Danicopan (ACH-4471), a selective and orally active small-molecule factor D inhibitor, shows high binding affinity to human Factor D with Kd value of 0.54 nM. Danicopan (ACH-4471) inhibits alternative pathway of complement (APC) activity, has potential to block the alternative pathway of complement in paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic uremic syndrome (aHUS).