A trispecific antibody induces potent tumor-directed T-cell activation and antitumor activity by CD3/CD28 co-engagement.

A novel CD19xCD3xCD28 trispecific antibody with a tandem single-chain variable fragments (scFv) structure was developed for the treatment of B-cell malignancies. The trispecific antibody in inducing tumor-directed T-cell activation and cytotoxicity was evaluated and and compared with its bispecific counterpart BiTE-CD19xCD3 lacking a CD28-targeting domain. The trispecific antibody with a co-stimulatory domain exhibited augmented T-cell activation and memory T-cell differentiation capability and it induced faster tumor cell lysis than the bispecific antibody. RNAseq analysis revealed that the trispecific antibody modulates CD3/TCR complex-derived signal and upregulates antiapoptotic factors to influence the survival of T cells. By CD3/CD28 co-engagement, the trispecific antibody demonstrated its advantages in T-cell immunity and potential use as a more powerful and long-lasting T-cell engager.