Immune tolerance induction in patients with haemophilia A with inhibitors: a systematic review

In some patients with haemophilia A, therapeutically administered factor VIII (FVIII) comes to stimulate the production of antibodies (inhibitors) which react with FVIII to render it ineffective. As a result, FVIII cannot be used prophylactically and patients become liable to recurrent bleeds. There are two elements to the management of patients with inhibitors: the treatment of bleeding episodes, and attempts to abolish inhibitor production through the induction of immune tolerance. This paper reports a systematic review of the best available evidence of clinical effectiveness in relation to immune tolerance induction (ITI) in patients with haemophilia A with inhibitors. Owing to the lack of randomized controlled trials on this topic, broad inclusion criteria with regard to study design were applied in order to assess the best available evidence for each intervention. As a result of the clinical and methodological heterogeneity of the evidence, it was not appropriate to pool data across studies; instead, data were synthesized using tabulation and qualitative narrative assessment. The International Registry provides the most reliable estimate of the proportion of successful cases of ITI [48.7%, 95% confidence interval (CI) 42.6-52.7%]. The duration of effect is unclear, but relapses appear to be infrequent. The International Registry shows a rate of relapse of 15% at 15 years. The comparative effectiveness of different protocols is uncertain, as no trials have been undertaken which compare them directly. However, the evidence suggests that the Bonn protocol may be more effective than the Malmo or low-dose protocols. There is no good evidence that immunosuppressive drug regimens are effective.