Novel Strategies to Clear Bacteria from the CF Lung

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. Thus, there
is a critical unmet need for novel, CFTR mutation-agnostic therapies to help clear bacteria from CF lungs and
limit neutrophilic lung damage. Short Palate LUng and Nasal epithelial Clone 1 (SPLUNC1) is a secreted protein
that is highly expressed in the lung, where it plays a key role in maintaining lung health. SPLUNC1 is a CF gene
modifier, and patients with reduced SPLUNC1 levels have lower FEV1 and exacerbate more frequently. Orai1 is
a ubiquitously expressed plasma membrane Ca2+ channel that regulates inflammation. We found that SPLUNC1
inhibits Orai1. However, SPLUNC1 is rapidly degraded by neutrophil elastase (NE), which we posit results in
greater Orai1 activity and more inflammation. Consistent with this, our preliminary data indicate that Orai1 is
upregulated in CF patient lung immune cells. Given Orai1’s proximal role in the immune response, Orai1 is thus
an attractive target whose inhibition is predicted to help resolve CF inflammation. Eldec Pharma has developed
a robust, novel peptidomimetic called ELD607, which reprises SPLUNC1’s ability to inhibit Orai1, yet is
significantly more stable in the presence of NE, and significantly more potent/efficacious. ELD607 is stable in
proteolytic CF sputum, and inhibits Ca2+-influx in freshly-isolated CF patient peripheral neutrophils and in CF
sputum-derived immune cells in a mutation-agnostic fashion. In murine lung infection models with common CF
pathogens including P. aeruginosa and S. aureus, a single, inhaled dose of ELD607 reduced lung inflammation
(neutrophilia, cytokines, NE) by 90%, decreased lung bacterial infection by 3-4 log10 CFUs and increased
survival. 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 enhances the
lungs’ natural ability to clear pathogens. In this proposal, we will use wild-type and CF mice to understand which
immune effector cells are regulated by ELD607. The CF ferret model developed by Dr Engelhardt and coworkers
at the University of Iowa spontaneously develops chronic CF lung disease including inflammation and bacterial
infection. We will first validate that we can deliver sufficient doses of ELD607 via nebulizer to safely inhibit Orai1
in wild-type and CF ferret lungs. Then we will chronically administer ELD607 to CF ferrets with existing lung
disease in order to study the impact of ELD607 on CF disease progression.

Grant Number: 5R44HL165964-02
NIH Institute/Center: NIH
Principal Investigator: Saira Ahmad