The purpose of this study is to confirm the improvement in pulmonary function and cytokine levels observed in the recently completed multidose aerosol study for the treatment of Cystic Fibrosis (CF).

Cystic Fibrosis is an autosomal recessive disorder with an incidence of approximately 1 in 33000 live births. It is due to defects in the CFTR gene, which is located on chromosome 7. Gene Therapy holds the promise of addressing the primary defect in CF by reconstituting the CFTR function in the lung. tgAAVCF, which has been genetically engineered to contain the CFTR gene, has been extremely well tolerated following single and multiple dose administrations to the nose, sinus, and lung. Dose-dependent gene transfer has been demonstrated. Although vector gene expression has not been detected, evidence consistent with biological activity was observed in maxillary sinus study, and statistically significant changes in the FEV1 and IL-8 levels were observed in the recently completed multidose aerosol study. These findings are worthy of further investigation.

Eligible subjects will be randomized to two aerosolized doses of either tgAAVCF or placebo 30 days apart. Subjects will undergo pulmonary function testing every two weeks during the active portion of the study (three months) and will be followed for safety for a total of seven months.