- Pa-positive NCFB patients experienced a significant reduction in annualised exacerbation rate from 3.4 in the prior 12 months to 1.2 on RESP-X treatment
- Only one exacerbation meeting the Hill/EMBARC criteria was observed across all patients dosed with RESP-X during the study
- Data also show reductions in Pseudomonas aeruginosa (Pa) burden and inflammatory biomarkers, alongside improvements in patient-reported quality of life
- Results build on the positive topline safety, tolerability and pharmacokinetic data announced in May 2026, and support the Company's plans to engage regulators on the next stage of 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.
About RESP-X
RESP-X (INFEX702) is a first-in-class anti-virulence humanized IgG4 monoclonal antibody in-licensed from Japanese pharmaceutical company Shionogi. RESP-X targets Pseudomonas aeruginosa’s Type 3 Secretion System (T3SS), specifically the PcrV protein, a critical virulence mechanism by which Pa causes organ injury, evades the immune system and gains a foothold in humans.
Unlike traditional antibiotics that kill bacteria directly, RESP-X works by blocking Pa exotoxin delivery through the T3SS. By deactivating this virulence system, RESP-X downgrades the ability of Pa to attack human tissues and restores the ability of immune cells to control Pa, enabling the patient’s own immune system to more efficiently fight the infection.
RESP-X is initially being developed as a long-term preventative treatment to reduce disease flares and exacerbations in NCFB patients colonised with Pseudomonas aeruginosa. The programme has potential for expansion into additional indications, including cystic fibrosis, COPD, and acute settings such as hospital and ventilator-acquired pneumonia and bloodstream infections due to Pa, in addition to Pa involvement in burn injuries, diabetic ulcers, and prosthetic joint infections.
About Non-Cystic Fibrosis Bronchiectasis
Non-cystic fibrosis bronchiectasis (NCFB) is a chronic and debilitating respiratory disease defined by irreversible and progressive dilatation of bronchi due to chronic bronchial inflammation. The disease is characterised by periods of stable disease punctuated by flare-ups, known as exacerbations, that increase in frequency and severity over the patient’s lifetime.
There are currently up to six million NCFB patients in major global markets, of which up to 30% have chronic Pa colonisation. Colonisation with Pa increases the severity of NCFB, leading to recurring episodes of debilitating and life-threatening infection. NCFB exacerbations are closely associated with acute bacterial infections, with Pa being one of the leading causes. In the most severe cases, patients have multiple exacerbations per year, resulting in high hospitalisation and mortality rates.
Despite its prevalence and severity, there are currently no licensed treatments for the prevention of infective exacerbations due to Pa colonisation in NCFB patients, representing a significant unmet medical need.
About Pseudomonas aeruginosa
Pseudomonas aeruginosa is a difficult-to-treat, drug-resistant pathogen recognised by the World Health Organization (WHO) as a serious threat to human health. Pa is a leading cause of healthcare-associated infections and is particularly problematic in patients with chronic respiratory diseases, where it can establish persistent colonisation leading to recurrent, severe infections.
About Infex Therapeutics
Infex Therapeutics Holdings plc is a leader in critical-priority infectious diseases, with a broad and diverse pipeline of innovative best-in-class and first-in-class drug candidates to address the urgent global shortage of novel anti-infective treatments. The Company is building a differentiated pipeline through in-house drug discovery, acquisition, co-development and in-licensing of early stage/pre-clinical candidates, developing them to clinical proof of concept before licensing to commercial pharma partners.
To learn more, visit our website: https://www.infextx.com/
Contact
Infex Therapeutics
Carl Curran, Head of Business Development
E-mail: info@infextx.com
ICR Healthcare
Stephanie Cuthbert, Louis Ashe-Jepson
E-mail: infex@icrhealthcare.com
