PDCD1 and breast cancer: Furthermore, concurrent PD-1 blockade and OX40 agonist in breast cancer murine models dampened the efficacy of OX40 agonist, with significantly reduced CD4+ and CD8+ lymphocyte infiltration, whilst applying OX40 agonist followed by PD-1 blockade enhanced efficacy, regressing breast tumors in 30% of cases (93).