Recombinant factor C (rFC) has been available since 2003.

TFA alludes to it: “They have created a lab-made alternative to test medicines, so no crabs are needed.

“It is the exact same protein, it is just made through biotechnology,” Bolden said.

Bolden said scientists at Eli Lilly tested thousands of samples on hundreds of different products and determined the alternative performs the same or better than purified horseshoe crab blood does.

Starting in 2016, Eli Lilly started to switch its testing to the lab-made version. Now 80 percent of it is done using the alternative.

The company plans to entirely eliminate the use of crab blood.”

They are a (relatively) recent part of the production pipeline. Before introducing horseshoe crab blood, they used to inject rabbits and wait a couple of weeks. Now the wait has been reduced to minutes - which reduces storage costs and increases certainty.

But there are other options.

It’s in the article - Eli Lilly has largely switched to a synthetic protein.

There's economics wrapped up in finding a reproducible synthetic replacement against harvesting. If climate change causes a drop in horseshoe crab availability we might see the pressure here.