To determine the efficacy of PUL-042 Inhalation Solution in decreasing the severity of COVID-19 in subjects: 1) who have documented SARS-CoV-2 infection, and 2) if receiving oxygen, should have pulse oximetry ≥ 93% on 3 liters per minute of oxygen or less delivered by nasal prongs (Ordinal Scale for Clinical Improvement 4 or less) at the time of enrollment.

The primary endpoint analysis is the evaluation of the number of patients with clinically meaningful worsening of COVID-19 within 28 days from the start of experimental therapy, as indicated by an increase of at least 2 points on the Ordinal Scale for Clinical Improvement (OSCI). The OSCI used in this study is derived from a draft scale proposed by the World Health Organization for clinical improvement. Higher values represent a worse outcome.

The OSCI is a nine-point scale (0-8) with 0 being no clinical or virological evidence of infection and 8 being death.

The number of Baseline Participants (99) differs from the numbers in the Participant Flow (101) as two participants were randomized but not treated. The ITT (Intent-to-treat) population is 99 total (49 for PUL-042, 50 for placebo).

SARS-Co-V-2 positivity up to 28 days from the start of experimental therapy.

Analysis Population: number of ITT (Intent-to-Treat) participants with non-missing test results (Positive or Negative) at the end of the study or early termination visit

To determine the difference in the proportion of COVID-19 patients with clinically meaningful worsening of COVID-19 within 14 days from the start of experimental therapy, as indicated by an increase of at least 2 points on the Ordinal Scale for Clinical Improvement (OSCI).

The OSCI is a nine-point scale (0-8) with 0 being no clinical or virological evidence of infection and 8 being death.

The number of Baseline Participants (99) differs from the numbers in the Participant Flow (101) as two participants were randomized but not treated. The ITT (Intent-to-treat) population is 99 total (49 for PUL-042, 50 for placebo).

To assess the progression of COVID-19 severity during the study as measured by the SARS-CoV-2 Symptom Score.

The SARS-CoV-2 Symptom Score measures 3 elements on a 0-3 scale (cough, shortness of breath or difficulty breathing, and muscle aches or fatigue) ranging from 0 for none to 3 for severe. The fourth element is fever and it is rated on a 0-4 scale with 0 being no fever and 4 being life-threatening.

The time to respiratory symptom improvement is measured in days. Time to improvement of symptoms was prospectively defined as the time from an initial symptom score of ≥1 to a reduction of ≥1 point. The time to improvement of symptoms was evaluated for each individual symptom listed above.

Analyzed was the number of ITT participants (total 99) with at least 1 symptom score of >=1 for one symptom (total 92).

The time to resolution of COVID-19 symptoms during the study was measured by the SARS-CoV-2 Symptom Score: The SARS-CoV-2 Symptom Score measures 3 elements on a 0-3 scale (cough, shortness of breath or difficulty breathing, and muscle aches or fatigue) ranging from 0 for none to 3 for severe. The fourth element is fever and it is rated on a 0-4 scale with 0 being no fever and 4 being life-threatening.

The time to the first occurrence of resolution of symptoms (in days) was defined as the time from the first symptom score of ≥1 to a symptom score of 0.

Analyzed was the number of ITT participants (total 99) with at least 1 symptom score of >=1 for one symptom (total 92).

The requirement for ICU admission within 28 days from the start of the experimental therapy.

The number of Baseline Participants (99) differs from the numbers in the Participant Flow (101) as two participants were randomized but not treated. The ITT (Intent-to-treat) population is 99 total (49 for PUL-042, 50 for placebo).

The requirement for mechanical ventilation within 28 days from the start of the experimental therapy.

The number of Baseline Participants (99) differs from the numbers in the Participant Flow (101) as two participants were randomized but not treated. The ITT (Intent-to-treat) population is 99 total (49 for PUL-042, 50 for placebo).

All-cause mortality at 28 days from the start of experimental therapy.

The number of Baseline Participants (99) differs from the numbers in the Participant Flow (101) as two participants were randomized but not treated. The ITT (Intent-to-treat) population is 99 total (49 for PUL-042, 50 for placebo).