Trial Outcomes & Findings for Safety and Efficacy of Sildenafil in Cystic Fibrosis (CF) Lung Disease (NCT NCT00659529)

Last Updated: 2026-05-14

Results Overview

Exploratory analysis for efficacy of sildenafil on sputum biomarkers of inflammation, including sputum elastase. This measure will indicate whether sildenafil will increase or decrease sputum elastase activity.

Recruitment status

COMPLETED

Study phase

PHASE1/PHASE2

Target enrollment

36 participants

Primary outcome timeframe

Baseline and 6 weeks

Results posted on

2026-05-14

Participant Flow

Participant milestones

Participant milestones
Measure	Open-label (All Subjects) All subjects will receive oral sildenafil three times per day during the study. Study endpoints will be measured before the treatment period and at the end of the treatment period. sildenafil: Sildenafil will be given 20mg po tid for 1 week, and then will be give 40mg po tid for 5 weeks.
Overall Study STARTED	36
Overall Study Received at least one dose of study drug	27
Overall Study COMPLETED	20
Overall Study NOT COMPLETED	16

Reasons for withdrawal

Reasons for withdrawal
Measure	Open-label (All Subjects) All subjects will receive oral sildenafil three times per day during the study. Study endpoints will be measured before the treatment period and at the end of the treatment period. sildenafil: Sildenafil will be given 20mg po tid for 1 week, and then will be give 40mg po tid for 5 weeks.
Overall Study Withdrawal by Subject	4
Overall Study Protocol Violation	3
Overall Study Screen failure	9

Baseline Characteristics

Safety and Efficacy of Sildenafil in Cystic Fibrosis (CF) Lung Disease

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure	Open-label (All Subjects) n=27 Participants All subjects will receive oral sildenafil three times per day during the study. Study endpoints will be measured before the treatment period and at the end of the treatment period. sildenafil: Sildenafil will be given 20mg po tid for 1 week, and then will be give 40mg po tid for 5 weeks.
Age, Continuous	25.7 years STANDARD_DEVIATION 5.5 • n=1512 Participants
Sex: Female, Male Female	16 Participants n=1512 Participants
Sex: Female, Male Male	11 Participants n=1512 Participants
FEV1% predicted	77.5 % predicted STANDARD_DEVIATION 19.6 • n=1512 Participants

PRIMARY outcome

Timeframe: Baseline and 6 weeks

Population: Subjects who completed 6 weeks of sildenafil and had available data for pre/post 6 weeks of sildenafil were analyzed. One subject presented to the final study visit with 1 week of previously unreported symptoms consistent with pulmonary exacerbation, and therefore, efficacy data was not analyzed on that subject as pre-specified in the protocol.

Outcome measures

Outcome measures
Measure	Open-label (All Subjects) n=18 Participants All subjects will receive oral sildenafil three times per day during the study. Study endpoints will be measured before the treatment period and at the end of the treatment period. sildenafil: Sildenafil will be given 20mg po tid for 1 week, and then will be give 40mg po tid for 5 weeks.
Change in Sputum Elastase Activity	-57 micrograms/mL Interval -119.0 to -18.0

SECONDARY outcome

Timeframe: Baseline and 6 weeks

Endogenous airway acidification can be assessed by measuring pH in exhaled breath condensate, a non-invasive measure of response to therapy. This measure will indicate whether sildenafil will improve, worsen, or cause no change in exhaled breath condensate pH.

Outcome measures

Outcome measures
Measure	Open-label (All Subjects) n=18 Participants All subjects will receive oral sildenafil three times per day during the study. Study endpoints will be measured before the treatment period and at the end of the treatment period. sildenafil: Sildenafil will be given 20mg po tid for 1 week, and then will be give 40mg po tid for 5 weeks.
Change in Exhaled Breath Condensate pH	-0.09 pH Interval -0.29 to 0.11

SECONDARY outcome

Timeframe: 6 weeks

Population: Subjects who completed 6 weeks of sildenafil and had available data for pre/post 6 weeks of sildenafil were analyzed.

The CFQ-R is designed to measure CF-specific patient-reported health-related quality of life. It is a validated CF-specific quality of life measure. The CFQ-R Respiratory domain score (scale 0-100 with higher scores indicating better quality of life). This measure will indicate whether sildenafil will improve, worsen, or cause no change in the CFQ-R respiratory domain scores from baseline at 6 weeks.

