Low Endotoxin Recovery: A Comprehensive Overview for Biologic Drug Manufacturers

Low Endotoxin Recovery (LER) is a complicated phenomenon in which there is a loss of detectable endotoxin activity over time when undiluted products are spiked with a known amount of endotoxin.

Endotoxin detection is an integral part of the quality control process, and LER muddles the reliability of results, which can result in risks to patient safety and noncompliance with regulations. 

LER was first reported by Chen & Vinther in 2013, although it had no doubt been occurring for years before it was formally introduced to the scientific community. As early as 1998, the impact of masked endotoxin in biologic formulations was being researched and highlighted as a major quality concern.

Since then, studies have revealed that LER can also be surfactant-specific and that masked endotoxins can activate immune responses. In response, the Parenteral Drug Association (PDA) formed an LER task force in 2015, which has since published a detailed report providing information, guidance, recommended procedures, and scientific findings.

LER is a temperature- and time-dependent process. Formulation matrix components like surfactants and buffers disrupt endotoxin aggregation, preventing detection via routine Bacterial Endotoxin Testing (BET). The result? False negatives or reduced recovery, despite biological activity remaining.

LER is highly variable. A 2019 study showed that endotoxin masking is dependent on the endotoxin source used, and parameters such as bacterial strain and growth conditions can lead to different masking susceptibilities. Because of this, it is impossible to predict the susceptibility of bacterial endotoxin contamination to LER. To address this variability in routine testing, it is recommended to use RSE (Reference Standard Endotoxin) to check the LER susceptibility of the matrix/drug.

LER raises serious concerns for patient safety, product quality, and regulatory compliance. If endotoxins are released into the human bloodstream, a reaction can occur that may lead to life-threatening conditions. Undetected endotoxins can still activate immune responses and interfere with the intended purpose of the drug or therapy.

To ensure the validity of test methods, regulatory agencies require hold-time studies in addition to pharmacopoeia requirements, to assess detection over time and ensure the chosen detection method recovers the expected amount of endotoxin at each time point.

As part of the PDA TR 82, one study includes data on the use of our ENDO-RS kit to overcome LER: the application of the ENDO-RS sample-preparation method was assessed, and the results showed that endotoxins were reliably detected/unmasked under all the conditions tested. Implementing and validating a robust method like ENDO-RS is critical, but the process can be overwhelming. That’s where our ENDOXPERTS™ services step up to the plate. Our global team of experts with deep experience in rFC-based testing is on hand to support the design and optimization of a routine endotoxin testing strategy. From identifying your product’s LER challenges to establishing a validated, release-ready endotoxin testing strategy, our ENDOXPERTS™ team is by your side throughout the entire process.

LER is a complex and critical issue, but it’s not one you have to fight alone. Continued investment in innovative testing methods is vital, and bioMérieux can be your partner on this journey.

Complete the form below to get in touch with our ENDOXPERTS™ team. A bioMérieux expert will be happy to contact you. By providing your information, you agree to receive additional emails from bioMérieux about endotoxin testing.