Preclinical pharmacokinetic and toxicology assessment of red blood cells prepared with S-303 pathogen inactivation treatment

Background: A system has been developed to inactivate a wide spectrum of blood-borne pathogens in red blood cells (RBCs) before transfusion. The system utilizes S-303 to target nucleic acids of pathogens and white blood cells. The safety of pathogen inactivated RBC was assessed using S-303-treated RBCs (S-303 RBCs) and S-300, the primary degradation product of S-303.

Study design and methods: As part of a preclinical safety evaluation program, intravenous toxicity, safety pharmacology, toxicokinetic, and pharmacokinetic studies were conducted in rats and dogs with S-303 RBCs and S-300.

Results: Single and repeated transfusions of S-303 RBCs were well tolerated in rats and dogs at S-303 concentrations up to five times higher than that used to prepare RBCs for clinical use. For S-300, the doses ranged from the lowest level representative of a clinical exposure from transfusion of 1 unit (0.052 mg/kg/day) to up to the amount of S-300 that would result from exposure to more than 1900 units of RBCs (100 mg/kg/day). There were no related effects of S-303 RBCs or S-300 on mortality, clinical status, body weight, or clinical laboratory assessments and no evidence of organ toxicity. S-300 did not accumulate in the plasma of rats and dogs after repeated transfusions. For all the studies, plasma S-303 was consistently below the limit of quantitation.

Conclusion: The level of residual S-303 and S-300 in the treated blood component is well below that at which no adverse effects were observed. These results support further clinical development of S-303 RBCs for prevention of transfusion-transmitted infections.