Aer Therapeutics’ fexlamose failed to improve lung function or reduce mucus-plug burden in a Phase 2a COPD trial, with more respiratory adverse events.
Written By: Saniya Katakdhond, PharmD
Reviewed By: Pharmacally Editorial Team
Aer Therapeutics announced on October 30, 2026, that its investigational therapy fexlamose failed to meet the primary and secondary efficacy endpoints in a Phase 2a proof-of-concept trial involving patients with moderate-to-severe chronic obstructive pulmonary disease (COPD).
The study evaluated fexlamose 90 mg administered once daily through nebulization. After 28 days of treatment, the therapy did not demonstrate improvements in trough forced expiratory volume in one second (FEV1), forced vital capacity (FVC), or other spirometric measures. It also failed to demonstrate an overall reduction from baseline in the Mucus Plug Segment Score (MPSS), an imaging-based biomarker designed to assess pharmacodynamic activity, target engagement and efficacy.
Beyond the lack of demonstrated efficacy, respiratory adverse events, including COPD exacerbations, occurred more frequently in the fexlamose treatment arm. Treatment discontinuations were also more frequent than with placebo, adding to the challenges for the programme.
AER-01-002 Evaluated Fexlamose in 119 Patients
The AER-01-002 study (NCT06731959) was a randomized, double-blind, placebo-controlled, parallel-group trial evaluating the efficacy and safety of fexlamose 90 mg against placebo.
The trial enrolled 119 patients with moderate-to-severe COPD across Australia, New Zealand, the United Kingdom, Poland, Spain and Bulgaria. More than 75% of participants had severe or very severe airflow limitation according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) classification.
Participants received once-daily nebulized treatment over a 28-day dosing period. The study assessed whether targeting pathological airway mucus could produce measurable improvements in pulmonary function and reduce mucus-plug burden.
The absence of demonstrated benefits across the reported efficacy assessments represents a setback for the evaluated dose and treatment regimen.
Fexlamose Targets Disulfide Bonds in Pathological Mucus
Fexlamose is an investigational inhaled, thiol-based therapeutic developed to address pathological mucus accumulation in muco-obstructive respiratory diseases.
In conditions such as COPD, disulfide cross-linking between mucin polymers contributes to increased mucus viscosity and airway mucus-plug formation. These plugs can obstruct airflow, impair pulmonary function and contribute to respiratory morbidity.
Fexlamose is designed to cleave these disulfide bonds, potentially reducing mucus viscosity and facilitating mucus clearance.
Mucus plugs are reported in up to half of patients with moderate-to-severe COPD and asthma. Their presence is associated with impaired lung function, reduced quality of life and increased mortality. Despite this disease burden, effective treatments specifically targeting pathological mucus obstruction remain limited.
Although the mechanism provides a biological rationale, the Phase 2a findings did not establish the anticipated clinical or imaging-based benefits.
Respiratory Safety Findings Add to Development Challenges
Aer Therapeutics reported a higher incidence of respiratory adverse events with fexlamose compared with placebo. Most respiratory adverse events, including COPD exacerbations, occurred in the treatment arm. Adverse events leading to treatment discontinuation were also more frequent among patients receiving fexlamose.
These observations warrant attention in a population already vulnerable to respiratory complications. However, the topline announcement did not provide detailed adverse-event counts, severity distributions, exposure-adjusted rates or statistical comparisons.
Consequently, the available information does not establish causality or allow a definitive assessment of the magnitude of the safety difference.
Development Outlook and Next Steps
Aer Therapeutics has not disclosed a definitive update on the future development strategy for fexlamose following the COPD results.
The company is also developing the therapy for other muco-obstructive respiratory diseases, including asthma, non-cystic fibrosis bronchiectasis and cystic fibrosis. However, the current findings relate specifically to COPD and do not establish the therapy’s potential in these other indications.
Further evaluation of the complete AER-01-002 dataset will be important for understanding the efficacy, biomarker and safety findings and determining their implications for subsequent development.
Clinical Interpretation
The Phase 2a results highlight the difficulty of translating a plausible mucus-targeting mechanism into measurable clinical benefits in COPD.
The findings are particularly relevant because neither pulmonary-function assessments nor the imaging-based MPSS outcome demonstrated the anticipated improvement. FEV1 and FVC provide functional measures of respiratory performance, while MPSS was intended to assess changes in mucus-plug burden and treatment-related pharmacodynamic activity. The absence of improvement across both assessment types does not support the expected clinical benefit of the evaluated regimen.
Nevertheless, the MPSS findings alone cannot establish whether fexlamose failed to engage its molecular target, produced insufficient pharmacodynamic activity or encountered other limitations affecting mucus clearance. Detailed biomarker results will be necessary to distinguish these possibilities.
The respiratory safety observations further complicate the interpretation. More respiratory adverse events and treatment discontinuations in the fexlamose arm raise questions about tolerability, although the available topline information is insufficient to establish a treatment-related safety signal or quantify the overall benefit-risk profile.
Importantly, the 28-day treatment period limits conclusions about longer-term effects. However, the absence of demonstrated benefit across functional and imaging-based assessments represents a substantial challenge for fexlamose’s current COPD development strategy.
The central question is whether the observed outcome reflects limitations of the evaluated dose and treatment duration or a broader challenge in translating mucus modification into meaningful clinical improvements in COPD. The complete clinical dataset will be important in determining the implications for fexlamose’s future development.
Reference
Aer Therapeutics Announces Top-Line Results from its Phase 2a Proof-of-Concept Trial of Fexlamose in Chronic Obstructive Pulmonary Disease (“COPD”), Air Therapeutics via GlobeNewsWire, 30 October 2026
A Study to Investigate Using Inhaled Fexlamose to Treat Adult Participants Who Have Moderate to Severe COPD (AER-01-002), ClinicalTrials.gov ID NCT06731959
About the Writer
Saniya Sanjay Katakdhond (Linkedin) is a Doctor of Pharmacy professional with hands-on experience in patient case review, clinical documentation, medical record analysis, and patient care.
Her hospital experience has strengthened her understanding of clinical conditions, treatment approaches, and multidisciplinary healthcare practices.
With ICH-GCP certification and a research-oriented approach, she brings clinical insight and attention to detail to healthcare content development.
As a healthcare writer, Saniya focuses on translating clinical knowledge and patient-care experience into clear, accurate, and evidence-informed medical content.