PNEUMOSTEM® consists of ex vivo cultured allogeneic, unrelated, human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) and it is intended for use as a cellular therapy product for prevention of Bronchopulmonary Dysplasia (BPD). This study is an open-label, single-center, dose escalation study to evaluate of safety and efficacy of PNEUMOSTEM® in premature infants at high risk for BPD.

Inclusion Criteria:

• A male or female infant whose postnatal age is 3 to 14 days, inclusive (for treatment between 5 and 14 days after birth)
• A subject whose gestational age is between 23 and 28 weeks (23 weeks ≤ gestational age (GA) < 28 weeks)
• A subject whose birth weight is between 500g and 1000g, inclusive
• A subject who is intubated and receiving mechanical ventilation within 5-14 days after birth, with a fraction of inspired oxygen (FiO2) of 0.25 or greater at Screening
• A subject who has had either a deterioration or no change in the setting of mechanical ventilation within the 24 hours before trial enrollment
• A subject whose parent/guardian can give a written informed consent

Exclusion Criteria:

• A subject who has a congenital heart defect, except for patent ductus arteriosus (PDA), atrial septal defect (ASD) or a small, restrictive ventricular septal defect (VSD)
• A subject who has a serious malformation of the lung such as pulmonary hypoplasia/aplasia congenital diaphragmatic hernia, or other congenital lung anomaly
• A subject who has a chromosomal abnormality (e.g., Trisomy 18, Trisomy 13 or Trisomy 21) or a severe congenital malformation (e.g., hydrocephalus and encephalocele, tracheo-esophageal fistula, abdominal wall defects, and major renal anomalies)
• A subject who has had a severe congenital infectious disease (i.e., herpes, toxoplasmosis rubella, syphilis, HIV, etc.)
• A subject who has evidence of severe sepsis or septic shock due to an active infection at Screening
• A subject who underwent a surgical procedure within 72 hours before study drug administration or who is anticipated to have a surgical procedure within 72 hours before or following study drug administration
• A subject who was administered surfactant within 24 hours before study drug administration
• A subject who has had a bilateral grade 3 or 4 intracranial hemorrhage
• A subject who has active pulmonary hemorrhage or an active air leak syndrome at Screening
• A subject who is currently participating in any other interventional clinical trial
• A subject who is, in the opinion of the Principal Investigator, considered inappropriate for the trial due to any reasons other than those listed above