PROJECT SUMMARY Cystic fibrosis (CF) is a genetic disease caused by mutations in the cystic fibrosis transmembrane regulator (CFTR) gene. CF airways are immunocompromised and become colonized with bacteria soon after birth. Chronic bacterial infection leads to persistent and severe neutrophil-dominated pulmonary inflammation, high lung protease levels, lung damage and a decline in FEV1. CFTR modulator/correctors from Vertex such as TRIKAFTA significantly increase CF patient lung function by >10% but do not bring it into the normal range and for patients with pre-existing bacterial lung infections, do not clear bacteria from their lungs. Moreover, these compounds do not treat CF patients with nonsense mutations where no CFTR protein is produced. Orai1 is a ubiquitously expressed plasma membrane Ca2+ channel that is upstream and regulates neutrophilic inflammation. Our preliminary data indicate (i) that Orai1 levels remain elevated in CF patient neutrophils regardless of Trikafta treatment and (ii) that Orai1 levels inversely correlate with CF patient FEV1. Thus, there is a critical unmet need for novel, CFTR mutation-agnostic therapies to reduce neutrophilic inflammation and prevent further CF lung damage. Given Orai1’s proximal role in the immune response, Orai1 is thus an attractive target whose inhibition is predicted to help resolve CF inflammation. We have developed a robust, novel peptidomimetic called ELD607, which potently inhibits Orai1, and is stable in proteolytically-rich CF sputum. In murine lung infection models with common CF pathogens including P. aeruginosa and S. aureus, a single, inhaled dose of ELD607 reduced lung inflammation by 90% and increased survival by ~50%. In a chronic CF model (SCNN1B mice), ELD607 reduced neutrophilia and increased survival. These experiments demonstrate that rebalancing the lung’s inflammatory response by inhibiting Orai1 may be beneficial for the treatment of CF. However, ELD607 is limited by solubility. In this Catalyst application, for Phase 1, we will optimize ELD607 structure and/or formulation to increase its solubility. For Phase 2, we will determine the maximum tolerated dose and pharmacokinetics of the fully optimized ELD607, determine ELD607’s specificity for Orai1 vs other Ca2+ channels and test the hypothesis that ELD607 is an allosteric Orai1 modulator that causes Orai1 degradation, rather than acting as a traditional channel pore blocker. We anticipate that these data will help differentiate ELD607 from existing pore-blocking Ca2+ channel antagonists and help make it ready for advancement into clinical trials.

Public Health Narrative Due to a genetically induced imbalance in salt and water transport in cystic fibrosis (CF) lungs, mucus is dehydrated and the lungs fail to eradicate bacteria, leaving the airways prone to chronic infection and inflammation that ultimately destroy the lung. In this application, we propose to develop peptide-based therapies that can shift the lung’s immune balance to efficiently clear bacteria from the lung.