Sildenafil for PNTM Infection

Pulmonary nontuberculous mycobacterial (PNTM) infection has increased over the past several decades, especially in older women. No consistent immunological abnormalities have been found despite extensive investigation. In cystic fibrosis and primary ciliary dyskinesia, mucociliary dysfunction predisposes individuals to high rates of PNTM disease that increases markedly with age.

We studied the respiratory biology of subjects with PNTM and healthy controls and found decreased levels of nasal nitric oxide (nNO) in vivo. Ex vivo analysis of ciliated respiratory epithelium from subjects with PNTM demonstrated an abnormally low resting ciliary beat frequency (CBF) and an abnormal response to toll-like receptor ([TLR]2,TLR3, TLR5, TLR7/8, and TLR9) agonists, compared with respiratory samples from healthy controls. The low CBF response was normalized ex vivo by augmenting the nitricoxide-cyclic guanosine monophosphate pathway; this supplementation had no appreciable effect on the differences in TLR responses observed in subjects with PNTM and healthy controls. The reduced CBF and nNO levels in these subjects reveal possible mechanisms of susceptibility to respiratory infections, as well as possible avenues of directed investigation and therapy.

This is an open-label, interventional study evaluating the effects of sildenafil on CBF in subjects with PNTM infection. The study will also measure the effects of sildenafil on nNO, and it will evaluate the quality of life, exertional capacity, pulmonary function, lower airway microbiology, inflammatory markers, and the safety and tolerability of sildenafil treatment in this population.

The first 5 subjects will receive an oral bolus of sildenafil (40 mg) on day 0 followed by an oral dose of 20 mg 3 times a day (tid) starting on day 1 for approximately 6 days until the study visit on day 7. The remaining 5 subjects will receive an oral dose of sildenafil (20 mg) tid on day 0 for approximately 1 week until the study visit on day 7. Subsequently, the dose will be increased for all subjects to 40 mg tid and will be administered for another 3 weeks until the study visit on day 30 (4 weeks in total). Administering an initial oral bolus will help us examine sildenafil s immediate effects on CBF and safety parameters. The dosing necessary to modulate CBF in this subject population is not yet known, thus, we feel that undertaking a dose-ranging study will allow a thorough evaluation of sildenafil s effects on CBF.

• INCLUSION CRITERIA:

• Adults (18 years of age or older) with PNTM who are currently enrolled on the 01-I-0202 protocol Natural History, Genetics, Phenotype and Treatment of Mycobacterial Infections will be eligible for participation.
• Subjects must have CBF in the range observed in subjects with PNTM (CBF 8.1 plus or minus 1.4 Hz or lower).
• Women of childbearing potential must have a negative pregnancy test result.
• Women of childbearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry and for the duration of study participation.

Exclusion criteria

• Any subject who, in the opinion of the investigator, is unable or unwilling to comply with the study procedures, medication schedule, or study visits.
• Use of nitrate medicines, other PDE inhibitors, or other drugs known to have unsafe interactions with sildenafil.
• Known allergy to sildenafil.
• History of the following:

• Recurrent epistaxis.
• Diabetes or impaired glucose intolerance (risk of retinal hemorrhage with sildenafil is highest in diabetics).
• Portal hypertension.
• Active pulmonary veno-occlusive disease (PVOD).
• Use of daytime oxygen supplementation.
• Unstable or uncontrolled hypertension.
• Active retinopathy, history of retinal detachment, or hemorrhage.
• Initiation of agents known to be potent CYP3A4 inhibitors or inducers (e.g., itraconazole, ritonavir, ketoconazole).
• Any subject who, in the opinion of the investigator, may be at a greater risk of cardiovascular disease or congestive heart failure.
• Breastfeeding.

Co-Enrollment Guidelines: Subjects will be co-enrolled in the 01-I-0202 protocol. They may also be enrolled in 07-I-0142 entitled Research Respiratory Tract Procedures .Co-enrollment in other trials is restricted, other than enrollment in observational studies or those evaluating the use of a licensed medication. Study staff should be notified of co-enrollment as it may require the approval of the principal investigator.