Infex Therapeutics Reports Phase IIa Signal in Bronchiectasis

Annualised exacerbation rates falling from 3.4 to 1.2 in a population with no approved preventative treatment: Infex Therapeutics presented Phase IIa data for RESP-X (INFEX702) at the ERS Congress 2026 in Barcelona on 8 September, adding exploratory efficacy and biomarker findings to the safety, tolerability, and pharmacokinetic profile disclosed in May 2026.

RESP-X is a first-in-class anti-virulence monoclonal antibody targeting PcrV, a conserved virulence factor on Pseudomonas aeruginosa (Pa). Pa is implicated in up to 30% of non-cystic fibrosis bronchiectasis (NCFB) cases and drives recurring, life-threatening infective exacerbations. Across all patients dosed with RESP-X during the six-month study, only one exacerbation meeting Hill/EMBARC criteria was observed, a result the company's Chief Clinical Officer, Prof Colm Leonard, described as directionally encouraging given the cohort's documented exacerbation history.

Microbiology data confirmed that all Pa isolates collected during the study continued to encode the PcrV target, indicating complete target coverage was maintained. Sputum Pa burden decreased following treatment, and reductions in inflammatory biomarkers were accompanied by improvements in patient-reported quality-of-life scores. Lung exposure data from the 10 mg/kg cohort showed RESP-X detectable in epithelial lining fluid at 1.9% of serum concentration, supporting drug delivery to the site of infection, a parameter relevant to any future regulatory discussion on pharmacodynamic justification.

For regulatory affairs leads tracking anti-infective development programs, the PK profile supporting three-month dosing intervals is a notable design consideration. Quarterly administration differentiates RESP-X from daily inhaled or oral regimens and may influence both the Phase IIb/III trial design and the labelling strategy submitted to regulators. Infex has indicated plans to engage regulators on the next development stage, though no specific agency interactions or timelines have been disclosed.

The Phase IIa data carry the limitations inherent to a small, single-site dose-finding study; the company has acknowledged that the exploratory efficacy findings require confirmation in a larger, adequately powered efficacy trial before conclusions on treatment effect can be drawn. No comparative arm was described in the available data.

The measurable outcome to track is the outcome of regulatory engagement on Phase IIb/III design, where the Hill/EMBARC exacerbation endpoint and the three-month dosing interval will face their first formal scientific advice scrutiny.

Source: Infex Therapeutics via company press release, 8 September 2026. Data presented as a late-breaking poster abstract at ERS Congress 2026, Barcelona, 12:30–14:00 CEST.