Pyrogen detection methods: comparison of bovine whole blood assay (bWBA) and monocyte activation test (MAT)

Development of the general chapters of the Chinese Pharmacopoeia 2020 edition: A review

The Chinese Pharmacopoeia 2020 edition was reviewed and approved by the National Medical Products Administration and the National Health Commission of the People's Republic of China in July 2020. The current edition was officially implemented on December 30, 2020. The general chapters of the Chinese Pharmacopoeia discuss the general testing methods and guidelines, which are the common requirements and basis for the implementation of drug standards in the Chinese Pharmacopoeia. Owing to adherence to the principles of scientificity, versatility, operability, and sustainable development, there is an improvement in the general chapters of the 2020 edition over those of the previous editions. Further, the application of advanced and mature analytical techniques has expanded, the development of testing methods for exogenous pollutants in traditional Chinese medicines has been strengthened, and technical requirements are now better harmonized with international standards. The updated edition provides technical and methodological support to ensure safety, effectiveness, and control of pharmaceuticals in China and will play an important and active role in encouraging the application of advanced technologies, improving the quality control of medicines, and strengthening the means of drug regulation in China. This review provides a comprehensive introduction of the main features of and changes to the general chapters in the Chinese Pharmacopoeia 2020 edition and aims to provide reference for its correct understanding and accurate implementation.

Development of a rabbit monocyte activation test as an alternative to the rabbit pyrogen test and its application in the analysis of plasma-derived products

The rabbit pyrogen test (RPT) is a safety test conducted as a part of mandatory requirements of regulatory agencies. RPT is currently performed for routine quality control (QC) by manufacturers and for national lot release of biological products, such as plasma-derived products. However, RPT involves the use of many rabbits, counter to the international efforts to minimize the use of animals in research. Furthermore, pyrogen amount cannot be discerned from the test results and the results may be considerably affected by various factors. Therefore, a need exists for substituting RPT with in vitro assays. As a viable alternative to RPT, we here established a rabbit monocyte activation test (RMAT) based on the human MAT in the European Pharmacopoeia. RMAT uses rabbit peripheral blood mononuclear cells as the source of monocytes instead of live animals. The test detected endotoxin, lipoteichoic acid, peptidoglycan, and zymosan with high sensitivity, showing high correlation with the in vivo RPT results. The results of RMAT and RPT testing of non-pyrogenic plasma-derived products were also consistent. Furthermore, RMAT showed satisfactory recovery rates in an interference test with product samples and spiked-in pyrogens. We conclude that RMAT could replace the existing RPT for routine QC.

Applicability of Monocyte Activation Test for Pyrogen Detection in Succinylated Gelatin Injection

Background::

Pyrogens are fever-inducing substances and pyrogen detection is mandatory in parenteral pharmaceuticals. Succinylated Gelatin Injection (SGI) is a biopharmaceutical product, containing multi-component, and it is administered parenterally.

Objective:

The study aimed to assess pyrogen in SGI and to evaluate the feasibility of the Monocyte Activation Test (MAT) for pyrogen detection in a multi-component pharmaceutical product.

Method:

In the present study, the Bacterial Endotoxin Test (BET) and the Monocyte Activation Test (MAT) were employed to assess pyrogen in SGI. The MAT method was developed on the basis of the HL-60/IL-6 assay. HL-60 cells were incubated with lipopolysaccharide (LPS) standards and sample solutions. The endotoxin produced by the incubation, interleukin-6 (IL-6), was measured by ELISA. The MAT method was validated and main parameters were investigated. Finally, the pyrogenicity of SGIs from two different enterprises was determined by the developed MAT method.

Results:

The BET failed in the test for interfering factors and the MAT was proved suitable for the pyrogen detection of SGI. All the products examined showed negative results in the pyrogen detection test.

Conclusion:

The MAT method is feasible in pyrogen detection of SGI. It can be applied in pyrogen detection for quality and safety control of multi-component biological products.

