['cystic fibrosis']
['p-1037', 'hypertonic saline', 'saline']

        Inclusion Criteria:

          -  Male or female, 12 years of age or older.

          -  Diagnosis of cystic fibrosis as determined by the 1997 CF Consensus criteria (NIH
             Consensus Statement, 1997)

          -  Non-smoker

          -  FEV1 at Screening Visit 1 between 40% and 90%

          -  Stable regimen of CF medications and chest physiotherapy for the 28 days prior to
             Screening. Must be willing to discontinue use of hypertonic saline for the duration of
             the study.

          -  Clinically stable for at least 2 weeks

          -  All females of child-bearing potential must have a negative serum pregnancy test and
             if sexually active must agree to practice a highly effective form of contraception
             throughout the study and for 28 days after the last dose of study medication.

        Exclusion Criteria:

          -  History of any organ transplantation or any significant disease or disorder

          -  Use of diuretics (including amiloride) or renin-angiotensin antihypertensive drugs or
             trimethoprim in the 28 days prior to Screening

          -  History of significant intolerance to inhaled hypertonic saline, as determined by the
             Investigator

          -  Known hypersensitivity to the study drug or amiloride

          -  Any clinically significant laboratory abnormalities at Screening Visit 1 as judged by
             the investigator, or any of the following:

               -  Potassium ≥ 5 milliequivalent per Liter (mEq/L)

               -  Abnormal renal function

               -  Abnormal liver function, defined as ≥ 3 x upper limit of normal (ULN)

               -  Hemoglobin level < 10.0 g/dL

          -  Female who is pregnant or lactating

          -  History of sputum or throat swab culture yielding Burkholderia species or
             Mycobacterium abscessus within 2 years of screening

          -  Has previously participated in an investigational trial involving administration of
             any investigational compound or use of an investigational device with 28 days prior to
             Screening

          -  Currently being treated with any ivacaftor containing regimen
      