FDA Endotoxin Testing Update Falls Short for Nonanimal Methods

WASHINGTON, D.C. — A recent guidance update from the U.S. Food and Drug Administration (FDA) on pyrogen and endotoxins testing represents a missed opportunity to meaningfully advance alternatives to horseshoe-crab-blood-based tests.

Endotoxins —bacterial toxins that can contaminate medical products—have traditionally been detected using horseshoe crab blood. This practice has contributed to significant declines in horseshoe crab populations along the Atlantic coast, with cascading effects on coastal ecosystems.

Reliable, synthetic methods to detect endotoxins that can replace the use of horseshoe crabs have been available and in use for decades. These approaches, including recombinant bacterial endotoxin testing (rBET), offer a scientifically robust alternative and are recognized in updated industry standards, including the U.S. Pharmacopeia's Chapter <86>, adopted in 2024.

The Physicians Committee has long advocated for the FDA to update the endotoxin guidance to include acceptance of nonanimal methods in the manufacturing of new and existing products. The organization has also worked with Congress to secure appropriations report language directing the FDA to support the use of synthetic endotoxin testing approaches.

While the FDA’s guidance, Pyrogen and Endotoxins Testing: Questions and Answers (Edition 2), removes certain references to horseshoe crab-based testing, it falls short of meeting the intent of congressional directives. Notably, the guidance does not explicitly incorporate USP <86> into FDA-recognized standards or provide clear regulatory pathways for adopting the synthetic rBET methods. Without this clarity, manufacturers still face significant barriers when transitioning to newer synthetic tests.

“The FDA took an important step by acknowledging synthetic approaches in their news release, but without clear direction in guidance, companies are left navigating uncertainty,” said Jon McCord, PhD, science policy specialist at the Physicians Committee. “Reliable animal-free approaches are already available and widely used. The FDA should ensure its guidance reflects that reality and removes any unnecessary barriers to their adoption.”

These shortcomings mean the revised guidance does not fulfill the congressional directive instructing FDA to include acceptance of appropriate synthetic endotoxin methods for both new and existing products.   As a result, the regulatory landscape remains largely unchanged, and companies continue to face regulatory uncertainty in transitioning away from horseshoe-crab-blood-based tests.

The Physicians Committee urges the FDA to make further revisions to the Pyrogen and Endotoxins Testing: Questions and Answers (Edition 2) guidance to recognize recombinant endotoxin methods under USP <86> and to direct companies to update their existing product testing without laborious regulatory approval.

These congressionally directed changes will strengthen the guidance and the FDA’s stated commitment to advancing nonanimal methods, while modernizing endotoxin testing standards. The Physicians Committee will continue working with industry collaborators and government officials to address these remaining policy needs.