This was a phase Ib study of PDR001 in combination with regorafenib in adult patients with previously treated metastatic microsatellite stable (MSS) colorectal cancer. The study assessed primarily the safety and tolerability of PDR001 in combination with regorafenib.

Key inclusion criteria:

1. Patients with metastatic colorectal adenocarcinoma.
2. Patients must provide a newly obtained or an archival tumor sample corresponding to CRC diagnosis (primary tumor) with sufficient tissue quality (qualified) for analysis
3. Patients must provide a newly obtained tumor tissue sample from a metastatic site
4. Patients with the presence of at least one lesion with measurable disease as per RECIST
5. Patients previously treated with two prior regimen as per standard of care and have experienced disease progression (including -VEGF and EGFR targeted therapies (if KRAS wild).
6. Patient has an Eastern Cooperative Oncology Group (ECOG) performance status 0-1

Key exclusion criteria:

1. Patients with MSI-H colorectal adenocarcinoma as defined per local assessment using standard of care testing
2. Patients with metastatic disease amenable to be resected with potentially curative surgery
3. Patients who have had chemotherapy, radiation, or biological cancer therapy within 14 days prior to the first dose of study treatment
4. Patients with a history of prior treatment with anti-PD-1, anti-PD-L1, anti-PDL2, anti- CTLA-4 antibodies, other checkpoint inhibitors