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Advancing alternatives to horseshoe crab blood

Every year, hundreds of thousands of horseshoe crabs are harvested for their blood, despite the availability of safe and effective alternatives.

Horseshoe crabs are an ancient and ecologically critical species. Yet every year, hundreds of thousands are harvested for a chemical compound in their blood (limulus amebocyte lysate, LAL), which is used to test the safety of injectable vaccines and medications.

The bleeding of live horseshoe crabs is a gruesome process that kills up to 30% of individuals. It is ecologically unsustainable for both horseshoe crabs and the shorebirds that rely on their eggs as a primary food source during spring migration.

Together with scientific, legal, and industry partners, we are working to end horseshoe crab harvests by advocating for the adoption of the safe, effective and commercially scalable synthetic alternatives to LAL that are available for endotoxin testing. These alternatives have existed for decades but have lagged in adoption due to regulatory hurdles.

Endangered horseshoe crab being bled in a factory

We need your help to save the horseshoe crab!

On August 22, 2023, the U.S. Pharmacopeia (USP) announced a long-awaited new regulatory chapter, known as Chapter <86>, which provides guidance on endotoxin testing using recombinant Factor C (rFC), a synthetic alternative to horseshoe crab blood.

Chapter <86> allows manufacturers to use rFC, in addition to current methods for endotoxin testing. In addition to preserving horseshoe crab species, the new standard will enable manufacturers and pharmaceutical companies that adopt rFC to more easily meet their environmental goals and avoid the use of animal products. The chapter is an important step in ensuring the future for horseshoe crabs, as well as safety and supply of biopharmaceutical products.

Please join us in voicing public support for the adoption of Chapter <86>.

History of the project

Horseshoe crabs have been living in the ocean for half a billion years, surviving five mass extinctions. They are an ancient and ecologically critical species that needs our protection. Since 2018, Revive & Restore has collaborated with scientific, legal, and industry partners to promote the adoption of rFC and stop the bleeding of this threatened keystone species, including

  • Highlight the efficacy, safety, and equivalency data of rFC
  • Advance the use of rFC equivalency guidelines from the European Pharmacopeia
  • Urge the US Pharmacopeia and the FDA to catch up with international standards
  • Raise awareness of the importance of the horseshoe crab and rFC


In 2018, Revive & Restore co-founder and executive director Ryan Phelan, colleague Tom Maloney, and former Wilson Sonsini attorney Naira Simmons co-authored a peer-reviewed research article that confirmed the efficacy of rFC and found that the biomedical industry could achieve a 90-percent reduction in the use of reagents derived from horseshoe crabs by using the synthetic alternative—a huge step toward protecting horseshoe crab populations. The study also found that:

  • rFC is just as efficacious and safe as LAL.
  • rFC is more consistent than LAL.
  • rFC causes fewer false positives than LAL and is more cost-effective.
  • rFC is more widely available than ever.
  • rFC for testing of injectable medications is allowed by the FDA.
  • rFC can reduce the need to use horseshoe crab blood by 90%.

To date, the synthetic alternative rFC has been studied in the development of 213 pharmaceutical products in 8 categories, providing significant efficacy, equivalency, and safety data in vaccines, raw materials, and large- and small-molecule drug products.


Pharmacopeia organizations set quality, purity, strength, and identity standards for medicines around the world. By recognizing equivalency between LAL and rFC, pharmacopeias can help reduce the need to harvest blood from hundreds of thousands of crabs each year and help protect migratory shorebirds, who depend on horseshoe crab eggs to fuel their journey.

The European Pharmacopeia has endorsed the use of rFC since 2019. On July 1, 2020, the European Pharmacopeia published compendial chapter 2.6.32., stating, “A test for bacterial endotoxins using rFC can be used in the same way as LAL-based methods.” In fact, European, Japanese, and Chinese Pharmacopeias all recognize rFC as an equivalent to LAL. 

Unfortunately, the U.S. Pharmacopoeia (USP) has not kept pace with international standards. Currently, pharmaceutical manufacturers in America have to prove to regulators that synthetic alternatives are as effective for LAL for each product—a process that takes time and money.


On August 22, 2023, the U.S. Pharmacopeia (USP) announced a long-awaited new regulatory chapter, known as Chapter <86>, which provides guidance on endotoxin testing using rFC. rFC can be developed at scale and eliminates the need for harvesting (bleeding) horseshoe crabs. The draft guidelines are a “first and important step” toward changing how companies test for dangerous bacterial contamination in their products, says Jaap Venema, chief science officer at USP in a 2023 Science article.


In 2018, Revive & Restore hosted a press event in Cape May, New Jersey, a location renowned for its concentrations of shorebirds and breeding horseshoe crabs. The event was joined by the state’s First Lady Tammy Murphy, the New Jersey Audubon Society, and representatives of Eli Lilly to announce research findings that dispel the barriers to adopting the synthetic alternative, rFC.

This event led to a wide array of much-needed media coverage of the horseshoe crab and rFC. It also led to several environmental groups joining forces for the horseshoe crab. Now, several Atlantic Coast state Audubon societies, the National Wildlife Federation, the National Resource Defense Council, Eli Lilly, the American Bird Conservancy, Revive & Restore, and dozens of other organizations make up the Horseshoe Crab Recovery Coalition. This group is leading a science-based campaign that aims to stem years of decline in horseshoe crab populations and fully restore them by 2030.