Characterization of Charge Variant Profile of Non-Cleavable Conjugated Antibodies

The objective of this work was to study the charge variant profile of some monoclonal antibodies (mAbs) conjugated to maytansine derivative (mAb-1) or tomaymycin molecules (mAb-2 and mAb-3) via non-cleavable linkers. The imaging capillary isoelectric focusing method (icIEF) was emolpyed for this purpose. Initially, the charge variant profiles were determined for the three naked mAbs. The analysis revealed that these mAbs exhibited major species as well as minor species. Specifically, mAb-1 and mAb-2 displayed two charge species (pI values: 9.00 and 8.95). In the case of mAb-3, a main charge variant (pI values: 8.50) along with two minor charge species (pI values: 8.30 and 8.60) were observed. The investigated non-cleavable conjugates were less homogen and less basic than corresponding naked antibodies. pI values ranged from 7.4 to 8.9 for the non-cleavable mAb-1 maytansinoid conjugates (∆pI: 1.4), from 8.2 to 8.9 (∆pI: 0.7) for the non-cleavable mAb-2 tomaymycin conjugates, and 7.4 to 8.4 (∆pI: 1) for the mAb-3 conjugates. The icIEF profiles of both naked mAbs and ADCs showed good intra-day and inter-day repeatability.