Intrapulmonary delivery of TLR agonists to treat metastatic cancer

The TLR7/8 agonist 3M-052 and the TLR9 agonist CpG ODN both trigger innate immune responses that support the induction of tumor-specific immunity. Previous studies showed that intra-tumoral delivery of this agonist combination was synergistic and led to the eradication of large primary tumors and the establishment of long-term protective immunity in murine tumor models. We explored the effect of delivering 3M-052 plus CpG ODN to the lungs of mice bearing breast-derived lung metastases. 66Cl4-Luc cells (a luciferase-expressing variant of the 4T1 murine mammary carcinoma) were orthotopically implanted in the fourth mammary fat pad of Balb/c mice. Progression of the primary tumor and lung metastases was monitored by bioluminescence. TLR agonist treatment by intratracheal instillation was initiated after mets were detected in the lungs. Results show that intra-pulmonary treatment with the combination of TLR7/8 and TLR9 agonists slowed the growth of the lung metastases compared to either agonist alone. This treatment decreased pulmonary tumor burden and significantly prolonged survival when compared to control (untreated) animals. In contrast, pulmonary therapy had no significant effect on the primary tumor. Results from ongoing studies examining the effect of higher/more frequent lung delivery combined with direct treatment of the primary tumor will be presented.