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 biological products generated for various cellular therapies. Endotoxin is a critical measure for the presence of Gram-negative bacteria, known to cause endotoxemia. Cellular products are currently regulated as medical devices. Each location engaged in clinical protocols is responsible for establishing a quality assurance program. Methods In this study, endotoxin levels were assayed using both the gel-clot and kinetic chromogenic Limulus amebocyte lysate (LAL) assays on 33 patients' cellular products, produced in clinical laboratory settings as part of a clinical trial or approved protocol. These patient samples include tumor infiltrating lymphocytes (TIL), activated T cell (ATC), coactivated lymphocytes (COACT) and herpes simplex thymidine kinase transduced lymphocytes (HSVtk). We sought to identify the more reliable and informative method for the determination of endotoxin levels in a variety of cellular products, to meet the growing demand for standardization of product quality assessment. Comparison of the most sensitive gel-clot LAL test (0.03 EU/ml), with the kinetic chromogenic LAL test, with a lysate sensitivity of 0.005 EU/mL, found many advantages of the more sensitive method. Results The kinetic chromogenic LAL test, which has the greatest sensitivity, increased 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 kinetic chromogenic LAL test provided valid spike recoveries on 81 % of all samples tested. Discussion In the interest of providing the highest quality and safety in the finished cellular product, the determination of endotoxin by the kinetic chromogenic LAL test is a rapid, effective, easy-to-use method to detect the presence of Gram-negative bacterial contamination.