CCR4 Antagonists Inhibit Treg Trafficking into the Tumor Microenvironment.

Recruitment of naturally occurring suppressive CD4+, CD25+, and FOXP3+ regulatory T cells (Treg) to the tumor microenvironment (TME) has the potential to weaken the antitumor response in patients receiving treatment with immuno-oncology (IO) agents. Human Treg express CCR4 and can be recruited to the TME through the C-C chemokines CCL17 and CCL22. We have recently developed a series of potent, orally bioavailable small molecule antagonists of CCR4 that can block recruitment of Treg into the TME.