title: Heterobivalent ligands target cell-surface receptor combinations in vivo.
abstract: A challenge in tumor targeting is to deliver payloads to cancers while sparing normal tissues. A limited number of antibodies appear to meet this challenge as therapeutics themselves or as drug-antibody conjugates. However, antibodies suffer from their large size, which can lead to unfavorable pharmacokinetics for some therapeutic payloads, and that they are targeted against only a single epitope, which can reduce their selectivity and specificity. Here, we propose an alternative targeting approach based on patterns of cell surface proteins to rationally develop small, synthetic heteromultivalent ligands (htMVLs) that target multiple receptors simultaneously. To gain insight into the multivalent ligand strategy in vivo, we have generated synthetic htMVLs that contain melanocortin (MSH) and cholecystokinin (CCK) pharmacophores that are connected via a fluorescent labeled, rationally designed synthetic linker. These ligands were tested in an experimental animal model containing tumors that expressed only one (control) or both (target) MSH and CCK receptors. After systemic injection of the htMVL in tumor-bearing mice, label was highly retained in tumors that expressed both, compared with one, target receptors. Selectivity was quantified by using ex vivo measurement of Europium-labeled htMVL, which had up to 12-fold higher specificity for dual compared with single receptor expressing cells. This proof-of-principle study provides in vivo evidence that small, rationally designed bivalent htMVLs can be used to selectively target cells that express both, compared with single complimentary cell surface targets. These data open the possibility that specific combinations of targets on tumors can be identified and selectively targeted using htMVLs.
authors.affiliation: Department of Cancer Imaging and Metabolism, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL 33612, USA.
authors.forename: Liping
authors.initials: L
authors.lastname: Xu
authors.forename: Jatinder S
authors.initials: JS
authors.lastname: Josan
authors.forename: Josef
authors.initials: J
authors.lastname: Vagner
authors.forename: Michael R
authors.initials: MR
authors.lastname: Caplan
authors.forename: Victor J
authors.initials: VJ
authors.lastname: Hruby
authors.forename: Eugene A
authors.initials: EA
authors.lastname: Mash
authors.forename: Ronald M
authors.initials: RM
authors.lastname: Lynch
authors.forename: David L
authors.initials: DL
authors.lastname: Morse
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Gillies
mesh_terms: D000818:Animals; D002232:Carbocyanines / Q000378:metabolism; D002470:Cell Survival; D005063:Europium / Q000378:metabolism; D005453:Fluorescence; D045325:HCT116 Cells; D006801:Humans; D021621:Imaging, Three-Dimensional; D007700:Kinetics; D008024:Ligands; D051379:Mice; D056004:Molecular Dynamics Simulation; D009369:Neoplasms / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism*; D013194:Staining and Labeling
chemical_list: D002232:Carbocyanines; D008024:Ligands; D011956:Receptors, Cell Surface; C085321:cyanine dye 5; D005063:Europium