The Effect of NAC on Lung Function and CT Mucus Score

  • End date
    Mar 19, 2022
  • participants needed
  • sponsor
    University of California, San Francisco
Updated on 19 August 2020
pulmonary function test


This study evaluates 20% n-acetylcysteine (NAC) in the treatment of moderate-to-severe asthma that is complicated by mucus in the airway, as determined by CT imaging. The study is a crossover design, which means that half the study participants will get 20% NAC in the first 14-day treatment period and placebo in the next 14-day treatment period; and the other half will get placebo in the first 14-day treatment period and 20% NAC in the next 14-day treatment period.


N-acetylcystine (NAC) is a mucolytic medication, meaning that it breaks apart mucus. Investigators know that mucus is a factor in severe asthma attacks. However, mucus may be a factor in chronic severe asthma as well. This role has been hard to prove because of difficulty in showing that mucus occludes the lumen in chronic severe disease. Using a novel approach of scoring mucus occlusion, investigators have used CT imaging to uncover that a majority of people with severe asthma have at least one lung segment with a mucus plug and 27% have more than four lung segments with mucus plugs.

Historically, studies of mucolytics, like NAC, have not shown benefit in other obstructive lung diseases, like Chronic Obstructive Pulmonary Disease (COPD). However, utilizing CT mucus scores as a biomarker, investigators believe that mucolytic treatment may prove useful for those with significant mucus impaction.

This is a randomized, double-blind, placebo-controlled phase 4 study of 20% NAC in patients with asthma who also have evidence of mucus in their lungs as determined by CT imaging. Investigators hypothesize that by treating asthmatics, chosen based on the presence of mucus in the airways, with a mucolytic like NAC, will result in an improvement of lung function.

Treatment n-acetylcystine + albuterol, 0.9% saline + albuterol
Clinical Study IdentifierNCT03822637
SponsorUniversity of California, San Francisco
Last Modified on19 August 2020

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Inclusion Criteria

Is your age between 18 yrs and 80 yrs?
Gender: Male or Female
Do you have any of these conditions: Asthma or Asthma (Pediatric) or Allergies & Asthma?
Male or female between the ages of 18 and 80 years of age at Visit 1
Written informed consent obtained from subject and ability for subject to comply with the requirements of the study
Able to perform reproducible spirometry according to American Thoracic Society (ATS) criteria
Physiological evidence of airflow obstruction (FEV1 bronchodilator reversibility of 12% or hyperreactivity to methacholine reflected by a methacholine provocative concentration that results in a 20% fall in FEV1(PC20) 16 mg/mL)
Clinical history of asthma per patient report or medical record
Pre-bronchodilator FEV1 > 35% predicted
Post-bronchodilator FEV1 > 40% but < 90% predicted
Asthma requiring treatment with inhaled corticosteroids (ICS) for 3 months or greater
CT mucus score 5
Ability to tolerate study drug reflected by a post-treatment FEV1 80% of pretreatment, pre-bronchodilator FEV1

Exclusion Criteria

Pregnant, breastfeeding, or unwilling to practice birth control during participation in the study
Presence of a condition or abnormality that in the opinion of the Investigator would compromise the safety of the patient or the quality of the data
Smoking of tobacco or other recreational inhalants in last year and/or >10 pack-year smoking history
Adherence to study drug 70% after first treatment period
Current participation in an investigational drug trial
Other chronic pulmonary disorders, including (but not limited to) cystic fibrosis, chronic obstructive pulmonary disease, chronic bronchitis, vocal cord dysfunction (that is the sole cause of respiratory symptoms and at the PI's discretion), severe scoliosis or chest wall deformities that affect lung function, or congenital disorders of the lungs or airways
Unwillingness to follow study procedures
History of allergy or intolerance to study drug
Any other criteria that places the subject at unnecessary risk according to the judgment of the Principal Investigator
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