Inhaled Sodium Nitrite as an Antimicrobial for Cystic Fibrosis

Pseudomonas aeruginosa infects the airways of 80% of adults with Cystic Fibrosis (CF). In
these patients, P. aeruginosa forms extremely antibiotic resistant biofilm communities that
accelerate progression of obstructive lung disease. Current treatment of airway infection
focuses on monthly cycles of inhaled antibiotics. However up to 20% of adults are infected
with multi drug resistant P. aeruginosa for which we have no effective inhaled treatments.
These isolates are more common as patients age so with the increasing life expectancy of the
CF population, MDR P. aeruginosa is likely to remain a clinical problem. Another 10% of
patients are infected with other Gram-negative organisms such as Burkholderia cepacia and
Achromobacter species, for which we have inadequate suppressive treatment. Following lung
transplant, MDR airway infections remain a problem as the allografts are colonized by strains
carried in the paranasal sinuses. Sodium nitrite may present a new antimicrobial approach to
treating respiratory infection with Gram-negative organisms, because it is able to prevent
biotic biofilm formation.

Within the CF lung, P. aeruginosa grows as a biotic biofilm in association with airway
epithelial cells and mucous plaques. This environment has an acidic pH and low oxygen tension
with many bacteria subsisting through denitrification (both conditions where traditional
antibiotics are less effective). Because biotic biofilms can be up to 500-fold more resistant
than biofilms grown on abiotic surfaces, with support from our CF Research Development
Program (RDP) Cores, we showed that nitrite prevents biofilm formation on the surface of
primary CF airway epithelial cells. Moreover, nitrite dose-dependently potentiates the
effects of colistin sulfate in liquid culture, and in biotic biofilms on airway epithelial
cells. These data support the hypothesis that nebulized sodium nitrite will inhibit growth of
Pseudomonas aeruginosa in CF airways, and identify a potential therapeutic benefit for
nitrite alone and cooperatively with colistin as a novel therapy to inhibit P. aeruginosa in
CF airways. Nebulized nitrite has been through extensive animal toxicology, and is well
tolerated by subjects with pulmonary arterial hypertension where it is being studied as a
pulmonary vasodilator.

To determine the therapeutic potential of sodium nitrite for CF, we propose two specific
aims:

Aim 1: Determine the safety of nebulized sodium nitrite administered in two doses to patients
with CF.

Aim 2: Explore the effects of inhaled sodium nitrite on measures of lung function, exhaled
airway nitric oxide, and bacterial burden as measured by quantitative sputum cultures.

To accomplish these aims, we propose a Phase I/II open-label study of sodium nitrite in CF.
Key inclusion criteria include individuals over the age 18 with cystic fibrosis as documented
by clinical features of CF, and genotyping or a positive sweat test. Exclusion criteria
include advanced lung disease, inability to discontinue inhaled antibiotics for four weeks,
hospitalization or medication change within 4 weeks of enrollment, baseline systemic
hypotension (SBP<90 mm hg), chronic kidney disease (Cr >2.5), severe anemia (Hgb <9 gm/dL in
the last six months). The primary outcome is safety, defined as FEV1 measured before and
after initial doses on days 0 and 7, and at week 4. Other safety data for the initial doses
include pulse oximetry and transcutaneous methemoglobin levels. Secondary endpoints include
quantitative sputum cultures, exhaled nitric oxide, sputum nitrite concentration, and patient
symptoms as assessed by a CF specific respiratory questionnaire.

Completion of this study will guide the development of sodium nitrite as a single agent for
CF infections, and inform future studies examining the effects of sodium nitrite in
combination with inhaled colistin for patients with drug resistant bacterial pathogens that
are an increasing problem. In addition, the study will provide important safety and efficacy
data that may inform future development of inhaled sodium nitrite as a therapy in young
patients to augment airway host defense and prevent biofilm formation.

Inclusion Criteria:

- Cystic Fibrosis as documented by clinical features, and documentation of a positive
sweat test or two disease causing mutation of the CF gene.

Exclusion Criteria:

- use of supplemental oxygen, FEV1 < 40% predicted, inability to discontinue inhaled
antibiotics for 4 weeks,

- hospitalization within 4 weeks prior to enrollment,

- change in maintenance CF therapies within 4 weeks of enrollment,

- severe anemia, significant chronic liver disease, severe pulmonary hypertension, prior
organ transplantation