Targeting programmed cell death-1 receptor (PD-1) or its ligand PD-L1 has failed to provide durable clinical benefit for a majority of patients with solid carcinomas. Recent preclinical and clinical data suggests that addition of the IL-15 superagonist N-803 improves response rates to anti-PD-1 or anti-PD-L1 therapy. Thus, we hypothesized that N-809, a novel bifunctional agent comprised of N-803 fused to two single chain anti-PD-L1 variable region domains, would promote potent anti-tumor efficacy and immune activation in murine models of solid carcinomas.
The functionality of the N-809 components was examined in vitro. Anti-tumor efficacy of N-809 versus a clinically relevant dose of N-803 + anti-PD-L1 was assessed using murine MC38 colon and 4T1 triple negative breast tumor models. The immune-mediated mechanism of N-809 was examined in spleen and tumor using comprehensive flow-based analyses and functional assays. Serum cytokine levels were also measured. Finally, effects on tumor gene expression were examined using Nanostring. Nant biosciences provided N-809 as per Cooperative Research and Development Agreement with NCI.
In vitrostudies confirmed that both components of N-809 were functional. N-809 drastically reduced MC38 tumor burden leading to increased survival and significantly reduced spontaneous lung metastasis of 4T1 tumors. In both tumor models, N-809 had improved efficacy versus a clinically relevant dose of N-803 + anti-PD-L1. In the MC38 model, N-809 increased serum levels of IFNg, TNFa, and IL-10. Depletion studies revealed that CD8+T and NK cells are required for the anti-tumor efficacy of N-809. The immune analysis showed enhanced CD8+ T and NK cell tumor infiltration, activation, and function. To determine the mechanism of the increased CD8 and NK cell infiltration, analyses were performed to examine tumor chemokines and inhibition of immune cell migration. Gene analysis revealed changes in chemokines, chemokine receptors, and immune response genes.
N-809 has anti-tumor efficacy in two murine carcinoma model mediated by increasing the number, activation, and function of CD8+ T cells and NK cells.
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Laboratory of Tumor Immunology and Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
All authors have declared no conflicts of interest.