A double-blind, dose escalation gene transfer trial was conducted in subjects with cystic fibrosis (CF), among whom placebo (saline) or compacted DNA was superfused onto the inferior turbinate of the right or left nostril. The vector consisted of single molecules of plasmid DNA carrying the cystic fibrosis transmembrane regulator- encoding gene compacted into DNA nanoparticles, using polyethylene glycol-substituted 30-mer lysine peptides. Entry criteria included age greater than 18 years, FEV1 exceeding 50% predicted, and basal nasal potential difference (NPD) isoproterenol responses (> or = -5 mV) that are typical for subjects with classic CF. Twelve subjects were enrolled: 2 in dose level I (DLI) (0.8 mg DNA), 4 in DLII (2.67 mg), and 6 in DLIII (8.0 mg). The primary trial end points were safety and tolerability, and secondary gene transfer end points were assessed. In addition to routine clinical assessments and laboratory tests, subjects were serially evaluated for serum IL-6, complement, and C-reactive protein; nasal washings were taken for cell counts, protein, IL-6, and IL-8; and pulmonary function and hearing tests were performed. No serious adverse events occurred, and no events were attributed to compacted DNA. There was no association of serum or nasal washing inflammatory mediators with administration of compacted DNA. Day 14 vector polymerase chain reaction analysis showed a mean value in DLIII nasal scraping samples of 0.58 copy per cell. Partial to complete NPD isoproterenol responses were observed in eight subjects: one of two in DLI, three of four in DLII, and four of six in DLIII. Corrections persisted for as long as 6 days (1 subject to day 28) after gene transfer. In conclusion, compacted DNA nanoparticles can be safely administered to the nares of CF subjects, with evidence of vector gene transfer and partial NPD correction.