Used in immunology research and therapeutic development, particularly in modulating T-cell activation. Acts as a selective CD28 antagonist, blocking the costimulatory signal required for full T-cell activation without depleting T-cells. This property makes it valuable in studying immune tolerance and treating autoimmune diseases or preventing transplant rejection. Investigated in preclinical and clinical settings for its potential to suppress pathological immune responses while maintaining immune surveillance. Also serves as a reference standard in bioassays evaluating CD28 pathway inhibitors.