Effects of an amustaline (S‐303)/glutathione pathogen reduction system on the in vitro quality of plasma and platelets in treated whole blood

BACKGROUND: A pathogen reduction (PR) system for whole blood (WB) that maintains component quality could enable a universally pathogen-reduced blood supply. The goal of this study was to assess the effects of an amustaline (S-303)/glutathione PR process on platelets and plasma in treated WB. METHODS: We analyzed the effects of an S-303/glutathione PR process on platelet and plasma function in treated WB using in vitro platelet aggregation response (impedance aggregometry), expression of platelet activation markers (flow cytometry), and plasma coagulation parameters (clotting, chromogenic, and WB viscoelastic assays). RESULTS: At S-303 concentrations from 0.1 to 0.4 mM, the treatment had significant, dose-dependent effects on plasma and platelet function. Plasma clotting times were prolonged, and the largest loss of activity was in vitamin K-dependent factors. Effects were rapid (within 15 min of treatment) and evident in clot-based, chromogenic, and viscoelastic assays, with significant impact on clot firmness and kinetics. Platelet aggregation responses to collagen were partially preserved and S-303 dose-dependent, while responses to other agonists were largely eliminated. Platelets from treated WB showed an S-303 dose-dependent increase in surface expression of CD62P, CD63, PAC1, and phosphatidylserine, and partially retained responses to TRAP-6 agonist. DISCUSSION: The results demonstrate that S-303/glutathione PR of WB for preparation of hemostatic components is limited by detrimental off-target effects. The pattern of detrimental effects identifies opportunities for optimization of similar approaches to PR and provides insight into the hemostatic activity of S-303-treated WB.