Raymond Wong, MD, Prince of Wales Hospital, Sha Tin, Hong Kong, discusses how inhibition of C3 with pegcetacoplan results in normalization of markers of intravascular and extravascular hemolysis in patients with paroxysmal nocturnal hemoglobinuria (PNH). The only approved treatment for PNH is eculizumab, a C5 inhibitor which targets intravascular hemolysis; however, a certain patients treated with this agent continue to experience ongoing anemia. Here, Dr Wong describes the promising results of the clinical trial of pegcetacoplan in PNH.