DSP-0509, a TLR7 agonist, exerted synergistic anti-tumor immunity combined with various immune therapies through modulating diverse immune cells in cancer microenvironment

Revised Passage:

Toll-like receptor 7 (TLR7) plays a key role in the innate immune system. Upon binding to its ligand, TLR7 activates myeloid cells, such as dendritic cells (DCs) and macrophages, which are essential for initiating adaptive immunity. Due to this function, TLR7 agonists have been utilized in cancer immunotherapy. In this study, we synthesized DSP-0509, a systemic injectable TLR7 agonist, and investigated its effects on tumor-infiltrating lymphocytes (TILs) using single-cell RNA sequencing (scRNA-seq) in a mouse tumor model.

Our analysis revealed that DSP-0509 expanded immune cell populations, including Natural Killer (NK) cells, CD4+ T cells, and CD4+ regulatory T cells (Tregs). Given the observed increase in Tregs, which can suppress antitumor responses, we combined DSP-0509 with an Indoleamine 2,3-dioxygenase 1 (IDO1) inhibitor to enhance therapeutic efficacy by reducing Treg infiltration. This combination successfully decreased Treg levels within the tumor and improved antitumor activity.

To further enhance immune responses and prevent CD8+ T cell exhaustion, we combined DSP-0509 with an anti-PD-1 antibody and evaluated TIL alterations using scRNA-seq. This combination led to a marked increase in CD8+ T cells expressing key immune markers such as *Gzmb*, *Prf1*, *Ctla4*, and *Icos*, compared to DSP-0509 alone. Additionally, we observed a significant rise in M1-like macrophages within the tumor microenvironment following combination therapy.

To explore the modulation of myeloid cells as a therapeutic strategy, we also Dubermatinib tested the combination of DSP-0509 with an AXL receptor tyrosine kinase inhibitor. In bone marrow-derived macrophages (BMDMs), the AXL inhibitor amplified DSP-0509-induced TNFα secretion while reducing IL-10 levels, suggesting a shift toward a pro-inflammatory profile. When tested in vivo, the combination of DSP-0509 and the AXL inhibitor exhibited enhanced antitumor efficacy.

In summary, our study highlights the immune-modulating effects of DSP-0509 within the tumor microenvironment and demonstrates the potential of combining DSP-0509 with other therapies to improve antitumor outcomes. These findings offer new insights for developing innovative combination immunotherapy strategies.