Molecular Basis for Necitumumab Inhibition of EGFR Variants Associated with Acquired Cetuximab Resistance

Abstract

Acquired resistance to cetuximab, an antibody that targets the EGFR, impacts clinical benefit in head and neck, and colorectal cancers. One of the mechanisms of resistance to cetuximab is the acquisition of mutations that map to the cetuximab epitope on EGFR and prevent drug binding. We find that necitumumab, another FDA-approved EGFR antibody, can bind to EGFR that harbors the most common cetuximab-resistant substitution, S468R (or S492R, depending on the amino acid numbering system). We determined an X-ray crystal structure to 2.8 Å resolution of the necitumumab Fab bound to an S468R variant of EGFR domain III. The arginine is accommodated in a large, preexisting cavity in the necitumumab paratope. We predict that this paratope shape will be permissive to other epitope substitutions, and show that necitumumab binds to most cetuximab- and panitumumab-resistant EGFR variants. We find that a simple computational approach can predict with high success which EGFR epitope substitutions abrogate antibody binding. This computational method will be valuable to determine whether necitumumab will bind to EGFR as new epitope resistance variants are identified. This method could also be useful for rapid evaluation of the effect on binding of alterations in other antibody/antigen interfaces. Together, these data suggest that necitumumab may be active in patients who are resistant to cetuximab or panitumumab through EGFR epitope mutation. Furthermore, our analysis leads us to speculate that antibodies with large paratope cavities may be less susceptible to resistance due to mutations mapping to the antigen epitope. .

Clinical relevance of circulating tumor DNA assessed through deep sequencing in patients with metastatic colorectal cancer

“…In contrast, ctDNA of 13 patients showed the presence of RAS mutations that were not detected on tissue, and they were likely to have received anti‐EGFR inhibitor therapy before or at the time of liquid biopsy (11 cases; 84.6%, Table (upper)) compared to those without RAS mutation in both plasma and tissue (29 out of 47 cases; 61.7%, Table ) . As one of the mechanisms of acquiring resistance to anti‐EGFR therapy for CRC, point mutation in extracellular domain of EGFR (S492R) has been reported to make resistant to this therapy, and amplification of receptor tyrosine kinase genes such as ERBB2 or MET is also associated with acquiring resistance to anti‐EGFR inhibitor . Furthermore, resistance to anti‐EGFR inhibitors is related to constitutive activation of signaling pathways downstream of EGFR including KRAS , NRAS , and BRAF .…”

Inhibition of MEIS3 Generates Cetuximab Resistance through c-Met and Akt

“…Part of the cetuximab resistance was due to compensation by the NF- κ B pathway [ 21 ]. Most of the secondary resistance was due to mutations in EGFR [ 22 ].…”

Case Reports of DRESS Syndrome and Symptoms Consistent with DRESS Syndrome Following Treatment with Recently Marketed Monoclonal Antibodies

“…The reported overall cutaneous adverse events were significantly high for necitumumab. Molecularly, necitumumab's large paratope cavities are speculated to make it less susceptible to resistance through EGFR epitope mutation [37], a characteristic which could theoretically be a contributing factor to latent cutaneous adverse effects. In treatment with daclizumab, observed cutaneous adverse events are likely related to the immunomodulatory effects it exerts on innate lymphoid cells, including natural killer cells [38].…”