Impact of PEGylation on the mucolytic activity of recombinant human deoxyribonuclease I in cystic fibrosis sputum.

Highly viscous mucus and its impaired clearance characterize the lungs of patients with cystic fibrosis (CF). Pulmonary secretions of patients with CF display increased concentrations of high molecular weight components such as DNA and actin. Recombinant human deoxyribonuclease I (rhDNase) delivered by inhalation cleaves DNA filaments contained in respiratory secretions and thins them. However, rapid clearance of rhDNase from the lungs implies a daily administration and thereby a high therapy burden and a reduced patient compliance. A PEGylated version of rhDNase could sustain the presence of the protein within the lungs and reduce its administration frequency. Here, we evaluated the enzymatic activity of rhDNase conjugated to a two-arm 40 kDa polyethylene glycol (PEG40) in CF sputa. Rheology data indicated that both rhDNase and PEG40-rhDNase presented similar mucolytic activity in CF sputa, independently of the purulence of the sputum samples as well as of their DNA, actin and ions contents. The macroscopic appearance of the samples correlated with the DNA content of the sputa: the more purulent the sample, the higher the DNA concentration. Finally, quantification of the enzymes in CF sputa following rheology measurement suggests that PEGylation largely increases the stability of rhDNase in CF respiratory secretions, since 24-fold more PEG40-rhDNase than rhDNase was recovered from the samples. The present results are considered positive and provide support to the continuation of the research on a long acting version of rhDNase to treat CF lung disease.

Inhalable DNase I microparticles engineered with biologically active excipients.

Highly viscous mucus poses a big challenge for the delivery of particulates carrying therapeutics to patients with cystic fibrosis. In this study, surface modifying DNase I loaded particles using different excipients to achieve better lung deposition, higher enzyme stability or better biological activity had been exploited. For the purpose, controlled release microparticles (MP) were prepared by co-spray drying DNase I with the polymer poly-lactic-co-glycolic acid (PLGA) and the biocompatible lipid surfactant 1,2-dipalmitoyl-Sn-phosphatidyl choline (DPPC) using various hydrophilic excipients. The effect of the included modifiers on the particle morphology, size, zeta potential as well as enzyme encapsulation efficiency, biological activity and release had been evaluated. Powder aerosolisation performance and particle phagocytosis by murine macrophages were also investigated. The results showed that more than 80% of enzyme activity was recovered after MP preparation and that selected surface modifiers greatly increased the enzyme encapsulation efficiency. The particle morphology was greatly modified altering in turn the powders inhalation indices where dextran, ovalbumin and chitosan hydrochloride increased considerably the respirable fraction compared to the normal hydrophilic carriers lactose and PVP. Despite of the improved aerosolisation caused by chitosan hydrochloride, yet retardation of chitosan coated particles in artificial mucus samples discouraged its application. On the other hand, dextran and polyanions enhanced DNase I effect in reducing cystic fibrosis mucus viscosity. DPPC proved good ability to reduce particles phagocytic uptake even in the presence of the selected adjuvants. The prepared MP systems were biocompatible with lung epithelial cells. To conclude, controlled release DNase I loaded PLGA-MP with high inhalation indices and enhanced mucolytic activity on CF sputum could be obtained by surface modifying the particles with PGA or dextran.

Inhalable antibiotic delivery using a dry powder co-delivering recombinant deoxyribonuclease and ciprofloxacin for treatment of cystic fibrosis.

PURPOSE: To achieve efficient antibiotic delivery to the cystic fibrosis (CF) airway using a single inhalable powder co-encapsulating a mucolytic and an antibiotic. METHODS: Inhalable dry powders containing deoxyribonuclease and/or ciprofloxacin (DNase, Cipro, and DNase/Cipro powders) were produced by spray-drying with dipalmitylphosphatidylcholine, albumin, and lactose as excipients, and their antibacterial effects were evaluated using the artificial sputum model. RESULTS: All powders showed mass median aerodynamic diameters below 5 microm. Both drugs were loaded in the dry powders without loss in quantity and activity. Dry powders containing DNase significantly decreased the storage modulus of the artificial sputum medium in less than 30 min. When applied to artificial sputum laden with Pseudomonas aeruginosa, Cipro/DNase powder showed better antibacterial activity than Cipro powder. The higher activity of the Cipro/DNase powder is attributable to the mucolytic activity of DNase, which promotes penetration of the dry powder into the artificial sputum and efficient dissolution and diffusion of ciprofloxacin. CONCLUSIONS: Inhalational delivery of antibiotics to the CF airway can be optimized when the sputum barrier is concomitantly addressed. Co-delivery of antibiotics and DNase using an inhalable particle system may be a promising strategy for local antipseudomonal therapy in the CF airway.

