An ACE2 Microbody Containing a Single Immunoglobulin Fc Domain Is a Potent Inhibitor of SARS-CoV-2

Soluble forms of angiotensin-converting enzyme 2 (ACE2) have recently been shown to inhibit severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We report on an improved soluble ACE2, termed a “microbody,” in which the ACE2 ectodomain is fused to Fc domain 3 of the immunoglobulin (Ig) heavy chain. The protein is smaller than previously described ACE2-Ig Fc fusion proteins and contains an H345A mutation in the ACE2 catalytic active site that inactivates the enzyme without reducing its affinity for the SARS-CoV-2 spike. The disulfide-bonded ACE2 microbody protein inhibits entry of SARS-CoV-2 spike protein pseudotyped virus and replication of live SARS-CoV-2 in vitro and in a mouse model. Its potency is 10-fold higher than soluble ACE2, and it can act after virus bound to the cell. The microbody inhibits the entry of β coronaviruses and virus with the variant D614G spike. The ACE2 microbody may be a valuable therapeutic for coronavirus disease 2019 (COVID-19) that is active against viral variants and future coronaviruses. [Display omitted] •An ACE2 microbody inhibits entry of SARS-CoV-2 spike protein pseudotyped virus•ACE2 microbody inhibits replication of live virus in vitro and in a mouse model•Antiviral potency of the ACE2 microbody is 10-fold higher than that of soluble ACE2•ACE2 microbody inhibits entry of the D614G spike and other β coronavirus spikes Tada et al. generate an ACE2 “microbody” in which the ACE2 ectodomain is fused to immunoglobulin heavy chain Fc domain 3. The ACE2 microbody protein potently inhibits the entry of SARS-CoV-2 spike protein pseudotyped virus into cells and replication of live SARS-CoV-2 in vitro and in a mouse model.