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

An adverse event (AE) is any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of study drug, whether or not considered related to the study drug. A serious adverse event (SAE) is an AE resulting in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening situation (immediate risk of dying); persistent or significant disability/incapacity of a participant who received MEDI8897. TEAEs and TESAEs were the events that occurred between administration of study drug (Day 1) and Day 361 that were absent before treatment or that worsened relative to pre-treatment state.

An AESI was one of scientific and medical interest specific to understanding of study product and may have required close monitoring and rapid communication by investigator (that is, within 24 hrs of knowledge of the event) to the sponsor. The AESIs for this study were hepatic function abnormality meeting the definition of Hy's law, hypersensitivity reactions including anaphylaxis, immune complex disease, and thrombocytopenia. Treatment-emergent AESIs were collected from the time of dosing until Day 361 post-dose.

Laboratory abnormalities determined by the investigator to be clinically significant that occurred after study drug dosing through 151 days post-dose that were absent before treatment or that worsened relative to pre-treatment state were reported as TEAEs. Laboratory evaluations (haematology and serum chemistry) of blood samples were performed.

The Tmax defined as time at which maximum observed concentration of MEDI8897 (Cmax) was observed.

The Cmax is the maximum observed serum concentration of MEDI8897.

Area under the concentration-time curve of the MEDI8897 in serum over the time interval from day 1 to day 151 (AUC1-151).

The pharmacokinetic (PK) parameter AUC (0-infinity) was estimated based on the serum concentrations of MEDI8897.

Terminal phase elimination half-life (t1/2) is the time required for half of the drug to be eliminated from the serum.

Drug clearance is a quantitative measure of the rate at which a drug substance is removed from the body.

Volume of distribution is defined as the theoretical volume in which the total amount of drug would need to be uniformly distributed to produce the desired serum concentration of a drug.

A participant was considered ADA-positive if the participant had a positive reading at any time point post baseline. Titers greater than or equal to 50 were considered positive.