Invenra Inc., a biotechnology company specializing in the discovery and development of multispecific antibodies,  announced that its collaboration partner, Exelixis, Inc. (NASDAQ: EXEL), has initiated the dose-escalation stage of the first-in-human Phase 1 clinical study of XB628 in participants with recurrent advanced or metastatic solid tumors.

XB628 is a first-in-class bispecific antibody natural killer (NK) cell engager that targets NK group 2 member A (NKG2A), an inhibitory receptor on NK cells, and programmed cell death-ligand 1 (PD-L1). The molecule was discovered in part through a collaboration between Exelixis and Invenra.