Assay Variability Research Articles

Demonstration of physicochemical and functional similarity between Stimufend (pegfilgrastim-fpgk) and Neulasta (pegfilgrastim): A comparative analytical assessment.

Pegfilgrastim is a long-acting recombinant human granulocyte colony-stimulating factor biologic that is indicated to reduce the incidence of infections, manifested by febrile neutropenia, in patients receiving myelosuppressive anti-cancer drugs and to increase survival in patients acutely exposed to myelosuppressive doses of radiation. Due to the high cost of biologic therapy and the scarcity of biosimilar alternatives, there is an unmet medical need for targeted biologics. This comparative analytical investigation aimed to confirm the similarity of biosimilar Stimufend® (pegfilgrastim-fpgk) to reference product Neulasta® (pegfilgrastim). The analysis was designed using state-of-the-art orthogonal techniques and side-by-side testing to compare the physicochemical and biological properties of these two products. The measured quality attributes included the primary structure and higher order structure of the molecule, purity/impurity profiles, product variants, process-related impurities, composition, content, and biological activity. The statistical analysis was based on risk ranking of the critical quality attributes (very low, low, moderate, high, very high), and scientific considerations in combination with the characteristics of the assay (sensitivity, selectivity, and variability). In addition, non-quantitative parameters were compared using a descriptive assessment of the product profile. Analytical similarity was concluded by quality attributes falling within the defined range of the originator product. The results of this study confirm that Stimufend® is biosimilar to Neulasta® for all measured quality attributes. There are no clinically significant differences between Stimufend® and Neulasta®, which was confirmed by the marketing approval for Stimufend® by the Food and Drug Administration and the European Medicines Agency. The findings of this study provide robust evidence supporting the structural and functional biosimilarity between Stimufend® and Neulasta®.

Highly Sensitive Analysis of Cervical Mucosal HIV-1 Infection Using Reporter Viruses Expressing Secreted Nanoluciferase.

Ex vivo cervical tissue explant models offer a physiologically relevant approach for studying virus-host interactions that underlie mucosal HIV-1 transmission to women. However, the utility of cervical explant tissue (CET) models has been limited for both practical and technical reasons. These include assay variation, inadequate sensitivity for assessing HIV-1 infection and replication in tissue, and constraints imposed by the requirement for using multiple replica samples of CET to test each experimental variable and assay parameter. Here, we describe an experimental approach that employs secreted nanoluciferase (sNLuc) and current HIV-1 reporter virus technologies to overcome certain limitations of earlier ex vivo CET models. This method augments application of the CET model for investigating important questions involving mucosal HIV-1 transmission.

Exploring the potential of spice‐derived phytochemicals as alternative antimicrobial agents

AbstractThe emergence and spread of pathogenic bacterial resistance to many antibiotics are on the rise globally, thereby posing a significant threat to public health. In response, scientists are actively investigating alternative therapeutic agents to combat antibiotic‐resistant microorganisms. This review focuses on the antimicrobial effects of commonly consumed spices, namely garlic, chilli peppers, turmeric, ginger and black pepper, which have shown promising results in previous research. The review highlights the key phytochemicals, including allicin, ajoene, capsaicin, dihydrocapsaicin, curcumin, 6‐gingerol, 6‐shogaol and piperine, responsible for their antimicrobial activities. Various pharmacological experiments to elucidate the action mechanism and metabolism of those bioactive compounds are described. Moreover, the synergistic effects of these phytochemicals with conventional antibiotics are discussed, emphasizing the potential to reduce the required antibiotic dosage for effective microbial inhibition. The review also addresses the gaps in current research, such as the variations in antimicrobial assay results across different research groups and the incomplete understanding of the synergistic mechanisms between antibiotics and phytochemicals. Finally, future research directions and opportunities are suggested to further explore the antimicrobial potential of these spice‐derived phytochemicals and bridge the existing knowledge gaps.

Automated Online Deconjugation of Antibody-Drug Conjugate for Small Molecule Drug Profiling

