Data from Phase Ia Study of FoxP3<sup>+</sup> CD4 Treg Depletion by Infusion of a Humanized Anti-CCR4 Antibody, KW-0761, in Cancer Patients

Abstract

<div>Abstract<p><b>Purpose:</b> FoxP3<sup>+</sup> Tregs inhibit immune responses against tumors. KW-0761 is a humanized anti-human CCR4 monoclonal antibody (mAb) that has antibody-dependent cellular cytotoxicity activity. Depletion of CCR4-expressing FoxP3<sup>+</sup> CD4 Tregs by KW-0761 infusion was investigated in solid cancer patients.</p><p><b>Experimental Design:</b> We conducted a phase Ia clinical trial of KW-0761 infusion in 7 lung and 3 esophageal cancer patients. Toxicity, clinical efficacy, changes in lymphocyte subpopulations, including Tregs, and induction of immune responses were analyzed.</p><p><b>Results:</b> The results showed that KW-0761 infusion in a dose range between 0.1 mg/kg and 1.0 mg/kg was safe and well tolerated. No dose-limiting toxicity was observed. Four of 10 patients showed stable disease during treatment and were long survivors. The monitoring of FoxP3<sup>+</sup> Tregs in the peripheral blood mononuclear cells during treatment indicated efficient depletion of those cells, even at the lowest dose of 0.1 mg/kg used. The reduction in Th 1 CD4 T cells and CD8 T cells was limited, whereas a significant reduction was observed with Th 2 and Th 17 CD4 T cells. Immune responses to cancer/testis (CT) antigens and an autoantibody response to thyroid peroxidase were observed in some patients.</p><p><b>Conclusions:</b> The findings showed Tregs depletion and the possible occurrence of an immune response following KW-0761 infusion. Combined use of KW-0761 to deplete FoxP3<sup>+</sup> Tregs with other immunotherapies, such as cancer vaccines or checkpoint inhibitors, is a promising approach to augment immune responses. <i>Clin Cancer Res; 21(19); 4327–36. ©2015 AACR</i>.</p></div>