Stability of rhbFGF as determined by UV spectroscopic measurements of turbidity

Loss of potency of a protein formulation due to precipitation of the protein is a major concern to the pharmaceutical scientist. A simple screening method was developed to study the effect of excipients on protein precipitation. It will not provide accurate stability data but it allows the rejection of excipients that may interfere with the stability of a protein formulation. The method is based on measuring the increase in turbidity at 277 nm by UV-spectroscopy and was sensitive and reproducible enough to obtain data within 15 hr at 30 degrees C or 40 degrees C, which will allow prediction of precipitation behavior that would need with conventional methods 2-3 years. Human recombinant basic fibroblast growth factor (rhbFGF or bFGF) was formulated at various pH-values as well as in the presence of various concentrations of preservatives, surfactants, gelling agent, EDTA, NaCl, sodium sulfate, sucrose, and glycosaminoglycans (GAG). Most excipients increased bFGF aggregation rate when their concentrations were increased. Exceptions were heparin and some of its derivatives, and sodium sulfate; high concentrations of sucrose and sodium chloride suppressed aggregation.