Severe acquired aplastic anaemia (SAA) is a bone marrow failure disease characterized by pancytopenia and a hypocellular bone marrow. The corn pathophysiological mechanism is the destruction of hematopoietic stem/progenitor cells mediated by auto-reactive effector T cells. Immunosuppressive therapy with horse antithymocyte globulin (ATG) plus cyclosporine (CSA) is currently the standard of treatment in patients with aplastic anaemia who are not eligible for bone marrow transplantation and with response rates from 40% to 70%. Previous studies showed that horse ATG (hATG) is apparently more effective than rabbit ATG (rATG) as the latter has higher treatment related mortality (TRM). Unfortunately hATG is unavailable in China, so we conduct a optimized standard treatment (9 days protocol) of rATG plus CSA and Levamisole (LMS) Sequential maintaining (termed Optimized Standard Protocol, OSP) for severe aplastic anemia. This prospective study is designed to evaluate the efficacy and safety of Optimized Standard Protocol as first line therapy in newly diagnosed severe aplastic anemia patients.

During the treatment period, rATG is administered at a dose of 1.97 mg/kg/day for 9 days by slow intravenous infusion. CSA is administered orally at a dose of 3 mg/kg qod, and Levamisole was administered orally at a dose of 2.5 mg/kg qod. The CSA and Levamisole (LMS) is designed to alternately every other day.

Inclusion Criteria:

• Newly diagnosed SAA (according to the standard criteria)

  1. Bone marrow cellularity less than 30% (excluding lymphocytes)
  2. At least two of the following: Absolute neutrophil count less than 500/ uL; Platelet count less than 20,000/ uL; Absolute reticulocyte count less than 20,000/ uL.

• Age greater than or equal to 6 years old

Exclusion Criteria:

• Serum creatinine greater than 2.5 mg/dL
• Underlying carcinoma (except local cervical, basal cell, squamous cell)
• Prior immunosuppressive therapy with ATG, antilymphocyte globulin (ALG), or high dose cyclophosphamide.
• Current pregnancy or lactation or unwillingness to take oral contraceptives or use an effective method of birth control.
• Diagnosis of Fanconi anemia or other congenital bone marrow failure syndromes
• Evidence of a clonal disorder on cytogenetics. Patients with super severe neutropenia (ANC less than 200/uL) will not be excluded if results of cytogenetics are not available or pending.
• Underlying immunodeficiency state including seropositivity for HIV
• Inability to understand the investigational nature of the study or give informed consent
• Moribund status or concurrent hepatic, renal, cardiac, neurologic, pulmonary, infectious, or metabolic disease of such severity that it would preclude the patient s ability to tolerate protocol therapy, or that death within 7-10 days is likely.