Structural insights into the mechanism of action of a biparatopic anti-HER2 antibody

Vaheh Oganesyan,Li Peng,Jared S Bee,John Li,Samuel R Perry,Frank Comer,Linda Xu,Kimberly Cook,Kannaki Senthil,Lori Clarke,Kim Rosenthal,Changshou Gao,Melissa Damschroder,Herren Wu,William Dall’Acqua

doi:10.1074/jbc.m117.818013

Abstract

Pathways of human epidermal growth factor (EGF) receptors are activated upon ligand-dependent or -independent homo- or heterodimerization and their subsequent transphosphorylation. Overexpression of these receptors positively correlates with transphosphorylation rates and increased tumor growth rates. MEDI4276, an anti-human epidermal growth factor receptor 2 (HER2) biparatopic antibody–drug conjugate, has two paratopes within each antibody arm. One, 39S, is aiming at the HER2 site involved in receptor dimerization and the second, single chain fragment (scFv), mimicking trastuzumab. Here we present the cocrystal structure of the 39S Fab–HER2 complex and, along with biophysical and functional assays, determine the corresponding epitope of MEDI4276 and its underlying mechanism of action. Our results reveal that MEDI4276's uniqueness is based first on the ability of its 39S paratope to block HER2 homo- or heterodimerization and second on its ability to cluster the receptors on the surface of receptor-overexpressing cells.

Highlights

Pathways of human epidermal growth factor (EGF) receptors are activated upon ligand-dependent or -independent homo- or heterodimerization and their subsequent transphosphorylation
The family of epidermal growth factor receptors consists of four members (HER1– 4; 1), each of which contains an extracellular domain, a single-span transmembrane helix, and an intracellular kinase domain that can interact with signaling molecules
Inhibition of human epidermal growth factor receptor 2 (HER2) activity by using mAb, antibody– drug conjugate (ADC),7 or smallmolecule kinase inhibitor approaches is frequently used as a therapy for treating HER2-positive metastatic breast cancer

Summary

Edited by Peter Cresswell

Pathways of human epidermal growth factor (EGF) receptors are activated upon ligand-dependent or -independent homo- or heterodimerization and their subsequent transphosphorylation. Inhibition of HER2 activity by using mAb, antibody– drug conjugate (ADC), or smallmolecule kinase inhibitor approaches is frequently used as a therapy for treating HER2-positive metastatic breast cancer These HER2-targeting therapies have improved the overall survival rate, there are still many more cases refractory to these treatments. An anti-HER2, biparatopic, monospecific, tetravalent ADC, MEDI4276, was developed to treat a broad range of HER2-expressing metastatic breast cancers [11] It has demonstrated antitumor efficacy in models that are refractory or ineligible to trastuzumab, pertuzumab, or T-DM1 treatment and shows promise as an effective therapy for cancer patient populations not qualified for the abovementioned treatments [11]. MEDI4276 contains four antigen-binding sites, two on each arm, that are capable of interacting with HER2 (Fig. 1B) Such a biparatopic, tetravalent, monospecific antibody was shown to induce robust receptor. These studies suggest a coherent mechanism of action for MEDI4276

Results

Multisignal sedimentation velocity analytical ultracentrifugation

Discussion

Experimental procedures