Grooved Microneedle Patch Augments Adoptive T Cell Therapy Against Solid Tumors via Diverting Regulatory T Cells

Abstract The efficacy of adoptive T cell therapy (ACT) for the treatment of solid tumors remains challenging. In addition to the poor infiltration of effector T (Teff) cells limited by the physical barrier surrounding the solid tumor, another major obstacle is the extensive infiltration of regulatory T (Treg) cells, a major immunosuppressive immune cell subset, in the tumor microenvironment. Here, this work develops a grooved microneedle patch for augmenting ACT, aiming to simultaneously overcome physical and immunosuppressive barriers. The microneedles are engineered through an ice‐templated method to generate the grooved structure for sufficient T‐cell loading. In addition, with the surface modification of chemokine CCL22, the MNs could not only directly deliver tumor‐specific T cells into solid tumors through physical penetration, but also specifically divert Treg cells from the tumor microenvironment to the surface of the microneedles via a cytokine concentration gradient, leading to an increase in the ratio of Teff cells/Treg cells in a mouse melanoma model. Consequently, this local delivery strategy of both T cell receptor T cells and chimeric antigen receptor T cells via the CCL22‐modified grooved microneedles as a local niche could significantly enhance the antitumor efficacy and reduce the on‐target off‐tumor toxicity of ACT.