Occurrence of inhibitors in previously untreated or minimally treated patients with haemophilia A after exposure to a plasma‐derived solvent‐detergent factor VIII concentrate

A solvent-detergent virus-inactivated plasma-derived FVIII concentrate (SD-pdFVIII) has been employed for treatment of Italian patients with haemophilia A for 15 years. This product is a non-monoclonally purified, high purity FVIII concentrate, containing large amounts of von Willebrand factor (VWF). A retrospective survey was carried out in Italy in order to evaluate the immunogenicity of SD-pdFVIII in previously untreated patients (PUPs) or in minimally treated patients (MTPs), i.e. previously exposed for up to 5 days only to other plasma-derived concentrates. The survey included 99 patients with ages ranging from 6 to 64 years (median=21.3) of whom 31 PUPs and 68 MTPs, the latter with a median of four exposure days (EDs; range 1-5) to other plasma products. Surveyed patients had been exposed to SD-pdFVIII for a median of 83 EDs (range 21-1580). Seven patients (three PUPs and four MTPs), all with severe haemophilia, had developed inhibitors [7.1%, 95%; confidence interval: 3-14%] after a median of 11 EDs (range 4-22). Of them, two were low responders (