The aim of this study is to investigate the safety and tolerability of intratracheal administration of two different single doses of CHF 5633 in preterm neonates with RDS in terms of adverse events, adverse drug reactions, hematology and biochemistry values, the incidence of major neonatal morbidities including bronchopulmonary dysplasia (BPD) and mortality.

The study will be a multicentre, open-label, single escalating dose, per-cohort design.

Inclusion Criteria:

• Written informed consent obtained by parents/legal representative (according to local regulation) prior to any study-related procedures
• Inborn and outborn, preterm neonates of either sex with a gestational age of 27 weeks up to 33 weeks+6
• Clinical and radiological findings typical of RDS
• Age on admission to the study < 24 hours from birth
• Requirement of endotracheal intubation for surfactant administration
• Fraction of inspired oxygen (FiO2) > 0.35 to maintain SpO2 between 90-95 %
• Documentation of normal cranial ultrasound scan

Exclusion Criteria:

• Use of surfactant prior to study entry and need for intratracheal administration of any other treatment (e.g. nitric oxide)
• Known genetic or chromosomal disorders, major congenital anomalies (cardiac malformations, myelomeningocele etc)
• Maternal drug abuse (heroin, methadone, methamphetamine, or cocaine) or significant alcohol consumption during pregnancy
• Clinical chorioamnionitis (Appendix III)
• Strong suspicion of congenital pneumonia/infection, sepsis
• Evidence of severe birth asphyxia or a 5 minutes Apgar score less / equal 3
• Presence of air leaks prior to study entry
• Neonatal seizures prior to study entry
• Mothers with prolonged rupture of the membranes (> 3 weeks duration)
• Any condition that, in the opinion of the Investigator, would place the neonate at undue risk
• Participation in another clinical trial of any placebo, drug or biological substance conducted under the provisions of a protocol