Antibody-drug conjugates (ADCs) are designed by chemically linking highly potent cytotoxic small molecule drugs to monoclonal antibodies of unique specificity for targeted destruction of cancer cells. This innovative class of molecules incurs unique developmental challenges due to its structural complexity of having both small molecule and protein components. The stability of the small molecule payload on the ADC is a critical attribute as it directly relates to product efficacy and patient safety. This study describes the use of an end-to-end automated workflow for effective and robust characterization of the small molecule drug while it is conjugated to the antibody. In this approach, online deconjugation was accomplished by an autosampler user defined program and 1D size exclusion chromatography was utilized to provide separation between small molecule and protein species. The small molecule portion was then trapped and sent to the 2D for separation and quantification by reversed-phase liquid chromatography with identification of impurities and degradants by mass spectrometry. The feasibility of this system was demonstrated on an ADC with a disulfide-based linker. This fully automated approach avoids tedious sample preparation that may lead to sample loss and large assay variability. Under optimized conditions, the method was shown to have excellent specificity, sensitivity (LOD of 0.036 µg/mL and LOQ of 0.144 µg/mL), linearity (0.04 – 72.1 µg/mL), precision (system precision %RSD of 1.7 and method precision %RSD of 3.4), accuracy (97.4% recovery), stability-indicating nature, and was successfully exploited to analyze the small molecule drug on a panel of stressed ADC samples. Overall, the workflow established here offers a powerful analytical tool for profiling the in-situ properties of small molecule drugs conjugated to antibodies and the obtained information could be of great significance for guiding process/formulation development and understanding pharmacokinetic/pharmacodynamic behavior of ADCs.

The Effect of Deuteration and Homologation of the Lactam Ring of Nirmatrelvir on Its Biochemical Properties and Oxidative Metabolism.

This study explores the relationship between structural alterations of nirmatrelvir, such as homologation and deuteration, and metabolic stability of newly synthesized derivatives. We developed a reliable synthetic protocol toward dideutero-nirmatrelvir and its homologated analogues with high isotopic incorporation. Deuteration of the primary metabolic site of nirmatrelvir provides a 3-fold improvement of its human microsomal stability but is accompanied by an increased metabolism rate at secondary sites. Homologation of the lactam ring allows the capping group modification to decrease and delocalize the molecule's lipophilicity, reducing the metabolic rate at secondary sites. The effect of deuteration was less pronounced for the 6-membered lactam than for its 5-membered analogue in human microsomes, but the trend is reversed in the case of mouse microsomes. X-ray data revealed that the homologation of the lactam ring favors the orientation of the drug's nitrile warhead for interaction with the catalytic sulfur of the SARS-CoV-2 Mpro, improving its binding. Comparable potency against SARS-CoV-2 Mpro from several variants of concern and selectivity over human cysteine proteases cathepsin B, L, and S was observed for the novel deuterated/homologated derivative and nirmatrelvir. Synthesized compounds displayed a large interspecies variability in hamster, rat, and human hepatocyte stability assays. Overall, we aimed to apply a rational approach in changing the physicochemical properties of the drug to refine its biochemical and biological parameters.

THU596 Heteromerization Of The Angiotensin II Type 1 Receptor And The Bradykinin Type 2 Receptor

Abstract Disclosure: E.K. Johnstone: Grant Recipient; Self; Australian Research Council. K.D. Pfleger: Grant Recipient; Self; Australian Research Council. Stock Owner; Self; Dimerix Bioscience Pty Ltd. Background: Receptor heteromerization is the phenomenon whereby two different receptors form a functional complex that attains unique pharmacological properties. Consequently, receptor heteromers can be considered novel drug targets, with the potential to achieve greater therapeutic selectivity and specificity. In a landmark study, the first receptor heteromer to be associated with a disease was the heteromer that forms between the angiotensin II type 1 (AT1) receptor and the bradykinin type 2 (B2) receptor (1). The AT1-B2 heteromer reportedly led to increased angiotensin II signalling, which was implicated in the angiotensin II hypersensitivity involved in pre-eclampsia. However, the validity of this study was questioned by a collaboration of several groups who were unable to find any evidence for a physical or a function interaction between the two receptors (2). As a consequence of these conflicting studies, the existence of the AT1-B2 receptor heteromer has remained controversial. Aim: Investigation of evidence for heteromerization of the AT1 receptor and the B2 receptor. Methods: AT1 receptor and B2 receptor pharmacology and potential heteromerization was investigated in HEK293FT cells using various bioluminescence resonance energy transfer (BRET)-proximity based assays, as well as Dimerix’s Receptor-Heteromer Investigation Technology (Receptor-HIT) (3). Receptor-HIT enables the investigation of receptor heteromers through their specific ligand-induced proximity to interacting proteins. BRET assays, including in the Receptor-HIT configuration, allow real time, live cell monitoring of proximity between biomolecules of interest. Results: Using the Receptor-HIT assay, we confirmed the existence of the AT1-B2 receptor heteromer in HEK293FT cells. We found that the heteromer was able to recruit various GPCR interacting proteins, such as G proteins and arrestin in a bradykinin-dependent manner. Additionally, the heteromer also internalised and trafficked through the cell upon treatment with bradykinin. The close proximity of the two receptors was confirmed using a variation of the Receptor-HIT assay, which monitors receptor-ligand binding rather than protein-protein interactions. Discussion: Our study supports the existence of the AT1-B2 receptor heteromer and identifies various pharmacological properties of the complex. Further studies are required to relate these molecular properties to physiological consequences of heteromerization. (1)AbdAlla et al. Nat Med2001, 7 (9), 1003 1009.(2)Hansen et al. J Biol Chem2009;284(3):1831 1839.(3)Johnstone et al. Biochem Soc T. 2021;49:1555–65. Presentation: Thursday, June 15, 2023

