The development of potent, competitive CXCR4 antagonists for the prevention of cancer metastasis

Cancer metastasis is the cause of up to 90 % of cancer related mortality. The CXCR4 receptor and its cognate ligand, CXCL12, have major roles in enabling cancer metastasis and consequently, the CXCR4 receptor has become an attractive therapeutic target for the prevention of metastasis. Despite this, CXCR4 antagonists have had limited success in clinical trials due to cellular toxicity and poor stability and efficacy. In this study, we developed a novel, competitive CXCR4 antagonist (IS4) that through copper-catalysed-azide-alkyne-cycloaddition can be clicked to other chemical moieties such as fluorescent dyes (IS4-FAM) for CXCR4-based imaging. We determined that these CXCR4 antagonists were non-toxic and could be used to specifically label the CXCR4 receptor. Furthermore, IS4 and IS4-FAM inhibited both CXCL12-stimulated cancer cell migration and Ca2+ release in both adherent and suspension cell lines with similar or improved potency as compared to two literature CXCR4 antagonists. Our results highlight the potential of IS4 and IS4-FAM as research tools and as potent CXCR4 antagonists for the prevention of metastasis.