C5 and paroxysmal nocturnal hemoglobinuria: There are two classes of complement inhibitors currently used to treat PNH: C5 inhibitors—eculizumab, ravulizumab, and crovalimab—and C3 inhibitors, which include pegcetacoplan and peptide inhibitors of C3 [9, 10, 11, 12, 13, 14].