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Background: The aim of the BSP090 project is the establishment of European Pharmacopoeia Chemical Reference Substances (CRSs) in combination with corresponding standard ELISA methods for quantification of major allergens in allergen products. Here, we present data of a Phl p 5‐specific sandwich ELISA that proved suitable for the quantification of Phl p 5, one of the major Timothy grass (Phleum pratense) pollen allergens. Methods: A Phl p 5‐specific ELISA system was assessed with respect to accuracy, precision, inter‐assay (within laboratory) and inter‐laboratory variations, in a ring trial including 14 laboratories in Europe and the USA. Model samples containing recombinant Phl p 5a CRS as well as native grass pollen extracts were analysed. Each participant was instructed to perform at least one preliminary assay to familiarise with the protocol, followed by three independent assays. Results: The candidate standard ELISA proved suitable to quantify recombinant and native Phl p 5 with satisfactory precision (93% of results within ±30% acceptance range). Inter‐assay variation (max. GCV 24%) and especially inter‐laboratory variation (max. GCV 13%) showed conclusive results. When assessing accuracy by means of recovery of recombinant spikes from a grass pollen extract matrix, similarly satisfactory spike recovery results were observed for the two spikes with higher concentrations (all within ±30% acceptance range), whereas recovery of the lowest concentration spike was slightly poorer with mean results of six laboratories exceeding acceptance range. Conclusions: Based on the collaborative study results, the assessed Phl p 5‐specific immunoassay is appropriate to be proposed as European Pharmacopoeia standard method. [ABSTRACT FROM AUTHOR]

Direct LC/MS/MS methods have recently been developed for measuring triphosphate anabolites of several nucleosidic reverse transcriptase inhibitor (NRTI) in peripheral blood mononuclear cells (PBMCs) from HIV-positive patients. Whereas AZT is one of the most-used NRTIs, no such method has been developed for AZT-TP, its active anabolite, mainly because of the presence of endogenous nucleotides that interfere with such an assay. In this paper, we first describe the development of two enzyme immunoassays (EIA) of AZT-TP in PBMCs: one directly measuring AZT-TP content; the other, measuring the nucleoside AZT after selective extraction of AZT-TP and dephosphorylation. The precision of these two assays was too low to achieve precise determination of AZT-TP in PBMC samples. Direct LC/MS/MS is not specific enough for AZT-TP, since at least two interfering endogenous nucleotides (same m/z ratio and fragment as well as retention time close to that of AZT-TP) are found in the intracellular medium of PBMCs. The off-line combination of immunoaffinity extraction (IAE) and LC/MS/MS proved to be a successful strategy allowing without dephosphorylation appropriate specificity and sensitivity (limit of quantification established as 9.3 fmol/[10.sup.6] cells) to determine AZT-TP in PBMCs from 7 mL of blood of HIV-infected patients. Validation of this IAE-LC/MS/MS method demonstrated CV percent for repeatability and intermediate precision lower than 15%. More than 150 samples/ week can be analyzed by one analyst, making this method suitable for routine analysis during clinical studies.

An international collaborative study was organised to establish the 3rd World Health Organization (WHO) International Standard (IS) for Erythromycin. Fifteen laboratories from different countries participated. Potencies of the candidate material were estimated by microbiological assays with sensitive micro-organisms. To ensure continuity between consecutive batches, the 2nd IS for Erythromycin was used as a reference. Based on the results of the study, the 3rd IS for Erythromycin was adopted at the meeting of the WHO Expert Committee on Biological Standardization (ECBS) in 2018 with an assigned potency of 925 International Units (IU) per mg. The 3rd IS for Erythromycin is available from the European Directorate for the Quality of Medicines & HealthCare (EDQM)., (© Council of Europe 2020.)