Systematic molecular engineering, biomarker-driven patient selection, and rational tumour microenvironment modulation are now collectively transforming TCEs from experimental agents into an adaptable platform therapy for solid tumours.<h4>Methods</h4>Review of 55 phase I-III trials of CD3-based TCEs in solid tumours, including tarlatamab (DLL3-targeted, small-cell lung cancer) and xaluritamig (STEAP1-targeted, prostate cancer). Here, DLL3 is linked to prostate cancer.