Differentiation between the EGFR antibodies necitumumab (Neci), cetuximab (Cetux), and panitumumab (Pan): Glycosylation and IgE reactivity.

Abstract

e13023 Background: Cetux, Pan and Neci are monoclonal antibodies (mAb) against the human EGFR. Hypersensitivity reactions (HSR) to Cetux have been linked to preexisting anti-α-Gal IgE, suggesting that IgE reactivity to biologics may predict HSR. This study evaluated the levels of α-Gal and N-glycolyl neuraminic acid (NGNA) expressed by Cetux, Pan and Neci, and assessed the reactivity of the three mAb with normal human serum IgE. Methods: To evaluate the levels of α-Gal and NGNA expressed by Cetux, Pan and Neci, the N-linked oligosaccharides were released by PNGase F from the mAb and analyzed by NP-HPLC and MALDI-TOF mass spectrometry. A sensitive electrochemiluminescent assay was developed to detect drug-specific IgE in human serum. Results: Cetux has the highest expression of α-Gal and NGNA. Neci has at least 10 fold less α-Gal or NGNA and Pan has no detectable amount. Sixty lots of serum from individual normal donors from Tennessee were screened for IgE reactivity with mAb either expressing α-Gal and NGNA (Cetux and mab1) or not (mab2). Fifteen serum lots exhibited high IgE reactivity with Cetux and mab1 but minimal reactivity with mab2, and were designated high IgE. The rest of serum lots showed minimal reactivity with the three mAb and were designated low IgE. Fifteen serum lots from each group were used to assess the IgE reactivity to the mAb. Cetux exhibited high reactivity with each lot of the high IgE sera, while Pan and Neci had minimal reactivity. All three mAb did not exhibit any significant reactivity with the low IgE sera. An α-Gal compound, GN334, abolished Cetux-mediated IgE signal completely, indicating that the IgE is specific for α-Gal. GN334 had little or no effect on Pan- and Neci-mediated IgE signal. In comparison, GN334 did not have effect in the low IgE sera across mab tested. Conclusions: High expression of α-Gal and NGNA was detected on Cetux compared to low or no expression by Neci and Pan respectively. IgE reactivity data correlated with the glycosylation expression levels and suggest that Neci and Pan have no or little reactivity against human serum IgE in comparison to Cetux. Further studies are warranted to determine if this leads to a lower incidence of HSR.