Drug targeting of erythropoietin across the primate blood-brain barrier with an IgG molecular Trojan horse.
Erythropoietin (EPO) is a neurotrophic factor that could be developed as a new drug for brain disorders. However, EPO does not cross the blood-brain barrier (BBB). In the present study, human EPO was re-engineered by fusion to the carboxyl terminus of the heavy chain of a chimeric monoclonal antibody (MAb) to the human insulin receptor (HIR). The HIRMAb acts as a molecular Trojan horse to ferry the EPO into the brain via receptor-mediated transport on the endogenous BBB insulin receptor. The HIRMAb-EPO fusion protein was immunoreactive with antibodies to both human IgG and EPO. The HIRMAb-EPO fusion protein bound with high affinity to the extracellular domain of both the HIR (ED(50) = 0.21 +/- 0.05 nM) and the EPO receptor (ED(50) = 0.30 +/- 0.01 nM) and activated thymidine incorporation into human TF-1 cells with an ED(50) of 0.1 nM. Differentially radiolabeled EPO and the HIRMAb-EPO fusion protein were injected intravenously into adult rhesus monkeys. Whereas EPO did not cross the primate BBB, the HIRMAb-EPO fusion protein was rapidly transported into brain, at levels that produce pharmacologic elevations in brain EPO at small systemic doses. The HIRMAb fusion protein selectively targeted the brain relative to peripheral organs. In conclusion, a novel IgG-EPO fusion protein has been engineered, expressed, and shown to be bifunctional with retention of high-affinity binding to both the insulin and EPO receptors. The IgG-EPO fusion protein represents a new class of EPO neurotherapeutics that has been specifically re-engineered to penetrate the human BBB.
ArmaGen Technologies, Inc., Santa Monica, California, USA.
Ruben J
RJ
Boado
Eric Ka-Wai
EK
Hui
Jeff Zhiqiang
JZ
Lu
William M
WM
Pardridge
D000818:Animals; D019677:Artificial Gene Fusion; D001692:Biological Transport / Q000187:drug effects; D001812:Blood-Brain Barrier / Q000187:drug effects*; D001921:Brain / Q000187:drug effects; D016466:CHO Cells; D019556:COS Cells; D002460:Cell Line; D002522:Chlorocebus aethiops; D002850:Chromatography, Gel; D006224:Cricetinae; D003412:Cricetulus; D016503:Drug Delivery Systems; D004591:Electrophoresis, Polyacrylamide Gel; D004921:Erythropoietin / Q000008:administration & dosage* / Q000235:genetics; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000235:genetics / Q000494:pharmacology*; D008253:Macaca mulatta; D015202:Protein Engineering; D011869:Radioligand Assay; D017467:Receptors, Erythropoietin / Q000187:drug effects; D011994:Recombinant Proteins; D013205:Staphylococcal Protein A / Q000378:metabolism
D007074:Immunoglobulin G; D017467:Receptors, Erythropoietin; D011994:Recombinant Proteins; D013205:Staphylococcal Protein A; D004921:Erythropoietin