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November 16th, 2004 WFH Joint Symposium Review – Natural Proteins in the Treatment of Blood Disorders: Return to Reason During the World Federation of Hemophilia Congress in Bangkok, three PPTA member companies, Octapharma, Biotest, and Kedrion , organised a joint Satellite Symposium. The 90 minute Symposium took place on Tuesday, October 19.
From these presentations, evidence is emerging for the superiority of pdFVIII containing the von Willebrand factor (VWF) over rFVIII, which lacks VWF, and pdFVIII from which VWF has been removed, in the key area of immunogenicity. PdFVIII complexed with VWF appears to be less immunogenic in previously untreated patients (PUPs), causing the less frequent development of inhibitor antibodies to FVIII, and more effective in immune tolerance induction (ITI) in previously treated patients (PTPs) who have developed an inhibitor. This reverses the current clinical paradigm of preferably treating haemophilia A patients with rFVIII, given the equivalent clinical efficacy and pathogen safety of pdFVIII today.
A similar trend was given by ITI results from Bonn and Bremen in the periods pre-1990 and 1990 to July, 2001. Until 1990, when the only concentrates used were those containing VWF, the success rate of ITI was 87 %. Thereafter, a difference in success rate was seen, depending on the type of concentrate: pdFVIII containing VWF was more effective in ITI than rFVIII. These success rates were compared to those in the literature. In 102 ITI cases using the Bonn protocol and giving only VWF-containing concentrates, the success rate was 88 %, compared to [other] treatments in other countries where the concentrate did not contain VWF and the success rate was 63 % in 78 patients. The majority of inhibitors are specific for the light chain of the FVIII molecule. There are theoretical considerations that, because VWF binds to the C2 domain of FVIII, it may sterically interfere with inhibitor binding. In addition, VWF may also protect FVIII against proteolysis, allowing prolonged presentation of FVIII to the immune system and improved immune tolerance. Concluding, FVIII concentrates containing VWF may have less immunogenic potential. It appears reasonable to treat those patients who fail ITI under another type of FVIII preparation with a pdFVIII preparation containing VWF. © Octapharma AG, 2004 |
