(705f) Feasibility of NIR Spectroscopy for Monitoring Enzymic Digestion Process of Proinsulin Producing Insulin Glargine

Enzymic digestion is an important step in insulin glargine (IG) manufacturing. Due to the fact that proinsulin has multiple tryptic digestion sites, excessive digestion leads to lower yields and more undesirable by-products. However, analytes of interest have not been monitored in real time during digestion process and end-point of the process could not be determined accurately. In this study, feasibility of using near-infrared (NIR) spectroscopy to monitor four analytes of interest was investigated. Partial least squares (PLS) calibration models were developed using reference measurements by high performance liquid chromatography (HPLC) and in situ NIR spectra acquired continuously by an immersion probe. The achieved root mean square errors of prediction (RMSEP) were 0.06 mg/mL for intermediate product (IP), 0.06 mg/mL for IG, 0.03 mg/mL for mono-Arg impurity (mAI) and 0.05 mg/mL for isomer of IG (iso-IG). Results indicated that change trends of the four analytes were defined by the developed models, but probably with poor robustness. More variations might be involved in model calibration so that NIR spectroscopy can be utilized for digestion process monitoring and end-point determination, which contributes to increased yields and decreased by-products in this step.