Expired Study
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Denver, Colorado 80206


Dehydrated airway surfaces resulting from sodium hyperabsorption and lack of chloride secretion are critical to the pathology that leads to the morbidity and mortality from Cystic Fibrosis (CF) lung disease. Previously published work in CF cell lines has demonstrated that by increasing cGMP and restoring inhibition of ENaC, sodium hyperabsorption may be reversed following administration of a phosphodiesterase inhibitor (PDEi,) such as sildenafil. Additionally it has been shown in CF cell lines and animal models, that phosphodiesterase inhibitors/analogues can enhance chloride secretion and/or correct surface localization of ΔF508 CFTR. The goal of this project is to translate the results of this work from the laboratory into a clinical trial in patients with CF using an FDA-approved therapy. The Specific Aims of this project are to: 1) Evaluate the effect of systemically administered phosphodiesterase inhibitors on ion transport in CF by measurement of Na+ and Cl- conductance by NPD and Na+ and Cl- concentration in sweat utilizing pilocarpine iontophoresis 2) To establish appropriate dosing of sildenafil in CF by performing a dose-escalation study during which patients are carefully monitored for side effects, plasma sildenafil levels are obtained and outcome measures are compared based on the dose of sildenafil administered. The results of this study in conjunction with those from an ongoing study examining the role of sildenafil as an anti-inflammatory in CF will aid in establishing safety, pharmacokinetics and mechanism of action of sildenafil in the treatment of CF lung disease.


Inclusion Criteria: 1. Confirmed diagnosis of CF based on the following criteria: Positive sweat chloride ≥60mEq/liter (by pilocarpine iontophoresis) and genotype with two F508del CFTR mutations, and accompanied by one or more clinical features consistent with the CF phenotype 2. Male or female subjects ≥ 18 years of age 3. FEV1 ≥ 50% predicted (Hankinson) 4. Clinically stable without evidence of acute upper or lower respiratory tract infection or current pulmonary exacerbation within the 14 days prior to the screening visit 5. Ability to reproducibly perform spirometry (according to ATS criteria) 6. Ability to understand and sign a written informed consent or assent and comply with the requirements of the study 7. Willing and able to perform nasal potential difference testing 8. No changes in use of nasal medications within 2 weeks of screening visit 9. If on Orkambi, has been on stable Orkambi dose for at least 4 weeks at day 1. Exclusion Criteria: 1. History of hypersensitivity to sildenafil 2. Use of an investigational agent within the 4-week period prior to Visit 1 (Day 0) 3. Breastfeeding, pregnant, or verbal expression of unwillingness to practice an acceptable birth control method (abstinence, hormonal or barrier methods, partner sterilization or intrauterine device) during participation in the study 4. History of significant hepatic (SGOT or SGPT > 3 times the upper limit of normal at screening, documented biliary cirrhosis, or portal hypertension), cardiovascular (history of aortic stenosis, coronary artery disease, pulmonary hypertension with right ventricular systolic pressure >55 mmHg or life-threatening arrhythmia), neurological (history of stroke), hematologic (history of bleeding diathesis), ophthalmologic (history of retinal impairment or non-arteritic ischemic optic neuritis) or renal impairment (creatinine >1.8 mg/dL.) 5. Inability to swallow pills 6. Previous lung transplantation 7. Use of concomitant nitrates, α-blocker, or Ca channel blocker 8. Use of concomitant medications known to be potent inhibitors of CYP3A4 (e.g. ketoconazole, itraconazole, ritonavir, clarithromycin, erythromycin, rifampin, verapamil) 9. Presence of a condition or abnormality that in the opinion of the investigator would compromise the safety of the subject or the quality of the data 10. Weight less than 40 kg 11. History of sputum or throat swab culture yielding Burkholderia cepacia within 2 years of screening 12. History of nasal disease or nasal surgery that would, in the opinion of the investigator, impede accurate measurements of NPD 13. Use of anticoagulant medication (e.g. heparin, coumadin) 14. Resting room air oxygen saturation <93% 15. Use of nighttime oxygen 15) History of migraine headaches 16) Baseline BP of < 90/50 mm Hg

Study is Available At:

Original ID:

Sildenafil CFTR



Secondary ID:

Study Acronym:

Brief Title:

Effects of Sildenafil on CFTR-dependent Ion Transport Activity

Official Title:

Phase II Study of the Effects of Sildenafil on CFTR-dependent Ion Transport Activity

Overall Status:


Study Phase:

Phase 2



Minimum Age:

18 Years

Maximum Age:


Quick Facts

Healthy Volunteers
Oversight Has DMC
Study Is FDA Regulated
Study Is Section 801
Has Expanded Access

Study Source:

National Jewish Health

Oversight Authority:

  • United States: Food and Drug Administration
  • United States: Cystic Fibrosis Foundation

Reasons Why Stopped:

Study Type:


Study Design:

Number of Arms:


Number of Groups:


Total Enrollment:


Enrollment Type:


Overall Contact Information

Official Name:Jennifer L Taylor-Cousar, MD
Principal Investigator
National Jewish Health

Study Dates

Start Date:October 2015
Completion Date:May 2017
Completion Type:Actual
Primary Completion Date:May 2017
Primary Completion Type:Actual
Verification Date:March 2019
Last Changed Date:March 2, 2019
First Received Date:April 16, 2010
First Results Date:September 6, 2018

