EP395, a novel non-antibiotic macrolide, enhances antiviral responses in bronchial epithelial cells from asthma patients

Macrolide antibiotics such as azithromycin have been shown to reduce asthma exacerbations and improve anti-viral properties of bronchial epithelial cells (BECs). However, its long-term use has been associated with increased antimicrobial resistance. EP395 is a novel macrolide with negligible antimicrobial activity being developed as a potential treatment to reduce exacerbations of chronic respiratory diseases (Hohlfeld et al., 2025. Pulm. Pharmacol. Ther. 90). We have now studied its effect on rhinoviral-induced anti-viral and pro-inflammatory responses in BECs.

Primary BECs from asthma patients (n=6–9) were pre-treated with EP395 (10 µM) or azithromycin (10 µM) for 24 hours before infection with rhinovirus (RV) 1B for 24 or 48 hours. Gene expression of IFN-β, MDA5, CCL20 and TNF-α as well as viral RNA was measured using RT-qPCR. Lactate dehydrogenase (LDH) activity was measured in cell supernatants as a marker of cell toxicity.

EP395 treatment of RV1B infected BECs did not alter the LDH activity in cell supernatants, indicating a lack of cytotoxicity. Furthermore, EP395 significantly increased RV-induced mRNA expression of IFN-β (6.6-fold compared to RV alone, p=0.01) and, concomitantly, significantly reduced viral load (mRNA) (0.7-fold compared to RV alone, p=0.003), in BECs at 24 hours post infection. There was also a trend towards an increased RV-induced expression of MDA5 (3-fold compared to RV alone, p=0.1). EP395 treatment did not alter RV-induced mRNA expression of TNF-α nor CCL20. Compared to azithromycin, the effects of EP395 on the BEC anti-viral and pro-inflammatory response were similar.

EP395 improves the IFN-β response and anti-viral activity in BECs from asthma patients, without affecting the pro-inflammatory response. This suggests EP395 could, by modulating epithelial antiviral immunity, be a beneficial treatment for reducing viral-induced exacerbations in asthma without the risk of contributing to antimicrobial resistance.