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The purpose of this work is to study the effect of pH, buffer species, and temperature on the physicochemical stability of a humanized monoclonal antibody LA298. The study was carried out in solution state of the antibody in the presence of different buffer species at different pH values and storage temperature. No significant changes in total protein content were observed for any of the solutions with different buffers at different pH values when stored for 8 weeks at both 5 °C and 25 °C or at 37 °C for 1 week. Known asparagines (Asn55) deamidation of LA298 was found to be dependent on pH, buffer type, and temperature. The estimated rate constant of the double heavy chain Asn55 deamidation in phosphate buffer at pH 6.5 and 7.0 was much higher than that in citrate buffer under the same storage conditions. However, comparable results were obtained for single heavy chain Asn55 deamidation in citrate and phosphate buffer. Aggregation of LA298 was not significant for samples at different pH values, buffers, and temperatures as the monomer of LA298 decreased dramatically over time. Less decrease in monomeric LA298 was observed in citrate buffer, pH 5.0–5.5. In conclusion, to minimize deamidation and loss of LA298 monomer, it is important to optimize its solution pH, buffer species, and storage temperature.