Use of a common spreadsheet program to demonstrate the ability of Bayesian forecasting to estimate the pharmacokinetic parameters of antibiotics.

Recent guidelines for vancomycin have incorporated the use of Bayesian forecasting, reinforcing the need to inform students in pharmacy and clinical pharmacology of its use in therapeutic drug monitoring. The goal was to devise a PharmD research project that could demonstrate to students through simulation and data generation the utility of the Bayesian approach in estimating the pharmacokinetics of gentamicin and vancomycin. A series of steps were devised using Microsoft Excel to simulate patient data based on study-derived means and variances, pharmacokinetic modelling, random selection of sparse blood samples, introduce random error into the selected concentrations based on assay variability measure, and finally, inputting of the information into an add-in computer program to find the pharmacokinetic estimates using Bayesian forecasting. Excellent correlations were seen between Bayesian estimates and true clearances. Lower assay variability tended to provide better estimates than larger assay variability for gentamicin, and for vancomycin, selecting a sample during the distribution phase and near the trough values tended to provide estimates with less bias and greater precision. The approach used was able to demonstrate all aspects involved in Bayesian forecasting, and the results supported its use for these antibiotics.

Development of Simple HPLC-UV Method for the Simultaneous Determination of Repaglinide, Dexamethasone, and Remdesivir, and its Application to Synthetic Mixture and Human Plasma

Background:: The onset of the COVID-19 pandemic caused numerous difficulties in the treatment of cardiovascular diseases and diabetes mellitus. A persistent risk of developing severe complications and increased mortality from the COVID-19 infection has been reported. In the clinical studies, patients receiving remdesivir and dexamethasone as COVID-19 combination therapy simultaneously with some type II diabetes therapeutic regimens had been reported to have a considerably better state and recover faster. Unfortunately, there is not enough information on the combination of meglitinides, remdesivir, and dexamethasone, and therefore, careful monitoring of the patients' everyday health condition is needed. Objectives:: The present study aimed to describe a high-performance liquid chromatographic method for the determination of repaglinide, dexamethasone, and remdesivir in laboratoryprepared mixtures and human plasma by UV detection. Methods:: Isocratic elution of the mobile phase (consisting of 0.1% trifluoroacetic acid in water and acetonitrile in the ratio 70:30 v/v) was set at a flow rate of 1.0 ml/min, and the developed analytical procedure has been found to be fast and simple. Chromatographic determination was performed on a Purospher® RP – 18 column at room temperature and a UV detector was set at 235 nm. result: The developed method was validated for linearity in the range 2-32 μg/ml. Calibration curves were linear over the selected range with correlation coefficients (R2) greater than 0.996. The coefficients of variation for intraday and interday assay were <2% and the recovery percentages from plasma ranged from 93.83 to 106.49%. Conclusion:: The developed effective and specific method can be applied in routine quality control and clinical laboratory practice.

B-090 Evaluation of Clinical Serology Assays Through the Development of Linearity Materials for aHBs IgG, Rubella IgG, and Toxoplasma IgG

