Definition

A radioimmunoconjugate consisting of fianlimab, a human monoclonal antibody directed against the inhibitory receptor lymphocyte activation gene-3 protein (LAG-3; LAG3; CD223), linked, via the chelator desferrioxamine (DFO), to the positron-emitting radionuclide zirconium Zr 89 (Zr89), with potential use as an imaging agent upon positron emission tomography (PET) imaging. Upon administration of zirconium Zr 89-DFO- fianlimab, the fianlimab moiety specifically targets and binds to LAG-3. Upon binding, the radioisotope moiety may be detected using PET, thereby allowing the imaging and quantification of LAG-3-expressing tumor infiltrating lymphocytes (TILs). LAG-3, a member of the immunoglobulin superfamily (IgSF), is expressed on various immune cells; its expression on TILs is associated with tumor-mediated immune suppression and the negative regulation of both cellular proliferation and T-cell activation.