Optimizing NGF for Topical Treatment of Glaucoma

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ABSTRACT Glaucoma is a leading cause of irreversible vision loss, which is characterized by progressive degeneration of retinal ganglion cells (RGC) and their optic nerve axons. While age is a key risk factor, elevated intraocular pressure (IOP) is the only modifiable risk factor, with topical IOP-lowering drugs as the first line treatment. However, RGC degeneration and vision loss continues in half the patients taking these medications. By the time when characteristic visual field defects are detected, 30-50% of the RGCs have already been lost. Thus, there is an urgent need to develop novel therapies, independent of IOP reduction, which protect RGCs from degeneration and boost the function of RGCs challenged in the disease. The binding of nerve growth factor (NGF) to TrkA attenuates reactive astrocytosis and promotes RGC survival and proliferation. In contrast, the binding to p75NTR leads to astrocytosis and RGC apoptosis. Serum levels of NGF are reduced in early and moderate glaucoma patients compared to healthy controls. Wildtype human NGF (OxervateTM, Cenegermim, Dompe) was approved by FDA in 2018 as eye drops to treat neurotrophic keratitis. In a recent Phase 1b clinical trial, it has been shown that topical use of Cenegermim was safe and tolerable in open-angle glaucoma patients. However, wildtype NGF treatment failed to provide neuroprotection in preclinical models of established glaucoma, antagonized by up-regulated p75NTR activity. Moreover, inefficient manufacturing of Cenegermim using an E coli expression system compromises protein stability and quality at a prohibitive cost for chronic treatment. In the Phase 1 study, we successfully reached all the milestones by designing and validating a human NGF mutein, HC201. The mutein preserves protein stability and expression with enhanced TrkA receptor activities but abrogated p75NTR binding and signaling. In rat models of glaucoma induced by episcleral vein cauterization, topical treatment with HC201 robustly protected RGCs. In contrast, wildtype NGF was not effective. HC201 efficacy was also observed in diabetic corneal ulcer and dry eye disease models. Meanwhile, we have developed a highly cost-effective and scalable process to produce HC201 in mammalian cells. In the Phase II SBIR application, we will continue to validate the efficacy and elucidate mechanism of action in the inducible microbead occlusion model of glaucoma in rats and squirrel monkeys. The use of different approaches to elevate IOP in two species will significantly improve the success for translation to human clinical trials. With a highly experienced drug development team, we also will initiate critical activities necessary to enable IND filing. Specific Aims include: 1) Determine whether topical treatment with HC201 preserves retinal integrity and function compared to the placebo control using the microbead occlusion model of glaucoma in rats and squirrel monkeys; 2) Manufacture cGMP grade HC201 from 100L engineering run; 3) Evaluate nonclinical safety of repeat dose HC201. The long-term goal is to develop HC201, alone or in combination with current hypotensive medication, to preserve and even restore vision in glaucoma patients.