Process for solubilizing glucagon-like peptide 1 compounds
Disclosed is a method of preparing a GLP-1 compound that is soluble in aqueous solution at pH 7.4 from a GLP-1 compound that is substantially insoluble in aqueous solution at pH 7.4. The insoluble GLP-1 compound is dissolved in aqueous base or in aqueous acid to form a GLP-1 solution. The GLP-1 solution is then neutralized to a pH at which substantially no amino acid racemization of the GLP-1 compounds occurs, after which the soluble GLP-1 compound is isolated from the neutralized solution.
1. A method of preparing Val 8 -GLP-1(7-37)OH [SEQ ID NO:15] that is soluble in aqueous solution at physiological pH, said Val 8 -GLP-1(7-37)OH being referred to as “soluble Val 8 -GLP-1(7-37)OH”, from Val 8 -GLP-1(7-37)OH that is insoluble in aqueous solution at physiological pH, said Val 8 -GLP-1(7-37)OH being referred to as an “insoluble Val 8 -GLP-1(7-37)OH”, said method comprising the steps of:
a) dissolving insoluble Val 8 -GLP-1(7-37)OH in aqueous base having a pH between about 12.1 to about 12.5 to form a Val 8 -GLP-1(7-37)OH solution;
b) pH-adjusting the Val 8 -GLP-1(7-37)OH solution within about thirty minutes after dissolution of Val 8 -GLP-1(7-37)OH to a pH at which substantially no amino acid racemization of the dissolved Val 8-GLP-1(7-37)OH occurs, wherein the pH is between about 7.0 to about 8.5;
c) filtering the pH-adjusted solution of step b) through a filter membrane having a porosity of between about 0.20 μm to about 0.25 μm; and
d) isolating soluble Val 8 -GLP-1(7-37)OH from the filtered solution of step c).
2. The method of claim 1 wherein the soluble Val 8 -GLP-1(7-37)OH [SEQ ID NO:15] is isolated from the filtered solution of step c) by spray drying, lyophilization or crystallization.