(531) Developing Nebulized Phage Therapy for Chronic Pseudomonas aeruginosa Pulmonary Infections in Cystic Fibrosis (CF) Patients

Background: Among CF patients, Pseudomonas aeruginosa (PsA) infection is associated with progressive lung function decline and increased mortality. Chronic anti-PsA antibiotic therapy leads to multi-drug resistant (MDR) PsA infections in adults [1]. Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) modulators improve sweat chloride, lung function, and nutritional status [2]. Despite these improvements, ~80% CF patients remain infected with PsA [2,3]. Lytic bacteriophages (phages) offer an alternative or adjunctive approach for the treatment of multi-drug resistant (MDR) chronic PsA lung infections. Phages are natural, species-specific viruses that infect bacteria and amplify locally and are able to penetrate biofilm using specific depolymerizing enzymes [4]. Our goal is to develop a nebulized phage therapy for the treatment of chronic PsA pulmonary infections in CF patients.

Methods: A panel of more than 100 clinical PsA bacterial strains isolated from US and European CF patient sputum samples were used for phage isolation and characterization. Isolated natural phages were sequenced and analyzed. Phage host range was established by plaque assay, and activity within biofilms was determined by BacTiter-Glo™ and crystal violet staining. A breathing simulator was used to determine the delivered dose by nebulization of a phage cocktail. Droplet size distribution was tested by laser diffraction. Phage distribution within the aerosols was analyzed by qPCR and New Generation Impactor (NGI). Phage safety was demonstrated in ex-vivo and in vivo models.

Results: Lytic phages with wide host range coverage against clinical PsA strains were selected and evaluated for additional characterization. Genomic analysis confirmed the absence of undesirable genes. The selected combination targeted most of the strains in the panel and significantly reduced PsA embedded in biofilm. Breathing simulation results revealed phage viability following nebulization and all tested phages were distributed homogeneously within the aerosol. Safety assessments conducted using human epithelial cells and animal models demonstrated that treatment with BX004 was safe and well tolerated.

Conclusions: BX004 demonstrated a broad host range against CF clinical PsA isolates, potent in vitro antimicrobial activity, including within biofilm, and high viability following delivery by nebulization. Nebulized phage therapy may offer a novel treatment approach for chronic PsA pulmonary infections in CF patients carrying PsA infection.

Acknowledgements:

References: [1] CFF Annual Data report 2020 (file:///C:/Users/mayah/Downloads/Patient-Registry-Annual-Data-Report%20(7).pdf)

[2] Durfey et al., Combining Ivacaftor and Intensive Antibiotics Achieves Limited Clearance of Cystic Fibrosis Infections, 2021

[3] Nichols et al., Elexacaftor/Tezacaftor/Ivacaftor Markedly Reduces Sputum Pathogen Density in People with CF:
The PROMISE Microbiology Sub-study, 2020

[4] Chegini et al.,Bacteriophage therapy against Pseudomonas aeruginosa biofilms: a review, 2020