FDA Clarifies Current Thinking on Pyrogen and Endotoxins Testing

The Food and Drug Administration (FDA, Agency, or we) is announcing a level 2 revision of the final guidance entitled, “Pyrogen and Endotoxins Testing – Questions and Answers,” published in June 2012, and reissuing the final guidance as “Edition 2.” We are providing minor updates to better reflect FDA’s current thinking. Notably, the revision removed certain references to Limulus Amoebocyte Lysate (LAL) testing to accommodate a broader scope of recombinant reagents. Sponsors using recombinant reagents should verify that the assay method is suitable for its intended purpose.

This action aligns with USP Chapter 〈86〉 Bacterial Endotoxins Test Using Recombinant Reagents published in May 2025. USP states, “This proposed new test chapter provides additional techniques using nonanimal derived reagents to the Bacterial Endotoxins Test 〈85〉. This general chapter is not currently being introduced into a specific monograph or listed in General Notices. It is the responsibility of the user to review the supplier's primary validation package and to verify product suitability for use in testing specific products or materials. This verification must include specific experiments to confirm that the method is suitable for its intended purpose under the conditions of use for the material, drug substance, and/or drug product. The selected verification experiments should be based on an assessment of the complexity of the material to which the method is being applied.” 

The guidance revisions are consistent with the agency’s long-term goal to reduce, refine, and replace animal testing and provide flexibility for manufacturers to transition to the use of recombinant reagents for bacterial endotoxin testing of drugs and devices regulated by FDA.