Dornase alfa for cystic fibrosis

Effect of Dornase Alfa on the Lung Clearance Index in Children with Cystic Fibrosis: A Lesson from a Case Series

BACKGROUND

Dornase alfa (DNase) is the only mucus-degrading agent that has proven efficacy in cystic fibrosis (CF). Few studies have evaluated the effects of DNase on the lung clearance index (LCI). We report the experience of two CF centers in which LCI monitoring was used to evaluate the efficacy of DNase therapy.

METHODS

This is a prospective and observational study, evaluating the effects of DNase therapy on LCI values in three CF children followed at CF centers in Florence and Catania, Italy. In both centers, LCI was performed routinely, every 3-6 months, based on the clinical picture and severity of the lung disease. In this study, we evaluated the LCI before and after long-term DNase therapy.

RESULTS

DNase improved LCI values in the absence of respiratory exacerbations: in case n. 1 LCI decreased by 39% in 16 months (from 11.1 to 6.8); in case n. 2 by 20% in 12 months (from 9.3 to 7.4); in case n. 3 by 24% in 16 months (from 9.3 to 7.0).

CONCLUSIONS

This case series confirms the efficacy of DNase therapy in CF children, as demonstrated by the LCI reduction in treated patients. Furthermore, our results suggest that LCI is a sensitive marker of disease and can be used for the evaluation of response to treatment.

Use of recombinant human deoxyribonuclease in pediatric intensive care unit - a single-center experience

OBJECTIVE

Dornase alfa (rhDNase) reduces the viscosity of purulent sputum in the lungs. The use in patients with cystic fibrosis (CF) is proven. However, the evidence of its applicability to other conditions is limited. This study aims to present the authors' experience with the use of rhDNase in non-CF patients admitted to the Pediatric Intensive Care Unit (PICU). At the study center, rhDNase was used during flexible bronchoscopies in 24 cases, of which 20 (83%) had atelectasis and seven (29%) were admitted to PICU. Four patients (57%) were on invasive mechanical ventilation (MV).

CASE DESCRIPTION

Two cases of daily rhDNase administration at PICU are presented: patient A was an 8-year-old boy admitted with septic shock and acute respiratory distress syndrome (ARDS). The patient required mechanical ventilation with aggressive settings and experienced several clinical complications. On D50, he started rhDNase treatment with an improvement in FiO2, PaCO2 and PaO2/FiO2 ratio according to radiologic findings. He was extubated on D23 of treatment.Patient B was a 17-month-old girl admitted with a convulsive status epilepticus who experienced respiratory complications (infectious and barotrauma) with ARDS, requiring aggressive ventilation. She initiated rhDNase treatment on D60. During the treatment an improvement in FiO2, PaO2/FiO2 ratio and a tendency of PaCO2 decrease were found. She had radiological improvement. No complications were described.

COMMENTS

RhDNase may be a helpful and safe tool to use in PICU prolonged intubated patients with ventilator-induced lung injury. Further studies are needed to assess and propose valid indications.

Mucus, mucins, and cystic fibrosis

Cystic fibrosis (CF) is both the most common and most lethal genetic disease in the Caucasian population. CF is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene and is characterized by the accumulation of thick, adherent mucus plaques in multiple organs, of which the lungs, gastrointestinal tract and pancreatic ducts are the most commonly affected. A similar pathogenesis cascade is observed in all of these organs: loss of CFTR function leads to altered ion transport, consisting of decreased chloride and bicarbonate secretion via the CFTR channel and increased sodium absorption via epithelial sodium channel upregulation. Mucosa exposed to changes in ionic concentrations sustain severe pathophysiological consequences. Altered mucus biophysical properties and weakened innate defense mechanisms ensue, furthering the progression of the disease. Mucins, the high-molecular-weight glycoproteins responsible for the viscoelastic properties of the mucus, play a key role in the disease but the actual mechanism of mucus accumulation is still undetermined. Multiple hypotheses regarding the impact of CFTR malfunction on mucus have been proposed and are reviewed here. (a) Dehydration increases mucin monomer entanglement, (b) defective Ca²⁺ chelation compromises mucin expansion, (c) ionic changes alter mucin interactions, and (d) reactive oxygen species increase mucin crosslinking. Although one biochemical change may dominate, it is likely that all of these mechanisms play some role in the progression of CF disease. This article discusses recent findings on the initial cause(s) of aberrant mucus properties in CF and examines therapeutic approaches aimed at correcting mucus properties.

Dornase Alfa Ototoxic Effects in Animals and Efficacy in the Treatment of Clogged Tympanostomy Tubes in Children: A Preclinical Study and a Randomized Clinical Trial

Importance

Many treatments for clogged tympanostomy tubes (TTs) have been proposed, but none have met scientific rigor for safety and efficacy, including the popular empirical use of ototopical antibiotic drops. Dornase alfa, a recombinant molecule with the unique property of cleaving DNA, may be ideal in treating clogged TTs because both middle-ear effusion and the plug are abundant with DNA.

Objective

To investigate the ototoxic effects of dornase alfa in a chinchilla model and its efficacy in a clinical trial in children with clogged TTs.

Design, Setting, and Participants

The safety profiles of dornase alfa (full-strength and 1:10 strength) were evaluated in chinchilla middle ears using serial auditory brainstem response. The efficacy of ototopical dornase alfa (full-strength) was evaluated in children with clogged TTs in a prospective, single-blind randomized clinical trial. The animal study included 21 chinchillas and was conducted at Loma Linda University, Loma Linda, California, and the clinical trial was conducted at Children's Hospital Colorado, Aurora. A total of 40 children (50 ears with tubes) were enrolled.

Interventions

In the animal study, chinchillas were assigned to 3 groups: controls (saline), full-strength dornase alfa, or 1:10 dornase alfa dilution. Children were randomly assigned to receive either topical dornase alfa or ofloxacin for clogged TT, 5 drops each ear twice a day for 7 days.

Main Outcomes and Measures

Animal study: Auditory brainstem responses. Randomized trial of children participants: The primary outcome was patency of TT at day 14 assessed by otoscopy and tympanometry.

Results

The chinchilla study showed similar auditory brainstem response degradation during a 6-hour period between the control (n = 5) and treatment groups (n = 21). In the clinical trial, a total of 40 clogged TTs (in 33 children, including 25 boys [76%]; mean age, 4.3 years; median [range] age, 3.4 [1.0-14.3] years) were analyzed. The number of unclogged TTs was higher in the dornase alfa group (13 [59%]) compared with the ofloxacin group (8 [44%]), with a difference of 15% (odds ratio, 1.8; 95% CI, 0.54-6.72).

Conclusions and Relevance

The chinchilla model suggests that dornase alfa is likely nonototoxic. The pilot clinical trial failed to show efficacy of dornase alfa to unclog TTs. With the difference seen between the treatment groups, a sample size estimate could be calculated for a future large-scale trial.

Trial Registration

ClinicalTrials.gov identifier: NCT00419380.