Study to Assess the Prophylactic Efficacy and Safety of Sebaloxavir Marboxil Tablets/Oral Suspension for Influenza Prevention in Household Contacts Aged ≥2 Years.

NCT07730346 | Not Yet Recruiting Phase 3

• 1 other identifier: ZX-7101A-212
• Study Type: interventional
• Target: 858
• Locations: 1 country
• Sites: 1

Brief Summary

This study is a randomized, double-blind, placebo-controlled phase III clinical trial. The trial participants include index participants (IP) and household contacts (HHC). A total of 536 index participants (the first person in the household diagnosed with influenza) and 858 household contacts (family members living with the index participant) are planned to be enrolled. After the index participants and their household contacts have signed informed consent form and passed screening eligibility, randomization will be performed at the household level in a 1:1 ratio, stratifying by the time from onset of the index participant's initial influenza symptoms to signing of informed consent form (\<24 hours, ≥24 hours), index participant's viral subtype (influenza A, influenza B), and household contact's age (\<12 years, ≥12 years). Household contacts will be assigned to either the Sebaloxavir marboxil group or the placebo group. The study objective is to compare the prophylactic efficacy and safety of Sebaloxavir marboxil tablets/oral suspension versus placebo in household contacts (HHCs).

Conditions

Influenza Prevention

Outcome Measures

Primary Outcomes (1)

• The percentage of household contacts (HHCs) with PCR-positive influenza virus infection accompanied by fever (axillary temperature ≥37.5°C) and at least one additional influenza symptom (e.g., nasal congestion, sore throat, cough) after dosing.

  From day1 up to day10

Secondary Outcomes (6)

• Percentage of HHCs with PCR-positive influenza virus infection but no influenza symptoms after dosing.

  From day1 up to day10

• Percentage of HHCs with PCR-positive influenza virus infection accompanied by fever (axillary temperature ≥37.5°C) or at least one other influenza symptom after dosing.

  From day1 up to day10

• Time from dosing to PCR-positive influenza virus infection accompanied by fever or at least one other influenza symptom after dosing.

  From day1 up to day10

• Time from dosing to meeting the primary endpoint criteria (influenza virus infection accompanied by fever [axillary temperature ≥37.5°C] and at least one other influenza symptom).

  From day1 up to day10

• Percentage of households with at least one HHC achieving the primary endpoint criteria after dosing, relative to all households.

  From day1 up to day10

Other Outcomes (1)

• Plasma concentration of ZX-7101

  On Day5 and Day 15

Study Arms (2)

Sebaloxavir marboxil group

EXPERIMENTAL

Drug: Sebaloxavir marboxil

Placebo group

PLACEBO COMPARATOR

Drug: Placebo

Interventions

Sebaloxavir marboxil DRUG

Dosing Regimen for Household Contacts: Sebaloxavir marboxil tablets/oral suspension is administered based on age as follows: * 18 years: Single dose, Sebaloxavir marboxil tablets: 2 tablets; * 12 years and \<18 years: Single dose, Sebaloxavir marboxil tablets: 1 tablet; * 2 years and \<12 years: Single dose, Sebaloxavir marboxil oral suspension, administered according to body weight.

Sebaloxavir marboxil group

Placebo DRUG

Dosing Regimen for Household Contacts: Household contacts will receive the placebo of Sebaloxavir marboxil tablets/oral suspension based on age as follows: * 18 years: Single dose, placebo of Sebaloxavir marboxil tablets: 2 tablets; * 12 years and \<18 years: Single dose, placebo of Sebaloxavir marboxil tablets: 1 tablet; * 2 years and \<12 years: Single dose, placebo of Sebaloxavir marboxil oral suspension, administered according to body weight.

Placebo group

Eligibility Criteria

• Age: 2 Years+
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Child (0-17), Adult (18-64), Older Adult (65+)

You may qualify if:

• \. The index participant (aged ≥18 years), or the index participant (aged \<18 years) together with their legal guardian, understands and voluntarily provides written informed consent form (ICF). The index participant must be ≥1 year of age at the time of ICF signing, with no gender restriction.
• \. The index participant must be the first case of influenza virus infection in the household during the current influenza season.
• \. The index participant must have a positive result from a rapid influenza diagnostic test (RIDT) or polymerase chain reaction (PCR) assay.
• \. At the time of HHC randomization, the interval from the onset of the index participant's initial influenza symptoms to informed consent must be ≤48 hours. Symptom onset is defined as: first axillary temperature ≥37.5°C, or the presence of at least one other influenza symptom.
• \. The index participant must not have used any anti-influenza antiviral medications (including traditional Chinese medicines or Western medicines) since symptom onset, and must be willing to receive oseltamivir phosphate treatment after signing informed consent form.

You may not qualify if:

• \. Participants who are diagnosed with bacterial or other non-influenza virus infections at screening requiring systemic antibacterial or antiviral treatment;
• \. Participants with suspected hypersensitivity to the active ingredients or excipients of oseltamivir phosphate oral suspension/capsules.
• Household contact:
• \. Aged ≥2 years at the time of randomization, with no gender restriction;
• \. Has been living in the same household with the index participant for at least 48 hours at the time of randomization;
• \. Is able to reside with the index participant from screening/randomization through Day 10 (must live in the same household with the index participant for at least 7 days);
• \. Tests negative by rapid influenza diagnostic test (RIDT) or polymerase chain reaction (PCR);
• \. Meets all of the following criteria and is judged by the investigator to have no influenza virus infection:
• Axillary temperature \<37°C at screening;
• No influenza-related symptoms at screening (such as nasal congestion, sore throat, cough, myalgia or arthralgia, fatigue, headache, chills/sweating, or other influenza symptoms assessed by the investigator);
• \. The HHC is ≥18 years of age, or the HHC is \<18 years of age and together with their parent(s)/legal guardian(s) understands and voluntarily signs the informed consent form (ICF), and agrees to comply with all study procedures, including completion of diary cards (the guardian may assist in assessment/completion).
• \. The HHC must sign the informed consent form (ICF) within 24 hours after the index participant signs the ICF;
• \. The HHC and their partner must agree to practice complete abstinence or use effective contraceptive measures from screening through 3 months after the end of study drug administration.
• \. Participants with suspected hypersensitivity to the active pharmaceutical ingredients or excipients of the investigational product;
• \. Participants whose household contacts or other family members (excluding the index participant) have been diagnosed with influenza within 3 months before randomization;

Sponsors & Collaborators

• Nanjing Zenshine Pharmaceuticals: lead

Study Sites (1)

China Japan friendship hospital

Beijing, Beijing Municipality, 100029, China

Location

Study Design

• Study Type: interventional
• Phase: phase 3
• Allocation: RANDOMIZED
• Masking: TRIPLE
• Who Masked: PARTICIPANT, CARE PROVIDER, INVESTIGATOR
• Purpose: PREVENTION
• Intervention Model: PARALLEL
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: July 23, 2026
• First Posted: July 28, 2026
• Study Start (Estimated): November 7, 2026
• Primary Completion (Estimated): December 31, 2027
• Study Completion (Estimated): January 30, 2028
• Last Updated: July 28, 2026

Record last verified: 2026-07

Data Sharing

• IPD Sharing: Will not share

Locations

CN (1)