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David Rusnak
Posted by David Rusnak BioAgilytix Insight, Cell-Based Assays

What’s Your System for Cell-Based Assay Method Selection?

What’s Your System for Cell-Based Assay Method Selection?

Cell-based assays are a key component in the creation of new medicine, from early target and drug discovery efforts through clinical trial and manufacturing support. Complex biochemical processes in the body can often be investigated and understood in cell-based model systems, and there is a near limitless variety of cell-based assay platforms that can be developed.

Clinical pharmacology studies are a critical part of demonstrating this ‘biosimilarity’, and provide the data for the biosimilarity in drug exposure between the biosimilar and the originator / reference product to confirm no clinically meaningful differences. These studies also include pharmacodynamic (PD) endpoints and pharmacometric analysis – which is the assessment of the clinical relevance of the PD endpoints. This clinical pharmacology data becomes an important point of justification for clinical extrapolation, and more critically is used to demonstrate immunogenic similarity.

Cell-based model systems can include primary cells, freshly isolated from patients; cell lines established for long-term culture and experimentation via generation of a well-characterized master cell banks (MCB) and working cell banks (WCB); and genetically modified cells designed for very specific pathways and diseases. Detection platforms can range from cell growth and apoptosis and gene expression profiles to biochemical and immunoassays measuring signaling and secretion. With this plethora of options, it is critical to carefully weigh the advantages and disadvantages of each system for your study, as the path you choose can directly impact the success of your analysis.

In this post, I will detail several of the key considerations that should be assessed as part of your cell-based system selection.

Multiple Methods for Early Phase Discovery
In early phase discovery, a variety of systems and platforms can be used to select and validate targets, and optimize the molecules designed to act on these targets. Because novel therapies often have limited commercial reagent availability, time is largely spent generating model systems and custom reagents.

Cell transfections, western blot analysis and proliferation assays are typical procedures for early phase drug discovery. Medium to high-throughput automated screens are useful for prosecuting a large number of molecules efficiently and accurately as projects gain momentum.

Making Selections for Clinical Trials
As drug discovery programs enter into clinical trials, assays require higher levels of precision and reproducibility to evaluate activity. At this stage of drug development, it is critical that the assay responses are shown to be specific to the drug of interest in order to avoid confounding or misleading results. Alternative stimuli, drug depletion or other methodologies can determine assay specificity. Multiple platforms can still be used, but should be selected to ensure the most robust assays possible.

Clinical trial support also includes the development of precise and robust cell-based assays for evaluation anti-drug neutralizing antibodies, vaccines and drug activity assays from human matrices. Any quantifiable measure of drug activity in a cell-based system may be evaluated for its use as a model assay. These assays are often very specific biochemical measures, such as enzyme activity, protein secretion, receptor phosphorylation or ligand stimulated proliferation. Once activity is defined, the assay is validated for its reproducibility in its appropriate clinical trial sample, such as human serum.

In this phase, it is critical to understand if the measures of accuracy, precision, specificity, selectivity and stability of your chosen method can be performed to ensure long-term reliability of the assay for supporting the clinical trial. For example, gene reporter assays are often used to help overcome the disadvantages of classical cell assays, which often yield low reproducibility, precision, specificity, and selectivity.

Moving into Manufacturing Support
With the discovery of new biological molecules as therapy, it has become critical to be able to quantify drug activity across batches and manufacturing processes of medicines. Manufacturing support requires tightly controlled processes to permit the validation and execution of cell-based analytical assays under GMP. Like assays supporting clinical trials, manufacturing support is typically performed in assays with very specific biochemical measures, along with rigorous data analysis procedures to ensure the most quantitative assays possible.

Because of this, data analysis methods must take into account not only the EC50 of the drug, but the equivalence of the drug response across manufacturing runs. Parallel line analysis and equivalence testing can show that the key parameters of the drug response—maximum, minimum, and rate of response—are consistent, yielding the most reliable assessment of relative potency across batches. This analysis can be applied to the wide range of assays performed in support of product development and release.

As you can see, a critical component of proper cell-based assay development is the knowledge and experience to weigh these considerations carefully to select the most appropriate model.

BioAgilytix’s experienced team of cell biologists brings that knowledge to bear for our customers, with a proven track record of developing and validating robust cell-based assays. We can help you select the optimal method, and perform evaluation using absorbance, luminescence and fluorescence, flow cytometry, imaging, and more.

If you have questions or would like to further discuss cell-based assay considerations specific to your needs, please feel free to contact me. I look forward to hearing from you!

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