BackgroundA new protocol has been developed on the Amicus Separator that enables the device to perform online extracorporeal photopheresis (ECP) procedures when used in conjunction with the Phelix photoactivation device and associated disposable kit. The objective of this study was to evaluate the safety and performance of the Amicus ECP System in adult subjects with steroid‐refractory or dependent chronic graft vs host disease (cGVHD).Study Design and MethodsEight subjects with mild to severe cGVHD underwent 31 procedures. Subject safety evaluations were performed pre and post procedure and adverse events (AEs) were recorded during treatment and 24 hours after the last procedure. In vitro evaluations of the treated cells included hematology counts and lymphocyte apoptosis, viability and proliferation as measures for ECP procedure validation.ResultsFor n = 23 evaluable procedures, median (range) procedure time was 88 (78‐110) minutes, during which 2.9 (0.6‐4.7) × 109 TNCs (approximately 90% MNCs) were treated and reinfused to the subjects. All subject safety evaluations (vitals, cell counts, plasma hemoglobin and bacterial and endotoxin testing) were within expected ranges. All device or procedure related AEs were mild in nature. After 24 hours in culture, 86 (52‐98)% of treated lymphocytes were apoptotic compared to 27 (15‐51)% in controls. Inhibition of lymphocyte proliferation was >91% in all procedures.ConclusionECP procedures were safely completed in adult subjects with SR‐cGVHD treated using the new online Amicus ECP system.