Chalcone 4 (compound 1) is a small molecule that neutralizes the CXC chemokine CXCL12 and prevents it from acting on the CXCR4 and CXCR7 receptors. To overcome its poor solubility in aqueous buffers, we designed highly soluble analogues of compound 1, phosphate, L-seryl, and sulfate, all inactive by themselves on CXCL12 but when cleaved in vivo into 1, highly active locally at a low dose in a mouse airway hypereosinophilia model.

Background: The chemokine CXCL12 and its receptor CXCR4 are widely distributed and contribute to the physiopathology of inflammation.Results: Recruitment of eosinophils in the inflamed airway is selectively attenuated by short lived antagonists that block CXCL12-mediated activation of CXCR4.Conclusion: CXCL12/CXCR4 signaling regulates local leukocyte-mediated inflammation.Significance: Antedrugs of neutraligands allow dissecting the physiological role of chemokines, especially when expression occurs in multiple tissues.

We previously reported Chalcone-4 (1) that binds the chemokine CXCL12, not its cognate receptors CXCR4 or CXCR7, and neutralizes its biological activity. However, this neutraligand suffers from limitations such as poor chemical stability, solubility, and oral activity. Herein, we report on the discovery of pyrimidinone 57 (LIT-927), a novel neutraligand of CXCL12 which displays a higher solubility than 1 and is no longer a Michael acceptor. While both 1 and 57 reduce eosinophil recruitment in a murine model of allergic airway hypereosinophilia, 57 is the only one to display inhibitory activity following oral administration. Thereby, we here describe 57 as the first orally active CXCL12 neutraligand with anti-inflammatory properties. Combined with a high binding selectivity for CXCL12 over other chemokines, 57 represents a powerful pharmacological tool to investigate CXCL12 physiology in vivo and to explore the activity of chemokine neutralization in inflammatory and related diseases.