Novel nanoparticle-based enzyme replacement therapy for Hunter Syndrome

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ABSTRACT Significance: With overall prevalence of ~1:5-7000 live births, lysosomal storage diseases (LSD) as a class are one of the most common childhood diseases. LSD are caused by lysosomal dysfunction, mainly due to lysosomal enzyme mutations, and are usually fatal in the first two decades of life. CNS pathology is present in ~75% of LSD, however, currently marketed enzyme replacement therapy (ERT), is not effective for LSD with significant CNS pathology because negligible enzyme levels are achieved in brain at therapeutic serum concentrations of enzyme. Inefficient enzyme uptake in somatic tissues, neutralizing antibody development, poor cost-effectiveness, and weekly IV infusions are other suboptimal attributes. Hunter Syndrome, caused by X-linked iduronate-2-sulfatase (I2S) mutations in 1:100,000 male births, is associated with severe neuropathology and broad somatic tissue pathology. Elaprase®, human recombinant I2S, does not address CNS pathology yet is offered to all patients and has sales approaching $600M yearly. Intrathecal I2S is currently in development. Innovation: NeuroNano Pharma proposes to develop an innovative polymer- based nanoparticle formulation of I2S which will be delivered subcutaneously to achieve therapeutic brain levels of I2S. This product will have a transformative impact on Hunter Syndrome patients and, by extension, holds promise for application of the technology to other LSD caused by enzyme mutations. Approach: Preliminary data from Dr. Alexander Kabanov’s laboratory with PICs containing enzymes shows that brain delivery, protection from antibody response, and negligible toxicity can be achieved with these formulations. After expression and purification at the UNC Center for Structural Biology, I2S will be incorporated into nanoscale core-shell polyion complexes (PICs) which form spontaneously in aqueous conditions via electrostatic interactions upon mixing of the anionic enzyme with a copolymer consisting of a cationic block and a hydrophilic nonionic block. Dr. Kabanov and Dr. Judy Riffle, experts in this field, will serve as consultants. I2S PIC formulations will be characterized with respect to physicochemical properties, enzyme activity, cytotoxicity, lysosome localization and brain levels. Two formulations will be selected for full pharmacokinetic characterization by Dr. William Banks (VA Puget Sound Health Care System), a blood brain barrier expert. In addition to its own laboratory facilities, NNP has access to all necessary equipment through the UNC Nanomedicines Characterization Core Facility. Expected Results: An optimized I2S PIC will be identified that will achieve at least a five-fold increase of I2S in brain parenchyma and lysosomes compared to free I2S and at least 50% serum bioavailability after SC injection. Extended serum t1/2 and broad somatic tissue uptake compared to free I2S is also desirable. In phase II, the I2S PIC will be tested in I2S knockout mice to demonstrate enhanced enzyme activity in the brain, efficacy against neuropathology, and protection from immune response. An optimized I2S PIC will be scaled up and tested in pre-IND GLP toxicology.