Molecular basis for antagonistic activity of anifrolumab, an anti-interferon–α receptor 1 antibody

Abstract

Anifrolumab (anifrolumab) is an antagonist human monoclonal antibody that targets interferon a receptor 1 (IFNAR1). Anifrolumab has been developed to treat autoimmune diseases and is currently in clinical trials. To decipher the molecular basis of its mechanism of action, we engaged in multiple epitope mapping approaches to determine how it interacts with IFNAR1 and antagonizes the receptor. We identified the epitope of anifrolumab using enzymatic fragmentation, phage-peptide library panning and mutagenesis approaches. Our studies revealed that anifrolumab recognizes the SD3 subdomain of IFNAR1 with the critical residue R 279 . Further, we solved the crystal structure of anifrolumab Fab to a resolution of 2.3 A . Guided by our epitope mapping studies, we then used in silico protein docking of the anifrolumab Fab crystal structure to IFNAR1 and characterized the corresponding mode of binding. We find that anifrolumab sterically inhibits the binding of IFN ligands to IFNAR1, thus blocking the formation of the ternary IFN/ IFNAR1/IFNAR2 signaling complex. This report provides the molecular basis for the mechanism of action of anifrolumab and may provide insights toward designing antibody therapies against IFNAR1.

Overview of pathophysiology and treatment of human lupus nephritis

“…Anifrolumab, a human monoclonal antibody against the interferon α receptor 1(56), is currently being studied as a potential new therapy for lupus. A phase II open label trial in 17 Japanese patients with SLE showed that anifrolumab suppressed interferon gene signatures in 85% of patients at the 300 mg dose at day 169 and 95% of patients in the 1000 mg dose at day 85 without any safety signals(57).…”

Robust Antibody–Antigen Complexes Prediction Generated by Combining Sequence Analyses, Mutagenesis, In Vitro Evolution, X-ray Crystallography and In Silico Docking

“…20 Several teams have also used peptide-based technologies to identify antibody epitope and even model antibody-target complex. 6,21 Nevertheless, despite being very well adapted to linear epitope, this approach was not suitable for the study of Hu 15C1 as its epitope is conformational. Several studies have also used computational protein docking in order to predict antibody epitope and paratope before experimental validation by site directed mutagenesis, 22 but these approaches do not provide information of potential amino acids contacts at the interface between the antibody and its target.…”

Differential Responsiveness of Monocyte and Macrophage Subsets to Interferon

“…There are 2 potential explanations for this. The anti‐IFNAR monoclonal antibody might compete with IFNα2 for binding to IFNAR‐1, as is true of other anti–IFNAR‐1 monoclonal antibodies . Alternatively, since type I IFN binding induces IFNAR‐1 internalization , receptor expression could be modulated by endogenous type I IFN (SLE patients) or exogenous IFNα2b (in vitro).…”