The determination of endotoxin in the finished cellular product

Background With the advancement of genetics and hematopoiesis resulting in therapeutic applications, a growing focus has developed on the quality assessment of b iological products generated for various cellular therapies. Endotoxin is a critical measure for the presence of Gram-negative bacteria, known to caus e endotoxemia. Cellular products are currently regulated as medical devices . Each location engaged in clinical protocols is responsible for establishi ng a quality assurance program. Methods In this study, endotoxin levels were assayed using both the gel-clot and ki netic chromogenic Limulus amebocyte lysate (LAL) assays on 33 patients' cel lular products, produced in clinical laboratory settings as part of a clini cal trial or approved protocol. These patient samples include tumor infiltr ating lymphocytes (TIL), activated T cell (ATC), coactivated lymphocytes (C OACT) and herpes simplex thymidine kinase transduced lymphocytes (HSVtk). W e sought to identify the more reliable and informative method for the deter mination of endotoxin levels in a variety of cellular products, to meet the growing demand for standardization of product quality assessment. Comparis on of the most sensitive gel-clot LAL test (0.03 EU/ml), with the kinetic c hromogenic LAL test, with a lysate sensitivity of 0.005 EU/mL, found many a dvantages of the more sensitive method. Results The kinetic chromogenic LAL test, which has the greatest sensitivity, incre ased the percentage of samples with spike recoveries compared with the gel- clot LAL test from 65% to 70% at a 1 : 10 sample dilution; and from 81 % to 88 % at a 1 : 100 sample dilution. At a sample dilution of 1 : 50 the kine tic chromogenic LAL test provided valid spike recoveries on 81 % of all sam ples tested. Discussion In the interest of providing the highest quality and safety in the finished cellular product, the determination of endotoxin by the kinetic chromogeni c LAL test is a rapid, effective, easy-to-use method to detect the presence of Gram-negative bacterial contamination.