Nimotuzumab, an Antitumor Antibody that Targets the Epidermal Growth Factor Receptor, Blocks Ligand Binding while Permitting the Active Receptor Conformation

Abstract

Overexpression of the epidermal growth factor (EGF) receptor (EGFR) in cancer cells correlates with tumor malignancy and poor prognosis for cancer patients. For this reason, the EGFR has become one of the main targets of anticancer therapies. Structural data obtained in the last few years have revealed the molecular mechanism for ligand-induced EGFR dimerization and subsequent signal transduction, and also how this signal is blocked by either monoclonal antibodies or small molecules. Nimotuzumab (also known as h-R3) is a humanized antibody that targets the EGFR and has been successful in the clinics. In this work, we report the crystal structure of the Fab fragment of Nimotuzumab, revealing some unique structural features in the heavy variable domain. Furthermore, competition assays show that Nimotuzumab binds to domain III of the extracellular region of the EGFR, within an area that overlaps with both the surface patch recognized by Cetuximab (another anti-EGFR antibody) and the binding site for EGF. A computer model of the Nimotuzumab-EGFR complex, constructed by docking and molecular dynamics simulations and supported by mutagenesis studies, unveils a novel mechanism of action, with Nimotuzumab blocking EGF binding while still allowing the receptor to adopt its active conformation, hence warranting a basal level of signaling. [Cancer Res 2009;69(14):5851-9]

A fibronectin scaffold approach to bispecific inhibitors of epidermal growth factor receptor and insulin-like growth factor-I receptor

“…The Adnectin binding site overlaps with the EGF and TGFα binding sites on EGFR, but not with the cetuximab or nimotuzumab binding sites, which are in domain III. 34,35 Biacore experiments using sequential injections of the EGFR, bispecific Adnectin and IGF-IR demonstrated that bispecific Adenctin is capable of binding to EGFR and IGF-IR at the same time (Fig. 5B).…”

Lonely killers

“…Both mAbs bind to the EGFR, which is a validated target for cancer immunotherapy. 73 Nimotuzumab has a lower affinity, 74 and coincidently the adverse effects (mainly a skin rash) it provokes are much less serious compared with those of cetuximab. [75][76][77] Non-mutually exclusive hypotheses have been offered to explain its toxicity profile, including its preferential accumulation in tumor tissues, which have a higher antigen density; 75 the need of bivalent binding for exertion of its activity; 78 and its unique binding site on the EGFR extracellular domain III.…”

“…[75][76][77] Non-mutually exclusive hypotheses have been offered to explain its toxicity profile, including its preferential accumulation in tumor tissues, which have a higher antigen density; 75 the need of bivalent binding for exertion of its activity; 78 and its unique binding site on the EGFR extracellular domain III. 74 Nevertheless, in the case of 14F7 mAb-induced cell death, affinity plays a central role. Evidences of an affinity maturation process were found in 14F7 mAb variable region.…”

Temperature and Stretching Effects on Complementarity Determining Regions (CDRs) Conformation and Stability of Nimotuzumab F(ab)-Fragment

“…Although nimotuzumab is not included in the 12 antibodies which have been approved by the Food and Drug Administration (FDA), its use would be interesting because of the absence of side effects such as skin rashes [3,10]. This is in contrast to the use of other of monoclonal antibodies targeting EGFR which cause skin rashes in every use [11,12].…”