Study provides rationale for adding COX-2 inhibitors to improve anti-PD1 immunotherapy response In preclinical studies, tumors that consitutively expressed the protein indoleamine 2,3-dioxygenase (IDO1) responded to the cyclooxygenase-2 (COX-2) inhibitor celecoxib (Celebrex) and had improved infiltration of certain subsets of T cells, making them more likely to respond to anti-PD1 therapies, report researchers in Cancer Immunology...