The constructed MC38 cell line stably expressing mouse CEA (Fig. S2A-B) was used in the animal experiments as outlined in Fig. 3A. Significantly stronger and rapid inhibition of tumor progression was observed in BsAb-treated CRC mice compared with that in PD-1 scFv-, TREM2 scFv-, and PBS-treated CRC mice, as indicated by fluorescence intensity measurements (Fig. 3B-C). Here, CEACAM5 is linked to colorectal carcinoma.