For each of the 2 study donation periods, this study will have the following procedures: single or double dose platelet apheresis collection, pathogen inactivation with INTERCEPT Blood System treatment, storage for 6 or 7 days (depending on the period and randomization scheme) at 20°C to 24°C with agitation, collection of "fresh" autologous platelets, radiolabeling, infusion of fresh and stored INTERCEPT Blood System-treated radiolabeled autologous platelets, and collection of blood samples for assessment of platelet recovery and survival (lifespan). There will be a minimum wash-out period of two weeks between the two study periods.
Apheresis platelets will be collected using the Amicus separator and stored for 6 or 7 days (depending on the period and randomization scheme) in 35% plasma/65% InterSol.
Procedures will be as follows: On Day 0, each healthy volunteer subject has apheresis platelets collected. INTERCEPT Blood System treatment will begin on either the day of donation (Day 0) or the day following donation (Day 1) and will be completed within 24 hours after collection. Platelets will then be stored for 6 or 7 days after collection (depending on the period and randomization scheme) at 22°C ±2°C with agitation. Aliquots for in vitro platelet function will be taken on Day 0/1 before INTERCEPT Blood System treatment and on Day 6 or 7. On Day 6 or 7, healthy volunteers will return to the site, and 43 mL of blood will be drawn into a syringe containing 9 mL of Anticoagulant Citrate Dextrose Solution, Formula A (ACD-A). Fresh platelets will be prepared from this sample. An aliquot (10-20 mL) of the stored INTERCEPT Blood System for platelets will be aseptically removed from each subject's test container.
Previously stored (Test) and fresh (Control) platelets will be radiolabeled according to randomization assignment with either Chromium-51 (51Cr) (≤20 μCi) as sodium radiochromate (Na251CrO4) or Indium-111 (111In) (≤15 μCi) as indium oxine, following the labeling and washing procedures outlined by the Biomedical Excellence for Safer Transfusion (BEST) Collaborative. The isotope labels will be assigned randomly with equal probability that fresh platelets and stored INTERCEPT Blood System for platelets will be labeled with each isotope., and the same randomization assignment of isotope labels will be utilized for both donation periods for the same subject. Aliquots of the fresh and stored platelets will be radiolabeled in tubes with the standard techniques. After radiolabeling, the autologous fresh and stored INTERCEPT Blood System for platelets will be simultaneously infused into the subject (approximately 10-30 mL). Negative pregnancy test for females of childbearing potential are required before infusion.
Blood samples for radioactivity measurements will be drawn immediately before infusion and at approximately 0, 0.5, 1, and 2 hours post-infusion, and then 6 more samples will be drawn at 1, 2, 3, 4 (or 6), 7, and 11±1 days post-infusion, at approximately the same time of day as the radiolabeled platelet infusion was administered (±4 hours).
Patients will be monitored for safety (adverse events) from the beginning of the study until 10 days following the infusion of radiolabelled platelets in period 2.
Radioactivity measurements Samples will be obtained from the radiolabeled fresh and stored INTERCEPT Blood System for platelets before infusion and used as a radioactive standard. By measuring the volume infused, the total dose of radioactivity infused will be calculated. In vitro elution of the label from the transfused platelets will be determined by the BEST elution assessment method, as well as the in vivo elution of radioactivity from the serial blood samples obtained post-infusion of the labeled platelets.
The standard as well as the subject's whole-blood samples will be corrected for elution and also for the residual activity in the cellular fraction one day after the infusion. Data points 24 hours post-infusion will be used to calculate in vivo recovery after all radioactive corrections have been made. The radioactivity of the samples will be determined by use of a gamma counter. A multiple-hit model will be used to estimate the survival of the radioactively labeled platelets.
