Drug Targeting of Erythropoietin Across the Primate Blood-Brain Barrier with an IgG Molecular Trojan Horse

Abstract

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 ϭ 0.21 Ϯ 0.05 nM) and the EPO receptor (ED 50 ϭ 0.30 Ϯ 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.

Delivery of Neurotherapeutics Across the Blood Brain Barrier in Stroke

“…This TAT-Bcl-xL greatly reduced infarct size and improved neurological performance after 90-min of MCAO [98]. TAT-Bcl-xL also exerted neuroprotec- HIRMAb-EPO fusion protein is rapidly transported into brain [80] HIRMAb-EPO fusion protein icv rat permanent MCAO Reduces infarct volume and reduces neurological deficits [81] HIRMAb-GDNF (Glial-derived neurotrophic factor bind to HIRMAb) icv rat permanent MCAO…”

“…Exemplary HIRMAb fusion proteins used for the uptake of various drugs into the brain are listed in (Table 3). Among these fusion proteins, HIRMAb-EPO and HIRMAb-GDNF have been shown to cross the BBB after intravenous injection in rhesus monkeys [80] and both protect against cerebral ischemia following intracerebral administration in rat model of stroke [81,82].…”

“…Produces therapeutic concentrations of IDS in the brain [151] HIRMAb-TNFR fusion protein (type II TNF receptor conjugated to HIRMAb ) iv rhesus monkeys Fusion protein selectively targets brain more than peripheral organs; 3% of the injected dose is taken up by the primate brain [80] HIRMAb-ScFv (a single chain Fv antibody against the Abeta peptide conjugated to HIRMAb) iv rhesus monkeys…”

Hypoxic-Ischaemic Encephalopathy and the Blood-Brain Barrier in Neonates

“…The utility of MTH has enabled large molecules such as TNFα inhibitors [86] and erythropoietin [87] to be delivered across the BBB. We use these examples as agents being investigated for the treatment of HIE [88] .…”

Neuroprotection in Glaucoma

“…Since Epo does not cross the bloodbrain barrier (BBB) there is a tendency to recombine its structure that way that it will became permeable to BBB. Boado et al (2010) developed new drug (HIRMAb(IgG)-EPO fusion protein) enabling Epo to cross the BBB.…”