PDCD1 and glioblastoma: In a preclinical setting of a more “cold”, non-immunogenic tumor, such as GBM, G47Δ showed the best efficacy when in “triple combination”, i.e., administered simultaneously with both anti-PD-1 and anti-CTLA-4 antibodies, with up to 89% long-term survivors, the establishment of immunological memory, and the lack of recurrence of the tumor [100,178,179].