Abstract Background The human body produces immunoglobulin antibodies as a response to various viruses, bacteria, and pathogens. Automated antibody assays, developed to detect immune response or infectious state, are typically qualitative or semi-quantitative where a positive or negative designation is reported out based on a comparison of signal intensity from the chemical reaction and a predetermined signal to cut-off ratio. In these assays the result is not suggestive of a concentration but rather the strength of the antibody antigen avidity. Use of daily QC, in conjunction with linearity materials, can be used to monitor the performance of these assays. Although the signal response may be linear, serological assays can show variability due to the assay’s antigen specificity to the antibodies present in the sample and the antibody heterogeneity within the samples. Understanding these variables is crucial in interpreting patient and control results, as well as developing controls and linearity material to meet the needs of regulatory requirements for clinical testing. Methods Evaluation of high and low titer patient samples was carried out across multiple platforms including the Roche cobas®, Abbott Alinity, Ortho Vitros, and Siemens Centaur, where applicable, for analyte recovery of aHBs IgG, Toxoplasma IgG and Rubella IgG. These patient samples were then used to evaluate the linear response across the analyzer measuring range using equal delta admixtures, as well as serial dilution studies. Results The serology assays tested here, for Rubella IgG, show a significant difference in recovery of approximately 50% when comparing a 60% diluted patient sample run across multiple platforms. Results vary at both the low and high end of the assays. The linearity of aHBs IgG assays and linear variability in the Rubella IgG and Toxoplasma IgG assays is demonstrated via equal delta analysis. These results demonstrate the incongruity in results within a patient sample, likely due to the heterogeneity of antibodies in the patient samples and the non-linear dilution effect this can cause. Conclusion Since serology assays are based on antigen antibody avidity, patient pools taken from recently infected patients, while ideal low positives, can be variable lot to lot and assay to assay as the antibodies are not matured and contain a mix of IgG and IgM, decreasing avidity. Lot to lot variability is decreased in third party controls and linearity materials such as VALIDATE by diluting high titer patient samples or by using recombinant antibodies. Laboratories must set their own acceptance criteria for daily QC and calibration verification linearity testing, keeping in mind inherent assay variability and variability in the controls themselves. It is important to keep in mind that in-kit controls and linearity materials are typically optimized for that specific lot of reagent and calibrators and that although they may be required as part of the manufacture’s IFUs, use of a third-party quality control and linearity material in conjunction with the in-kit controls can help to ensure laboratories are monitoring the assay for changes over time and allows for comparison against peer data when determining clinical significance of assay performance.

B-010 Comparison of Manual Urine Dipstick and Microscopy With Automated UC-3500 and UF-4000 Sysmex UN Series Urinalysis; A Comparative Experimental Research Approach at an Urban Referral Hospital in Ghana

Abstract Background Urine analysis is one of the most common tests for assessing urinary-tract and kidney diseases. In recent years several automated instruments examining urine have been introduced. Though the introduction of automated urine analyzers is expected to reduce the labour involved, turnaround time and potential assay variations, manual urine analysis remains the gold standard or reference method for the analysis of urine. The new Sysmex UN-Series is believed to offer superior performance than other automated systems and manual methods. Methodology A total of 67 routine freshly voided midstream urine samples were analyzed within 1 hour in our study. The results of the automated system were compared with the results of the manual processing which consisted of physical, dipstick chemistry and sediment analysis. Correlation and concordance/agreement between the automated and the manual system were assessed by Bland-Altman plot and Cohen’s Kappa analysis respectively. Results There was a significant fair agreement between the manual analysis and Sysmex UF-3500, in the determination of urine physicochemical parameters (k = 0.193, P = 0.004). Both showed a significant moderate correlation (r = 0.593, P < 0.001) and a significant fair agreement (κ = 0.109, P < 0.001) for specific gravity and pH determination respectively. The best concordance between the two methods was in the nitrates (κ = 1.000, P < 0.001). Both systems recorded strong positive correlation for RBC (r = 0.951 and R2 = 0.904) and WBC (r = 0.91 and R2 = 0.822, P < 0.001) counts. Together, they had a significant good agreement [(65/67(97.0%), κ = 0.734, P < 0.001)] and a significant fair agreement [(48/67 (71.6%) κ = 0.065, P = 0.491)] for cast and bacteria counts correspondingly. Conclusion We conclude that the new automated Sysmex-UN series urine analyzer can be safely used in our laboratory since it demonstrated good performance and compatibility with the manual method. We recommend that microscopy results of the automated platform should be confirmed by manual microscopy, particularly in pathological samples.

A Robust and Standardized Approach to Quantify Wound Closure Using the Scratch Assay.

The scratch assay is an in vitro assay that allows for high-throughput quantification of wound closure by keratinocytes and fibroblasts with relative ease. However, this assay is amenable to experimental variables, which can result in false-positive and false-negative data, making the interpretation of such data difficult. Also, data variability decreases the sensitivity of the scratch assay. Here, we identify important sources of data variation in the scratch assay and provide rational mitigation strategies that enable robust and highly reproducible quantification of scratch width and area, and ultimately the scratch closure rates. By eliminating these sources of variability, the sensitivity of the scratch assay is enhanced, thereby allowing for identification of dependent variables with wide-ranging impacts on wound closure in a robust and standardized manner.

