PDCD1 and cancer: Notably, OVs armed with PD-1 blockers but not unarmed OVs could elicit effective antitumor activity in the late-stage tumor model (tumor volume >350 mm3), which suggests that only an appropriately armed OV can effectively modulate this more immunosuppressive TME, as supported by other recent studies.38 Here, we also demonstrated that intratumoral expression of hPD-1scFv by YST-OVH favored antitumor responses via not only inhibition of the PD-1/PD-L1 axis in the TME but also alteration of the cancer-immune set point.