Use of isothermal calorimetry for predicting the shelf life of biologics in formulation
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Historically, drugs have mainly been small chemical compounds synthesized from natural sources. But with the advent of recombinant DNA technology, protein-based drugs, or biologics, have become a significant fraction of the pharmaceutical industry. Biologics are larger and more complex than standard small molecule drugs which gives them greater specificity and potency, but also makes them difficult to characterize and formulate. The primary issue is that at the high protein concentrations used in many formulations, biologics are prone to aggregation which can cause unsafe and painful drug administration. Common methods for characterization and analysis of protein stability and/or aggregation often require different physical or chemical conditions than those present in formulation and provide little or no predictive power, necessitating long incubation times for shelf life determination. To combat this problem and further our understanding of protein aggregation I have developed isothermal calorimetry for use in measuring the rates of unfolding and aggregation for high concentrations of protein at temperatures well below those used in traditional DSC experiments. I have compared and confirmed isothermal calorimetry results for a candidate HIV vaccine called VRC07-523LS in formulation to data obtained using other widely used experimental techniques and found that predictions of long-term stability rank order for a set of buffers correlate precisely with the results obtained using SEC. The ability to measure unfolding and aggregation rates at high protein concentrations and with relatively mild denaturing conditions results in more accurate predictions of the shelf life of biologics and allows the direct investigation of protein stability at the high concentrations used in formulations, improving our understanding of aggregation as a whole.