Intratumoral Virus-Like Particles Containing a TLR9 Agonist Combined with Systemic αPD-1 Activate Tumor-Specific CD8+...

Area of Science:

• Immunology
• Cancer Research
• Virology

Background:

• Enhancing anti-cancer immune responses involves modifying the tumor microenvironment (TME) with immunostimulatory agents.
• Vidutolimod (Vidu), a virus-like particle with a CpG-A TLR9 agonist, shows pre-clinical and early clinical anti-tumor activity.
• The precise impact of Vidu on tumor-specific CD8+ T cells requires further definition.

Purpose of the Study:

• To investigate the effects of Vidutolimod (Vidu) on the activation, cytotoxicity, and anti-tumor activity of tumor-specific CD8+ T cells.
• To evaluate Vidu's impact on T cell exhaustion markers.
• To assess the efficacy of Vidu in combination with αPD-1 immune checkpoint blockade.

Main Methods:

• Utilized the OT-1 mouse model for in vitro and in vivo assessments.
• Administered Vidutolimod (Vidu) via intratumoral injections.
• Analyzed T cell proliferation, activation, exhaustion markers (PD-1), and anti-tumor activity.
• Combined Vidu treatment with αPD-1 blockade.

Main Results:

• In vitro, Vidu reduced CD8+ T cell proliferation but increased activation and exhaustion markers.
• In vivo, Vidu induced a transient increase in intratumoral tumor-specific CD8+ T cells and enhanced anti-tumor activity.
• Combination therapy with Vidu and αPD-1 resulted in persistent CD8+ T cell increases and sustained tumor control.
• Vidu treatment increased markers of terminal exhaustion on intratumoral CD8+ T cells and expanded circulating CD8+ T cells with high PD-1 expression.

Conclusions:

• Vidutolimod (Vidu) expands both intratumoral and circulating tumor-specific CD8+ T cells.
• The addition of αPD-1 to Vidu sustains CD8+ T cell numbers and anti-tumor responses.
• These findings support the continued investigation of Vidu, particularly in combination with immune checkpoint inhibitors, for cancer immunotherapy.