This article concerns the intersection of the natural world around us with the world of science, in this case, biological science and genetic engineering. Science has not always been kind to our environment and the creatures who share the Earth with mankind, but increasingly we find examples where breakthroughs can significantly alter the prospects for creatures that are under threat of extinction. In this case, the beneficiary is the humble horseshoe crab, a quiet but important inhabitant of Harpswell waters.

In April 2021 I profiled the prehistoric horseshoe crab and the problems they face, so you might find that article of interest. Not only are the crabs at risk from ocean pollution, over-fishing and people using the crabs as bait, but hundreds of thousands of crabs are harvested each year for biomedical purposes. While the crabs have played a critical role in saving human lives, many of the crabs perish during the harvest process. In 2012 the International Union for Conservation of Nature (IUCN) established a subcommittee to keep an eye on crab populations and labeled the crabs as “vulnerable.”

Horseshoe crabs are part of the web of life, and as with other arthropods like the lobster, they are essentially unchanged in over 450 million years of history. In recent years scientists have recognized the importance of the crabs’ eggs to threatened species like sea turtles and shorebirds such as the plovers and sandpipers. The problem for the crabs is that scientists discovered in the 1970’s that the crabs produce unique blood components known as amebocytes that serve to fight off dangerous bacterial pathogens, making the crabs medically vital for human health.

Once the Food & Drug Administration (FDA) approved a new endotoxin safety test in 1977, a specialized industry grew up around the horseshoe crabs. The Atlantic States Marine Fisheries Commission now estimates that roughly 700,000 crabs are harvested each year for this application. Numerous labs disinfect the crabs and withdraw up to 30 percent of their “blood,” known as hemolymph. An isolation and extraction process then results in a unique reagent known as limulus amebocyte lysate (LAL). More on that in a moment.

The crabs are then released to the waters near where they were captured but you can imagine that the entire process is extremely disruptive for them. First, the crabs are loyal to their breeding sites so being released any distance from the point of capture is traumatizing. Then imagine having 30 percent of your blood drawn in a procedure; that would mean roughly three pints of the 10 pints in your body, or three times the recommended limit. It is no wonder that as many as 30 percent of the crabs perish to support this process. Scientists believe the harvesting and blood draw also impacts the breeding potential of the female crabs.

The other side of the story is the importance of the endotoxin testing based upon LAL that is currently the industry standard. We all know that certain bacteria are harmful, even deadly, to humans. This includes Salmonella, Typhoid, Plague, and Escherichia coli (implicated in the recent McDonald’s scare with infected onions). Before a patient receives an intravenous drug or an implanted device, it has been tested for bacterial contamination. The same procedure applies for water and raw materials used in pharmaceutical manufacturing, as well as the vials and syringes used for vaccines. An estimated 70 – 100 million endotoxin tests were done annually but then came the Covid-19 pandemic.

Suddenly the pharmaceutical industry was producing billion of doses of vaccine each year and scientists were concerned that the supply of LAL would be inadequate to support ongoing endotoxin testing. After all, there are only so many horseshoe crabs out there and if the harvesting process continued to kill large numbers of crabs, a supply issue looked inevitable. Fortunately, biological science offered a potential solution.

In the 1990’s, scientists at the National University of Singapore achieved genetic cloning of the key protein in horseshoe crab blood that detects lipopolysaccharides of pathogenic bacteria. Their goal was to develop new endotoxin assays based on that protein, known as recombinant factor C (rFC), eventually eliminating the need for crab-derived LAL. As early as 2003 the Swiss company Lonza began selling rFC-based endotoxin tests, followed by the French company bioMerieux in 2016. Was this the beginning of a large-scale conversion from crab-based endotoxin testing to rFC based tests?

Unfortunately, the pharmaceutical industry is a very conservative business when it comes to introducing new technologies, especially if those technologies will require scrutiny by the FDA. No company is keen to be the first to take a new technology to the FDA unless they have years of scientific data to back them up and compelling clinical trial data to demonstrate both efficacy and safety. Government bureaucrats have few incentives to support new technologies and the legal risks of launching new products are significant, even with widespread support from Congress and the public.

In 2018 Indianapolis-based drug company Eli Lilly & Company achieved the first FDA approval of a new drug using rFC endotoxin testing, a monoclonal antibody for prevention of migraines named Emgality. According to a recent article by Laurel Oldach in C&E News from the American Chemical Society, scientists expected that other pharmaceutical companies would follow the success of Emgality with more rFC endotoxin-tested drug products. But the wheels of change turn slowly.

Since LAL testing was considered the gold standard within the industry, drug companies had to perform a good deal of additional testing if they proposed using an rFC test and were required to submit a formal dossier documenting the results of those tests with a new drug application. Not surprisingly, companies resisted spending the extra time and money when LAL testing was readily available to them. Ms. Oldach has now reported that there was considerable resistance within the US Pharmacopeia, an independent non-profit organization that plays a key role in recommending new policies that drive regulatory practice at FDA. There was also a good deal of lobbying in favor of the status quo since suppliers of LAL endotoxin tests such as Charles River Labs naturally wished to protect their existing markets.

While process improvements had gradually allowed more efficient use of LAL, it became clear that ongoing dependence upon the crab extraction process would not support continued expansion in the endotoxin testing market. This was driven both by the pandemic-triggered growth in vaccines and ongoing needs for testing other materials such as titanium and ceramic hip. Environmentalists and public interest groups were also exerting more pressure on US Pharmacopeia to support a conversion to rFC endotoxin testing.

I will not go into all the drama behind the scenes but the good news is that as of May 2025 the pharmaceutical industry will at last pivot away from near total dependence upon crab-extracted LAL to growing use of the rFC endotoxin testing. This will quickly impact testing for materials like sterile water used in drug manufacturing and more slowly impact the decisions made when submitting new drugs for marketing approvals from the FDA.

After more than 75 years of human life saving efforts on the part of horseshoe crabs, it finally looks like the crabs will soon be allowed to live out their existence in the deep waters and on the mud flats and beaches of Harpswell. We and the crabs are the beneficiaries of stunning scientific advances in medical technology, but the crabs will no doubt be happy just to be left alone.

If you like Ed Robinson’s writing, check out his two Nature Notes books! Click here for more information.