• ORR: 16% (95% CI, 5–36) in MSS CRC without prior anti–PD-1/PD-L1 Ab.• The median duration of response was 8.6 months (95% CI, 2.9-NR) in 4 MSS CRC.• mPFS: 3.2 months (95% CI, 2.8-4.4) in MSS CRC without prior anti–PD-1/PD-L1 Ab. The PFS rate at 4 months or 6 months was 36.0% or 24.0% in MSS CRC without prior anti–PD-1/PD-L1 Ab.• mOS: 13.5 months (95% CI, 8.2–15.1) in MSS CRC without prior anti–PD-1/PD-L1 Ab. The gene discussed is CD274; the disease is colorectal carcinoma.