rFC & EndoLISA® Service Portfolio

The implementation of an rFC-based method follows a structured path similar to other pharmacopoeial methods.

Phase I: Preliminary Testing (Inhibition/Enhancement Screening)
As required by all compendial endotoxin test methods, this phase is conducted to determine the appropriate, non-interfering dilution for the product. The product is tested at various dilutions, with and without a known spike of endotoxin (Positive Product Control, or PPC). The dilution at which the recovery of the PPC falls within the compendial range of 50-200% is identified as the valid testing dilution.

Phase II: Method Development and Optimization
For complex matrices that exhibit interference even at the Maximum Valid Dilution (MVD), this phase involves developing sample pre-treatment steps to neutralize the interference. This may include pH adjustment or the use of specific dispersing agents. The EndoLISA® platform is often evaluated during this phase as a powerful problem-solving tool for samples that fail standard interference screening.

Phase III: Product-Specific Validation
The regulatory requirements for validation differ based on jurisdiction.

• European Pharmacopoeia: The rFC method is now a standalone compendial chapter (EP 2.6.32). This means that for European submissions, a full, de novo method validation is not required. Instead, a product-specific validation, which consists of successfully performing the inhibition/enhancement testing from Phase I, is sufficient to demonstrate the method's suitability.

• USP/FDA: The rFC assay is now a standalone compendial method in the United States, described in the official chapter USP <86> Bacterial Endotoxins Test Using Recombinant Reagents (official since May 2025). This chapter makes rFC a compendial, not "alternative," method. Therefore, for new products, a formal validation study to demonstrate equivalency to the LAL method (per USP <1225> or <1223>) is no longer required. Instead, a product-specific validation—the same inhibition/enhancement screening performed in Phase I—is sufficient to prove the method's fitness for purpose.