Exploring the Effect of Halogenation in a Series of Potent and Selective A(2B) Adenosine Receptor Antagonists

[Image: see text] The modulation of the A(2B) adenosine receptor is a promising strategy in cancer (immuno) therapy, with A(2B)AR antagonists emerging as immune checkpoint inhibitors. Herein, we report a systematic assessment of the impact of (di- and mono-)halogenation at positions 7 and/or 8 on both A(2B)AR affinity and pharmacokinetic properties of a collection of A(2B)AR antagonists and its study with structure-based free energy perturbation simulations. Monohalogenation at position 8 produced potent A(2B)AR ligands irrespective of the nature of the halogen. In contrast, halogenation at position 7 and dihalogenation produced a halogen-size-dependent decay in affinity. Eight novel A(2B)AR ligands exhibited remarkable affinity (K(i) < 10 nM), exquisite subtype selectivity, and enantioselective recognition, with some eutomers eliciting sub-nanomolar affinity. The pharmacokinetic profile of representative derivatives showed enhanced solubility and microsomal stability. Finally, two compounds showed the capacity of reversing the antiproliferative effect of adenosine in activated primary human peripheral blood mononuclear cells.