XMT-2056 is a systemically-administered Immunosynthen STING agonist antibody drug conjugate (DAR 8) that is designed to target a novel HER2 epitope (distinct from pertuzumab and trastuzumab) and locally activate STING signaling in both tumor-resident immune cells and in tumor cells (a “one-two punch”), providing the potential to treat patients with HER2-high or -low tumors as monotherapy or in combination with standard-of-care HER2 agents.

The U.S. Food and Drug Administration (FDA) has granted orphan drug designation to XMT-2056 for the treatment of gastric cancer.