Human Anti-CCR4 Minibody Gene Transfer for the Treatment of Cutaneous T-Cell Lymphoma

Background: Although several therapeutic options have become available for patients with Cutaneous T-cell Lymphoma (CTCL), no therapy has been curative. Recent studies have demonstrated that CTCL cells overexpress the CC chemokine receptor 4 (CCR4). Methodology/Principal Findings: In this study, a xenograft model of CTCL was established and a recombinant adenoassociated viral serotype 8 (AAV8) vector expressing a humanized single-chain variable fragment (scFv)-Fc fusion (scFvFc or ‘‘minibody’’) of anti-CCR4 monoclonal antibody (mAb) h1567 was evaluated for curative treatment. Human CCR4 + tumorbearing mice treated once with intravenous infusion of AAV8 virions encoding the h1567 (AAV8-h1567) minibody showed anti-tumor activity in vivo and increased survival. The AAV8-h1567 minibody notably increased the number of tumorinfiltrating Ly-6G + FccRIIIa(CD16A) + murine neutrophils in the tumor xenografts over that of AAV8-control minibody treated mice. Furthermore, in CCR4 + tumor-bearing mice co-treated with AAV8-h1567 minibody and infused with human peripheral blood mononuclear cells (PBMCs), marked tumor infiltration of human CD16A + CD56 + NK cells was observed. The h1567 minibody also induced in vitro ADCC activity through both mouse neutrophils and human NK cells. Conclusions/Significance: Overall, our data demonstrate that the in vivo anti-tumor activity of h1567 minibody is mediated, at least in part, through CD16A + immune effector cell ADCC mechanisms. These data further demonstrate the utility of the AAV-minibody gene transfer system in the rapid evaluation of candidate anti-tumor mAbs and the potency of h1567 as a potential novel therapy for CTCL.