A Double-Blind, Randomised, Placebo-Controlled Exploratory Study to Estimate the Prophylactic Efficacy of Palivizumab in Healthy Adult Participants Inoculated with Respiratory Syncytial Virus (RSV)

INTERVENTION: Trade Name: Synagis Product Name: Synagis Pharmaceutical Form: Solution for injection/infusion Pharmaceutical form of the placebo: Solution for injection/infusion Route of administration of the placebo: Intravenous use CONDITION: Respiratory Syncytial Virus Infection ; MedDRA version: 20.0 Level: SOC Classification code 10021881 Term: Infections and infestations System Organ Class: 10021881 ‐ Infections and infestations Therapeutic area: Diseases [C] ‐ Virus Diseases [C02] PRIMARY OUTCOME: Main Objective: This is an exploratory study and therefore objectives are not defined as primary and secondary. All objectives of this study are exploratory. These are listed here:; ; Part 1 Objectives; ; •To confirm the planned dose of Palivizumab to be given to participants in Part 2; •To assess safety of Palivizumab in healthy adults; ; Part 2 Objectives; ; •To estimate the margin and variance of prophylactic effect of Intravenous (IV) treatment with Palivizumab administered 1 day prior to inoculation in the RSV human challenge model in healthy adults compared to Placebo [assessed by quantitative reverse transcriptase‐polymerase chain reaction (qRT‐PCR)].; •To estimate the margin and variance of prophylactic effect of IV treatment with Palivizumab administered 1 day prior to inoculation in the RSV human challenge model in healthy adults compared to Placebo [assessed by cell culture (pfu/mL)].; •To estimate the margin and variance of prophylactic effect of IV treatment with Palivizumab administered 1 day prior Primary end point(s): This is an exploratory study and therefore outcome measures / endpoints are not defined as primary and secondary. All objectives of this study are exploratory. These are listed here:; ; Part 1: ; Duration: Throughout (D‐1 to D18); ; •Evaluation of PK levels after intravenous administration of Palivizumab; •Frequency and severity of Adverse Events (AEs) and serious AEs (SAEs); •Frequency and severity of Treatment Emergent Adverse Events (AEs) and serious AEs (SAEs); •Frequency and severity of drug related Treatment Emergent Adverse Events (AEs) and serious AEs (SAEs); ; Part 2:; Duration listed within each outcome measure description.; ; The margin and variance will be estimated as follows:; •Area under the viral load‐time curve (VL‐AUC) of RSV‐A Memphis 37b as determined by qRT‐PCR on nasal samples collected twice daily starting two days post‐viral challenge (Day +2) up to the end of quarantine.; •Area under the viral load‐time curve (VL‐AUC) of RSV‐A Memphis 37b as determined by cell culture on nasal samples collected twice daily starting two days post‐viral challenge (Day +2) up to the end of quarantine.; •Area under the total symptom score‐time curve (TSS‐AUC) collected daily in the participant symptom diary card starting one day post‐viral challenge (Day +1) up to the end of quarantine.; •Sum Total symptom score‐time curve (TSS‐Sum) collected daily in the participant symptom diary card starting one day post‐viral challenge (Day +1) up to the end of quarantine.; •Total weight of nasal discharge produced starting one day post viral challenge (Day +1) up to the end of quarantine.; •Total number of tissues used by participants starting one day post viral challenge (Day +1) up to the end of quarantine.; •Incidence of symptomatic RSV infection, as defined by:; oIncidence of infection, and; oAt least one grade 2 symptom from one or more respiratory categories from the participant symptom diary card.; •Number of days with symptoms of grade 2 or more, starting one day post viral challenge (Day +1) up to the end of quarantine.; •Peak symptom score defined by the maximum daily sum of Symptom score starting one day post viral challenge (Day +1) up to the end of quarantine.; •Frequency and severity of Adverse Events (AEs) and serious AEs (SAEs); •Frequency and severity of Treatment Emergent Adverse Events (AEs) and serious AEs (SAEs); •Frequency and severity of drug related Treatment Emergent Adverse Events (AEs) and serious AEs (SAEs); •Palivizumab serum concentrations and serum PK parameters through study Day +28; •Nasal concentrations and serum PK parameters through study Day +28; •Anti‐Palivizumab antibody (ADA) through Day 28; ; •Assessments of spirometry, PEF, and FOT; •The average amount of instrument‐assessed change for all participants who rate themselves as "a little better" or "somewhat better"; The above endpoints may be explored in relation to the baseline status of volunteers and the response to treatment. Baseline status and response can be regarding, but not limited to:; •Immune assays related to Palivizumab (e.g. IgG anti‐F ELISA, PCA); •Baseline immunity to RSV; •Response to Palivizumab treatment; •Immune assays related to Palivizumab; •RSV baseline immunity and immune responses to infection Secondary Objective: Please refer to section A10. Timepoint(s) of evaluation of this end point: Timepoints listed thin each outcome measure description.; SECONDARY OUTCOME: Secondary end point(s): This is an exploratory study and therefore outcome measures / endpoints are not defined as primary and secondary. All objectives of this study are exploratory. Please refer to section E5‐1.; Timepoint(s) of evaluation of this end point: Please refer to section E5‐1. INCLUSION CRITERIA: Please refer to Section 5.1 of the Protocol for full Inclusion criteria. Below is an abbreviated list: 1. Informed Consent 2. Aged between 18 and 55 years. 3. In good health with no history, or current evidence, of clinically significant medical conditions, and no clinically significant test abnormalities that will interfere with participant safety, as defined by medical history, physical examination, (including vital signs), Electrocardiogram (ECG), and routine laboratory tests as determined by the Investigator. 4. A documented medical history prior to enrolment. 5. Females of childbearing potential must have a negative pregnancy test prior to enrolment. 6. Female participants of childbearing potential must use one form of highly effective contraception. Hormonal methods must be in place from at least 2 weeks prior to the first study visit. The contraception use must continue until 30 days after the date of viral challenge/last dosing wit