Designing out a BRD4 liability from dual TLR7/8 antagonists for lupus
- Structure-based optimization of 2-(pyridin-2(1H)-one)indoles gave dual TLR7/8 antagonists with better permeability, less ion-channel activity and lower volume of distribution than the earlier series.
- Early pyridone leads unexpectedly suppressed immune-cell proliferation, which the team traced to a hypothesized BRD4 off-target.
- Optimizing away BRD4 binding removed the anti-proliferative effect while keeping potent inhibition of TLR7/8-driven IL-6 in human whole blood.
💡 Points
This is a tidy example of phenotype-led off-target triage: odd toxicity in cell panels, a mechanistic guess, then SAR that separates the two activities. Endosomal TLR7/8 antagonists need to be both cell-permeable and cleanly selective, and BRD4 is an easy trap for flat heteroaromatics. I would check the pyridone's binding mode in the TLR7/8 dimer interface before borrowing the fix for other scaffolds.