Document resource
Introduction Pseudomonas aeruginosa (PA) airway infections in bronchiectasis are associated with increased disease severity and exacerbations. New treatment options are needed due to inconsistent results with inhaled antibiotics and increasing concerns over antimicrobial resistance. The GREAT-2 trial of gremubamab, a bispecific monoclonal antibody targeting PA Psl and PcrV, demonstrated reduced bacterial load at the end-of-treatment (EoT) (500 mg), and significantly prolonged time-to-first exacerbation (1500 mg) in patients chronically infected with PA. Whether PA adapts to evade monoclonal antibody treatment is unknown. This study aimed to characterise PA genetic variation in patients receiving treatment with gremubamab.Methods 37 patients were enrolled in the multinational (UK and Spain), randomized, double-blind, placebo-controlled trial of gremubamab for people with CT-confirmed bronchiectasis and chronic PA infection , randomised 1:1:1 to 1500 mg or 500 mg gremubamab, or placebo, once every four weeks for 12 weeks. 233 PA clones were isolated from sputum on days 1, 7, 14, 28, 56, 84 (EoT), and day 168 (12-week follow-up), with all clone morphologies stored. Whole-genome Illumina sequencing was followed by analysis of phylogenetic distances, sequence types, SNPs, and deletions relative to PAO1/baseline clone.Results The 233 PA clones are genetically diverse, comparable to global collections of bronchiectasis isolates. In a rooted phylogenetic tree, 163 patient-specific clades with ≥3 tips were identified ( figure 1A). 8 clones, from 2 patients in the placebo group, had a pcrV deletion. There was no significant difference in the frequency of psl deletions between treatment groups over the trial (placebo p=0.48, 500 mg p=NA, 1500 mg p= 0.62, figure 1B). When mapping variants to patient’s baseline clone, SNPs were not significantly changed between treatment groups.There were no significant changes in phylogenetic distance interactions between visit number and treatment group over the trial (χ2(12) = 13.9, p=0.307), suggesting little evolutionary adaptation (figure 1C).In all 233 clones, 23 unique sequence types were identified, plus novel sequence types in 8 patients. 25/37 patients had the same sequence type at all visits.Abstract T6 Figure 1Conclusion PA isolates showed stability through the 6-month treatment period in the GREAT-2 trial. There were no changes or adaptations in the PcrV and Psl targets, suggesting no resistance development.