Exploring the Effect of Halogenation in a Series of Potent and Selective A2B Adenosine Receptor Antagonists

The modulation of the A2B adenosine receptor is a promising strategy in cancer (immuno) therapy, with A2BAR 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 A2BAR affinity and pharmacokinetic properties of a collection of A2BAR antagonists and its study with structure-based free energy perturbation simulations. Monohalogenation at position 8 produced potent A2BAR 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 A2BAR ligands exhibited remarkable affinity (Ki < 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.

Automated summary

Modulation of the A2B adenosine receptor is a promising strategy in (immuno) cancer therapy. A systematic assessment was conducted on the impact of (di-and mono-)halogenation at positions 7 and/or 8 on A2BAR affinity and pharmacokinetic properties of A2BAR antagonists. The study revealed that monohalogenation at position 8 produced potent A2BAR ligands, while halogenation at position 7 and dihalogenation decreased affinity. Eight novel A2BAR ligands were discovered with remarkable affinity, subtype selectivity, and enantioselective recognition.