In summary, the current study demonstrates three important findings which warrant further investigation: (1) there is a functional effect of PD-1 blockade in ovarian cancer-derived TILs, (2) our ex vivo stimulation of patient-derived T-cells can be a valuable way to explore the use of PD-1-blocking agents in solid tumors, and importantly, (3) alternative molecular scaffolds with PD-1 antagonizing activity such as DARPin® proteins have the potential to compete with conventional monoclonal antibodies and should be further explored. The gene discussed is PDCD1; the disease is ovarian cancer.