Topical treatment of an optimized NGF for Dry Eye

Project Summary Dry eye disease (DED) is an increasingly frequency cause of visual dysfunction. It is characterized by loss of homoeostasis of the ocular surface, resulting in tear film instability, hyperosmolarity, and inflammation of the conjunctiva and cornea. Up to 30% of the population over age 50 suffers from DED in the US. The dense corneal nerve plexus is critical to maintaining homeostatic function of the ocular surface. Current treatments such as tear substitutes, immunosuppressive drugs, and steroids address inflammation and tear film instability, but do not address degradation of the corneal nerve bed, which is a key pathophysiological driver of DED. Therefore, improving nerve health will significantly improve vision function and quality of life. Increasing experimental and clinical evidence has shown that NGF is an essential factor for the trophism, sensitivity, and healing of the cornea and the conjunctiva. Wildtype NGF (NGF wt, OxervateTM, Cenegermim) was approved by the FDA in 2018 as eye drops to treat neurotrophic keratitis, an ocular disease characterized by impairment of corneal sensitivity, healing, and tear production. Topical use of Cenegermim was well tolerated and improved symptoms and tear production in patients with moderate to severe DED. It is known that NGF binding to TrkA receptors attenuates reactive astrocytosis and promotes neuron survival and proliferation. In contrast, NGF binding to p75NTR receptors leads to inflammation and neuron apoptosis. p75NTR activity is up- regulated under pathological conditions, potentially limiting the efficacy of NGF wt treatment for DED. Moreover, inefficient manufacturing of Cenegermim using an E coli expression system compromises protein stability and quality at a prohibitive cost for chronic treatment. We have designed and are developing for human use HC201, a human NGF mutein which improves TrkA binding and signaling while substantially abrogating p75NTR binding and signaling. In a rat model of glaucoma, topical treatment with HC201 robustly protected retinal ganglion cells (RGC), while wildtype NGF was not effective. Importantly, HC201 was also effective in a model of DED induced with scopolamine. Meanwhile, we have developed a highly cost-effective and scalable process to produce recombinant NGF in mammalian cells by optimizing the cleavage site to facilitate furin-mediated post-proteolytic modifications of pro-NGF into mature NGF. In this Phase I SBIR application, we will determine the efficacy and mechanism of action in a translational model of corneal nerve bed injury in mice. The specific aim is to determine whether topical treatment with HC201 more effectively improves tear film production and corneal sensitivity compared to wildtype NGF. The long-term goal is to develop HC201, alone or in combination with current tear substitutes or immunosuppressive drugs, to preserve and restore corneal homeostasis and sensitivity in patients with moderate to severe DED.