Viral Inhibition in Children for Treatment of RSV

Inclusion Criteria: * Male or female patients of any race or ethnicity with an age adjusted for any prematurity of ≥1 month and ≤24 months. * Diagnosis of RSV infection by virological means, which may include rapid diagnostic point-of-care testing, within 96 hours preceding screening for Part 1 and 72 hours for Part 2. * Patient must weigh \>3 kg at screening and be within the 10th and 90th percentiles (inclusive) for the patient's age, based on the local child growth standards, i.e. the Australian Paediatric Endocrine Group Growth Charts. * The parent / legal guardian of the patient must have provided written informed consent for the patient to participate. * For patients aged \<12 months, an occipito-frontal head circumference within the normal range for age and gender. Exclusion Criteria: * The patient has taken, is currently taking or requires any restricted medications. * Patient is known to be HIV-positive (or the mother, if the potential patient is a child aged \<6 months). * Participation in an investigational drug or device study within 30 days prior to the date of screening. * Requires vasopressors or inotropic support at the time of enrolment. * Concurrent gastrointestinal conditions that could, in the opinion of the investigator, prejudice absorption of the Investigational Medicinal Product (e.g. protracted vomiting, malabsorption syndrome, a history of necrotising enterocolitis with consequent short gut syndrome). * Bronchopulmonary dysplasia or chronic lung disease requiring assisted ventilation at the time of enrolment. * Diminished ventilatory reserve at risk for hypercapnia (e.g. pulmonary hypoplasia, sequestration syndromes, cystadenomatoid malformation, a history of surgery for diaphragmatic hernia). * Left to right shunt meriting corrective therapy. * Renal failure including renal anomalies likely to be associated with renal insufficiency (e.g. clinical conditions of renal dysplasia, polycystic renal disease, renal agenesis). * Clinical evidence of hepatic decompensation (e.g. hepatic disorder with associated coagulopathy or associated encephalopathy). * Cerebral palsy with microcephaly, chronic or persistent feeding difficulties or seizures. * Symptomatic because of inborn errors of metabolism (e.g. mitochondrial disorders, disorders of carbohydrate metabolism, glycogen storage disorders). * Congenital or acquired immunodeficiency (e.g. congenital agammaglobulinaemia, common variable immunodeficiency, immunosuppressive therapy other than glucocorticoid or montelukast therapy forming part of care directed by the treating physician). * For Part 2 of this study, children with a history of having received palivizumab or any other monoclonal agent directed against RSV in the preceding 120 days. This exclusion criterion does not apply to Part 1. * Evidence of active or uncontrolled respiratory, cardiac, hepatic, central nervous system or renal disease unrelated to RSV infection at baseline or any other medical condition that in the opinion of the investigator renders the patient unsuitable for enrolment. * A history of epilepsy or seizures including febrile seizures. * Allergy to test medication or constituents. * Weight less than 10th percentile or greater than 90th percentile for age and gender adjusted for any prematurity. * The patient's parent or legally acceptable representative is an employee of the investigator or the study center, with direct involvement in the proposed study or other studies under the direction of that investigator of the study center, or any family members of the employees or the investigator. * Failure to satisfy the investigator of fitness to participate for any other reason.