A novel macrolide, EP395, with reduced antibacterial activity and an enhancing effect on respiratory epithelial barrier

Epithelial barrier failure, a feature of several inflammatory lung diseases, contributes to exacerbations and disease progression. Acute exacerbations are often treated with macrolides, including azithromycin (AZM). In part, this is due to both primary antimicrobial and additional immunomodulatory actions, complemented by recently reported enhanced integrity of respiratory epithelial barriers. However, long-term "off label" use of macrolides is associated with increased bacterial resistance. We now introduce a new class of compounds, "Barriolides" that are analogues of AZM promoting airway epithelial barrier integrity in vitro, with negligible antibacterial activity. The lead compound is EP395 which does not affect cell viability up to 100 μM in VA10 bronchial epithelial cells. Treatment with EP395 for three weeks enhanced epithelial barrier integrity, measured by increased transepithelial electrical resistance, reduced paracellular flux in air-liquid interface culture and increased expression of tight junction proteins. EP395 also induced epidermal differentiation and formation of lamellar bodies, complemented by a relevant genetic footprint. In mice exposed to sulphur dioxide, pre-treatment with EP395 reduced extravasation of human serum albumin into the bronchoalveolar lavage fluid. These data demonstrate epithelial barrier-protecting effects of EP395, a promising candidate for treatment of chronic respiratory diseases without risk of bacterial resistance.