Efficient inhibition of SARS-CoV-2 strains by a novel ACE2-IgG4-Fc fusion protein with a stabilized hinge region

Svilenov, Hristo L.; Sacherl, Julia; Reiter, Alwin; Wolff, Lisa; Chen, Cho-Chin; Wachs, Frank-Peter; Pippig, Susanne; Wolschin, Florian; Buchner, Johannes; Brockmeyer, Carsten; Protzer, Ulrike

The novel severe acute respiratory syndrome (SARS)-like coronavirus (SARS-CoV-2) enters its host cells after binding the angiotensin-converting enzyme 2 (ACE2) via its spike glycoprotein. This interaction is critical for virus entry and virus-host membrane fusion. Soluble ACE2 ectodomains bind and neutralize the virus but the short in vivo half-lives of soluble ACE2 limits its therapeutic use. Fusion of the constant (Fc) part of human immunoglobulin G (IgG) to the ACE2 ectodomain can prolong the in vivo half-life but bears the risk of unwanted Fc-receptor activation and antibody-dependent disease enhancement. Here, we describe optimized ACE2-Fc fusion constructs that avoid Fc-receptor binding by using IgG4-Fc as a fusion partner. The engineered ACE2-IgG4-Fc fusion proteins described herein exhibit promising pharmaceutical properties and a broad antiviral activity at single-digit nanomolar concentration. In addition, they allow to maintain beneficial enzymatic activity of ACE2 and thus are very promising candidate antivirals broadly acting against coronaviruses.