We conducted an integrated project that used virtual screening, Surface plasmon resonance (SPR) and an orthogonal fluorescence-displacement assay to help a client identify possible new structure cores for their lead compound.

We assisted the client in arranging a virtual screen of 10’s of thousands of compounds against their protein target. Approximately 100 compounds were identified and purchased for physical screening by Charnwood Molecular bioscientists who then developed a de novo SPR assay for protein target (and several related proteins).

The assay was validated with tool compound affinity measurements and all compounds were screened using the SPR assay in a spot-test format (20 µM, n=3, N=2), excluding poorly-behaved PAINS-like compound results from analysis.

After agreeing upon a hit threshold with the client, ~ 20 compounds were identified as hits and progressed to next stage.

For all hits, we measured affinities (KD) in the SPR assay and potencies (IC50) from a competition-based fluorophore-displacement assay.

KD and IC50 values were passed back to the client for SAR analysis and a second round of virtual screening based on the initial learnings

You can see further explanation of our findings below.

You can also find out more about our SPR capabilities and biophysical techniques too.

Reference and blank-subtracted response levels for all compounds in 20 µM SPR spot test. Some sensorgrams were excluded after failing Insight Evaluation software’s QC checks

Correlation plot showing the response levels measured in the N=1 and N=2 SPR spot test screens.

Different levels of hit threshold definition – and which compounds cross each threshold – are shown as shaded ovals.

Whilst fairly weak, we could measure affinities (KD) for majority of hits (e.g., left hand panel).

Some however were too weak to measure or appeared to be non-specific binders (e.g., right hand panel).

We could measure robust IC50 values for majority of hits in an orthogonal competition-based fluorescence-displacement assay.

Find out more about our SPR capabilities and range of biophysical techniques.

You can also read our case study BRD4 PROTAC Characterisation using SPR.

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