A human orthogonal IL-2 and IL-2Rβ system enhances CAR T cell expansion and antitumor activity in a murine model of leukemia

Abstract

A human IL-2 and IL-2Rβ orthogonal cytokine-receptor pair enables a tunable approach to enhancing CAR T cell engraftment and antitumor efficacy.

An orthogonal approach to cancer

Interleukin-2 (IL-2) is an important cytokine for T cell activation and has been considered as a treatment for cancer. However, systemic administration of IL-2 often leads to severe toxicity. To address this, Zhang et al. and Aspuria et al. engineered T cells to express an IL-2 receptor β (IL-2Rβ) that can only be activated by a modified, orthogonal IL-2. Orthogonal IL-2Rβ was introduced to CAR T cells targeting CD19, and the CAR T cells were transferred to mice bearing leukemias or lymphomas. Administration of orthogonal IL-2 to CAR T cell recipients drove activation, expansion, and antitumor efficacy of CAR T cells in both preclinical models with limited systemic toxicity. Thus, orthogonal cytokine-receptor pairs may offer a safer approach to enhance adoptive cell therapy.

Abstract

Interleukin-2 (IL-2) is a central T cell cytokine that promotes T cell proliferation and effector function; however, toxicity due to its pluripotency limits its application to enhance CAR T cell immunotherapy. Previously, mouse IL-2 and its cognate receptor were engineered to create an orthogonal ( ortho ) cytokine-cytokine receptor pair capable of delivering an IL-2 signal without toxicity. Here, we engineered a human orthogonal IL-2 ( ortho- hIL-2) and human orthogonal IL-2Rβ ( ortho- hIL-2Rβ) pair, containing human-specific mutations. Ortho- hIL-2 is selective toward ortho- hIL-2Rβ–expressing cells with no appreciable signaling on wild-type T cells. Ortho- hIL-2 induces IL-2 receptor signaling and supports proliferation of both an IL-2–dependent cell line and primary T cells transduced to express the ortho- hIL-2Rβ. Using CD19-specific chimeric antigen receptor (CAR) T cells, we show that ortho -hIL-2 induces a dose-dependent increase in ortho -hIL-2Rβ ⁺ CAR T cell expansion in vivo by as much as 1000-fold at 2 weeks after adoptive transfer into immunodeficient mice bearing CD19 ⁺ Nalm6 leukemia xenografts. Ortho -hIL-2 can rescue the antileukemic effect of an otherwise suboptimal CAR T cell dose. In addition, ortho -hIL-2 administration initiated at the time of leukemic relapse after CAR T cell therapy can rescue an otherwise failed antileukemic response. These data highlight the potential of combining an orthogonal cytokine approach with T cell–based immunotherapies to augment the antitumor efficacy of engineered T cells.