C3 inhibitors are used to treat paroxysmal nocturnal hemoglobinuria (PNH) and geographic atrophy (GA) secondary to age-related macular degeneration. These medications work by inhibiting complement C3 proteins, which play a role in inflammation. C3 inhibitors are available as under-the-skin and into-the-eye injections. One example is pegcetacoplan (Empaveli, Syfovre).