CD2 costimulation bridges potent CAR-induced cytolysis and durable persistence.

BACKGROUND

Current second-generation CAR T cell products rely on CD28 or 4-1BB costimulatory domains, additions that respectively favor rapid cytolysis or long-term persistence, but rarely both. Preclinical modeling and retrospective analysis have linked CD2-CD58 engagement to superior preclinical and clinical responses, yet the direct contribution of CD2 intracellular signaling remains undefined.

METHODS

We replaced the costimulatory domain of anti-mesothelin (SS1) and anti-TnMUC1 (5E5) CARs with the human CD2 cytoplasmic tail (CD2z) and benchmarked them against 28z and BBz formats. Transient mRNA expression was used to profile proximal Ca2+ flux and degranulation free of tonic viral signals; durable functional assays employed lentiviral CARs. Cytokine release, genome-wide transcriptional programs, and anti-tumor activity were assessed in vitro and in NSG xenograft models.

RESULTS

CD2z CAR T cells degranulated as efficiently as other z-containing CARs and generated a Ca2+ flux signal intermediate to 28z and BBz CARs. Lentiviral CD2z CARs released a Th1-skewed cytokine panel and matched 28z cytolysis despite a lower acute cytokine release. Transcriptomic analysis characterized CD2z cells in an early effector-memory state: glycolytic, mTORC1, and TNFa-NF-κB hallmarks were upregulated, whereas exhaustion-up signatures were selectively depleted vs 28z. In vivo, a single CD2z infusion induced deep and durable tumor regressions over the 60-day observation period in subcutaneous mesothelin-positive mesothelioma and orthotopic TnMUC1-positive pancreatic tumor models, achieving tumor control comparable to 28z and more rapid early tumor clearance than BBz, while supporting peripheral T cell persistence similar to BBz.

CONCLUSIONS

The CD2 cytoplasmic tail, in combination with CD3z, delivers balanced costimulation that couples brisk tumor debulking to T cell persistence. CD2z therefore may provide a simple, versatile alternative to canonical CD28 and 4-1BB modules for next-generation CAR T therapies.