Phase 1 Clinical Trial of Prion-Filtered Red Cell Concentrates (pfRCC) in Patients Requiring Allogeneic Blood Transfusion.

Background; Transmission of vCJD by blood transfusion from pre-symptomatic blood donors has occurred in 4 reported cases to date. Screening blood donors for infectivity is unlikely to be feasible for several years. Removing infectivity from blood using selective filtration may provide a useful degree of protection from transfusion transmission of the disease. A filter that may remove infectivity from red cell concentrates has been developed and trialed in volunteers receiving autologous blood. No studies have been carried out to date of pfRCC in allogeneic transfusions in the clinical setting.

Aims; To establish safety and tolerability of transfusion of prion filtered red cell concentrates.

Methods; Twenty patients scheduled to receive transfusion were recruited following ethical approval and with informed consent. Prion filtered units were prepared by the Irish Blood Transfusion Service. A mean loss of 9 gm of haemoglobin per unit of RCC occurred during the filtration process. Each patient received one unit of pfRCC, and a median of 2 units overall (range 1 to 4 units) per transfusion episode. A cross-match sample, full blood count (FBC), renal and liver profile was taken from each patient prior to transfusion. Patients were observed for adverse reactions. After 24 hours, FBC, renal and liver profile were repeated. Six weeks after the transfusion a further sample was tested for red cell antibodies. Six of these patients have consented to undergo re-transfusion with pfRCC. Two re-infusions have taken place uneventfully six months after the first exposure to pfRCC and 4 more are planned. Results No serious adverse events were encountered during the study, or at 24 hour and 6 week follow up after the initial transfusion episode. Mean haemoglobin increment per unit transfused was 0.68g (SD 0.45g; range −0.5 to 1.35g ). Recruitment and follow-up is ongoing in patients exposed to repeat transfusion challenge. Summary The first clinical transfusions of pfRCC were well tolerated. Two patients were rechallenged with transfusions of pfRCC without adverse effect. Further studies with transfusions of prion filtered red cells are now warranted to extend the safety data and to determine whether efficacy is comparable to standard transfusions in adult and paediatric populations.