It’s a bad week for horseshoe crabs as their defenders have failed to convince big pharma that synthetic crab blood is a viable alternative for endotoxin testing in drugs. Maryland-based US Pharmacopeia (USP) has blocked this effort.

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Real horseshoe crabs’ copper-rich blue blood clots when it comes into contact with bacterial endotoxins — which, if present in products, can cause severe diarrhea and even toxic hemorrhagic shock. Since partially replacing rabbit tests in 1977, horseshoe crabs’ blood has been the industry standard. Animal rights groups and Switzerland-based Lonza have pushed for synthetic versions called recombinant Factor C (rFC).

Related: Pacific Ocean’s elevated acidity is dissolving Dungeness crabs’ shells

At first, experts thought USP, which produces influential drug industry publications, would add rFC to its chapter on international endotoxin testing standards. Instead, the organization decided to give rFC its own chapter. This means that even if a company wants to use rFC, it will still have to do additional testing with real horseshoe crab blood to validate results, which ultimately defeats the purpose.

“Given the importance of endotoxin testing in protecting patients … the committee ultimately decided more real-world data [was needed],” USP said in a statement. USP said it supports shifting to rFC where possible, potentially including testing COVID-19 vaccines or medicines.

Some drug companies are already using the synthetic tests to improve human health. Eli Lilly uses rFC for testing Emgality, a migraine treatment.

Unlike most lab animals, the horseshoe crabs are captured, bled and released. John Dubczak, director of operations at Charles River Laboratories, told Scientific American that no more than 30% of a crab’s blood is removed and claimed a mortality rate of 4%. “One of my suppliers built a water slide to put the crabs back into the water,” Dubczak told Scientific American. “They love it!”

Conservationists suspect the mortality rate is much higher for the industry as a whole. “There’s not very good science-based information on the mortality of the crabs,” Michael De Luca, senior associate director at the Institute of Marine and Coastal Sciences at Rutgers University, said in the same article. “I’ve see figures range from 15% to 40% but nobody has a really good handle on that.”

Via The Guardian, Scientific American and Horseshoe Crab

Image via Chris Engel