Study of LAL and Recombinant Cascade Reagents Methods for Bacterial Endotoxin Testing in Pharmaceutical Products

The bacterial endotoxin method uses amebocyte lysate reagents from the horseshoe crab (Limulus polyphemus or Tachypleus tridentatus) to detect and quantify bacterial endotoxin in injectable medications and medical devices. Two types of recombinant reagents have been introduced by various manufacturers, and the equivalency of their results to those of the natural Limulus amebocyte lysate (LAL) reagents has been recently assessed by the United States, European, and Japanese Pharmacopoeias. Recombinant reagents and amebocyte lysate reagents appear to be highly comparable, according to several investigations. LAL assays are currently the gold standard. LAL is used in vitro for the precise detection of endotoxins and is based on the endotoxin-activated Factor C-mediated clotting cascade. In our quality control laboratory, we tested several categories of drug samples using different compendial methods for detection of bacterial endotoxin that provide reliable and consistent results. Since 2024, a bacterial endotoxin test based on recombinant cascade reagent (rCR)-composed of the endotoxin sensor recombinant Factor C (rFC), Factor B, and pro-clotting enzyme inside of LAL-has been used as an animal-free alternative to LAL. The non-animal-derived reagent rCR uses cloned genes from the genome of the Limulus polyphemus horseshoe crab to detect and measure bacterial endotoxins. In addition to providing ethical and environmental benefits over traditional LAL assays, rCR eliminates interfering horseshoe crab blood components, allowing for extremely specific endotoxin detection. For rCR test performance in a routine setting, a comparative study was conducted of compendial bacterial endotoxin testing by LAL with the alternative animal-free reagent rCR, and the evidence was summarized and presented by analyzing different categories of pharmaceutical products. According to the compendial endotoxin testing requirements, all results were acceptable. When the rCR assay was applied rather than the LAL test, no interference was seen in certain samples. In this study, the rCR and LAL were equivalent and comparable.