Identification and Activity Study of an Impurity Band Observed in the nrSDS-PAGE of Aflibercept

Aflibercept is a biopharmaceutical targeting vascular endothelial growth factor (VEGF) that has shown promise in the treatment of neovascular age-related macular degeneration (nAMD) and diabetic macular edema (DME) in adults. Quality control studies of aflibercept employing non-reduced SDS-PAGE (nrSDS-PAGE) have shown that a significant variant band (IM1) is consistently present below the main band. Considering the quality control strategy of biopharmaceuticals, structural elucidation and functional studies are required.

In this study, the variant bands in nrSDS-PAGE were collected through electroelution and identified by peptide mass fingerprinting based on liquid chromatography-tandem MS (LC–MS/MS). This variant was expressed using knob-into-hole (KIH) design transient transfection for the detection of ligand affinity, binding activity and biological activity.

The variant band was formed by C-terminal truncation at position N99 of one chain in the aflibercept homodimer. Then, this variant was successfully expressed using KIH design transient transfection. The ligand affinity of the IM1 truncated variant was reduced by 18-fold, and neither binding activity nor biological activity were detected.

The efficacy of aflibercept is influenced by the loss of biological activity of the variant. Therefore, this study supports the development of a quality control strategy for aflibercept.