Dual COX-2/sEH Inhibition and Immune Checkpoint Blockade Regress Bladder Cancer Tumors in Mice.

Unresolved inflammation plays a critical role in bladder cancer initiation and progression. Acute inflammation leads to eicosanoid-driven cytokine production. Controlling the local and systemic inflammatory response in bladder cancer is critical to preventing bladder cancer progression. Chemotherapy (e.g. gemcitabine and cisplatin), the standard of care for advanced bladder cancer, disrupts the resolution of inflammation and is only partially effective in preventing tumor recurrence after treatment. Although immunotherapy induces a durable response in 15 to 30% of patients in advanced bladder cancer, a majority of patients do not respond due to drug resistance mechanisms. Therefore, there is a critical unmet medical need to improve chemotherapy and immunotherapy in bladder cancer. To address this, we have developed dual COX-2/sEH inhibitors (e.g. PTUPB). This lead compound is representative of a newly patented class of "dual acting" molecules that target two important enzymes in the arachidonic acid cascade with nanomolar binding affinity: cyclooxygenase-2 (COX-2) and soluble epoxide hydrolase (sEH). Oral dosing of PTUPB is well-tolerated in animal models. Since chemotherapy and immunotherapy both induce tumor-promoting inflammation via an eicosanoid and cytokine storm, we hypothesized that dual COX-2/sEH inhibition using PTUPB would enhance immunotherapy in experimental bladder cancer via anti-inflammatory mechanisms. When syngeneic (MB49) bladder tumors reached ~200 mm3 in immunocompetent mice, treatment was initiated with PTUPB (oral, 30-60 mg/kg), anti-CTLA-4 (200 µg initial dose, 100 µg Q3D), anti-PD1 (200 µg Q3D), gemcitabine (75 mg/kg Q3D), cisplatin (5 mg/kg Q5D), or various combinations thereof. After 9 days of treatment, mice were sacrificed and bladder tumor tissues were analyzed for sEH and COX-2 expression, as well as endoplasmic reticulum (ER) stress. Here we demonstrate that chemotherapy stimulated sEH expression in tumor tissue which was counter-regulated by PTUPB. Importantly, PTUPB enhanced immunotherapy in the MB49 bladder cancer model. While monotherapy treatment with PTUPB, gemcitabine/cisplatin, anti-PD1 or anti-CTLA4 suppressed tumor growth compared to control, the tumors eventually escaped by the end of the study. Dual COX-2/sEH inhibition in combination with chemotherapy (gemcitabine and cisplatin) and/or immune checkpoint blockade (anti-CTLA-4 or anti-PD1) induced tumor regression via synergistic anti-tumor activities. Chemotherapy induced the expression of ER stress response genes (e.g. BiP and CHOP), COX-2, and pro-inflammatory cytokines in bladder cancer tissue which were repressed by PTUPB. Taken together, our results demonstrate dual COX-2/sEH inhibition as a novel therapeutic approach to enhance immunotherapy in bladder cancer without overt toxicity.