Patent ID: 7495072

Claim:
A process for obtaining a pharmaceutical composition containing a mixture of polypeptides which do not all have the same amino acid sequence, where each polypeptide consists essentially of alanine, glutamic acid, tyrosine and lysine, and wherein the mixture has a desired average molecular weight, which comprises i) treating a solution of hydrobromic acid in acetic acid with a bromine scavenger so as to prepare a treated hydrobromic acid in acetic acid solution, and ii) a) polymerizing N-carboxyanhydrides of tyrosine, alanine, y-benzyl glutamate and N-trifluoroacetyl lysine to form a mixture of protected polypeptides; b) deprotecting the protected polypeptides with the treated hydrobromic acid in acetic acid solution prepared in part i), to form a mixture of trifluoroacetyl polypeptides; c) reacting the mixture of trifluoroacetyl polypeptides with aqueous piperidine to form a solution of aqueous mixture of polypeptides, each of which consists essentially of alanine, glutamic acid, tyrosine and lysine; and d) purifying the mixture of polypeptides.