Outcome measures

Outcome measures
Measure	Open-label (All Subjects) n=19 Participants All subjects will receive oral sildenafil three times per day during the study. Study endpoints will be measured before the treatment period and at the end of the treatment period. sildenafil: Sildenafil will be given 20mg po tid for 1 week, and then will be give 40mg po tid for 5 weeks.
Change in Cystic Fibrosis Questionnaire - Revised (CFQ-R) Respiratory Domain, Average Unit Change From Baseline to 6 Weeks is Reported	0.3 units on a scale Interval -4.4 to 4.7

Adverse Events

Open-label (All Subjects)

Serious events: 2 serious events

Other events: 24 other events

Deaths: 0 deaths

Serious adverse events

Serious adverse events
Measure	Open-label (All Subjects) n=27 participants at risk All subjects will receive oral sildenafil three times per day during the study. Study endpoints will be measured before the treatment period and at the end of the treatment period. sildenafil: Sildenafil will be given 20mg po tid for 1 week, and then will be give 40mg po tid for 5 weeks.
Respiratory, thoracic and mediastinal disorders CF pulmonary exacerbation	7.4% 2/27 • Number of events 2 • All subjects who had at least one protocol-imposed intervention and/or received at least one dose of Sildenafil until the end of follow-up, up to 14 weeks.. Adverse events are defined as any unfavorable and unintended sign, symptom, or disease temporally associated with the use of Sildenfil/Revatio or other protocol-imposed intervention, regardless of attribution. Participants were questioned and/or examined by the Investigator, with monitoring of clinical assessments and laboratory tests completed as needed, followed to resolution or stabilization of the event(s).
Gastrointestinal disorders Distal Intestinal Obstruction Syndrome	3.7% 1/27 • Number of events 1 • All subjects who had at least one protocol-imposed intervention and/or received at least one dose of Sildenafil until the end of follow-up, up to 14 weeks.. Adverse events are defined as any unfavorable and unintended sign, symptom, or disease temporally associated with the use of Sildenfil/Revatio or other protocol-imposed intervention, regardless of attribution. Participants were questioned and/or examined by the Investigator, with monitoring of clinical assessments and laboratory tests completed as needed, followed to resolution or stabilization of the event(s).

