INFEX Therapeutics presents new Phase IIa data for RESP-X providing further evidence on exploratory efficacy endpoints supporting progression to later stage development

Alderley Park, Cheshire, U.K. – 8 September 2026 – Infex Therapeutics, a leading anti-infectives specialist, today announced new data from its Phase IIa study of RESP-X (INFEX702), a first-in-class anti-virulence monoclonal antibody, in non-cystic fibrosis bronchiectasis (NCFB) patients colonised with Pseudomonas aeruginosa (Pa), which will be presented in a late-breaking poster abstract at the European Respiratory Society (ERS) Congress 2026 at 12:30-14:00 CEST in Barcelona, Spain.

The data will be presented by Prof Colm Leonard, Chief Clinical Officer of Infex Therapeutics, and provide further detail on RESP-X’s exploratory efficacy and biomarker findings. Pa is a critical factor in up to 30% of NCFB cases, leading to recurring episodes of life-threatening infection – there are currently no approved preventative treatments.

Exacerbation rate, clinical outcomes and microbiology
Pa-positive NCFB patients treated with a single dose of RESP-X experienced a reduction in reported annualised exacerbation rate, from 3.4 in the 12 months prior to dosing 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.

Microbiology data showed that all Pa isolates collected during the study continued to encode the RESP-X target (PcrV), consistent with the complete target coverage reported in May, and additionally showed reductions in sputum Pa burden following treatment.

Biomarker and quality-of-life findings
The analysis also showed reductions in inflammatory biomarkers following treatment, alongside an improvement in patient-reported quality of life scores. The data also confirmed strong lung exposure in the 10 mg/kg cohort, with RESP-X detected in the epithelial lining fluid at a level equivalent to 1.9% of serum concentration, supporting the drug’s ability to reach the site of infection.

Together with the positive safety, tolerability and PK profile reported in May 2026, which supports dosing at three-month intervals, the study concluded that this dosing schedule could offer a viable approach to reducing exacerbation rates in Pa-colonised NCFB patients.

“These new analyses reinforce our confidence in RESP-X as a potential first anti-virulence therapy for Pseudomonas-colonised NCFB patients,” said Dr Peter Jackson, CEO of Infex Therapeutics. “For a population with no approved preventative treatment, the data showing a meaningful reduction in annualised exacerbations is an encouraging result, supporting onward clinical development and commercialisation.”

Prof Colm Leonard, Chief Clinical Officer at Infex Therapeutics, commented: “What is pleasing among the exploratory efficacy endpoints is the direction of the exacerbation data: only one exacerbation meeting the Hill/EMBARC criteria was observed over 180 days across a patient cohort with a history of infective exacerbations. Combined with the biomarker and quality-of-life improvements, and a PK profile that supports dosing every three months, this gives us further encouragement that RESP-X could offer NCFB patients colonised with Pa a significantly different treatment experience to daily or frequent interventions, as well as supporting the case for moving the programme into a larger efficacy study.”

Further development
These exploratory results are derived from a small, single-site Phase IIa dose-ranging study and were not powered for statistical significance on efficacy endpoints. The Company is using the new data, together with the previously reported safety and pharmacokinetic data, to inform its ongoing engagement with regulatory authorities on the design of a next-phase efficacy study in NCFB patients colonised with Pa.