Determining whether bespoke nanoBRET tracers work with ALK5

I have always wanted to establish nanoBRET target engagement assay for ALK5. Relative to dual luciferase promoter assay and immunofluorescent staining, nanoBRET is many times faster. With a robust ALK5 nanoBRET assay, I will be able to rapidly screen for cellular off-target activity. Since none of the commercial nanoBRET tracers worked with ALK5, we attempted to generate our own tracers. We chose to create these bespoke tracers based on M4K1046 because it has cellular IC50 of ~50nM for ALK5. David Drewry has helped to design linkers that will attach fluorophores (nanoBRET energy acceptor) to the solvent-facing end of M4K1046. Based on known structures, additional bulk in this region should not hinder the binding of the compounds to ALK5. Two versions of M4K1046 (with different linker length) were synthesised by the M4K pharma chemist team in OICR. They were subsequently sent to Carrow Wells for conjugation to nanoBRET fluorophore. For more description of the project, please visit my blog posts: https://openlabnotebooks.org/determining-whether-bespoke-tracers-work-with-alk5-in-nanobret-target-engagement-assay/