Hebb et al. demonstrate that direct intratumoral injection of agonist OX-40, agonist CD137, and anti-CTLA-4 antibodies produce a profound abscopal effect at a fraction of the dose used systemically, curing most mice in two tumor models. Moreover, s.c. injection of the combination treatment in the proximity of (1) the tumor, (2) the tumor draining lymph node (TDLN), or (3) a non-TDLN with irradiated tumor cells produced nearly similar results.
The delivery of immunomodulators directly into the tumor potentially harnesses the existing antigen, tumor-specific infiltrating lymphocytes, and antigen presenting cells. This can confer specificity and generate a potent systemic anti-tumor immune response with lower doses and less toxicity compared to systemic administration, in effect an in situ vaccine. Here, we test this concept using the novel combination of immunomodulators anti-CTLA4, -CD137, and -OX40. The triple combination administered intratumorally at low doses to one tumor of a dual tumor mouse model had dramatic local and systemic anti-tumor efficacy in lymphoma (A20) and solid tumor (MC38) models, consistent with an abscopal effect. The minimal effective dose was 10 mug each. The effect was dependent on CD8 T-cells. Intratumoral administration resulted in superior local and distant tumor control compared to systemic routes, supporting the in situ vaccine concept. In a single tumor A20 model, injection close to the tDLN resulted in similar efficacy as intratumoral and significantly better than targeting a non-tDLN, supporting the role of the tDLN as a viable immunotherapy target in addition to the tumor itself. Distribution studies confirmed expected concentration of antibodies in tumor and tDLN, in keeping with the anti-tumor results. Overall intratumoral or peri-tDLN administration of the novel combination of anti-CTLA4, anti-CD137, and anti-OX40, all agents in the clinic or clinical trials, demonstrates potent systemic anti-tumor effects. This immunotherapeutic combination is promising for future clinical development via both these safe and highly efficacious routes of administration.