Development of subtype-selective covalent ligands for the adenosine A2B receptor by tuning the reactive group

Signalling through the adenosine receptors (ARs), in particular through the adenosine A(2B) receptor (A(2B)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(2B)AR have the potential to irreversibly block the receptor, as well as inhibit all A(2B)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(2B)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(2B)AR. Altogether, this is the case for sulfonyl fluoride 24 (LUF7982), a covalent ligand that allows for novel ways to interrogate the A(2B)AR.