The trial uses a PD-1 blocker called dostarlimab.

The trial uses a PD-1 blocker called dostarlimab. It's narrowly tailored for locally advanced mismatch repair deficient (dMMR), microsatellite instability-high (MSI-H) colorectal cancer. PD-1 blockers have good results in other types of cancers but not the 100% remission seen in this one. It was so narrowly tailored because CRC expresses a very high level of PD-1/PD-L1. Specifically for dMMR/MSI-H because that type has a high level of genetic mutations. Which means that many of the reproducing tumor cells will be less viable and are easier to kill. Knock down the tumor protectant PD-1 and the immune system has an easier time killing off the tumor. This trial was also done before the tumor went metastatic.

Cytodyn went with mssCRC because that's a much higher market then the 5% - 10% of dMMR/MSI-H CRC. Of course also because dostarlimab already has this one covered. PD-1 blockers in mssCRC have not been highly effective.