A Case Study for Critical Reagent Qualification for Ligand Binding Assays Using Equivalence Test Methodology

Qualifying critical reagents in ligand binding assays by parallel testing of current and candidate reagent lots is recommended by regulatory agencies and industry groups, but specific guidance on the format of reagent qualification experiments is limited. Equivalence testing is a statistically sound approach that is consistent with the objective of critical reagent qualification. We present power analysis for equivalence regions ranging from 1.25- to 1.5-fold multiples of the GM ratio (centered on 1) of current and candidate lots, over a range of assay variability from 5 to 30% coefficient of variation (CV). A 1.25-fold equivalence region can be tested using 6 to 12 plates per lot for assays with up to 15% CV but is not practical for more variable assays. For these assays, wider equivalence regions are justified so long as care is taken to avoid assay drift and the assay remains suitable for the intended use. The equivalence test method is illustrated using historical data from passing and failing reagent qualification experiments. Simulation analysis was performed to support the design of qualification experiments using 6, 12, or 18 plates per lot over a broad range of assay variability. A challenge in implementing the equivalence test approach is selecting an appropriate equivalence region. Equivalence regions providing 90% power using 12 plates/lot were consistent with 1.5σ bounds, which are recommended for equivalence testing of critical quality attributes of biosimilars.Graphical

Pre-Analytical Variables Influencing Stability of Blood-Based Biomarkers of Neuropathology.

Sample collection and preanalytical protocols may significantly impact the results of large-scale epidemiological studies incorporating blood-based biomarkers of neuropathology. To evaluate the stability and assay variability of several blood-based biomarkers of neuropathology for common preanalytical conditions. We collected serum and plasma samples from 41 participants and evaluated the effect of processing delay of up to 72 h when stored at 4∘C, three freeze-thaw cycles, and a combination of 48-h processing delay when stored at 4∘C and three freeze-thaw cycles on biomarker stability. Using the Simoa assay (Quanterix Inc.), we measured amyloid-β 40 (Aβ40), amyloid-β 42 (Aβ42), neurofilament light (NfL), glial fibrillary acidic protein (GFAP), and phosphorylated tau 181 (p-tau-181). We found that Aβ40 and Aβ42 levels significantly decreased after a 24-h processing delay in both plasma and serum samples, and a single freeze-thaw cycle (p < 0.0001). Nevertheless, serum Aβ42/40 ratio remained stable with a processing delay up to 48 h while plasma Aβ42/40 ratio showed only small but significant increase with a delay up to 72 h. Both plasma and serum GFAP and NfL levels were only modestly affected by processing delay and freeze-thaw cycles. Plasma p-tau-181 levels notably increased with a 24-, 48-, and 72-h processing delay, but remained stable in serum. Intra-individual variation over two weeks was minimal for all biomarkers and their levels were substantially lower in serum when compared with plasma. These results suggest that standardizing preanalytical variables will allow robust measurements of biomarkers of neuropathology in population studies.

Quantitation and integrity evaluation of RNA genome in lentiviral vectors by direct reverse transcription-droplet digital PCR (direct RT-ddPCR)

Lentiviral vectors (LV) have proven to be powerful tools for stable gene delivery in both dividing and non-dividing cells. Approval of these LVs for use in clinical applications has been achieved by improvements in LV design. Critically important characteristics concerning quality control are LV titer quantification and the detection of impurities. However, increasing evidence concerning high variability in titration assays indicates poor harmonization of the methods undertaken to date. In this study, we developed a direct reverse transcription droplet digital PCR (Direct RT-ddPCR) approach without RNA extraction and purification for estimation of LV titer and RNA genome integrity. The RNA genome integrity was assessed by RT-ddPCR assays targeted to four distant regions of the LV genome. Results of the analyses showed that direct RT-ddPCR without RNA extraction and purification performs similarly to RT-ddPCR on purified RNA from 3 different LV samples, in terms of robustness and assay variance. Interestingly, these RNA titer results were comparable to physical titers by p24 antigen ELISA (enzyme-linked immunosorbent assay). Moreover, we confirmed the partial degradation or the incomplete RNA genomes in the prepared 3 LV samples. These results may partially explain the discrepancy of the LV particle titers to functional titers. This work not only demonstrates the feasibility of direct RT-ddPCR in determining LV titers, but also provides a method that can be easily adapted for RNA integrity assessment.

Variability of Replicates of Intraocular Inflammatory Biomarkers in Ocular Fluid Samples Analyzed with Multiplex Assays.

