Here's an interesting trial that I actually missed until recently.
"A Study of the Safety, Pharmacokinetics, and Therapeutic Activity of RO6958688 in Combination With Atezolizumab in Participants With Locally Advanced and/or Metastatic Carcinoembryonic Antigen (CEA)-Positive Solid Tumors"
https://clinicaltrials.gov/ct2/show/NCT02650713
It is something called a "CEA-CD3 bifunctional" in combination with a PDL1 inhibitor. The CEA it targets is a "membrane-bound" version, not the CEA that is floating around in your blood that everyone here knows is tested with a standard blood test.
The protein binds to CEA on tumor cells and physically pulls CD3 immune cells along with it - that is why it is an experimental strategy for "cold" tumors like MSS-CRC.
There is a safety window concern since CEA is produced by some normal cells - but hopefully they can find a dose that gets around that potential problem.
Cheers,
-DK