This is a randomized, double-blind, placebo-controlled Phase Ib/IIa study to evaluate the safety, tolerability, efficacy, pharmacokinetics, and immunogenicity of XW001 inhalation in children with RSV infection in China

In this study, eligible participants will be randomized in a 4:1 ratio to receive XW001 inhalation (one of three dosage groups) or placebo once a day for 7 days.

Inclusion Criteria:

1. Male or female, 1 to 24 months (inclusive) at screening;
2. Weight: 3-20 kg, inclusive;
3. Positive RSV test within 36 hours before randomization;
4. Symptomatic at screening and randomization, and the onset of RSV symptoms is within 5 days prior to the first dose of XW001;
5. Parents/legal guardians are able to understand the purpose and procedures of the study, and are able to provide informed consent.

Exclusion Criteria:

1. Immunocompromised as determined by the investigator;
2. Known to have undergone or planned for bone marrow, stem cells, or other organ transplants, or are currently on immunosuppressive treatment;
3. Positive for HBV, HCV or HIV, or patient <6 months old whose mother is positive for HIV;
4. History of seizures or epilepsy, including febrile seizure;
5. Known to have received any prohibited medications defined by the protocol within 3 days prior to randomization;
6. History of any surgery within 30 days prior to randomization;
7. Severe dental or facial deformity that will impact on usage of nebulizer;
8. History of receiving measles, mumps, rubella or other vaccines within 7 days prior to screening;
9. Known to have received any investigational medicinal products or devices in the past 30 days;
10. Any other underlying conditions that make the patient unlikely to complete the study in the opinion of the investigator.