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Crab Blood Can Save Your Life, but Not the Synthetic Stuff

Caroline Delbert
Photo credit: Daniela Duncan - Getty Images

From Popular Mechanics

  • A U.S. drug body has decided synthetic crab blood can't be listed alongside the real thing.
  • Scientists have found up to 30 percent of crabs used for their blood die after the procedure.
  • The synthetic will be listed in a separate chapter with different data requirements.

Animal rights activists have had their hopes dashed for a synthetic replacement for the crab blood the pharmaceutical industry relies on for testing. The United States Pharmacopoeia Convention (USP) was expected to approve a synthetic horseshoe crab blood substitute that would be listed alongside the real thing in the protocols scientists use when they test drugs.

Instead, the USP decided to relegate synthetic crab blood to a separate chapter from the rest of the endotoxin testing standards. That means anyone who sought to use the synthetic blood would need to build a persuasive case that their testing was equivalent, instead of simply using it as an accepted alternative right out of the box.

The murky world of horseshoe crab bleeding sounds like something PETA’s deftest marketers made up. Horseshoe crabs are taken from the ocean and drained of a third of their valuable blue blood—a third of a human’s blood is half a gallon—then the crabs are thrown back. They spend days out of the water, in varying temperatures and conditions, and little has been measured about what happens after that.

More recent studies have shown evidence that a previous belief that “just” 15 percent of crabs died is closer to twice that amount, with further damage to reproduction. Even if the previous idea was right, the crabs are taken in unlimited quantities that have continued to rise.

“They can take as many crabs as they like, and that harvest continues to grow, rising from around 130,000 in 1989 to 483,245 in 2017, according to the [Atlantic States Marine Fisheries Commission]’s latest stock assessment report,” Popular Mechanics reported last year. And half the bled females did not reproduce.

It’s into that troubled scenario that Swiss pharmaceutical company Lonza and others have made recombinant Factor C (rFC), which the European Pharmacopoeia Commission has announced it will accept alongside the real thing beginning with its 2021 documentation. The synthetic version is derived from the chemical makeup of the real blood, but manufactured without any animal materials.

Horseshoe crab blood and rFC are both used to screen injectable drugs for the presence of toxic contamination. The crabs' unique blood chemistry leads to unmistakably clear reactions to endotoxins, which include E. coli and salmonella.

The USP cited insufficient data as its rationale for rejecting a side-by-side inclusion of both options. “This means drug companies seeking to use it must continue to do extra validation work, to guarantee their methods of using rFC tests match those of tests made from horseshoe crab blood,” the Guardian reports. “The decision gives the drug industry fewer incentives to end its reliance on animal-based tests.”

Lonza hypes the approval of at least one drug tested with rFC despite the extra hurdles: an injectable migraine prevention drug called Emgality. Injectable drugs also include a future vaccine for COVID-19 (coronavirus) and a huge spread of other treatments and vaccines. And Emgality is a kind of drug called a biologic, which has special risk for contamination and an increased reliance on contamination testing. The U.S. Food and Drug Administration explains:

“In contrast to most drugs that are chemically synthesized and their structure is known, most biologics are complex mixtures that are not easily identified or characterized. Biological products, including those manufactured by biotechnology, tend to be heat sensitive and susceptible to microbial contamination.”

Eli Lilly is a huge company with deep pockets, but it's said outright that the extra and different regulations on rFC are discouraging other companies, per the Guardian. The USP decision is a further obstacle, but the USP has approved alternative testing regimens in the past, like the sterility testing that also affects injectable and biological drugs. If its complaint is a lack of data, then the more people who adopt the synthetic regimen, the more data will accumulate on their side.

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