Other adverse events

Other adverse events
Measure	Open-label (All Subjects) n=27 participants at risk All subjects will receive oral sildenafil three times per day during the study. Study endpoints will be measured before the treatment period and at the end of the treatment period. sildenafil: Sildenafil will be given 20mg po tid for 1 week, and then will be give 40mg po tid for 5 weeks.
Nervous system disorders headache	22.2% 6/27 • All subjects who had at least one protocol-imposed intervention and/or received at least one dose of Sildenafil until the end of follow-up, up to 14 weeks.. Adverse events are defined as any unfavorable and unintended sign, symptom, or disease temporally associated with the use of Sildenfil/Revatio or other protocol-imposed intervention, regardless of attribution. Participants were questioned and/or examined by the Investigator, with monitoring of clinical assessments and laboratory tests completed as needed, followed to resolution or stabilization of the event(s).
Respiratory, thoracic and mediastinal disorders rhinorhhea/congestion	33.3% 9/27 • All subjects who had at least one protocol-imposed intervention and/or received at least one dose of Sildenafil until the end of follow-up, up to 14 weeks.. Adverse events are defined as any unfavorable and unintended sign, symptom, or disease temporally associated with the use of Sildenfil/Revatio or other protocol-imposed intervention, regardless of attribution. Participants were questioned and/or examined by the Investigator, with monitoring of clinical assessments and laboratory tests completed as needed, followed to resolution or stabilization of the event(s).
General disorders Sore throat/throat clearing	22.2% 6/27 • All subjects who had at least one protocol-imposed intervention and/or received at least one dose of Sildenafil until the end of follow-up, up to 14 weeks.. Adverse events are defined as any unfavorable and unintended sign, symptom, or disease temporally associated with the use of Sildenfil/Revatio or other protocol-imposed intervention, regardless of attribution. Participants were questioned and/or examined by the Investigator, with monitoring of clinical assessments and laboratory tests completed as needed, followed to resolution or stabilization of the event(s).
Respiratory, thoracic and mediastinal disorders Increased cough	22.2% 6/27 • All subjects who had at least one protocol-imposed intervention and/or received at least one dose of Sildenafil until the end of follow-up, up to 14 weeks.. Adverse events are defined as any unfavorable and unintended sign, symptom, or disease temporally associated with the use of Sildenfil/Revatio or other protocol-imposed intervention, regardless of attribution. Participants were questioned and/or examined by the Investigator, with monitoring of clinical assessments and laboratory tests completed as needed, followed to resolution or stabilization of the event(s).
General disorders Flushing	18.5% 5/27 • All subjects who had at least one protocol-imposed intervention and/or received at least one dose of Sildenafil until the end of follow-up, up to 14 weeks.. Adverse events are defined as any unfavorable and unintended sign, symptom, or disease temporally associated with the use of Sildenfil/Revatio or other protocol-imposed intervention, regardless of attribution. Participants were questioned and/or examined by the Investigator, with monitoring of clinical assessments and laboratory tests completed as needed, followed to resolution or stabilization of the event(s).
Gastrointestinal disorders dyspepsia	14.8% 4/27 • All subjects who had at least one protocol-imposed intervention and/or received at least one dose of Sildenafil until the end of follow-up, up to 14 weeks.. Adverse events are defined as any unfavorable and unintended sign, symptom, or disease temporally associated with the use of Sildenfil/Revatio or other protocol-imposed intervention, regardless of attribution. Participants were questioned and/or examined by the Investigator, with monitoring of clinical assessments and laboratory tests completed as needed, followed to resolution or stabilization of the event(s).
Musculoskeletal and connective tissue disorders myalgia	14.8% 4/27 • All subjects who had at least one protocol-imposed intervention and/or received at least one dose of Sildenafil until the end of follow-up, up to 14 weeks.. Adverse events are defined as any unfavorable and unintended sign, symptom, or disease temporally associated with the use of Sildenfil/Revatio or other protocol-imposed intervention, regardless of attribution. Participants were questioned and/or examined by the Investigator, with monitoring of clinical assessments and laboratory tests completed as needed, followed to resolution or stabilization of the event(s).
Respiratory, thoracic and mediastinal disorders Increased/thicker sputum	14.8% 4/27 • All subjects who had at least one protocol-imposed intervention and/or received at least one dose of Sildenafil until the end of follow-up, up to 14 weeks.. Adverse events are defined as any unfavorable and unintended sign, symptom, or disease temporally associated with the use of Sildenfil/Revatio or other protocol-imposed intervention, regardless of attribution. Participants were questioned and/or examined by the Investigator, with monitoring of clinical assessments and laboratory tests completed as needed, followed to resolution or stabilization of the event(s).
General disorders Insomnia	11.1% 3/27 • All subjects who had at least one protocol-imposed intervention and/or received at least one dose of Sildenafil until the end of follow-up, up to 14 weeks.. Adverse events are defined as any unfavorable and unintended sign, symptom, or disease temporally associated with the use of Sildenfil/Revatio or other protocol-imposed intervention, regardless of attribution. Participants were questioned and/or examined by the Investigator, with monitoring of clinical assessments and laboratory tests completed as needed, followed to resolution or stabilization of the event(s).
Respiratory, thoracic and mediastinal disorders Chest tigntness/congestion	7.4% 2/27 • All subjects who had at least one protocol-imposed intervention and/or received at least one dose of Sildenafil until the end of follow-up, up to 14 weeks.. Adverse events are defined as any unfavorable and unintended sign, symptom, or disease temporally associated with the use of Sildenfil/Revatio or other protocol-imposed intervention, regardless of attribution. Participants were questioned and/or examined by the Investigator, with monitoring of clinical assessments and laboratory tests completed as needed, followed to resolution or stabilization of the event(s).

Additional Information

Jennifer L. Taylor-Cousar, MD

National Jewish Health

Phone: (303) 270-2764

Email: [email protected]

Results disclosure agreements

Principal investigator is a sponsor employee
Publication restrictions are in place