TARGETING THE ATP12A PROTON PUMP PROVIDES NEW THERAPEUTIC OPPORTUNITIES FOR CYSTIC FIBROSIS

Airway physiology-directed therapies could be essential for CF patients expressing undruggable CFTR mutants and could also be useful as an adjuvant therapy supporting the effect of CFTR rescue maneuvers. Indeed, it has been speculated that beneficial effects could be obtained by modulating other channels and transporters to increase CFTR-independent anion secretion (TMEM16A, SLC26A9, SLC26A4) or inhibit acidification (ATP12A). However, despite the growing interest toward putative alternative targets, their precise function and expression in the airways is largely unclear and sometimes controversial. Moreover, for most of them there are no specific modulators to be tested as drug candidates. To pursue this aim, we performed a detailed investigation of selected alternative targets expression in human airways (both in vivo and in vitro), then we investigated their role, and particularly their contribution to the regulation of the airway surface liquid properties. Finally, we aimed at developing cell models and assays suitable for drug screening in order to initiate the search of drug-like modulators for the most promising targets. We found that ATP12A was the major player in controlling airway surface liquid properties in both large and small airway epithelial models, and in patient-derived nasal epithelia. Inhibition of ATP12A always resulted in ASL pH and viscosity normalization, therefore it could be considered a novel candidate for airway physiology-directed therapies. A screening of a small library of antisense oligonucleotides in a newly developed endogenous high-throughput model for ATP12A expression and function revealed two active ASOs, whose activity was confirmed in CF patient-derived nasal epithelia.