A Multicenter, Randomized, Double-blind, Placebo-controlled Phase III Clinical Study to Evaluate the Safety and Efficacy of Onradivir Tablets in Participants Aged 12 to 17 Years With Uncomplicated Influenza A.

This randomized, double-blind, placebo-controlled study is designed to evaluate the efficacy and safety of Onradivir Tablets in participants aged 12 to 17 years with influenza A virus infection. The trial plans to enroll approximately 150 adolescent participants (12-17 years) with uncomplicated influenza A, confirmed by rapid antigen/nucleic acid testing and within 48 hours of symptom onset. Eligible participants who meet the inclusion criteria and do not meet any exclusion criteria will be randomized in a 2:1 ratio to receive either Onradivir Tablets or placebo once daily for 5 consecutive days. The study consists of a screening period, a treatment period, and a safety follow-up period. Each participant will be followed up until Day 14 after the first dose. Nasopharyngeal swabs will be collected at screening, Day 2, Day 4, Day 5, and Day 10 for virological testing, including: Viral load measurement by reverse transcription quantitative polymerase chain reaction (RT-qPCR) Viral titer determination by culture assay (50% tissue culture infectious dose, TCID₅₀) Throughout the treatment and safety follow-up periods, participants will record body temperature, influenza symptom scores, and daily activity scores using a diary card. Clinical laboratory tests will be performed at screening, Day 5, and Day 15. Physical examinations and vital signs measurements will be conducted at each follow-up visit. Adverse events and concomitant medications will be documented throughout the study.