Certain factors such as instrumental and sample processing errors may contribute to variability of ocular biofluid samples when they are run as replicates with multiplex assays. There is a paucity of literature on the variability of replicates in multiplex assays. This study aims to evaluate whether there is significant variability in replicate analyses of multiplex assays. A total of 152 human ocular biofluid samples (51 aqueous humor and 101 vitreous) were collected and assayed for 27 cytokine biomarker concentrations (pg/mL). Samples were evaluated as replicates (duplicate analysis) at four different time points. Statistical methods including paired samples t-test, 3-way ANOVA, intraclass correlation coefficient (ICC; <0.5-0.75=poor-moderate, 0.75->0.90 =good-excellent reliability), and coefficients of variation (CV) were employed to evaluate for statistical significance, with Bonferroni corrected P=0.002. Among the 4104 biomarker replicate assays for aqueous humor and vitreous, two analytes (PDGF-BB and IL-7) had a statistically significant difference between the sampled concentrations of the replicates in vitreous samples (mean (diff)=2.05, P<0.001, mean (diff)=1.56, P<0.001, respectively). Majority of the ICC values fell within the good-excellent range (86% of samples) with a minority falling in the poor-moderate range (14% of samples). More variability was noted in the vitreous humour, with five analytes (IL-2, IL-10, IL-12(p70), IL-13, IL-17) demonstrating an average ICC of less than 0.5. The CV calculated for each set of replicates suggested that 93% of replicates had an acceptable level of quantitative assay variability (CV<20%). This study demonstrates that the analysis of most biomarkers in ocular fluids may not require the use of replicates. However, certain analytes such as PDGF-BB and IL-7 may require the use of replicates to ensure reliable results. Caution should be taken when applying these findings to other laboratory settings as our study was conducted by an experienced technician using a standardized protocol. In less standardized settings, replicates may be required in order to ensure accuracy of results. These findings may guide researchers with the design of their studies on ophthalmic biomarker analysis.

Method development and validation of unbound saccharide content (serogroup A, C, Y, W, X) in novel pentavalent meningococcal polysaccharide conjugate vaccine with two different carrier proteins

Exclusive DOC-HCl formulations were developed for free polysaccharide content estimation in Meningococcal serogroup A, C, Y, W and X from pentavalent meningococcal vaccine (A, C, Y, W, X). The DOC precipitation method reported herein stands as an alternative to the ultra-filtration method for free polysaccharide estimation. DOC content was optimized for all the serogroups at a single concentration, where as effective acid concentration was altered as per serogroup. Briefly, two DOC-HCl formulations were developed for intended purpose, one for TT conjugated serogroups Men A & Men X where as other for CRM conjugated serogroups Men C, Men Y and Men W with effective HCl concentration of 23 mM and 193 mM for precipitation of Protein-DOC complex respectively. Furthermore, an exclusive buffer/DOC-HCl formulation for estimation of Men X free polysaccharide in fill finished product was developed. Accuracy of the method was proven at 12.5 %, 25 %, 50 % and 100 % of test specification where recoveries were found in the range of 70–130 %. In case of repeatability, intra assay variation ranged from 2 % to 7 % whereas inter assay variation was noted to be 2–14 %. Specificity studied revealed no interference of assay components such as sample excipients, DOC, acids. Critical quality and stability-indicating characteristics were measured. Monovalent polysaccharide standards of Men A, C, Y, W and X were developed and assigned the unitage concentration 1.01, 1.10, 1.09, 1.08 and 1.00 mg/mL respectively. Linearity curve was optimized from 0.17 to 27 µg/mL for Men A and C whereas from 0.33 to 27 µg/mL for Men Y and W considering free polysaccharide content estimation. The study suggests that DOC-HCl method meets all the criteria for free polysaccharide estimation in multivalent vaccines with additional advantages of high throughput and sized independent separation hence can be used for quality control testing.

Evaluation of thrombin generation in dogs administered clopidogrel.

The antiplatelet effect of clopidogrel can vary between patients. A modified thromboelastography (TEG) protocol (TEG-Platelet Mapping assay® [TEG-PM]) can be used for clopidogrel monitoring but is not widely available. Thrombin generation (TG) assays could offer a novel alternative. The main objective of this pilot study was to assess TG assay variables (lag time, peak, endogenous thrombin potential [ETP]) in dogs before and after 7 days of clopidogrel administration and compare with TEG-PM variables (maximum amplitude [MA]-ADP and percentage (%) inhibition). Six healthy mix-breed dogs were enrolled in this pilot study. Blood samples for platelet count, TG assays, and TEG-PM were obtained at two time points, corresponding to baseline, and after 7 days of clopidogrel administration (mean 2.3 +/- 0.3 mg/kg PO q24 hours). Data were then compared with a Student's t-test. There was no significant change in TG assay variables performed on platelet poor plasma after 7 days of clopidogrel administration: lag time (Day 1: 1.8 +/- 0.2 min, Day 7: 1.8 +/- 0.2 min, p = 0.42); peak (Day 1: 76 +/- 7 nM, Day 7: 72 +/- 10 nM, p = 0.49); and ETP (Day 1: 399 +/- 27 nM*min, Day 7: 392 +/- 32 nM*min; p = 0.49). There were significant changes in TEG MA-ADP (Day 1: 19 +/- 8 mm, Day 7: 9 +/- 6 mm, p = 0.04) and % inhibition (Day 1: 58 +/- 27, Day 7: 99 +/- 0.3, p = 0.02). Clopidogrel administration did not lead to changes in TG assay variables performed on platelet poor plasma samples, despite concomitant changes in TEG-PM variables consistent with platelet inhibition. Based on this pilot study, thrombin generation performed on platelet poor plasma may not be a useful antiplatelet monitoring tool in dogs.

