VWF/FVIII concentrates in high-risk immunotolerance: the RESIST study.

Immune tolerance induction (ITI), through the regular infusion of coagulation factor concentrates over a time period ranging from 1 to more than 24 months, is successful in about 75% of high responders. Among the issues of ITI treatment that are still open, the choice of the product to use is one of the most difficult. In fact, common practice is to start with the same product that induced the inhibitory response, but recent findings indicated that plasma-derived products containing large amounts of von Willebrand factor (VWF) can play a positive role. Two retrospective cohorts in Germany and in France and one prospective cohort have shown a high rate of success when VWF/factor VIII (FVIII) products are used to induce ITI. For these reasons, two prospective studies have been planned to complement the international ITI study already started: an observational study in patients who had already experienced a failure with a VWF-free FVIII concentrate, called RESIST(exp) (experienced); a randomized, controlled study in patients who have never tried an ITI treatment before and at high risk to fail, called RESIST(naïve) (naïve).