Episode 60: A trophoblast glycoprotein specific 5 T4-Vδ2 bispecific T cell engager recruits Vγ9Vδ2-T cells for tumor-selective cytotoxicity across solid malignancies

**Paper:** [A trophoblast glycoprotein specific 5T4-Vδ2 bispecific T cell engager recruits Vγ9Vδ2-T cells for tumor-selective cytotoxicity across solid malignancies](https://doi.org/10.1016/j.clim.2026.110707) **Authors:** Milon de Jong, Rok Žiberna, Myrthe Veth, Elisabetta Michielon, et al. **Journal:** Clinical Immunology, 2026 **Why it matters:** Solid tumors have largely resisted bispecific T cell engager therapies due to on-target toxicity in healthy tissue, and this study presents a strategy using gamma-delta T cells that may sidestep that problem. **Summary** Bispecific T cell engagers (bsTCEs) are antibody-like molecules that physically link a tumor antigen to a T cell receptor, forcing immune cells into proximity with cancer cells. While highly effective in blood cancers, their use in solid tumors has been hampered by "on-target off-tumor" toxicity — damage to healthy tissues that express the same antigen being targeted. This study addresses that problem by focusing on two components: the tumor antigen 5T4 (trophoblast glycoprotein), an oncofetal protein broadly overexpressed across solid malignancies but largely absent from healthy adult tissue, and Vγ9Vδ2-T cells, a subset of gamma-delta T cells known for potent anti-tumor activity and an intrinsic capacity to discriminate between stressed tumor cells and normal tissue. The researchers developed high-affinity VHHs — single-domain antibody fragments derived from camelid antibodies — specific to 5T4, and linked them to a VHH targeting the Vδ2 T cell receptor to create the 5T4-Vδ2 bsTCE. They validated 5T4 expression across a broad panel of solid tumor types and then tested the engager in both conventional 2D cell cultures and more clinically representative 3D patient-derived tumor models. In these systems, the bsTCE triggered robust Vγ9Vδ2-T cell activation, proinflammatory cytokine production, and tumor cell lysis. Critically, when the construct was tested against healthy tissues that do express 5T4 at low levels, Vγ9Vδ2-T cell cytotoxicity was not observed — suggesting that the gamma-delta T cell arm of the engager contributes an intrinsic selectivity that conventional alpha-beta T cell engagers lack. One caveat is that these remain preclinical findings, and whether the tumor-preferential activity holds in the more complex immunosuppressive environment of human tumors in vivo will require clinical investigation. **Three takeaways** 1. The 5T4-Vδ2 bsTCE induced potent Vγ9Vδ2-T cell-mediated killing and cytokine production in both 2D and 3D patient-derived solid tumor models. 2. 5T4 protein was expressed across the majority of solid malignancies evaluated, supporting its utility as a broad-spectrum therapeutic target. 3. Despite low-level 5T4 expression on some healthy tissues, the bsTCE did not trigger Vγ9Vδ2-T cell cytotoxicity against those tissues, demonstrating tumor-preferential activity in preclinical testing. **Read the paper:** https://doi.org/10.1016/j.clim.2026.110707