61P In-situ generation of cancer antigens with prolonged TLR7/8 agonist immunomodulator for cancer therapy in preclinical model

Cancer vaccines targeting tumor-specific antigens or individualized neoantigens are getting more attention. However, a significant number of cancers still lack precise knowledge of their specific antigens. An intra-tumoral administration of TLR 7/8 agonists has demonstrated inducing Th1 responses leading to tumor suppression and modulating tumor microenvironment. Immunogenic cancer cell death followed by robust immune boosting may represent an ideal strategy for in-situ vaccines. We conducted therapeutic in-situ vaccine strategy studies that combine cytotoxic chemotherapy with liposomal TLR7/8 agonist (ProLNG-001) to elicit an anti-cancer response. BALB/c mice were subcutaneously inoculated with TNBC (4T1) and randomly divided into four groups (control, Liposomal doxorubicin (LD), ProLNG-001, and LD+ProLNG-001 (LD/P)) at early (∼100 mm3), middle (∼350 mm3) and late (∼1000 mm3) stage tumors. For systemic immunity, BALB/c mice were subcutaneously inoculated with right and left flank on days 0 and 5. LD 80 μg was administrated intravenously once a week for two weeks. ProLNG-001 140 μg was intratumorally injected for a total of four times on 1 and 4 days after LD administration. For the memory response, the complete regression mice LD/P were re-inoculated with 4T1 at the opposite flank on day 50. Combination therapy of LD and ProLNG-001 induced a remarkable anti-cancer therapeutic effect regardless of the stage of the tumor (early stage, at day 40, P<0.001, control: 2031 mm3, LD: 1087 mm3, ProLNG-001: 1126 mm3, and LD/P: 37 mm3). LD/P elicited anti-cancer effects that affect distant tumors as well as primary tumors. LD/P induced antigen-specific T cells, activated T and NK cells, and reduced the number of MDSCs in spleen. LD/P treated mice elicited memory immunity, allowing recurrent cancers to grow slowly. These results indicate an improvement in the TME and suggest the induction of systemic immunity, ultimately leading to a significantly enhanced anti-cancer therapeutic effect. Our data suggest that an intra-tumoral ProLNG-001 combined with conventional chemotherapy could emerge as an effective anti-cancer immunomodulator in TNBC.