C3 and COVID-19: Indeed, different pharmacological complement inhibitors, such as C1 esterase inhibitor28, anti-C5 antibodies eculizumab, and ravulizumab26,29, C3 inhibitor AMY-10126, and anti-C5a antibody IFX-130 (the last two still in clinical trials) have been tested to treat severe cases of COVID-19, with promising results.