On the transport of lipoplexes through cystic fibrosis sputum.

PURPOSE: The aim of this study was to examine the extent to which plasmid DNA (pDNA) complexed to cationic liposomes diffuse through cystic fibrosis (CF) sputum. The influence of the physical and chemical properties of the sputa was evaluated. We further investigated whether degradation of the sputa by recombinant human DNase I (rhDNase I) enhances the transport. METHODS: The transport of lipoplexes was studied through layers of CF sputa placed between the donor and acceptor compartment of vertical diffusion chambers. The content of the acceptor compartment was analyzed by confocal fluorescence microscopy, gel electrophoresis and Southern blotting. The influence of linear DNA present in the CF sputa on the size, surface charge and gene expression of the lipoplexes was evaluated by dynamic light scattering, particle electrophoresis and transfection experiments. RESULTS: Lipoplexes were observed in the acceptor compartments. However, the percent of diffused lipoplexes was low: 0.05/% +/- 0.01%. It was found that both steric obstruction by the sputa as well as the long" distance the lipoplexes have to travel were responsible for this low transport. Surprisingly, the transport occurred better through more viscoelastic sputa. The DNA in the CF sputa also retarded the transport, which was attributed to aggregation of the lipoplexes by the DNA. Finally, rhDNase I moderately enhanced the diffusion of lipoplexes. CONCLUSIONS: CF sputum drastically retards the diffusion of lipoplexes. DNA in the sputa aggregates the lipoplexes. This may lower the transport of lipoplexes through the sputa and gene expression. Pretreatment of CF patients with rhDNase I may enhance the efficiency of CF gene therapy, as it allows a better transport of the lipoplexes through the sputum and as it partly removes the sputum which will result in a thinner sputum layer on top of the epithelial cells.

RhDNase I aerosol deposition and related factors in cystic fibrosis.

To identify factors influencing lung dose of aerosolized recombinant human deoxyribonuclease (rhDNase I), we used gamma camera and filter techniques to measure deposition in 15 clinically stable patients with cystic fibrosis (CF) (five males and 10 females, age 6-31 yr, mean 16.9) who were on chronic daily therapy. Total and regional deposition were correlated with breathing pattern, pulmonary function, demographic factors, and disease severity. In addition, the effects of each patient's measured lung dose on pulmonary function was estimated by stopping the drug and observing changes in spirometry over a 2-wk follow-up period. After discontinuance of the drug, all patients reported worsening of dyspnea and difficulty producing sputum. There was a significant decrease in FEV1 (% predicted, mean +/- SE, 86.9% +/- 5.57 to 77.8% +/- 5.73, p < 0.005), but all patients completed the study. In some patients, as much as 48% of the deposited aerosol was found in the pharynx (range 0.0 to 0.30 mg, mean 0.089 mg +/- 0.029), and pharyngeal deposition correlated negatively with tidal volume (r = -0.696, p < 0.006) and age (r = -0.743, p < 0.005). For the lungs, deposition ranged between 0.16 mg and 0.78 mg of the 2.5 mg nebulizer dose (mean 0.47 +/- 0.04 mg) and correlated negatively with FEV1 (% predicted, r = -0.611, p = 0.0152). However, the spirometric decrements following cessation of therapy did not correlate with the lung dose of the drug. Analysis of regional deposition within the lungs indicated a wide range of distribution between central and peripheral zones. In conclusion, the deposition pattern of rhDNase I aerosols in patients with CF is largely influenced by respiratory physiology, which itself depends upon age and severity of lung disease. As the patients grow there is a decrease in upper airway deposition and more particles are presented to the lungs where those patients with more airways disease have enhanced pulmonary deposition. Upper airway deposition of rhDNase I is significant, especially in younger patients, and may be related to laryngeal side effects.

