BiTEs targeting T cell co-stimulatory molecules such as CD3, CD28, and 4-1BB are the most prevalent T cell engagers, with these antibodies exhibiting notable promotion of T cell proliferation and activation, and several have been approved for the clinical treatment of hematological diseases.468–470 DuoBody-CD40×4-1BB exhibits conditional CD40 and 4-1BB agonist activity, which is strictly dependent on the cross-linking of the two targets. Here, TNFRSF9 is linked to hematologic disorder.