This is a double-blind, randomised, 2 single-doses and then repeated-dose (5 days), 2-arm, 2-period crossover phase 1 study in 24 healthy male or female subjects. Subjects will be randomised to one of two treatment sequences in 2 treatment periods: JHL1922 (test treatment) first and then Pulmozyme (reference treatment) or Pulmozyme (reference treatment) first and then JHL1922 (test treatment).

All 24 subjects will receive either JHL1922 or Pulmozyme as single doses of 2.5 mg and then 10 mg per eRapid nebulizer, followed after a washout by a 5-period of daily dosing of 10 mg of either JHL1922 or Pulmozyme per eRapid nebulizer.

The primary objective is to assess the similarity of safety and tolerability of test products, and the exploratory objective is to assess the similarity, if possible, of the systemic levels and sputum levels of dornase alfa after administration of test products.

Inclusion Criteria:

• 18-70 years, inclusive
• Body Mass Index: 18.0-30.0 kg/m2, inclusive
• Weight: between 55 and 105 kg
• Condition: healthy; normal pulmonary function by spirometry

Exclusion Criteria:

- Any medical condition that presents a potential risk to the subject and/or that may compromise the objectives of the study, incl. active, or history of, pulmonary disorders incl. asthma or chronic obstructive pulmonary disease (COPD)