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Horseshoe crabs have been living in the ocean for almost half a billion years, surviving five mass extinctions. However, their use in lab tests has put new pressure on these ancient creatures. Drug companies have been trying to change that.
The copper-based, blue-colored blood of the horseshoe crab is highly sensitive to bacterial endotoxins, and drug manufacturers have used the blood to test for contaminants in drugs for years. The labs producing Limulus amebocyte lysate (LAL) for drug testing drain blood from live horseshoe crabs and then release the animals again, but it’s been estimated that as many as 30% of the crabs captured for this purpose in the United States do not survive the process.
Fortunately, a synthetic substitute, recombinant factor C (rFC), can do the job as well as, or better than, horseshoe crab blood and costs less. Unfortunately, regulation in the United States has not yet caught up with the science, but that appears ready to change.
“The technical hurdles are gone,” according to Jay Bolden, Director of Global Quality Laboratories at Eli Lilly. “The hurdles that remain are regulatory and pharmacopeial in nature.”
The U.S. Pharmacopeia (USP), an independent nonprofit organization that sets standards for ensuring the quality of pharmaceuticals, has not given across-the-board approval to use the synthetic rFC for quality control tests. USP announced Aug. 22 that an expert committee has recommended USP change its policy, and it will open public comment.
Until the policy does change, drug makers can only gain approval for testing individual drugs with rFC after submitting data to the Food and Drug Administration (FDA), according to Bolden.
Although applying for rFC approval one drug at a time is a slow process, Lilly has been a leader in pushing for the use of rFC in quality control tests. Lilly has been joined by other major drug makers, like Sanofi, Pfizer, and Roche, in promoting the switch from horseshoe-crab-based LAL to synthetic rFC.
“We drew a line in the sand in 2016. And we said that we would start converting all of our new medicines and then anything that we could that wasn’t difficult to do from a regulatory standpoint,” Bolden said.
When Lilly releases a new drug, it can specify that rFC is the standard quality control test. The bigger challenge has been gaining permission to use rFC as a testing agent for drugs that Lilly has been producing for years. Lilly has had to conduct tests with rFC for each drug separately.
“It’s hard to make the regulatory changes. It takes a lot of effort and resources. But I think at this point we are about 80% converted,” Bolden said.
Sustainability, quality, supply chain, and cost
There are four very good reasons to make the switch: sustainability, supply chain, quality, and price.
Sustainability is important to Bolden, an avid birder. The eggs of the horseshoe crab are essential to the diet of the red knot, a shorebird. “The red knot was listed as threatened by the US Fish and Wildlife Service,” and reduced populations of horseshoe crabs along the Atlantic coast have had a negative impact, Bolden said.
Of course, the crabs themselves face pressure. In the United States, horseshoe crabs are considered a “vulnerable” species, but in Asia, the population has been badly depleted. The Asian genus of horseshoe crab, which is used to make a reagent like LAL called tachypleus amebocyte lysate (TAL), is an endangered species.
Along with conservation concerns, there are also concerns about the viability of a supply chain built on a reduced animal population.
Bolden works on a subcommittee of the Pharmaceutical Supply Chain Initiative that focuses on the use of LAL and TAL, and they recently released a report saying the use of TAL would cause problems for the industry.
“Everybody agreed that we should not have TAL in our supply chains—we shouldn’t be using an endangered animal to source test reagents. And then the second piece was we should start reducing use of LAL,” he said.
Regarding “quality,” Bolden pointed out that the word is in his job title. “I’m a quality guy,” he said, explaining that he’s responsible for ensuring Lilly’s manufacturing achieves the highest standards. He said rFC’s quality is supported by a lot of data.
“You would expect a recombinant produced from biotechnology, a validated manufacturing process, would be more consistent batch to batch than pulling live animals out of the sea,” said Bolden. He added that gaining exceptions to use rFC instead of LAL has required multiple tests, which means Lilly already has extensive sets of results proving the relative quality of the synthetic.
“We have loads and loads of data at this point that show that rFC is equivalent to, and in some cases better than LAL,” he said.
As for cost, rFC is less expensive than LAL, and as the scale of rFC production increases, it can be expected to be more favorable, Bolden said.
Change is coming for horseshoe crabs
Since making rFC use a priority in 2016, Lilly has been working with regulators to enable the switch away from LAL. The progress, at first slow, is beginning to build momentum, according to Bolden.
Ten years ago, there was only one company producing rFC for commercial use. “Now, there’s at least five commercial recombinant reagents,” he said.
Meanwhile, the USP is promising to consider recommending broader use of rFC. “There was the public statement out of the USP around October last year that said it would be a priority for them for this year,” Boden said. “If USP were to be able to issue an endotoxin test methodology using rFC, I think that would break down a lot of the perceived barriers for a lot of companies.”
The USP announcement on Aug. 22 that they would publish a public health standard for endotoxin testing using recombinant reagents was a monumental turning point, according to Bolden.
“I feel like we’ve actually turned the corner here in the last, I don’t know, six months or so,” he said. “We’re making meaningful progress.”