Development and characterization of stable reporter cells for fast and sensitive detection of pyrogen

Pyrogens are a class of heterogeneous compounds that cause fever and induce inflammatory responses in the host. Lipopolysaccharides (LPS, also known as endotoxin) is the major pyrogen in the category of drug quality control. Accurate and fast quantification of pyrogens is crucial for drug safety. In the present study, we aimed to develop a sensitive and reliable method for rapid detection of pyrogens using luciferase reporter assay. Stable human A549 luciferase reporter cells were constructed under the control of a NF-κB-responsive element or IFN-β promoter. Our results showed that several monoclonal stable cell clones responded to 0.1 EU/ml endotoxin, which was less than human fever threshold at 0.3 EU/ml of endotoxin. Further, compared with original A549 cells, TLR4 expression on the reporter cells were significantly increased after low amount LPS stimulation. In addition, reporter cells also responded to zymosan stimulation. Therefore, these results indicated that the stable luciferase reporter cells respond to endotoxin and non-endotoxin pyrogens and have the potential to further develop into a sensitive and fast pyrogen evaluation method.

Use of Toll-like receptor assays for the detection of bacterial contaminations in icodextrin batches released for peritoneal dialysis

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Monocyte test assays were poorly efficient for the detection of little bacterial contamination in icodextrin batches.

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TLR2- and TLR4-transfected cell lines were appropriate for detecting PGN and LPS contaminations.

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Mutanolysin treatment of icodextrins enhanced the response of TLR2-transfected cells to contaminating PGN.

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Using TLR-transfected cell lines is a valuable approach for selecting icodextrin batches for peritoneal dialysis solutions.

Icodextrin is a starch derivative used for preparing solutions of peritoneal dialysis. Unfortunately, peptidoglycans (PGN) and lipopolysaccharides (LPS) have been reported to contaminate certain icodextrin batches and to contribute to the development of sterile peritonitis. The decision of selecting or rejecting icodextrin batches is however difficult, because of limitations in the detection of these bacterial contaminants. Besides monocyte activation tests of cytokine release, a number of bio-assays using stably TLR-transfected cell lines have been developed. Here, we compared the efficacy of TLR2- and TLR4-transfected cells to detect bacterial contamination with the responses of monocytes exposed to the same icodextrin samples. In contrast to monocyte models of cytokine release, we found that TLR2- and TLR4-transfected cell lines are highly sensitive to detect little PGN and LPS contaminations in the presence of icodextrin. With the intent to increase PGN reactivity, mutanolysin was used to generate soluble fragments in icodextrin samples. We found that such an enzymatic treatment led to an enhanced response of TLR2-transfected cells, even though parental icodextrin samples were poorly reactive. Altogether, these findings indicate that the use of TLR2- and TLR4-transfected cell lines is a valuable approach for helping to the decision of selecting icodextrin batches for peritoneal dialysis.

In Vivo Effect of Innate Immune Response Modulating Impurities on the Skin Milieu Using a Macaque Model: Impact on Product Immunogenicity

Unwanted immune responses to therapeutic proteins can severely impact their safety and efficacy. Studies show that the presence of trace amounts of host cells and process-related impurities that stimulate pattern recognition receptors (PRR) can cause local inflammation and enhance product immunogenicity. Here we used purified PRR agonists as model impurities to assess the minimal level of individual innate immune response modulating impurities (IIRMIs) that could activate a local immune response. We show that levels of endotoxin as low as 10 pg (0.01 EU), 1 ng for polyinosinic:polycytidylic acid (PolyI:C), 100 ng for synthetic diacylated liopprotein, thiazoloquinolone compound, or muramyl dipeptide, 1 μg for flagellin or β-glucan, or 5 μg for CpG-oligodeoxynucleotide increased expression of genes linked to innate immune activation and inflammatory processes in the skin of rhesus macaques. Furthermore, spiking studies using rasburicase as a model therapeutic showed that the levels of PRR agonists that induced detectable gene upregulation in the skin were associated with increased immunogenicity for rasburicase. This study underscores the need for testing multiple IIRMIs in biologics, strengthening the connection between the local mRNA induction in skin, innate immune activation, and antibody development in primates, and provides an indication of the levels of IIRMI in therapeutic products that could impact product immunogenicity.