(501) Investigating the activity of pravibismane against bacterial isolates common in cystic fibrosis pulmonary infections

Background: Bacterial infection of airways is the major cause of morbidity and mortality in people with cystic fibrosis (CF) [1]. We evaluated the ability of a novel compound, pravibismane, to inhibit the growth of a panel of common microorganisms in CF pulmonary infections. Pravibismane is the first in a new class of therapeutics with a novel mechanism of action that demonstrates broad-spectrum anti-infective and anti-biofilm activity. In two independent studies, a total of 1,656 strains of CF bacterial pathogens were selected to evaluate the activity (minimum inhibitory concentrations, or MIC) of pravibismane. In parallel, comparator antibiotics was tested against the same pathogens. In addition, the potential impact of a pulmonary surfactant, Survanta® (beractant), on antimicrobial activity of pravibismane was investigated.

Methods: MIC testing was performed following the broth microdilution assay as stipulated by Clinical and Laboratory Standards Institute M100. Pravibismane stock solution was prepared at a concentration of 2 mg/mL in 100% DMSO and further diluted in media. Cation adjusted Mueller Hinton broth (CAMHB) or CAMHB+10% OADC supplement was utilized for M. avium. Bacteria for inoculation were prepared by suspending freshly grown bacterial colonies in sterile saline to a turbidity of 0.5 McFarland units. This bacterial suspension was dispensed into plates containing antibiotic dilutions to a final bacterial density of ~7.5x10⁶ cells/mL. Plates were incubated at 37°C until adequate growth was visible in no antibiotic wells.

Results: Study 1: A panel of gram-positive and gram-negative bacteria were tested against pravibismane and a range of antibiotics. The pravibismane MIC90 value for S. aureus was 1 µg/mL, for P. aeruginosa was 2 mg/mL, and S. maltophilia was 4 mg/mL (Table 1).



Study 2: Strains from early P. aeruginosa infection, mucoid and non-mucoid phenotypes isolated from CF respiratory cultures were tested against pravibismane and comparator antibiotics. Measured MICs for pravibismane against P. aeruginosa ranged from 0.0625- 4 µg/mL (Table 1). S. aureus, a principal pathogen in CF demonstrated MICs in the range of £0.031- 2 µg/mL. MICs for Burkholderia complex and S. maltophilia ranged from £0.031-16 µg/mL and £0.031-16 µg/mL respectively. The role of Acinetobacter in CF lung disease is not well defined, however it may harbor drug resistance. MICs for pravibismane against Acinetobacter isolates derived from CF population were 0.13- 2 µg/mL. MIC testing of pravibismane against M. abscessus was £0.031-16 mg/mL (Table 1).A pulmonary surfactant, Survanta®, was investigated against isolates of CF relevant microorganisms in parallel with imipenem and daptomycin. Pravibismane MIC values remained largely unaffected in the presence of Survanta®.

Conclusions: Pravibismane exhibited broad-spectrum activity against a panel of common CF pathogens, including nontuberculous mycobacteria. This work demonstrates that the antibacterial activity of pravibismane is not adversely impacted by natural surfactant in the human lung.

Acknowledgements: This research was supported by CARB-X. CARB-X’s funding was sponsored by Cooperative Agreement Number IDSEP160030 from ASPR/BARDA and by an award from Wellcome Trust. The content is solely the responsibility of authors and does not represent official views of CARB-X or its funders.

References: [1] LiPuma, J.J., The Changing Microbial Epidemiology in Cystic Fibrosis. Clinical Microbiology Reviews, 2010. 23(2): p. 299-323.