Selective Agonism of Intermediate-Affinity IL-2 Receptor Promotes Systemic Antitumor Responses in Combination with Radiotherapy in Metastatic Lung Cancer

Abstract

<h3>Purpose/Objective(s)</h3> For immune checkpoint inhibitor-resistant patients, adding interleukin-2 (IL-2) may aid antitumor responses by stimulating effector T cells and NK cells. Unfortunately, high-dose IL-2 therapy has limited clinical utility due to adverse events and stimulation of immunosuppressive regulatory T cells (T_regs). Nemvaleukin alfa (nemvaleukin) is a novel engineered cytokine that selectively binds to the intermediate-affinity IL-2 receptor, preferentially activating and expanding antitumor CD8⁺ T and NK cells, with minimal expansion of T_regs. Thus, Nemvaleukin may be beneficial in combination with radiation therapy (RT) and immunotherapy. This study aimed to evaluate the antitumor activity and mechanism of action of the combination of RDB 1462 (the murine ortholog of Nemvaleukin, a.k.a. mNemvaleukin), RT, and immunotherapy in multiple mouse tumor models. <h3>Materials/Methods</h3> In a bilateral 344SQ lung adenocarcinoma murine model, primary tumors were treated with high-dose RT (HDRT; 12 Gy per fraction for 3 fractions), and secondary tumors were observed for evidence of abscopal effects. In another model for low absolute lymphocyte count (ALC), we used 2 Gy total body irradiation (TBI) three days before HDRT and RDB 1462. In a third MC38-gp100 mouse model, tumors were irradiated with low-dose RT (LDRT; 3 fractions of 1 Gy each) followed by pmel-1 T cell infusion after 24 hours, and RDB 1462 administration 12 hours thereafter. We performed immune phenotyping by flow cytometry; analyzed 770 immune-related genes using a multiplex analysis platform; also performed T cell receptor (TCR) repertoire analysis. Serum pro-inflammatory cytokine markers were analyzed by 23-plex kit. <h3>Results</h3> In 344SQ-parental lung adenocarcinoma, we combined HDRT with escalating doses of RDB 1462 at various timepoints, resulting in significant tumor reduction in both irradiated and unirradiated (abscopal) tumors compared with HDRT or RDB 1462 therapy alone. HDRT+RDB 1462 increased the numbers and activity of tumor-specific CD8⁺ T cells, NK cells, and memory T cells without drastically increasing T_regs, as evidenced by peripheral and tumor-infiltrating immune phenotypic and functional analyses. T cells showed increased receptor clonality and diversity in groups receiving HDRT+RDB 1462. The addition of anti-PD-1 to HDRT+RDB 1462 further increased antitumor control of both irradiated and abscopal tumors, reduced lung metastases, and prolonged survival. The antitumor effects of HDRT and RDB 1462 persisted even in mice with low ALC. The addition of LDRT contributed to increased tumor-specific T cells that were expanded by RDB 1462 with increased infiltration of Thy1.1⁺ CD8⁺ T cells. <h3>Conclusion</h3> The addition of Nemvaleukin therapy may enhance responses to RT alone and in combination with anti-PD-1 or adoptive T cell therapy.