Privately held AgonOx LLC, which could afford to be picky with its hot T-cell technology, selected MedImmune LLC, a unit of AstraZeneca plc, over more than two dozen other potential suitors for an exclusive global agreement to develop agonists and other immune system activators for cancer therapy using AgonOx's OX40 platform.OX40 is a protein transiently expressed on the surface of effector T-cells, but only after activating the T-cells with immune-stimulating antigens, including tumor antigens.