ACH-4771 is a small Factor D inhibitor that blocks the catalytic side of Factor D. In presence of inactive Factor D, the alternative pathway convertase C3bBb is not formed and complement activation does not proceed. The other inhibitor LPN023, binds to the active site of Factor B and thus inhibits the alternative pathway C3 convertase and blocks C3 cleavage. Based on the different action sites of the inhibitor, it will be of interest to see which compound or which targeted pathway is most effective and which subform responds or benefits from which inhibitor. Besides, monoclonal antibody (mAb) was also designed by scientists to bind C3b, thereby preventing the formation of the C3 convertase.