Drs. Shirakami and Shimizu, Departments of Gastroenterology/Internal Medicine, Gifu University Graduate School of Medicine, discovered that RQ-15986/CJ-42,794, an AskAt’s EP4 antagonist having similar features with AAT-007/8 in discovery stage, demonstrates anti-tumor efficacy in rat colorectal cancer model, and published the results in PLOS ONE. Dr. Shirakami dosed RQ-15986 to azoxymethane and dextran sulfate-treated Kyoto APC delta (KAD) rats that have APC mutations and identified significant suppressions of colorectal tumor incidence and growth. In addition, RQ-15986 inhibited expressions of several inflammatory cytokines and IDO1, an immune-suppressive molecule in tumor tissues. The evidence supports the chemoprevention therapy for the colorectal cancer by EP4 antagonists.