Study Outcomes

Outcome Type:Secondary Outcome
Measure:Change in Lung Clearance Index
Time Frame:Baseline and day 28
Safety Issues:False
Description:The lung clearance index (LCI) measures how long it takes for an inert gas (e.g. nitrogen) to be washed out of the lungs during relaxed tidal breathing. A higher value of the LCI indicates worse disease. LCI is calculated as the number of functional resid
Outcome Type:Secondary Outcome
Measure:Change in CF Heath Related Quality of Life Questionnaire (CFQ-R)
Time Frame:Baseline and day 28
Safety Issues:False
Description:Respiratory domain of the CFQ-R; The range of scores is 0-100, with higher scores indicating better health.
Outcome Type:Secondary Outcome
Measure:Change in Serum Sildenafil Pharmacokinetics
Time Frame:Baseline and day 28
Safety Issues:False
Description:Trough sildenafil levels
Outcome Type:Secondary Outcome
Measure:Change in Pulmonary Function by Spirometry
Time Frame:Baseline and day 28
Safety Issues:False
Outcome Type:Secondary Outcome
Measure:Change in Sweat Chloride Concentration by Pilocarpine Iontophoresis
Time Frame:Baseline and day 28
Safety Issues:False
Description:Amount of chloride transport across the skin
Outcome Type:Secondary Outcome
Measure:Change in Chloride Conductance by NPD
Time Frame:Baseline and day 28
Safety Issues:False
Description:Amount of chloride transport across the nasal epithelium
Outcome Type:Primary Outcome
Measure:Change in Sodium Conductance by Nasal Potential Difference (NPD)
Time Frame:Baseline and day 28
Safety Issues:False
Description:Amount of sodium transported across the nasal epithelium

Study Interventions

Intervention Type:Drug
Description:During the course of the study, patients will receive 4 weeks of therapy: 28 days of placebo orally t.i.d. or 28 days of days of sildenafil orally t.i.d. Dosing of sildenafil will be escalated after the first week (20 mg orally t.i.d for the first week, then subjects will take 40 mg orally t.i.d. for 3 weeks). Patients not tolerating dose escalation will be discontinued from the study.
Arm Name:Sildenafil
Other Name:Revatio
Intervention Type:Drug
Description:Patients receiving placebo will have sham dose escalation to maintain blinding.
Arm Name:Placebo

Study Arms

Study Arm Type:Experimental
Arm Name:Sildenafil
Description:Subjects will receive escalating doses of sildenafil
Study Arm Type:Placebo Comparator
Arm Name:Placebo
Description:During the placebo arm, subjects receiving placebo will have sham dose escalation to maintain blinding.

Study Agencies

Agency Class:Other
Agency Type:Lead Sponsor
Agency Name:National Jewish Health

Sample and Retention Information

There are no available Sample and Retention Information

Study References

Reference Type:Reference
Citation:Robert R, Carlile GW, Pavel C, Liu N, Anjos SM, Liao J, Luo Y, Zhang D, Thomas DY, Hanrahan JW. Structural analog of sildenafil identified as a novel corrector of the F508del-CFTR trafficking defect. Mol Pharmacol. 2008 Feb;73(2):478-89. Epub 2007 Nov 1.
Reference Type:Reference
Citation:Dormer RL, Harris CM, Clark Z, Pereira MM, Doull IJ, Norez C, Becq F, McPherson MA. Sildenafil (Viagra) corrects DeltaF508-CFTR location in nasal epithelial cells from patients with cystic fibrosis. Thorax. 2005 Jan;60(1):55-9.
Reference Type:Reference
Citation:Lubamba B, Lecourt H, Lebacq J, Lebecque P, De Jonge H, Wallemacq P, Leal T. Preclinical evidence that sildenafil and vardenafil activate chloride transport in cystic fibrosis. Am J Respir Crit Care Med. 2008 Mar 1;177(5):506-15. Epub 2007 Nov 15.
Reference Type:Reference
Citation:Poschet JF, Timmins GS, Taylor-Cousar JL, Ornatowski W, Fazio J, Perkett E, Wilson KR, Yu HD, de Jonge HR, Deretic V. Pharmacological modulation of cGMP levels by phosphodiesterase 5 inhibitors as a therapeutic strategy for treatment of respiratory pathology in cystic fibrosis. Am J Physiol Lung Cell Mol Physiol. 2007 Sep;293(3):L712-9. Epub 2007 Jun 22.
Reference Type:Reference
Citation:Poschet JF, Fazio JA, Timmins GS, Ornatowski W, Perkett E, Delgado M, Deretic V. Endosomal hyperacidification in cystic fibrosis is due to defective nitric oxide-cylic GMP signalling cascade. EMBO Rep. 2006 May;7(5):553-9. Epub 2006 Apr 13.
Reference Type:Reference
Citation:Taylor-Cousar JL, Wiley C, Felton LA, St Clair C, Jones M, Curran-Everett D, Poch K, Nichols DP, Solomon GM, Saavedra MT, Accurso FJ, Nick JA. Pharmacokinetics and tolerability of oral sildenafil in adults with cystic fibrosis lung disease. J Cyst Fibros. 2015 Mar;14(2):228-36. doi: 10.1016/j.jcf.2014.10.006. Epub 2014 Nov 13.

Data Source: ClinicalTrials.gov

Date Processed: October 09, 2019

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