ALDERLEY PARK, Cheshire, U.K. — September 8, 2026
Infex Therapeutics presented new data from its Phase IIa study of RESP-X (INFEX702) in non-cystic fibrosis bronchiectasis (NCFB) patients colonized with Pseudomonas aeruginosa (Pa) at the European Respiratory Society (ERS) Congress 2026 in Barcelona. The late-breaking data provide additional exploratory efficacy and biomarker evidence supporting the company’s plans to advance RESP-X into later-stage clinical development. RESP-X is a first-in-class anti-virulence monoclonal antibody designed to target the PcrV protein within the Type 3 Secretion System (T3SS) of P. aeruginosa. Infex reported that Pa-positive patients receiving a single dose experienced a reduction in reported annualized exacerbation rate from 3.4 during the 12 months before treatment to 1.2 during the six-month study period. Across all patients dosed with RESP-X, only one exacerbation meeting Hill/EMBARC criteria was observed during the study, while additional findings included reductions in Pa burden and inflammatory biomarkers and improvements in patient-reported quality of life.
RESP-X Data Support Development Strategy
The new Phase IIa findings strengthen Infex Therapeutics’ development case for RESP-X as a potential preventative treatment for Pa-colonized NCFB patients, while the company emphasized that the efficacy observations are exploratory and were generated in a small, single-site dose-ranging study that was not powered for statistical significance on efficacy endpoints. Microbiology analyses showed that all Pa isolates collected during the study continued to encode the RESP-X target, PcrV, consistent with previously reported complete target coverage. The study also demonstrated reductions in sputum Pa burden following treatment, providing additional evidence of biological activity. Infex reported strong lung exposure in the 10 mg/kg cohort, with RESP-X detected in epithelial lining fluid at a level equivalent to 1.9% of serum concentration, supporting drug delivery to the site of infection. Combined with previously announced positive safety, tolerability, and pharmacokinetic results, the findings support the company’s view that a three-month dosing interval could be viable for longer-term management of Pa-colonized NCFB patients..
Infex Moves Toward Larger Efficacy Study
Infex is using the combined Phase IIa safety, pharmacokinetic, biomarker, and exploratory efficacy dataset to engage with regulatory authorities on the design of the next-phase clinical study. The company intends to determine the appropriate development pathway for RESP-X and evaluate the program in a larger efficacy setting involving NCFB patients colonized with P. aeruginosa. The potential for quarterly dosing is an important component of the program’s development strategy, particularly for patients who currently face recurrent exacerbations and frequent treatment interventions. Infex Chief Executive Officer Peter Jackson said the observed reduction in annualized exacerbations provides encouragement for onward clinical development and potential commercialization, while Chief Clinical Officer Prof Colm Leonard highlighted the limited number of qualifying exacerbations observed over 180 days. The company’s immediate focus is therefore on translating the Phase IIa evidence into a regulatory-supported next-stage development plan rather than treating the exploratory findings as definitive efficacy evidence.
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Anti-Virulence Platform Expands RESP-X Opportunity
RESP-X gives Infex Therapeutics an opportunity to establish an anti-virulence approach within the broader anti-infectives market, with potential applications extending beyond its initial NCFB development program. Unlike conventional antibiotics that directly kill bacteria, RESP-X is designed to block P. aeruginosa exotoxin delivery through the T3SS by targeting PcrV, thereby reducing the pathogen’s ability to damage host tissue and evade immune defenses. Infex is initially developing the therapy as a long-term preventative treatment for NCFB patients chronically colonized with Pa, but the company has identified potential expansion opportunities in cystic fibrosis, COPD, hospital- and ventilator-acquired pneumonia, bloodstream infections, burn injuries, diabetic ulcers, and prosthetic joint infections. With the ERS 2026 presentation adding new clinical and translational evidence and regulatory engagement planned for the next development stage, Infex is positioning RESP-X as a potential differentiated anti-infective program for a patient population with no approved preventative treatment targeting Pa colonization-related exacerbations.
Source:Infex Therapeutics press release
