Tacrolimus (FK506) and methotrexate as prophylaxis for acute graft-versus-host disease in pediatric allogeneic stem cell transplantation

Currently, limited data exist on the role of tacrolimus (FK506) in pediatric allogeneic marrow transplantation. Forty-one patients who received tacrolimus as prophylaxis were reviewed, with a median age of 9 years (range 0.2-16 years). Twenty-one patients underwent related donor transplants and 20 underwent unrelated donor transplants. All patients received tacrolimus beginning the day prior to transplant at a dose of 0.03 mg/kg/day by continuous i.v. infusion. When clinically possible, patients were switched to oral therapy in two divided doses, at four times the intravenous dose. Tacrolimus levels were monitored twice a week, and dosages adjusted to maintain serum levels 5-15 ng/ml. Common adverse effects included hypomagnesemia (98%), hypertension (49%), nephrotoxicity (34%), and tremors (32%). Less common side-effects (< 10% cases) included seizures and hyperglycemia. The median time to ANC recovery (ANC > 500 x 10⁶/l) was 15 days. For the related donor group, the incidence of grade II-IV acute GVHD was 33%, and grade III-IV GVHD 19%. For the unrelated donor group, the incidence of grade II-IV acute GVHD was 55%, and grade III-IV GVHD 30%. Overall, tacrolimus therapy was well tolerated as prophylaxis for acute GVHD in pediatric patients undergoing allogeneic transplantation.