C3 and acute respiratory distress syndrome: Therefore, ongoing clinical trials are investigating the effectiveness of a C3 inhibitor (AMY-101, Amyndas Pharmaceuticals S.A., PA) in Covid-19-induced acute respiratory distress syndrome (NCT04395456), and of a C5 inhibitor (Zilucoplan, UCB Pharma, Brussels, Belgium) in Covid-19-induced respiratory failure (NCT04382755).