The Atlantic horseshoe crab (Limulus polyphemus) is one of the marine species that best represents animals popularly known as living fossils. These xyphosurs of the order of marine lylicerates maintain a virtually equal body structure for 475 million years.
Over the last few decades, the long history of these saucepan-shaped animals has begun what could be the path of their extinction due to the unique characteristics of their blood. The hemolynfa (body fluid) of the Atlantic horseshoe crab is blue because it contains hemocylanin, a hemoglobin-related protein that carries oxygen through the animal’s body.
The pharmacological utility of hemocyanin (e.g. immunostimulant) has multiplied in recent years the capture of these animals, which are then sectioned in the laboratory to extract their blood.
The recent laboratory production – by a company is based in Switzerland, supported by animal advocacy groups – of a substance with characteristics similar to those of blue blood of these crabs, believing that it would end up – or at least reduce – the capture and use of animals in the laboratory, but, for the time being, it is not clear that this will be the case.
The leading U.S. pharmaceutical and drug data collection entity, US Pharmacopeia (USP), published a review of recombinant C-factor (rFC) data on May 29, the synthetic alternative to the reagent that is so far extracted from horseshoe crab.
In the first part of this medical product utility guide or notice, USP highlights its interest in “introducing more methods for the detection of bacterial endotoxins, an important initial step in the process for the development of vaccines and other injectable therapies”. In addition, this specialized entity, with great influence in the pharmaceutical sector worldwide, highlights the complementary values of such a synthetic product, among which are the uniformity of the product obtained in laboratory (as well as the variability of the products obtained from animals), the ease of production on a large scale and the reduction of the impact on natural life.
However, according to Zurich, Switzerland, John Miller, a journalist specializing in medicine and health at Reuters, the most important part of the instruction disseminated by the USP is that it places the new synthetic product in a different group than the natural substance, so that horseshoe crab blood would remain the ultimate reference in products such as endotoxin testing.
“The USP, whose influential publications guide the pharmaceutical industry, initially proposed adding the rFC to the chapter governing international endotoxin testing standards but has now reversed and opted to place rFC in a new independent chapter,” says John Miller. “This means that pharmaceutical companies that could use the rFC must continue to do additional validation work, to ensure that their methods of using rFC tests match those of tests made with crab blood.”
The decision gives the pharmaceutical industry less incentive to stop relying on animal testing, even when companies like Lonza and France’s bioMerieux promote synthetic alternatives and wildlife advocates insist on their opposition to the exploitation of horseshoe crab blood.
Representatives of the USP have told Reuters that there is “very little practical experience with rFC-tested pharmaceuticals to put synthetic tests on an equal footing with crab blood tests, which have been widely used for decades.” Reuters, on the other hand, cites some pharmaceutical companies that consider synthetic alternatives to be completely safe and warn that decisions like those of the USP only stop new therapies free of experiments and exploitation of animals.