A validated capillary electrophoresis method to check for batch-to-batch consistency during recombinant human glycosylated interleukin-7 production campaigns

This work reports the validation of a simple CZE method to be used in quality control of recombinant human glycosylated interleukin-7 (rhIL-7) batches produced in Chinese Hamster Ovary (CHO) cells. The separation buffer was a 25 mM sodium borate at pH 10 containing 12 mM diaminobutane (DAB) used as a dynamic coating agent of the capillary. This method allowed the separation of seven peaks ranging from low to high sialylated glycoforms. An extensive study on conditioning methods of the capillary has been conducted to yield repeatable results. Excellent RSD of EOF mobility (less than 0.6%) was obtained when conditioning included capillary equilibration under virtual analyses and storage in 0.1 M NaOH overnight. Method specificity has been demonstrated to be able to discriminate different rhIL-7 glycoforms produced in CHO from formulation matrix. Linearity was demonstrated between 0.5 and 4 mg/mL. LOQ was 0.5 mg/mL. Repeatability (RSD < 1.4 and 3.3% for tm and A%, respectively), intermediate precision of inter-day (RSD < 2.1 and 4.5), inter-analyst (RSD < 2.0 and 3.0) and inter-equipment (RSD < 3.8 and 3.7 for electrophoretic mobility and A%, respectively) were all very satisfactory. Evaluation of robustness revealed that pH and DAB concentration are critical parameters in the method while slight alteration of ionic strength of electrolyte or change of capillary source did not affect the results. Finally the method was shown to provide reliable informations to address comparability studies and batch-to-batch consistency of biomanufactured rhIL-7.