An agonistic humanized monoclonal antibody against the receptor, OX40 (CD134), with potential immunostimulatory and antineoplastic activities. Upon intravenous administration, vonlerolizumab selectively binds to and activates OX40, by mimicking the action of endogenous OX40 ligand (OX40L). OX40 activation induces proliferation of effector T-lymphocytes and inhibits the activity of regulatory T-cells. In the presence of tumor-associated antigens (TAAs), this may promote an immune response against the TAA-expressing tumor cells. OX40, a cell surface glycoprotein and member of the tumor necrosis factor (TNF) receptor superfamily, is expressed on T-lymphocytes and provides a co-stimulatory signal for the proliferation and survival of activated T-cells.