Presently, the two drugs used to treat SAA by slowing down the immune system (immunosuppression) are antithymocyte globulin (ATG) and cyclosporin A (CSA). When used in combination these two drugs can improve most patients condition. However, one third of the patients who respond to this therapy experience a relapse of SAA. In addition, some patients treated with ATG/CSA can later develop other disorders of the blood.