A Phase 1b/2a Randomized, Double-Blind, Placebo-controlled, Dose-escalation Study to Evaluate the Safety, Tolerability, and Pharmacokinetics of MEDI8897, a Monoclonal Antibody With an Extended Half-life Against Respiratory Syncytial Virus, in Healthy Preterm Infants

This Phase 1b/2a study will be a dose-escalation design to begin data collection on PK and
safety in children. The population to be enrolled is healthy preterm infants born between 32
weeks 0 days and 34 weeks 6 days gestation who would not receive RSV prophylaxis based on the
American Academy of Pediatrics (AAP) or other local guidelines. These subjects will not be
receiving palivizumab, allowing for a placebo comparator group to begin collecting data on
incidence rates of RSV medically attended lower respiratory illness (MA-LRI) and efficacy.
Enrollment is planned at approximately 20 sites in the USA, Chile, and South Africa.

Key Inclusion Criteria:

- Healthy infants born between 32 weeks 0 days and 34 weeks 6 days gestational age

- Infants who are entering their first RSV season at the time of screening

Key Exclusion Criteria:

- Gestational age < 32 weeks 0 days and >34 weeks 6 days

- Meets AAP or other local criteria to receive commercial palivizumab

- Any fever (≥ 100.4°F [≥ 38.0°C], regardless of route) or lower respiratory illness
within 7 days prior to randomization

- Acute illness (defined as the presence of moderate or severe signs and symptoms) at
the time of randomization

- Active RSV infection (a child with signs/symptoms of respiratory infection must have
negative RSV testing) or known prior history of RSV infection

- Receipt of palivizumab or any RSV vaccine, including maternal RSV vaccination