PROJECT SUMMARY This is a 5-year mentored K08 award to facilitate the transition of Dr. Neel Pasricha, an ophthalmologist with cornea subspecialty training, to an independent investigator in ocular surface eye translational research. A strong group of experienced mentors at UCSF, scientific advisors, and didactic work will assist Dr. Pasricha’s research skills transfer, including training in ocular surface electrophysiology, human corneal epithelial cell culture models, high-throughput screening for small-molecule drug discovery, experimental mouse models, and human subject clinical studies. The research is focused on dry eye disease (DED), a major unmet need in ophthalmology characterized by impaired tear film homeostasis accompanied by ocular symptoms. There are currently just four FDA-approved therapies for DED, each targeting only the inflammatory pathway and having limited efficacy. The ocular surface, comprised of the cornea and conjunctiva, is lined by stratified epithelial cells expressing ion transport proteins that facilitate active fluid secretion or absorption to regulate tear fluid volume and osmolarity. The goal of the proposed research is to discover and advance drug candidates to promote tear fluid secretion by epithelial cells lining the ocular surface. This research utilizes a novel ocular surface potential difference (OSPD) method introduced in animal studies and advanced for use in humans during my residency at UCSF. OSPD measures the electrical potential difference generated across epithelia from apical and basal membrane ion transporters. In Aim 1, in vivo OSPD measurements in mice will investigate the role of ion transporters in ocular surface fluid transport, with particular focus on chloride and potassium channels. Aim 2 will use ex vivo high-throughput screening in primary human corneal epithelial cell cultures and in vivo experimental mouse studies to advance potential drug candidates that target calcium-activated chloride channels to increase tear fluid secretion for treatment of DED. Aim 3 will use in vivo human OSPD measurements in healthy adults to test a pro-secretory drug candidate in phase 2 clinical trial that activates the CFTR chloride channel. The long-term career development goal is to build a robust cross-disciplinary research program that advances the fundamental understanding of ocular surface ion transport and translates that knowledge into novel diagnostic and therapeutic strategies for ocular surface diseases, including DED.