This is one of my favorite trials... PVSRIPO + Keytruda makes a lot of sense. The PVSRIPO is injected into the tumor and kills tumor cells. The Keytruda ramps up the immune system so that it learns from these destroyed tumor cells and seeks out and kills tumor cells anywhere else in the brain (and maybe the entire body). PVSRIPO by itself is a good treatment. For recurrent Glioblastoma, they reported a 3 year survival rate of 21% compared to historical controls of about 4%. Hopefully adding Keytruda will increase that significantly. Keytruda by itself did not really work out well with Glioblastoma, because it only revs up the immune system and there needs to be something there for the immune system to see. The PVSRIPO kills the cells, making them into a better target for the immune system.
Disclaimer: I am on the patient advisory board of the Brain Tumor Center at Duke.