More complement inhibitors are under investigation, including the C5a inhibitor vilobelimab.89,90 Recent clinical trials showed that in addition to standard of care, vilobelimab improved survival of invasive mechanically ventilated patients with coronavirus disease 2019 (COVID-19).91-93 The blood–brain barrier poses another challenge to use of complement inhibitors, including monoclonal antibodies. This evidence concerns the gene C5 and COVID-19.