Effect of rhDNase on airflow obstruction and mucociliary clearance in cystic fibrosis.

We tested the hypothesis that recombinant human deoxyribonuclease 1 (rhDNase) reduces airflow obstruction and improves mucociliary clearance in patients with cystic fibrosis (CF), and that improvements seen in FEV1 and FVC after rhDNase treatment are independent of chest physical therapy (CPT). CF patients inhaled placebo (10 patients) or 2.5 mg rhDNAse aerosol (10 patients) twice a day for six consecutive days. Compared with baseline, there were no statistically significant differences between the two study groups by Day 6 for indices of airflow obstruction obtained from gamma-camera images of the right lung following inhalation of 99mTc aerosol, or for mucociliary clearance or the rate of clearance of the radioaerosol, quantified over a 6-h period. By Day 6, FEV1 and FVC were significantly higher in the rhDNase-treated group than in the placebo group, increasing by an average of 9.4 +/- 3.5% and 12.7 +/- 2.6%, respectively, as compared with a decrease of 1.8 +/- 1.7% and an increase of 0.4 +/- 1.1%, respectively (p < 0.05). There was no significant change in the FEV1/FVC ratio on Day 6 (0.68 +/- 0.05) compared with baseline (0.70 +/- 0.05) in the rhDNase group. On Day 6, FEV1 and FVC decreased after CPT in both study groups, but the decreases were not significant. Our results indicate that aerosolized rhDNase improves FEV1 and FVC independent of CPT. We were unable to demonstrate that rhDNase reduces airflow obstruction or improves mucociliary clearance.

Dornase alfa: a new option in the management of cystic fibrosis.

Recombinant human DNase I, or dornase alfa, is the first new therapy developed specifically for cystic fibrosis in almost 30 years. It selectively digests extracellular DNA and reduces the viscosity of purulent sputum. In clinical trials dornase alfa modestly improved pulmonary function, slightly decreasing the number of respiratory exacerbations requiring parenteral antibiotics compared with placebo. Phase III studies suggest that patients receiving dornase alfa also spend slightly fewer days in the hospital than those treated with placebo. The aerosolized preparation is safe and generally well tolerated. Voice alteration and sore throat are the most commonly reported adverse effects. Further research is necessary to determine the optimum time to initiate therapy and to evaluate the agent's pharmacoeconomic impact on the treatment of cystic fibrosis. Aerosolized dornase alfa should always be given in conjunction with standard cystic fibrosis therapies including antibiotics, chest physiotherapy, and pancreatic enzyme supplementation.

Dornase alfa. A review of its pharmacological properties and therapeutic potential in cystic fibrosis.

By cleaving neutrophil-derived DNA present in the infected lungs of patients with cystic fibrosis (CF), dornase alfa (recombinant human deoxyribonuclease I) reduces the adhesiveness and viscoelasticity of CF sputum. Well designed clinical studies performed in patients with CF and mild to moderate pulmonary disease [forced vital capacity (FVC) > or = 40% of predicted value] show that aerosolised dornase alfa improves lung function, achieving a 6 to 7% increase from baseline in forced expiratory volume in 1 second (FEV1) after 6 months' therapy. Improvements in general well-being and CF-related symptoms were also noted by patients. Importantly, dornase alfa reduced the relative risk of respiratory exacerbations requiring parenteral antibiotics by 22 to 34% compared with placebo. Short term studies with dornase alfa in patients with more severe pulmonary disease (FVC < 40% of predicted value) and in those with acute infectious exacerbations did not reveal any significant improvements in pulmonary function, although long term studies are required to fully determine efficacy. Voice alteration, laryngitis or rash may develop with dornase alfa therapy, although more clinical experience with the agent is required to define its tolerability profile. Anaphylaxis has not been reported with dornase alfa to date. In summary, aerosolised dornase alfa offers modest improvements in lung function and, importantly, a reduced risk of respiratory exacerbations in patients with CF and an FVC > or = 40% of the predicted value, thus representing an important adjunct agent in this patient group.