CCR4-351

CCR4-351 is a small molecule antagonist of the C-C chemokine receptor type 4 (CCR4), developed by RAPT Therapeutics. It serves as a preclinical tool compound designed to inhibit the trafficking of immunosuppressive T-regulatory cells (Tregs) into the tumor microenvironment. Tregs express CCR4 and migrate toward the ligands CCL17 and CCL22, which are frequently upregulated in various solid tumors. By blocking this interaction, CCR4-351 reduces Treg accumulation, thereby potentially overcoming a major mechanism of immune evasion. Research has demonstrated that CCR4-351 can significantly enhance the antitumor efficacy of other immunotherapies, such as CAR T-cell therapy, in immunocompetent murine models of solid tumors like mesothelioma. It is chemically and functionally related to FLX475 (florexilant), a CCR4 antagonist that has advanced into clinical trials.