PT  - JOURNAL ARTICLE
AU  - Ruben J Boado
AU  - Eric Ka-Wai Hui
AU  - Jeff Zhiqiang Lu
AU  - William M. Pardridge
TI  - Drug Targeting of Erythropoietin Across the Primate Blood-Brain Barrier with an IgG Molecular Trojan Horse
AID  - 10.1124/jpet.109.165092
DP  - 2010 Jan 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - jpet.109.165092
4099  - http://jpet.aspetjournals.org/content/early/2010/03/16/jpet.109.165092.short
4100  - http://jpet.aspetjournals.org/content/early/2010/03/16/jpet.109.165092.full
AB  - 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). 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 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, ED50 = 0.21 ± 0.05 nM, and the EPO receptor, ED50 = 0.30 ± 0.01 nM, and activated thymidine incorporation into human TF-1 cells with an ED50 of 0.1 nM. Differentially radiolabeled EPO and the HIRMAb-EPO fusion protein were injected intravenously in the adult Rhesus monkey. 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 bi-functional 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.The American Society for Pharmacology and Experimental Therapeutics