These findings also open up the exciting possibility of using drugs already available that effectively target the C5a–C5aR1 axis at the level of C5 (e.g., Eculizumab), which prevents C5 from being cleaved into C5a and C5b and is currently used for treating patients with Atypical hemolytic uremic syndrome and Paroxysmal Nocturnal Hemoglobinuria) [352,353]. The gene discussed is C5AR1; the disease is paroxysmal nocturnal hemoglobinuria.