Surrogate potency assays:Comparison of binding profiles complements dose response curves for unambiguous assessment of relative potencies

Surface plasmon resonance(SPR) systems are widely used for detailed characterization of antibody activities including antigen and Fc-receptor binding. During the later stages of development, where the focus is to ensure that established critical quality attributes(CQAs) are maintained during cell culture,purification and formulation processes, analysis is simplified, and relative potencies are often determined. Here, simulation of binding data revealed that relative potency values, determined via parallel line analysis(PLA) and half maximal effective concentration(EC50) analysis accurately reflect changes in active concentration only if binding kinetics remain unchanged. Changes in the association rate constant shifted dose response curves, and therefore relative potencies, in the same way as changes in analyte concentration do. However, for interactions characterized by stable binding, changes in the dissociation rate constant did not result in any shift, suggesting that this type of change may go unnoticed in the dose response curve. Thus, EC50 and PLA analyses of dose response curves obtained with an anti-TNF-α antibody were complemented with the Biacore functionality for sensorgram comparison analysis, whereby changes in antigen and Fc-receptor binding profiles could be detected. Next, analysis of temperature stressed TNF-α antibody revealed that calibration free concentration analysis(CFCA) data correlated perfectly with relative potency values. Together, these results demonstrate that combinations of SPR based dose response curves, sensorgram comparison and CFCA can be used to strengthen the confidence in relative potency assessments, and suggest that SPR can potentially be used as a surrogate potency assay in the quality control of biotherapeutic medicines.

A Semi-quantitative Serological Method to Assess the Potency of Inactivated Rabies Vaccine for Veterinary Use

Potency is one of the most important indexes of inactivated vaccines.A number of methods have been established to assay the potency,of which the NIH test and single-dose mouse protection test are the "prescribed methods".Here,we report a method to semi-quantitatively assay the potency of an inactivated rabies vaccine,which uses fewer animals and takes less time to complete.Depending on the quality requirements of a vaccine(e.g.minimum potency),a rabies reference vaccine is,for example,diluted to the minimum potency,and 50 μL of the dilution is taken to inoculate 10 mice.The same amount of the test rabies vaccine is inoculated into another 10 mice.After two weeks,all mice are bled and serum samples are assayed for viral neutralizing antibody by the fluorescent antibody virus neutralization(FAVN) test.By comparing the median and interquartile range of antibody titers of the reference vaccine with those of the test vaccine,the test vaccine potency can be semi-quantitatively judged as to whether it is in accord with the required quality.The reliability of this method was also confirmed in dogs.The procedure can be recommended for batch potency testing during inactivated rabies vaccine production.

Establishment of animal model for potency evaluationof inactivated SARS virus experimental vaccine

The purpose of this study was to test the effectiveness of source virus strain for the manufacture of the inactivated SARS virus vaccine, and establish an experimental method and preliminary standard for potency evaluation. Mice were divided into groups for being immunized with corresponding serially diluted experimental SARS virus inactivated vaccine. And the rabbits were immunized with undiluted vaccine. Challenge assay was conducted with a heterologous SARS virus. And the neutralization antibody was determined with plaque reduction neutralization test (PRNT), to which the neutralization antibody in the convalescent serum of SARS patients was compared. The experimental vaccine viral strains were proved to be suitable for manufacturing the vaccine. Mice immunized by vaccines of serial dilutions were able to elicit neutralizing antibody. The antibody titer from mice immunized with the undiluted vaccine could reach up to 1∶495.2, while those of rabbits immunized with the undiluted vaccine could reach a GMT of 55.0-79.9. The capability of the antibody to neutralize the virus from Guangdong is more efficient than that from Beijing. The GMT of neutralizing antibody in SARS convalescents living in south and north China ranged from 50.12 to 54.95, and the titers of convalescents from north China were higher than those from south China. Mice and rabbits used as the model for evaluation of potency are of sensitivity, and the test is of reproducibility. The candidate challenge viral strains showed a relatively consistent effect on evaluating antibodies produced by various batches and different vaccine-source strains, hence they can be used to evaluate potency of the vaccine. The method for testing the vaccine potency and the evaluation standard was established preliminarily.

Selection of appropriate analytical tools to determine the potency and bioactivity of antibiotics and antibiotic resistance

Antibiotics are the chemotherapeutic agents that kill or inhibit the pathogenic microorganisms.Resistance of microorganism to antibiotics is a growing problem around the world due to indiscriminate and irrational use of antibiotics.In order to overcome the resistance problem and to safely use antibiotics,the correct measurement of potency and bioactivity of antibiotics is essential.Microbiological assay and high performance liquid chromatography（HPLC） method are used to quantify the potency of antibiotics.HPLC method is commonly used for the quantification of potency of antibiotics,but unable to determine the bioactivity;whereas microbiological assay estimates both potency and bioactivity of antibiotics.Additionally,bioassay is used to estimate the effective dose against antibiotic resistant microbes.Simultaneously,microbiological assay addresses the several parameters such as minimal inhibitory concentration（MIC）,minimum bactericidal concentration（MBC）,mutation prevention concentration（MPC） and critical concentration（Ccr） which are used to describe the potency in a more informative way.Microbiological assay is a simple,sensitive,precise and cost effective method which gives reproducible results similar to HPLC.However,the HPLC cannot be a complete substitute for microbiological assay and both methods have their own significance to obtain more realistic and precise results.