Immune tolerance induction in patients with severe hemophilia A with inhibitors

BACKGROUND: Inhibitory antibodies to factor VIII (FVIII) are an important complication when managing patients with hemophilia A. Immune tolerance induction (ITI) has been regarded as a useful method for eradicating inhibitors. We report the results of a retrospective study in Korean patients with hemophilia A who underwent ITI. METHODS: We reviewed the records of patients with hemophilia A with inhibitors who underwent ITI from March 2004 to December 2014. ITI was started with FVIII concentrates at 100 IU/kg, 3 times per week. The dose of FVIII was reduced according to the inhibitor titer and recovery of FVIII. Inhibitor elimination was defined as the time taken to achieve a negative inhibitor assay with no anamnestic response and normal FVIII recovery and/or normal half-life. RESULTS: In total, 17 patients with severe hemophilia A were evaluated. Complete tolerance was achieved in 14 of 17 patients (83%). The mean peak inhibitor titer before ITI was 38.4 BU/mL. The mean treatment duration was 26.2 months. The mean duration between inhibitor detection and ITI was 5.1 years in the complete tolerance group and 10.8 years in the partial tolerance and failed group. CONCLUSION: This study shows that ITI can be an effective and well-tolerated method for eradicating inhibitors. Possible influencing factors for ITI success were age at the start of ITI treatment and duration after inhibitor detection. More research to provide further insight about other factors and conditions is needed.