Effects of Sildenafil on CFTR-dependent Ion Transport Activity

Study Overview
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Brief Summary
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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.

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

Conditions
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Cystic Fibrosis

Intervention / Treatment
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* Drug: Sildenafil
* Drug: Placebo


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: 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 Male or female subjects ≥ 18 years of age FEV1 ≥ 50% predicted (Hankinson) 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 Ability to reproducibly perform spirometry (according to ATS criteria) Ability to understand and sign a written informed consent or assent and comply with the requirements of the study Willing and able to perform nasal potential difference testing No changes in use of nasal medications within 2 weeks of screening visit If on Orkambi, has been on stable Orkambi dose for at least 4 weeks at day 1. Exclusion Criteria: History of hypersensitivity to sildenafil Use of an investigational agent within the 4-week period prior to Visit 1 (Day 0) 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 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.) Inability to swallow pills Previous lung transplantation Use of concomitant nitrates, α-blocker, or Ca channel blocker Use of concomitant medications known to be potent inhibitors of CYP3A4 (e.g. ketoconazole, itraconazole, ritonavir, clarithromycin, erythromycin, rifampin, verapamil) 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 Weight less than 40 kg History of sputum or throat swab culture yielding Burkholderia cepacia within 2 years of screening History of nasal disease or nasal surgery that would, in the opinion of the investigator, impede accurate measurements of NPD Use of anticoagulant medication (e.g. heparin, coumadin) Resting room air oxygen saturation <93% Use of nighttime oxygen 15) History of migraine headaches 16) Baseline BP of < 90/50 mm Hg

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Sildenafil<br>Subjects will receive escalating doses of sildenafil | Drug: Sildenafil<br>* 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.<br>* Other names: Revatio;|
| Placebo Comparator: Placebo<br>During the placebo arm, subjects receiving placebo will have sham dose escalation to maintain blinding. | Drug: Placebo<br>* Patients receiving placebo will have sham dose escalation to maintain blinding.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in Sodium Conductance by Nasal Potential Difference (NPD) | Amount of sodium transported across the nasal epithelium | Baseline and day 28 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in Chloride Conductance by NPD | Amount of chloride transport across the nasal epithelium | Baseline and day 28 | 
| Change in Sweat Chloride Concentration by Pilocarpine Iontophoresis | Amount of chloride transport across the skin | Baseline and day 28 | 
| Change in Pulmonary Function by Spirometry | ppFEV1 | Baseline and day 28 | 
| Change in Serum Sildenafil Pharmacokinetics | Trough sildenafil levels | Baseline and day 28 | 
| Change in CF Heath Related Quality of Life Questionnaire (CFQ-R) | Respiratory domain of the CFQ-R; The range of scores is 0-100, with higher scores indicating better health. | Baseline and day 28 | 
| Change in Lung Clearance Index | 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 residual capacity (FRC) turnovers required to reduce the end-tidal concentration of nitrogen to 1/40th of the starting concentration and is calculated by dividing the sum of exhaled tidal breaths (cumulative exhaled volume (CEV)) by simultaneously measured FRC. | Baseline and day 28 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Cystic fibrosis, CFTR, Phosphodiesterase inhibitor, Nasal potential difference, Sweat test