Development of a membrane-based Gi-CASE biosensor assay for profiling compounds at cannabinoid receptors.

Introduction: The cannabinoid receptor (CBR) subtypes 1 (CB1R) and 2 (CB2R) are key components of the endocannabinoid system (ECS), playing a central role in the control of peripheral pain, inflammation and the immune response, with further roles in the endocrine regulation of food intake and energy balance. So far, few medicines targeting these receptors have reached the clinic, suggesting that a better understanding of the receptor signalling properties of existing tool compounds and clinical candidates may open the door to the development of more effective and safer treatments. Both CB1R and CB2R are Gαi protein-coupled receptors but detecting Gαi protein signalling activity reliably and reproducibly is challenging. This is due to the inherent variability in live cell-based assays and restrictions around the use of radioactive [35S]-GTPγS, a favoured technology for developing higher-throughput membrane-based Gαi protein activity assays. Methods: Here, we describe the development of a membrane-based Gαi signalling system, produced from membrane preparations of HEK293TR cells, stably overexpressing CB1R or CB2R, and components of the Gαi-CASE biosensor. This BRET-based system allows direct detection of Gαi signalling in both cells and membranes by monitoring bioluminescence resonance energy transfer (BRET) between the α and the βγ subunits. Cells and membranes were subject to increasing concentrations of reference cannabinoid compounds, with 10μM furimazine added to generate RET signals, which were detected on a PHERAstar FSX plate reader, then processed using MARS software and analysed in GraphPad PRISM 9.2. Results: In membranes expressing the Gi-CASE biosensor, the cannabinoid ligands profiled were found to show agonist and inverse agonist activity. Agonist activity elicited a decrease in the BRET signal, indicative of receptor activation and G protein dissociation. Inverse agonist activity caused an increase in BRET signal, indicative of receptor inactivation, and the accumulation of inactive G protein. Our membrane-based Gi-CASE NanoBRET system successfully characterised the potency (pEC50) and efficacy (Emax) of CBR agonists and inverse agonists in a 384-well screening format. Values obtained were in-line with whole-cell Gi-CASE assays and consistent with literature values obtained in the GTPγS screening format. Discussion: This novel, membrane-based Gαi protein activation assay is applicable to other Gαi-coupled GPCRs, including orphan receptors, allowing real-time higher-throughput measurements of receptor activation.

P-604 Inhibin B in Low Ovarian Reserve Patients: Correlation With Ovarian Reserve Markers and Oocyte Yield

