ACE2 and COVID-19: To test the hypothesis that ACE2 decoys are not susceptible to naturally selected mutations in the S protein that impart resistance to antibodies, we assessed the ability of an ACE2-Fc containing the complete ACE2 extracellular domain (PD-CLD-Fc) to neutralize the SARS-CoV-2 Omicron (B.1.1.529.1) variant, which is resistant to most antibodies that have been developed for COVID-19 treatment and prophylaxis (3).