Canadian multi-institutional survey of immune tolerance therapy (ITT) - experience with the use of recombinant factor VIII for ITT

Immune tolerance therapy (ITT) is currently the most effective approach to eradicate inhibitors in patients with haemophilia A. Limited evidence suggests that the use of plasma-derived factor VIII (pdFVIII) for ITT may be associated with a greater success rate than recombinant factor VIII (rFVIII). Analysis of ITT cases in Canada offered the opportunity to examine the success rate of using rFVIII for ITT, as rFVIII has been used almost exclusively for Canadian haemophilia A patients since 1994. The results of 32 patients from five haemophilia treatment centres were collated. Three patients continue on ITT. Of the 29 patients who completed ITT, 25 (86.2%) used rFVIII exclusively, and four used pdFVIII exclusively or pdFVIII followed by rFVIII. The initial FVIII dosing frequency was once per day in 72.4% of patients at an average dose of 98 U kg(-1) (range 50-200). Eight patients (25%) received one or more adjuvant therapies. The median duration of ITT was 1.1 years (mean 1.5 years, range 9 days to 6 years). The overall success rate of the 29 patients who completed ITT was 79.3% (23/29), which is comparable with the results of immune tolerance registries. Our results suggest that the success rate of ITT using rFVIII is not inferior to the results with pdFVIII.