Super2-expressing CAR T cells generate improved anti-tumor responses against solid tumors

Abstract

Abstract Chimeric antigen receptors (CAR) augment tumor specific immune responses by redirecting all T cells towards recognition of tumor antigen. Although CAR T cell treatment shows promising therapeutic effects in leukemia patients, current CAR therapies are inadequate against solid tumors, in part from exclusion or functional exhaustion in the suppressive microenvironment. Exogenously administered Interleukin 2 (IL-2) improves efficacy and expansion of CAR T cell therapy. However, IL-2 administration is limited by high toxicity and low half-life. Super2 is an engineered IL-2 variant that binds with high affinity to the beta and gamma chains of the IL-2 receptor even without IL-2R alpha chain expression. We found that Super2 leads to increased phosphorylation of STAT-5 and more effectively activates lymphocyte populations compared to endogenous IL-2 in vitro. We hypothesized that engineering CAR T cells to express Super2 will improve their functionality within the tumor microenvironment. CAR T cell-intrinsic Super2 may also increase activation of the endogenous tumor-reactive T cells resulting in enhanced tumor control and the establishment of long-term memory even after loss of CAR T cells. To test this hypothesis, we designed CAR T cells that produce Super2 constitutively or in response to CAR stimulation. We found that Super2-expressing CAR T cells increased tumor infiltrating leukocytes (TILs) compared to CAR T cell treatment alone in immune competent murine models. Additionally, Super2-expressing CAR T cells delayed B16F10 melanoma growth in comparison to CAR T cell alone. We conclude that Super2-expressing CAR T cells provide improved protection against solid tumors.