Biomedical subjects

Ronald R Bowsher

Publications and source records attributed to Ronald R Bowsher.

3 recordsLinked to original sources

PubMed2005

Method validation and measurement of biomarkers in nonclinical and clinical samples in drug development: a conference report.

Biomarkers are increasingly used in drug development to aid scientific and clinical decisions regarding the progress of candidate and marketed therapeutics. Biomarkers can improve the understanding of diseases as well as therapeutic and off-target effects of drugs. Early implementation of biomarker strategies thus promises to reduce costs and time-to-market as drugs proceed through increasingly costly and complex clinical development programs. The 2003 American Association of Pharmaceutical Sciences/Clinical Ligand Assay Society Biomarkers Workshop (Salt Lake City, UT, USA, October 24-25, 2003) addressed key issues in biomarker research, with an emphasis on the validation and implementation of biochemical biomarker assays, covering from preclinical discovery of efficacy and toxicity biomarkers through clinical and postmarketing implementation. This summary report of the workshop focuses on the major issues discussed during presentations and open forums and noted consensus achieved among the participants on topics from nomenclature to best practices. For example, it was agreed that because reliable and accurate data provide the basis for sound decision making, biomarker assays must be validated in a manner that enables the creation of such data. The nature of biomarker measurements often precludes direct application of regulatory guidelines established for clinical diagnostics or drug bioanalysis, and future guidance on biomarker assay validation should therefore be adaptable enough that validation criteria do not stifle creative biomarker solutions.

Biological Assay↗

PubMed2005

Development, validation, and implementation of a multiplex immunoassay for the simultaneous determination of five cytokines in human serum.

Quantification of biomarkers can provide important information about the safety and efficacy of candidate drugs. Unfortunately, limited sample volume and excess costs often limit analysis of multiple biomarkers. We developed, optimized, validated, and implemented a multiplex immunoassay for simultaneous measurement of multiple circulating cytokines: IL-1beta, TNFalpha, IL-6, IL-8, and IL-10. Multiplex immuoassays were performed using the Luminex LabMAP instrument. Capture antibodies for each cytokine were covalently bound to distinct microsphere subsets distinguished by differing dye ratios. The concentration of each individual cytokine determined by measuring orange fluorescence produced by a complex of a biotinylated cytokine-specific antibody and streptavidin-phycoerythrin. The lower limit of quantification for all assays was 20 pg/mL with the exception of IL-8 which was 100 pg/mL. The inter-assay precision was less than 25%CV for all analytes at all control levels both pre-study and in-study. The percent recovery ranged from 83 to 108% pre-study and 90 to 125% in-study. In a linearity assessment, a 15,000 pg/mL multi-analyte control could be diluted 1:50 and maintain expected accuracy. We measured the cytokine concentrations in more than 2000 serum samples from patients with sepsis. Multiplex results for IL-6 were compared to a conventional commercially available ELISA kit. The degree of agreement between the two methods as measured by the concordance correlation coefficient was 84.5%. Multiplex results were 2.36-fold higher than ELISA values on the average. After adjusting for this mean difference, the 95% empirical limits of agreement for the ratio of individual sample values were 0.33, 2.65. This multiplex immunoassay provided simultaneous measurement of circulating cytokines using 80% less patient specimen compared to traditional approaches and at a significantly decreased cost. Efficient use of this platform requires process improvements to fully maximize the positive impact of multiplex assays in clinical drug development.

Cytokines↗

PubMed2004

Relating glucose clamp profiles to reduction of blood glucose after insulin administration.

A model was established allowing prediction of blood glucose response from glucose clamp results performed in healthy volunteers. Data from published studies performed in healthy volunteers were used to establish, test, and validate a model for the evaluation of glucose reductions from glucose clamp results. Studies included those that measured blood glucose and glucodynamic response over time after administration of 0.05 U/kg of regular human insulin (HR) and insulin lispro (LP) with and without the benefit of a glucose clamp procedure. An inhibitory effect E(max) model was used to describe the relationship; the model differed between the HR and LP responses by the intensity of the counterregulatory response as assessed by glucagon measurements. The relationships were used to predict blood glucose responses from a clamp study assessing NPH insulin and HR administrations. Glucose concentrations measured after administration of NPH insulin and HR without a clamp were compared to the model-predicted results to assess the accuracy of the model predictions. The E(max) model successfully correlated the glucose clamp results with the blood glucose depressions in the presence and absence of a counterregulatory response. However, predictions of glucose depression were only accurately modeled in the absence of a counterregulatory glucagon response. The correlations established with a minimal counterregulatory response underscore the value of glucose clamp procedures in defining the time-activity profiles of insulins when the clamp is established at fasting glucose concentrations.

Blood Glucose↗