Screening Assay and Off-Rate Ranking Enables The Identification of Drug Candidates with Sought Binding Properties in a concentration independent manner

Bioanalytical technologies have rapidly changed over the past 10 years to offer unprecedented time and cost saving for drug lead candidatesidentification and optimization. Innovative and optimized screening approach in early stages of drug discovery and development has drastically decreased the workload further down the process.

During primary screening campaign, ELISA assay is commonly used. However clones that express high levels of low-affinity binders can give an equivalent signal to clones that express low level of high affinity binders. High throughput off-rate ranking BLI library screening assays enable the selection of clones according to binding kinetic parameters (koff instead of KD) without the need to know compound concentration or to perform filtration or purification steps. Ranking and selecting binders based on off-rate would ensure that high stable complexes are selected independently to the expression yield.

BLI Off-rate ranking is a concentration independent approach that can be directly applied to lysates or crude supernatant and in which the concentration of the compound is not required. Screening assay and Off-rate ranking give information on how fast a molecular complex dissociates per second. Indeed, slow Koff is usually more important than a fast on rate since a slow on rate can often be compensated with higher protein concentration or longer incubation time, whereas with a fast off rate the protein is washed off quickly.

This approach fits perfectly as a secondary screening platform for antibody fragments selection derived from phage display campaigns or hit identification from hybridoma supernatants. Off-rate ranking is the most powerful screening approach in order to select affinity matured binders with the best suitable binding kinetic properties.

High throughput library screening campaigns, independent of off-rate data, have been successfully conducted for various other applications. Functional screening assays enable for instance to identify competitor or select binders specific to an epitope. Single point KD measurement screening assays can be performed on purified material or on crude sample after capture on biosensors to rank binders according to approximate binding KD values. This screening assay is perfectly suited for germlining, PTM removal or paratope mapping campaigns.

Due to its high throughput design, Octet® RH16 is a label-free BLI platform that allows screenning up to 16 samples in parallel by immersing ligand-coated biosensors into samples distributed in 96- or 384-well microplates. Thus, several hundred of biomolecules can be screened over day.