A New Complement Inhibitor Shows Promise for Hard-to-Treat Autoimmune Hemolytic Anemia
Autoimmune hemolytic anemia, known as AIHA, is a condition in which the immune system produces antibodies that mistakenly mark a person's own red blood cells for destruction. The resulting anemia can range from mild to life-threatening, with symptoms including extreme fatigue, shortness of breath, rapid heart rate, and jaundice, a yellowing of the skin and eyes from the release of bilirubin as red blood cells break apart. In severe cases, urine can turn dark, even the color of soy sauce or tea, from the breakdown products accumulating in the body.
Most people with AIHA improve with standard treatments, which include corticosteroids to suppress the immune response, intravenous immunoglobulin, and blood transfusions when anemia becomes clinically urgent. For patients who relapse or don't respond adequately, rituximab, a drug that depletes the B cells making the harmful antibodies, has become a preferred second step. But a meaningful number of patients remain refractory, meaning the disease continues to cause significant destruction despite these approaches.
A case report published in Frontiers in Medicine in March 2025 describes the successful use of iptacopan, a recently approved oral inhibitor of complement factor B, in an elderly patient with severe warm antibody AIHA who was not responding well to conventional care. Complement factor B is a key protein in the alternative complement pathway, a branch of the immune system's rapid-response system that, when dysregulated, can amplify the destruction of red blood cells both inside blood vessels and in the spleen and liver.
Iptacopan works by blocking this amplification loop. Because it targets an upstream step in the complement cascade, it is able to address both the intravascular hemolysis that happens directly in the bloodstream and the extravascular hemolysis that occurs in the organs. Within 15 days of starting treatment, the patient experienced significant relief from fatigue, visible improvement in jaundice, and normalization of laboratory values measuring hemolysis. Crucially, the patient no longer required blood transfusions.
The authors note that this case adds to a small but growing body of evidence supporting complement inhibition as a viable approach in AIHA subtypes where the complement system plays a prominent role. Iptacopan was originally developed and approved for another complement-driven blood condition called paroxysmal nocturnal hemoglobinuria, and its use in AIHA represents an early example of expanded application. Researchers caution that this is a single case report and that larger controlled studies will be needed to establish safety, efficacy, and which AIHA patients are most likely to benefit from this approach. Still, for patients who have exhausted standard options, this report offers meaningful encouragement that new pathways of treatment are opening up.