutamic acid, L-tyrosine and L-lysine with a defined molecular weight between 12,000 and 30,000 Daltons, and a process for making same. |