To investigate the efficacy and safety of intravenous lanadelumab, a monoclonal antibody that inhibits plasma kallikrein, in COVID-19, we conducted a phase 2, open-label, randomized-controlled, proof-of-concept, interventional trial.<h4>Methods</h4>We recruited 40 patients hospitalized with moderate COVID-19 and randomized them 1:1 to receive either standard-of-care (SoC) treatment or SoC plus intravenous lanadelumab (300 mg on days one and four). The gene discussed is KLK4; the disease is COVID-19.