Development of subtype-selective covalent ligands for the adenosine A 2B receptor by tuning the reactive group

Signalling through the adenosine receptors (ARs), in particular through the adenosine A receptor (A AR), has been shown to play a role in a variety of pathological conditions, ranging from immune disorders to cancer. Covalent ligands for the A AR have the potential to irreversibly block the receptor, as well as inhibit all A AR-induced signalling pathways. This will allow a thorough investigation of the pathophysiological role of the receptor. In this study, we synthesized and evaluated a set of potential covalent ligands for the A AR. The ligands all contain a core scaffold consisting of a substituted xanthine, varying in type and orientation of electrophilic group (warhead). Here, we find that the right combination of these variables is necessary for a high affinity, irreversible mode of binding and selectivity towards the A AR. Altogether, this is the case for sulfonyl fluoride 24 (LUF7982), a covalent ligand that allows for novel ways to interrogate the A AR.