Sutimlimab for treatment of cold agglutinin disease: why, how and for whom?

Therapies for cold agglutinin disease have been directed at the pathogenic B-cell clone. Sutimlimab, a monoclonal antibody that targets C1s, is the first complement inhibitor to be extensively studied in cold agglutinin disease. Sutimlimab selectively blocks the classical activation pathway and leaves the alternative and lectin pathways intact. Trials have documented high response rates with rapid improvement in hemolysis, hemoglobin levels and fatigue scores and low toxicity. Sutimlimab was recently approved in the USA. This drug appears to be particularly useful in severely anemic patients who require a rapid response, in acute exacerbations that do not resolve spontaneously and in patients in whom chemoimmunotherapy is contraindicated or has failed. The choice of therapy in cold agglutinin disease should be individualized. In cold agglutinin disease (CAD), red blood cells are destroyed by cold agglutinin, a type of antibody against the patient's own red blood cells. Previous treatments for CAD have aimed at killing the cold agglutinin-producing abnormal cells in the bone marrow. Sutimlimab, a new drug for treatment of CAD, is an artificially produced antibody that binds to a protein called C1s. This binding results in inhibition of complement, a system of active proteins that is part of the immune system and promotes red blood cell destruction in CAD. Clinical trials have shown that most patients with CAD respond well to treatment with sutimlimab, with rapid improvement in anemia and fatigue. The risk of serious side effects is very low provided the patient is vaccinated against certain types of bacteria. Sutimlimab, which is administered by intravenous infusion, was recently approved in the USA. This drug appears to be particularly useful in CAD patients with severe anemia, in those who cannot tolerate other treatment options and in those in whom other therapies have failed. The choice of treatment in CAD should be individualized.