First prospective report on immune tolerance in poor risk haemophilia A inhibitor patients with a single factor VIII/von Willebrand factor concentrate in an observational immune tolerance induction study.

Introduction/background: Development of neutralizing inhibitors against factor VIII (FVIII) is a major complication of haemophilia A treatment.

Aim: The ongoing, international, open-label, uncontrolled, observational immune tolerance induction (ObsITI) study evaluates ITI, the standard of care in patients with inhibitors.

Patients/methods: Forty-eight prospective patients in this interim analysis received a single plasma-derived, von Willebrand factor-stabilized, FVIII concentrate (pdFVIII/VWF) for ITI.