Clinical Summary: 

• Design/Population: Investigators performed genome-wide and targeted CRISPR screens in primary human CD8-positive T cells to identify T cell–intrinsic regulators of response to the CD19×CD3 bispecific antibody blinatumomab. Findings were validated across hematologic and solid tumor models using multiple CD3-engaging T-cell engagers.
• Key Outcomes: CD5 was identified as a negative regulator of T-cell engager activity. Genetic deletion or antibody-mediated blockade of CD5 enhanced T-cell activation, cytokine production, proliferation, and antitumor efficacy across multiple CD3-engaging platforms.
• Clinical Relevance: These findings identify CD5 as a potential therapeutic target to improve responses to T-cell engagers across a broad range of malignancies.

Results from a translational study identified CD5 as a key negative regulator of T-cell engager activity and suggest that CD5 inhibition may enhance responses to multiple CD3-engaging therapies.

These results were presented by Weilin Wang, MD, PhD, Children’s Hospital of Soochow University, Suzhou, China, at the 2026 European Hematology Association (EHA) Congress in Stockholm, Sweden.

In this study, investigators performed genome-wide and targeted CRISPR knockout screens in primary human CD8-positive T-cells cocultured with B-cell acute lymphoblastic leukemia (B-ALL) cells in the presence of blinatumomab. Candidate genes were subsequently validated using genetic deletion and antibody-mediated blockade. Functional and mechanistic studies included cytotoxicity assays, cytokine profiling, transcriptomic and proteomic analyses, phospho-flow cytometry, single-cell RNA sequencing, and in vivo leukemia and multiple myeloma models.

The CRISPR screen identified CD5 as a negative regulator of blinatumomab-induced T-cell activation. Genetic deletion or antibody-mediated blockade of CD5 significantly enhanced blinatumomab-mediated cytotoxicity against B-ALL cell lines and primary leukemic blasts in vitro and improved leukemia control and survival in vivo. CD5 inhibition increased expression of activation markers including CD25 and CD69, enhanced production of interferon-γ and tumor necrosis factor-α, and promoted T-cell proliferation in a blinatumomab-dependent manner.

Transcriptomic and proteomic analyses demonstrated enrichment of effector programs, including IL2-STAT5, TNFα-NF-κB, and mTORC1 signaling pathways, accompanied by increased ERK and S6 phosphorylation. Single-cell RNA sequencing further revealed preferential expansion of CD5-low CD8-positive T-cells with increased expression of effector molecules following blinatumomab exposure.

In analyses of patient datasets, higher CD5 expression was associated with inferior responses to blinatumomab.

Mechanistic studies demonstrated that antibody engagement induced CD5 internalization followed by RAB7A-dependent lysosomal degradation. Additional analyses identified interactions between CD5 and several proximal T-cell receptor signaling proteins, including LCK, ZAP70, CBLB, and UBASH3A, supporting a model in which CD5 functions as an inhibitory signaling complex that suppresses ERK-mediated activation. CD5 inhibition enhanced the activity of multiple CD3-engaging T-cell engagers targeting CD20, BCMA, GPRC5D, DLL3, and GD2 across both hematologic and solid tumor models.

“These findings establish CD5 as a central, druggable target to optimal [T-cell engager] efficacy,” concluded Dr Wang. 

Source: 

Wang W, Zhao H, Yang X, et al. CD5 inhibition as a generalizable strategy to amplify T cell-mediated anti-tumor effects of bispecific T-cell engagers. Presented at EHA Congress. June 11 - June 14, 2026. Stockholm, Sweden. Abstract EHA-4564.