KEYSTEP-008: pembro-based combinations for MSI-H/dMMR mCRC

In the first-line setting (Cohort B) of KEYSTEP-008, pembrolizumab was tested alone and in combination with multiple immune checkpoint inhibitors including quavonlimab (anti-CTLA-4), favezelimab (anti-LAG-3), vibostolimab (anti-TIGIT), and MK-7684 (ILT4 inhibitor). What was the key finding?

Pembrolizumab + quavonlimab demonstrated superior PFS compared to pembrolizumab monotherapy, establishing a new standard of care
None of the pembrolizumab-based combinations showed additional benefit over pembrolizumab monotherapy in terms of ORR, PFS, or OS
The anti-LAG-3 combination (favezelimab) achieved significantly higher response rates than other combinations, warranting phase III investigation