Early intensified intravenous cyclosporine therapy predicts favorable response to immunosuppressive therapy with rabbit antithymocyte globulin in patients with severe aplastic anemia

• Early intensified CsA therapy with rATG predicted favorable outcome in SAA.
• Maintaining higher levels of CsA is important for achieving favorable outcomes.
• Adding other IST drugs could increase clinical outcomes to IST with rATG.

Because of relapse after horse ATG (hATG) therapy, rabbit ATG (rATG) would be a realistic alternative as second line immunosuppressive therapy (IST) in severe aplastic anemia (SAA) patients. We investigated whether intensified intravenous (IV) CsA therapy with rATG would increase the response of IST in SAA patients.Sixty-one of the 123 patients received IV CsA therapy with rATG during initial 2 weeks then changed to oral form (IV CsA group), while other 62 patients just received oral CsA therapy with rATG (oral CsA group).Hematologic response rates at 3 and 6 months were not different between IV CsA group and oral CsA group (p = 0.795, p = 0.079). However, CsA levels during initial 15 days were higher in response-achieved group than response-not-achieved group. Intensive IV CsA group maintained CsA level ≥300 ng/ml during 15 days had higher responses at 6 months than non-intensive IV CsA group and oral CsA group (p = 0.009, p = 0.021). Intensive IV CsA group (HR = 3.239, 95% CI = 1.095–8.997, p = 0.013) independently predicted favorable the hematologic response at 6 months of IST.Early intensified CsA therapy was important to achieve favorable outcomes in IST including rATG.