Low‐dose immune tolerance induction alone or with immunosuppressants according to prognostic risk factors in Chinese children with hemophilia A inhibitors

BACKGROUND: In developing countries, children with hemophilia A (HA) with high‐titer inhibitor and poor immune tolerance induction (ITI) prognostic risk(s) cannot afford the recommended high‐ or intermediate‐dose ITI. OBJECTIVES: To determine the efficacy of low‐dose ITI (plasma‐derived factor VIII [FVIII]/von Willebrand factor at 50 FVIII IU/kg every other day) by itself (ITI‐alone) or combined with immunosuppressants rituximab and prednisone (ITI‐IS) in children with HA with high‐titer inhibitor. METHODS: All enrolled patients had pre‐ITI inhibitor ≥10 BU. We used ITI‐alone if inhibitor titer was <40 BU pre‐ITI and during ITI, and ITI‐IS if titer was ≥100 BU (historic) or ≥40 BU (pre‐ or during ITI) or if the patient was nonresponsive on ITI‐alone. RESULTS: Fifty‐six children were analyzable, with median historic peak inhibitor titer 48.0 BU and followed for median 31.4 months. Overall, 35 (62.5%) achieved phase 2 success with negative inhibitor and normal FVIII recovery. The phase 2 success rate was 95% for the 20 patients receiving ITI‐alone. For the 36 patients receiving ITI‐IS, the phase 2 success rate was 44.4%, but would increase to 63.6% if the 14 patients with historic peak inhibitor titer ≥100 BU (and having phase 2 success rate of only 14.3%) were excluded. One patient developed repeated infection after IS treatment. Relapse occurred in 11.4% (4/35) patients with phase 2 success associated with rapid ITI dose reduction or irregular post‐ITI FVIII prophylaxis. Our strategy reduced the cost from high‐dose ITI by 74% to 90%. CONCLUSION: The use of low‐dose ITI with or without immunosuppressants according to ITI prognostic risk(s) is a clinically and economically feasible strategy for eradicating inhibitors in children with HA, particularly for those with historic peak inhibitor titer <100 BU.