Besides cancer, complement inhibitors such as eculizumab, ravulizumab, and the recently approved crovalimab have redefined paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome management, and the bispecific antibody emicizumab has transformed prophylaxis in hemophilia A. Furthermore, novel antibody formats such as the trifunctional anti-CD38 × CD3 antibody (Tri-31C2) exhibit enhanced anti-myeloma activity compared to chimeric CD38 antibodies, underscoring the future potential of T-cell–redirecting designs. The gene discussed is CD38; the disease is cancer.