Abstract Study question Is there a correlation between Inhibin B (InhB) serum levels and oocyte yield after ovarian stimulation (OS) in women with low ovarian reserve? Summary answer InhB presents a positive relationship with oocyte yield during OS in women with AMH&amp;lt;1.1ng/mL. What is known already InhB is produced by granulosa cells in the ovary with the goal of suppressing FSH production. Assay and intercycle variability have been the main limitations affecting specificity and reproducibility of InhB as a marker of ovarian reserve or oocyte yield after OS. This fact is attributed to low specific antibodies for the molecule in previous assays, exhibiting cross-reactivity with other glycoproteins in the transforming growth factor beta family. High specific ELISA assay,measuring bioavailable InhB (bio-InhB), may provide more accurate results, specially important in poor responders, as results may involve clinical decisions on whether or not to proceed with OS. Study design, size, duration Prospective observational study measuring bio-InhB in 72 women with low ovarian reserve, performing OS for IVF/ICSI, at a tertiary referral fertility center, from February 2019 to December 2021. Low ovarian reserve was defined as AMH serum levels &amp;lt;1.1ng/ml (Elecsys, Roche), following Bologna criteria. All patients performed OS for IVF/ICSI in a GnRH-antagonist protocol. Participants/materials, setting, methods On day 2/3 of cycle, before starting OS, AFC, FSH, LH, estradiol, progesterone and AMH (Elecsys, Roche) were measured. Extra serum samples were frozen at -20C for subsequent bio-InhB analysis (AnshLabs, Texas). Ethical approval was obtained (Research Ethics Committee-REFA033c) and informed consent was signed for all participants. Main results and the role of chance Patient characteristics were [Median(IQR)]: age: 39(36-42)years, BMI: 28.51(26.1-30.1) Kg/m2, AFC: 5.5(4-7), FSH:8.23(6.4-12.5) mIU/mL, LH: 6.54(4.51-8.91) mIU/mL, Estradiol: 41.18(28.47-56.44) pg/mL, AMH: 0.64(0.29-0.81)ng/mL, InhB: 62.69(33.78-97.92) pg/mL. Stimulation outcomes were: follicle number on day of trigger (Fdot): 5(3-7), cumulus-oocyte-complexes (COC’s): 3(2-4.5) andmetaphase II oocytes (MII): 3(1-4). Inh-B showed significant positive correlation (Spearman correlation) with AMH (rs = 0.35, p = 0.003), although was better with AFC (rs = 0.43, p &amp;lt; 0.001). Moreover, Inh-B serum levels presented positive association with oocyte yield: Fdot (rs = 0.41, p &amp;lt; 0.001), COC’s (rs = 0.36, p = 0.002) and MII (rs = 0.37, p = 0.002). AUROC analysis was performed to investigate which model predicted better a bad outcome (defined as &amp;lt; =3COC’s after OS) in low ovarian reserve women. No significant benefit was observed when Inh-B was added to AMH+AFC model (AUROC AMH+AFC: 0.757; AUROC AMH+AFC+Inh-B: 0.759, p = 0.843). Limitations, reasons for caution Although clinical assessment was performed in the same centre following the same methodology, inter-observer variability for AFC is a limitation. Besides, fresh AMH serum samples were analysed using Elecsys assay, yet frozen serum samples were shipped to Ansh Lab (Texas) for batched Inh-B analysis. Wider implications of the findings Bio-InhB is correlated to oocyte yield during OS. Although no additional benefit for prediction in women with AMH&amp;lt;1.1ng/mL was observed when added to other currently used markers, future research should explore the utility of bio-inhB on other outcomes associated to ovarian reserve, as embryo quality and ploidy. Trial registration number Not applicable

Impact of delayed PBMC processing on functional and genomic assays

Peripheral blood mononuclear cells (PBMCs) are commonly isolated from whole blood samples in clinical trials. Isolated PBMCs can be cryopreserved for use in downstream assays such as flow cytometry, single-cell RNA sequencing (scRNA-seq) and enzyme-linked immunosorbent spot (ELISpot) assays to aid understanding of disease biology and treatment effects, and biomarker identification. However, due to logistical practicalities, delays from blood collection to PBMC processing may exceed 24 h, which can potentially affect PBMC function and, ultimately, downstream assay results.Whole blood samples from 20 healthy adults were collected and incubated at 20–25 °C for 2–48 h before PBMC processing. PBMC viability was measured, and flow cytometry immunophenotyping, scRNA-seq and ELISpot were performed following increasing PBMC processing delays. The RosetteSep™ granulocyte depletion kit was used to evaluate the impact of granulocyte contamination following processing delay. Processed scRNA-seq reads were used to identify cell clusters based on marker genes. scRNA-seq data was further used to determine gene expression correlation and pathway activity score in major PBMC cell types (T cells, B cells, natural killer cells, monocytes and dendritic cells) between PBMC preparations subjected to shorter (2–4 h) and longer (8–48 h) processing delays. ELISpot assays evaluated the impact of processing delays on the number of interferon-γ (IFN-γ) secreting cells from ex vivo stimulated PBMCs.PBMC viability was reduced after a 48-h processing delay. Flow cytometry showed that granulocyte contamination of PBMCs increased after 24 h. Cluster analysis of scRNA-seq data identified 23 immune cell type gene expression clusters that were not significantly changed upon granulocyte depletion. Gene expression correlations across the major PBMC cell types were < 0.8 after 24 h of delay compared with 2 or 4 h of delay. Inflammatory, proliferation and signaling pathway activities increased, whereas IFN-γ and metabolic pathway activities decreased with increasing PBMC processing delays. The number of IFN-γ secreting cells trended towards a reduction as PBMC processing delays increased.PBMC processing delays should be minimised when designing clinical trials to reduce outcome variability in downstream assays. Ideally clinical trial sites should have on-site PBMC processing capabilities or be located close to such facilities.