The purpose of this study is to determine if an investigational drug, AT-100, can reduce the occurrence of Bronchopulmonary Dysplasia (BPD) in babies born premature, as compared to babies born premature who receive an air-sham alone.

Inclusion Criteria

1. Preterm neonates born between Gestional Age (GA):

   1. 25 0/7 weeks to 28 6/7 weeks in the initial dose escalation cohorts.
   2. 23 0/7 weeks to 28 6/7 weeks in the latter cohort.

2. Intubated and on mechanical ventilation.

3. Receiving at least 1 dose of standard-of-care-indicated surfactant treatment (Curosurf®) after birth, and able to receive the first dose of AT-100 or air-sham within 96 hours of birth given at any time point after 15 minutes following any of the subject's Curosurf® dose(s).

4. Parent or legal guardian is able to provide informed consent.

Exclusion Criteria:

1. Weight at time of birth < 400 g or > 1,800 g.

2. Major apparent congenital abnormalities impacting cardio and pulmonary function.

3. Active DNR (Do Not Resuscitate) order in place.

4. Known pulmonary air leaks (e.g. pneumothorax and pneumomediastinum) at the time of AT-100 or air-sham administration.

5. History of allergy or sensitivity to any surfactant or any component of the Investigational Product (AT-100).

6. AT-100 or air-sham dosing was set to occur before Data Safety Monitoring Committee recommendation to proceed to the next dose-escalation cohort.

7. Use of minimally invasive surfactant techniques (e.g., LISA, MIST) or INSURE or if, in the opinion of the care team, the infant is very likely too be extubated shortly after receiving Curosurf®.

   a. Subjects extubated and re-intubated after their Curosurf® dose(s) are eligible, so long as the subject meets Inclusion #3.

8. Birth mother:

   1. Has known active Hepatitis B, C, or E diagnosis.
   2. Has a known illness or exposure that, in the judgement of the Investigator, is serious enough to induce an immune deficiency such as Human Immunodeficiency Virus (HIV) and/or is receiving chemotherapy.
   3. Has known active Sexually Transmitted Infection (STI).
   4. Has known Cytomegalovirus (CMV) active infection.
   5. Has known history or evidence of alcohol or drug abuse, wit the exception of marijuana/marijuana-based products/THC, based on a positive maternal or infant drug screen as evidenced by the institution's standard-of-care practice.

9. Concurrent enrollment in an investigational drug, device, or treatment modulation trial that utilizes treatments outside of standard-of-care.

10. Any condition or situation which, in the Investigator's judgement, puts the mother or the neonate at significant risk, could confound the trial results, or may interfere significantly with the mother's or neonate's participation in the trial.

11. Symptomatic and confirmed COVID-19 infection of the mother around the time of birth.