Infex Therapeutics announces positive Phase IIa results for RESP-X in non-cystic fibrosis bronchiectasis patients colonised with Pseudomonas aeruginosa

• Study met its primary objective demonstrating excellent safety and tolerability, of RESP-X in patients with NCFB colonised with Pseudomonas aeruginosa (Pa)
• Secondary objectives met with no immunogenicity observed, favorable PK, and lung deposition supporting convenient quarterly dosing
• Encouraging early efficacy signals including reduced exacerbation rates for Pa-positive patients
• Results support RESP-X progress to the next stage of clinical development

 Alderley Park, Cheshire, U.K. – 21 May 2026 – Infex Therapeutics, a leading anti-infectives specialist, today announced positive results from its Phase IIa dose-ranging study evaluating RESP-X (INFEX702), a first-in-class anti-virulence monoclonal antibody, in non-cystic fibrosis bronchiectasis (NCFB) patients colonised with Pseudomonas aeruginosa (Pa). The data were presented yesterday at the American Thoracic Society (ATS) 2026 International Conference in Orlando, Florida.

The Phase IIa study was designed to evaluate the safety, pharmacokinetics, immunogenicity, lung deposition and exploratory efficacy endpoints of RESP-X. The study met its primary and secondary objectives, demonstrating that RESP-X was safe and well tolerated in NCFB patients colonised with Pa. RESP-X demonstrated favourable pharmacokinetics and lack of immunogenicity supporting quarterly dosing. The study also showed encouraging early efficacy signals, including reduced exacerbation rates in Pa-positive patients and complete target coverage. These results build on the previously reported Phase I, 32 healthy volunteer study and support the advancement of RESP-X into the next phase efficacy study.

“These highly encouraging Phase IIa results continue to demonstrate that RESP-X is safe and well tolerated while showing promising efficacy signals in NCFB patients colonised with Pseudomonas aeruginosa (Pa),” said Dr Peter Jackson, CEO of Infex Therapeutics. “The excellent safety profile, favorable pharmacokinetics supporting quarterly dosing, complete target coverage, and reduced exacerbation rates provide strong support for advancing RESP-X into the next phase of clinical development. These results represent an important milestone for Infex and offer hope for NCFB patients colonised with Pa, a population with significant unmet medical need and no approved preventative treatment options.”

Prof Colm Leonard, Chief Clinical Officer at Infex Therapeutics, commented, “I was delighted to share this exciting data on our novel anti-Pseudomonal therapy with the clinical and scientific community at the ATS. There is a lot of interest in RESP-X as a new approach to make a real difference to Pa-colonised patients with bronchiectasis.”