Frontiers in Immunology, an international scientific journal focusing on immunology, cancer immunity and immunotherapy, has published AskAt’s review article describing a mechanism of anti-tumor action of the EP4 antagonist. The review is based on immuno-oncological evidence recently published in scientific journals. It suggests a new concept for the mechanism of action of the EP4 antagonist, in combination with a cancer-immunity cycle theory, demonstrating a position for the therapy within current cancer immunotherapy. This new concept helps to advance understanding of AskAt’s EP4 antagonists, AAT-007 and AAT-008, in cancer immunotherapy, and provides an immunological background of EP4 antagonist therapy in combination with immune checkpoint inhibitors, chemotherapy, and tumor radiotherapy. Currently, AAT-007 and AAT-008 are being developed in the U.S. and China, initially targeting colorectal cancer and non-small cell lung cancer.