We have shown that TCEs robustly activate CD4 and CD8-positive T cells in co-culture models with CRC cell lines and patient tumour-derived cell lines that express CEA (Figures 1C–F), but in vivo efficacy is hindered by lack of TCE retention in the tumour and short TCE half-life (Supplementary Figure 3D), as demonstrated by HiBiT bioluminescent TCE-tagging technology (Supplementary Figures 3A–C). Here, CEACAM5 is linked to colorectal carcinoma.