Definition

An agonistic human immunoglobulin G1 (IgG1) monoclonal antibody that recognizes the co-stimulatory receptor OX40 (CD134; tumor necrosis factor receptor superfamily member 4; TNFRSF4), with potential immunomodulatory and antineoplastic activities. Upon administration, anti-OX40 agonist monoclonal antibody HFB301001 selectively targets and binds to a unique epitope on OX40, and activates OX40 without competing with the endogenous OX40 ligand (OX40L; tumor necrosis factor ligand superfamily member 4; TNFSF4). This may induce the proliferation of memory and effector T lymphocytes and inhibit the function of T-regulatory cells (Tregs) in the tumor microenvironment (TME), thereby enhancing anti-tumor immune responses and preventing Tregs-mediated immune suppression. OX40, a cell surface glycoprotein and member of the tumor necrosis factor receptor superfamily (TNFRSF), is expressed on T lymphocytes and plays an essential role in T-cell activation and differentiation. HFB301001 does not lead to a downregulation of OX40 following the co-stimulation of T cells.