Synthesis and Pharmacological Evaluation of Triazolopyrimidinone Derivatives as Noncompetitive, Intracellular Antagonists for CC Chemokine Receptors 2 and 5

Abstract

CC chemokine receptors 2 (CCR2) and 5 (CCR5) are involved in many inflammatory diseases; however, most CCR2 and CCR5 clinical candidates have been unsuccessful. (Pre)clinical evidence suggests that dual CCR2/CCR5 inhibition might be more effective in the treatment of such multifactorial diseases. In this regard, the highly conserved intracellular binding site in chemokine receptors provides a new avenue for the design of multitarget ligands. In this study, we synthesized and evaluated the biological activity of a series of triazolopyrimidinone derivatives in CCR2 and CCR5. Radioligand binding assays first showed that they bind to the intracellular site of CCR2, and in combination with functional assays on CCR5, we explored structure–affinity/activity relationships in both receptors. Although most compounds were CCR2-selective, 39 and 43 inhibited β-arrestin recruitment in CCR5 with high potency. Moreover, these compounds displayed an insurmountable mechanism of inhibition in both receptors, which holds promise for improved efficacy in inflammatory diseases.

Targeting chemokine receptors from the inside-out: discovery and development of small-molecule intracellular antagonists

“…In 2019, IJzerman and co-workers at the university of Leiden investigated a class of triazolopyrimidinones, previously disclosed in a patent by AstraZeneca, in a displacement study with CCR2-RA-[ R ], thereby providing proof for an intracellular binding mode for this class of compounds. 41 They also probed the SAR of these compounds and compound 56 (Fig. 9) was presented as the most potent compound in the series, with a K i of 0.4 nM for displacement of CCR-RA-[ R ] from CCR2.…”

“…31,33,34 (3) Lastly, a radioligand displacement assay of a known compound can be used, when an intracellular antagonist has been established for the investigated chemokine receptor. [35][36][37][38][39][40][41] A careful analysis, taking the above-mentioned points into account, revealed that many small-molecule chemokine receptor antagonists operate through this intracellular mode-of-action. The first intracellular chemokine receptor antagonist can be traced back to as early as 1998, 42 many years before a common druggable intracellular binding pocket in chemokine receptors was postulated.…”

“…Further antagonists in the pyrimidine-based class of chemokine antagonists have been reported by AstraZeneca R&D (53) 103,104 for CX 3 CR1 antagonism, Novartis (54 and 55) 105,106 for CXCR2 antagonism and the lab of A. IJzerman (56) 41 for dual CCR2/ CCR5 antagonism. A focused screen of an in-house compound library known to antagonize CXCR2 at AstraZeneca R&D yielded two compound series with potency for inhibiting CX 3 CL1 binding to CX 3 CR1: the thiazolopyrimidines and the thiazolopyrimidinones.…”

“…31,33,34 (3) Lastly, a radioligand displacement assay of a known compound can be used, when an intracellular antagonist has been established for the investigated chemokine receptor. 35–41…”

Anticancer opportunities at every stage of chemokine function

“…Clinical success may also be enhanced by uncovering novel strategies. In this context, it is worth noting that, although not tested against cancer yet, intracellular allosteric ligands have also been synthesized for many other chemokine receptors than those discussed in the main text, including CCR1, CCR4, CCR5, and CX3CR1 [77][78][79][80]. Long-residence time antagonists might provide another strategy to inhibit chemokine receptors in an insurmountable manner, such as those described for CCR2 [81,82].…”