The design of analytical methods for use in topical epidermal growth factor product development

Data from a reverse phase gradient elution HPLC assay for human epidermal growth factor (EGF) was compared and correlated with data obtained from a competitive heterogeneous radioimmunoassay (RIA). The RIA was established to measure very low concentrations of EGF in formulation drug release and compatibility studies. The HPLC assay, capable of resolving parent and possible modified or fragmented forms of EGF isolated from human urine, was studied as a potential development tool for stability and final product evaluation. As independent analytical methods, the HPLC and the RIA procedures produced correlated results when quantifying freshly prepared and certain degraded samples of EGF. The capacity of the HPLC method to serve as a stability indicating assay was examined. Degradation of EGF was induced by storage in 0.05 M phosphate buffer pH 7.4 at 25, 37 or 50 degrees C. The same three degradation products were detected at each temperature by the HPLC method, one of which was identified as L-isoaspartyl EGF.