Ranking Hits From Saturation Transfer Difference Nuclear Magnetic Resonance-Based Fragment Screening

Area of Science:

• Biophysics
• Medicinal Chemistry
• Computational Chemistry

Background:

• Fragment-based screening is crucial for identifying low-molecular-weight drug leads.
• High-affinity inhibitors require sensitive biophysical techniques for early hit characterization.
• Saturation transfer difference (STD) NMR is a popular sensitive method for low-affinity ligands.

Purpose of the Study:

• To investigate the validity of using high STD effects to select for higher-affinity fragments.
• To determine the boundaries under which the assumption of high STD effect correlating with high affinity holds true.
• To assess the predictive power of CORCEMA-ST calculations for STD NMR results.

Main Methods:

• Application of Complete Relaxation and Conformational Exchange Matrix (CORCEMA) theory adapted for saturation transfer (ST) measurements (CORCEMA-ST) calculations.
• Prediction of STD NMR results for a large dataset of fragment/receptor pairs.
• Analysis of the correlation between STD effect magnitude and fragment affinity.

Main Results:

• The assumption that a high STD effect directly selects for higher-affinity fragments was found to be invalid.
• CORCEMA-ST calculations were used to explore the relationship between STD effects and binding affinity.
• The study identified limitations in using STD NMR alone for affinity-based hit selection.

Conclusions:

• A high STD effect is not a universally reliable indicator of higher fragment affinity.
• The direct application of STD NMR for rank-ordering fragments by affinity is questionable.
• Further refinement of biophysical screening strategies is needed for accurate fragment-based drug discovery.