IRX-2 therapy with PD-L1 blockade in immunocompetent animal model.

Abstract

e14149 Background: Multiple therapeutic components in IRX-2 including IL-2, IL-1, IFN-γ, TNFα, IL-6, GM-CSF, and IL-8 work synergistically to activate various immune cells including T cells, dendritic cells, and natural killer cells to recognize and kill tumors. Previous Phase 1 and Phase 2a clinical trials in head and neck cancer with IRX-2 have shown a benign safety profile. Immunologically stimulating host immunity using IRX-2, while simultaneously blocking PD-1/PD-L1-mediated immune suppression, may have the potential to enhance the outcome of current immunotherapy using IRX-2 alone. Methods: Healthy C3H mice were inoculated with SCC7 murine head and neck cancer cells. Fourteen days after inoculation, the tumor-bearing mice were treated with subcutaneous injection of IRX-2 once a week for 3 weeks, followed with anti-mPD-L1(i.p.) injection after each IRX-2 administration. Tumor size and survival were monitored for the therapeutic efficacy evaluation. Two weeks after the last IRX-2 administration, all mice were sacrificed and spleen, blood and residual tumor samples were harvested for immune function assays. Results: High levels of PD-L1 were expressed on SCC7 cell line and fresh tumors. The FCM data suggested that PD-L1 was preferentially expressed on the ALDHhigh SCC7 cancer stem cells. IRX-2 alone significantly inhibited SCC7 tumor growth, and the anti-tumor efficacy of IRX-2 was significantly enhanced by anti-mPD-L1 injection in a dose dependent manner in the immunocompetent hosts. Serum IgG from animals subjected to IRX-2 plus anti-mPD-L1 treatment mediated significantly (p < 0.05) higher cytotoxicity on SCC7 cells via ADCC than the IgG from animals treated with IRX-2 alone. CD8+ lymphocytes isolated from purified, activated and expanded CD3+ splenic T cells harvested from the animals subjected to IRX-2+anti-mPD-L1 treatment mediated significantly (p < 0.05) higher cytotoxicity than those subjected to IRX-2 or anti-PD-L1 mono-therapy against SCC7 tumor cells. Conclusions: Co-administration of IRX-2 and anti-PD-L1 promoted more powerful antitumor immunity with both B cell and T cell modulation. The combination treatment increased the specific IgG production that could kill tumor cells via ADCC, and enhanced the T cell CTL activity. Therefore, IRX-2 therapy plus anti-PD-L1 administration may represent a promising novel strategy to treat cancer patients.