Discussion

Agnes C. L. Martin1, Sheila B. McLoughlin1, Paul Owen2, Michelle C. Pritchard1, Fabienne Saab, Louise M. Tonkin1, Edward R. Wheatley2, Simon Willies2

1Cancer Research Technology Discovery Laboratories, Jonas Webb Building, Babraham Research Campus, Cambridge CB22 3AT, UK.
2Cancer Research Technology Discovery Laboratories, London Bioscience Innovation Centre, 2 Royal College Street, London NW1 0NH, UK.

The validation of hits resulting from a high throughput screening campaign is a critical part of the development of small molecule drugs. After using a range of biochemical assays to eliminate false positives, demonstration of direct target engagement increases confidence in the hits and drives their progression to lead optimisation.
At CRT Discovery Laboratories we have established a portfolio of biophysical applications – label-free and label-requiring, immobilised and in solution – which are used for the characterisation of both target proteins and compounds of interest. While equilibrium KDs are routinely used to demonstrate direct target engagement, kinetic characterisation of compound binding has proved powerful for prioritising compounds with slower off rates. Assays aiming to determine the mechanism of inhibition of compounds have also been successfully developed, for example by comparing KDs generated in the absence or presence of substrate.
Each biophysical technique has specific advantages and limitations, and often target constraints such as protein availability, size, stability, tag, amino acid sequence and required cofactors will dictate which approaches are feasible. We keep abreast of emerging technologies, either by organising demonstrations via the vendor, by collaborating with partners who have already invested in the technology, or by outsourcing. We have recently compared the Corning Epic against the more traditional Biacore in collaboration with MRCT and Astra Zeneca, evaluated – and subsequently purchased – the Nanotemper Monolith NT.115 in collaboration with the MRC-LMB and Mission Therapeutics, and characterised compounds targeting a DNA binding protein using Dynamic Biosensors’ Switchsense technology.