Narsoplimab (OMS 721) is a high-affinity fully human immunoglobulin gamma 4 (IgG4) monoclonal antibody that binds MASP-2 and blocks lectin pathway activation. Narsoplimab can be used in research of hematopoietic stem-cell transplantation and SARS-CoV-2.In Vitro:Narsoplimab (100 nM; 3 h; Vero E6 cells and Vero E6 cells with SARS-CoV-2) inhibits the N protein potentiated MASP-2 deposition.In Vivo:Narsoplimab (10 mg/kg; i.v.; WT and Masp2-/- (KO) mice) decreases percentage of lymphocytes (Lym%) and increases percentage of neutrophils (Neu%).