Definition

An agonistic tetravalent nanobody, in which the four single, high affinity heavy chain variable domain (VHH) antibodies are separated by a peptide linker, targeting death receptor type 5 (DR5), with potential antineoplastic activity. Upon administration, DR5-targeting tetrameric nanobody agonist TAS266, with its four DR5-specific single-chain antibodies, specifically binds to and activates DR5 receptors. This results in the activation of caspase cascades and induction of apoptosis in DR5-expressing tumor cells. DR5, a cell surface receptor and member of the tumor necrosis factor (TNF)-receptor superfamily, triggers apoptosis. Compared to certain anti-DR5 antibody agonists, TAS266 shows increased receptor activation.