Pathogen inactivation of red cell concentrates and whole blood: II. In vivo human recovery studies, clinical trials and future directions.

Three technologies are currently under active development for pathogen inactivation of red cell concentrates or whole blood (WB): the Intercept technology using S-303 as an inactivating chemical; the Theraflex technology using UV-C illumination; and the Mirasol technology using riboflavin and UV light. For the UV-C technology, no in vivo data are available. For the other two technologies, recovery, survival and life span of the treated red blood cells (RBCs) are shortened but are within objective requirements, including a 24-h recovery >75%. S-303-treated RBCs were transfused in various patient groups and, so far, showed no relevant differences in the clinical endpoints. In early studies, S-303-reactive antibodies were observed, which prompted changes in the inactivation process, and no further antibody formation was seen. The one published study with the riboflavin/UV procedure showed good effectiveness of treated WB, with haemoglobin increment similar to that of untreated WB. When considering potential implementation of pathogen inactivation strategies, a balance should be struck between microbiological safety, component quality and cost. None of the current technologies is in a stage for large-scale blood bank application, either because of limited availability of evidence of satisfactory in vitro quality data or because of the ongoing requirement of clinical trials in a broad spectrum of patients.