Nanomolecular HLA-DR10 antibody mimics: A potent system for molecular targeted therapy and imaging.

To mimic the molecular specificity and cell selectivity of monoclonal antibody (mAb) binding while decreasing size, nanomolecules (selective high-affinity ligands; SHALs), based on in silico modeling, have been created to bind to human leukocyte antigen-DR (HLA-DR10), a signaling receptor protein upregulated on the malignant B-lymphocytes of non-Hodgkin's lymphoma and chronic lymphocytic leukemia. SHALs were synthesized with a biotin or DOTA chelate (1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid), using a solid-phase lysine-polyethyleneglycol backbone to link sets of ligands shown previously to bind to HLA-DR10. Using cell-binding and death assays and confocal microscopy, SHAL uptake, residualization, and cytocidal activity were evaluated in HLA-DR10 expressing and nonexpressing live, human lymphoma cell lines. All of the SHALs tested were selective for, and accumulated in, expressing cells. Reflecting binding to HLA-DR10 inside the cells, SHALs having the Ct ligand (3-(2-([3-chloro-5-trifluoromethyl)-2-pyridinyl]oxy)-anilino)-3-oxopropanionic acid) residualized in expressing cells greater than 179 times more than accountable by cell-surface membrane HLA-DR10. Confocal microscopy confirmed the intracellular residualization of these SHALs. Importantly, SHALs with a Ct ligand had direct cytocidal activity, similar in potency to that of Lym-1 mAb and rituximab, selectively for HLA-DR10 expressing lymphoma cells and xenografts. The results show that SHALs containing the Ct ligand residualize intracellularly and have cytocidal effects mediated by HLA-DR10. These SHALs have extraordinary potential as novel molecules for the selective targeting of lymphoma and leukemia for molecular therapy and imaging. Further, these SHALs can be used to transport and residualize cytotoxic agents near critical sites inside these malignant cells.