A Surveillance Study of Susceptibility to Baloxavir Marboxil in Participants With Influenza

Study Overview
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Brief Summary
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The purpose of this study is to evaluate the pre-treatment and single-dose post treatment susceptibility of baloxavir marboxil in participants aged 1 to <12 years with influenza.

Official Title
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A Phase IIIb Multicenter, Single-Arm, Open-Label Surveillance Study of Susceptibility to Baloxavir Marboxil in Patients With Influenza

Conditions
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Influenza

Intervention / Treatment
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* Drug: Baloxavir Marboxil


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Participants with symptoms suggestive of influenza with diagnosis confirmed by a positive local influenza test within 24 hours before full study screening. Participants with a negative severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) test within 48 hours before full study screening. The time interval between the onset of influenza symptoms and the pre-dose examinations at screening is 48 hours or less Exclusion Criteria: Participants with severe influenza virus infection requiring inpatient treatment. Severely immunocompromised participants [including participants receiving immunosuppressant therapy, or those with cancer or human immunodeficiency virus (HIV) infection] as defined by the investigator. Participants with concurrent (non-influenza) infections requiring systemic anti-microbial and/or anti-viral therapy at the pre-dose examinations. Treatment with baloxavir marboxil, peramivir, laninamivir, oseltamivir, zanamivir, rimantadine, umifenovir or amantadine within 30 days prior to screening. Treatment with an investigational influenza-specific monoclonal antibody within 6 months or 5 half-lives, whichever is longer, prior to screening. Treatment with an investigational therapy within 30 days or 5 half-lives, whichever is longer, prior to screening. Known hypersensitivity to baloxavir marboxil or the drug product excipients. Females who have commenced menarche (i.e., child-bearing potential).

Ages Eligible for Study
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Minimum Age: 1 Year
Maximum Age: 11 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Baloxavir Marboxil<br>Participants will receive a single oral dose of baloxavir marboxil on Day 1 (based on body weight and age). | Drug: Baloxavir Marboxil<br>* Baloxavir marboxil will be administered as oral suspension either as 2 milligrams per kilograms (mg/kg) (if weight less than 20 kg), or 40 mg (if weight more than or equal to 20 kg to less than 80 kg) or 80 mg (if weight more than or equal to 80 kg).<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Percentage of Participants with Resistance-Associated Pre-Treatment Substitutions |  | Day 1 (Baseline) | 
| Percentage of Participants with Resistance-Associated Treatment-Emergent Substitutions |  | Days 4, 6 and 10 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Percentage of Participants with Resistance-Associated Treatment-Emergent Substitutions by Age Groups (<5 years versus ≥ 5 years) |  | Days 4, 6 and 10 | 
| Percentage of Participants with Novel Treatment-Emergent Mutations in Polymerase Acidic Protein (PA) |  | Days 4, 6 and 10 | 
| Percentage of Participants with Resistance-Associated Treatment-Emergent Substitutions by Baseline Vaccination Status |  | Days 4, 6 and 10 | 
| Percentage of Participants with Influenza Virus Type (A or B) and Subtype (A/H1 or A/H3) |  | Day 1 (Baseline) | 
| Change from Baseline in Viral Titers by Quantitative Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) |  | Baseline (Day 1); Days 4, 6 and 10 | 
| Susceptibility to Baloxavir Marboxil by Phenotyping Post-Baseline Samples with Novel Genotypic PA Substitutions |  | Days 4, 6 and 10 | 
| Number of Participants with Adverse Events and Serious Adverse Events | Adverse events were reported according to the National Cancer Institute Common Terminology Criteria for Adverse Events, Version 5.0 (NCI CTCAE v5.0). | Up to Day 29 |