Microbial Solutions
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Eureka Staff
Recombinant Factor C Assay: Under the Microscope
Discover more about alternative endotoxin detection tests such as the animal-free Recombinant Factor C Assay.
About 40 years ago, the ancient horseshoe crab, which dates back at least 440 million years, assumed a new role. After researchers discovered that its blue blood contained a vital protein capable of detecting harmful endotoxins found on the outer membrane of Gram-negative bacteria, this species became a vital partner in fighting the spread of infection. Every drug or device approved for parenteral use, worldwide, must be evaluated using the bacterial endotoxin test (BET) for the potential to induce a fever in a patient (pyrogenicity). Today there are approximately 70 million Limulus Amebocyte Lysate (LAL) tests performed annually that are derived from horseshoe crab blood. Pharmaceutical and medical device manufacturers use the test to ensure their products remain endotoxin-free and that their patients remain safe.
Currently, the verified, FDA-approved standard for the BET is the LAL assay, which is produced by concentrating and lysing the blood of the Atlantic horseshoe crab. There are some, both in and outside of the pharmaceutical sector, who believe that the supply of LAL may not be able to keep pace with this growing demand. Citing this presumption, along with concerns that purports to eliminate the need for animal-derived products for bacterial endotoxin testing, alternative endotoxin detection assays, such as the Recombinant Factor C Assay, have been developed. While this could ostensibly be a way to reduce substantially our reliance on horseshoe crabs, the synthetic products carry their own sets of challenges. These methods promise laboratory-based, rapid, specific alternatives to the standard LAL assay. However, not only do these alternative methods require extensive validation, but concerns also exist regarding the accuracy, specificity, robustness, and reproducibility of these assays.
lan Hoffmeister, Senior Endosafe Product Specialist for the Microbial Solutions division of Charles River, which is an FDA-licensed LAL manufacturer, discusses some of the major differences between the recombinant factor C assay and LAL tests.
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Trillium utilizes a 3-Factor enzymatic cascade formulation that mimics the traditional LAL cascade reaction involving Factor C, Factor B, and pro-clotting enzyme. Our animal-free endotoxin testing solution revolutionizes the way we approach endotoxin testing while strengthening our united commitment to sustainability initiatives.
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Validation is key for any new product. How much data is available about synthetic products such as Recombinant Factor C?
Hoffmeister: Validation is a major component for any new testing method that is looking to be adopted. Without a scientifically sound validation, the reliability of the new method cannot be assured. All compendial methods must be validated in accordance with scientifically accepted principles, and this would often include independent multi-lab collaborative studies, designed to assure that the new method does indeed meet the validation requirements.
LAL, for instance, underwent years of testing before it was deemed suitable for use as an end-product release method for drug products and medical devices. That testing included side-by-side testing against the then-only compendial method available, the rabbit pyrogen test (RPT). Over a number of years, hundreds of thousands of LAL results were compared against tens of thousands of RPT, and these tests proved LAL to be more sensitive, reliable and reproducible than RPT. It was only after such exhaustive testing that LAL was officially accepted as a suitable replacement to RPT.
Firms wishing to adopt Recombinant Factor C as an alternative to LAL are required to carry out alternative methods validation, where they test for Specificity, Linearity, Range, Accuracy, Precision, Limit of Detection, Quantitation Limit and Robustness. Without this Recombinant Factor C cannot be used to replace the LAL assay for end product release.
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Across two one-hour webinars, we will explore how Trillium detects and quantifies natural environmental endotoxins by simulating the LAL enzymatic cascade.
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What are the regulatory requirements for recombinant products and LAL tests?
Hoffmeister: Recombinant products don’t need to be manufactured to FDA requirements and standards. Instead, companies wishing to use these recombinant products must perform their own alternative methods validation and must seek prior approval to use the alternative method from the respective competent authorities, for each drug or medical device they wish to release with the alternative method. Alternative methods validation must include specificity testing, to prove the method capable of detecting endotoxin from all relevant sources. This would entail testing endotoxin from a variety of Gram negative organisms, including organisms isolated from the natural flora of each company site performing the validation. The number of organisms included in this testing must be sufficient to prove specificity.
Endosafe® Trillium™ rCR Technical Report
To further demonstrate the robustness and validity of our Trillium rCR matrix and formulation, we published a technical report detailing the results of our comprehensive beta test study program. The report highlights assay equivalency to our FDA-licensed kinetic LAL assay via our primary alternate method validation.
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Are recombinant products bound by the same FDA scrutiny as LAL?
Hoffmeister: No. Because it was being used to replace the rabbit pyrogen test and because it is derived from blood—in this case from the horseshoe crab—the FDA decided LAL reagents should be monitored and licensed, so you have to be a licensed approved manufacturer to produce LAL. But that is all the FDA licenses. Every other product we produce, our endotoxin, water, buffers, software, instrumentation, none of that is licensed. The reason the FDA does not license recombinant products such as Recombinant Factor C is that they do not come from the blood of the horseshoe crab. That means they don’t have oversight over the manufacturers of these products. Any manufacturer can set up and produce Recombinant Factor C without needing to meet specific regulatory requirements.
There seems to be a push for a 3R’s initiative, how do endotoxins methods like the Recombinant Factor C Assay play into this approach?
The 3Rs principle (Replacement, Reduction, and Refinement) was developed over 50 years ago to provide an ethical framework for performing animal research. A prominent area where sustainability and innovation intersect is bacterial endotoxin testing. Endotoxin testing methods have been influenced by the 3Rs with the ultimate goal of replacing, reducing, or refining tests that rely on animals. Advancements in technology and scientific research have unlocked new possibilities for creating sustainable alternatives to animal-derived products, such as the Recombinant Factor C Assay. Today, organizations worldwide are pursuing animal-free options to ensure sustainable supply chains and business operations, while affirming their commitment to corporate citizenship
References
- 2.6.30. Monocyte-Activation Test. In European Pharmacopoeia; Council of Europe: Strasbourg: Council of Europe.
For more information about our animal-free endotoxin methods, discover the Endosafe® Trillium™ Recombinant Cascade Reagent (rCR).