A monoclonal antibody against mannan-binding lectin (MBL)-associated serine protease-2 (MASP-2), with potential anti-thrombotic and immunomodulating activities. Upon subcutaneous administration, OMS721 binds to and inhibits MASP-2. This prevents the activation of MASP-2, the cleavage of certain complement components, and the activation of the complement lectin pathway. This inhibits complement deposition and complement-induced thrombus formation. MASP-2, a pro-inflammatory protein, plays a key role in the activation of the lectin complement pathway, which is a key component in the immune system, and is associated with complement-mediated diseases, such as thrombotic microangiopathies (TMAs), which includes hematopoietic stem cell transplant (HSCT)-related TMA, atypical hemolytic uremic syndrome (aHUS), and thrombotic thrombocytopenic purpura (TTP).