First Attempt at Immune Tolerance Induction with Factor VIII/von Willebrand Factor Concentrates in Hemophilia A Children with High‐Titer Inhibitors

Review article

First Attempt at Immune Tolerance Induction with Factor VIII/von Willebrand Factor Concentrates in Hemophilia A Children with High‐Titer Inhibitors

Helen Platokouki, Helen Pergantou, Anna Komitopoulou and Panagiota Xafaki
Affiliations: Haemophilia/Haemostasis Unit, “Aghia Sophia” Children’s Hospital


ABSTRACT

Immune tolerance induction (ITI) has been used for years to eradicate factor VIII (FVIII) inhibitors, a serious complication of treatment for children with hemophilia A. The optimal product to be used and dosing regimens are still under investigation. The possibility that the use of FVIII/von Willebrand factor (FVIII/vWF) concentrate might improve the success rate and shorten the duration of ITI has been suggested. The charts of seven children (current age 92.3±12.6 months) with severe hemophilia A and high‐titer inhibitors (53.7±44.3 BU) who received FVIII concentrates containing vWF (five children received a concentrate with a vWF:FVIII content ratio of 2.4:1 and two received a concentrate with a ratio of 0.96:1) in a dosing regimen of 100 IU/kg/48 h were reviewed. The results of the treatment were analyzed on tolerance, morbidity, and safety. ITI was completely successful after a mean period of 20.4 months in all seven children who received the product for initial ITI. Three of the seven children only achieved tolerization after an increase in the dose to 150 IU/kg/48 h, at least 17 months after initiation of ITI. Permanent tolerance is maintained for a mean observation period of 28.1 months. A dramatic drop was found in the frequency of hemorrhages per month after ITI in comparison with those before ITI initiation (0.36±0.20 vs 0.84±0.60, P = 0.023). Furthermore, the patients had the same proportionate drop in hemorrhage frequency, falling after ITI to one‐third of the number they had before ITI (correlation coefficient: r = 0.859). No side‐effects were noticed. In conclusion, the use of FVIII/vWF concentrates for ITI seemed to be effective on tolerization of severely affected hemophilia A children with high‐titer inhibitors, additionally resulting in a decreased number of bleeding episodes.

Keywords: hemophilia A, factor VIII (FVIII) inhibitor, immune tolerance, factor VIII (FVIII)/von Willebrand factor concentrate
Correspondence: Helen Platokouki, Haemophilia/Haemostasis Unit, “Aghia Sophia” Children’s Hospital, Thivon/M. Asias, 115 27 Athens, Greece