Safety and efficacy of onradivir in adults with acute uncomplicated influenza A infection: a multicentre, double-blind, randomised, placebo-controlled, phase 2 trial.

Background: Onradivir (ZSP1273) is a novel anti-influenza A virus inhibitor. Preclinical studies show that onradivir can inhibit influenza A H1N1 and H3N2 replication and increase the survival rate of infected animals. In this study, we aimed to evaluate the safety and efficacy of three onradivir dosing regimens versus placebo in outpatients with acute uncomplicated influenza A virus infection.

Methods: We did a multicentre, double-blind, randomised, placebo-controlled, phase 2 trial at 20 clinical sites in China. Eligible participants were adults (18-65 years) with an influenza-like illness screened by rapid antigen testing at the first clinical visit, had the presence of a fever (axillary temperature ≥38·0°C), and had the presence of at least one moderate systemic and one respiratory symptom within 48 h of symptom onset. Patients were excluded if they were pregnant, allergic to onradivir, or had received any influenza antiviral medication within 7 days before enrolment. Participants were randomly assigned (1:1:1:1) into four groups by an interactive web response system: onradivir 200 mg twice per day group, onradivir 400 mg twice per day group, onradivir 600 mg once per day group, and a matching placebo group. A 5-day oral treatment course was initiated within 48 h after symptoms onset. The primary outcome was the time to alleviate influenza symptoms in the modified intention-to-treat population. Safety was a secondary outcome. We evaluated the patients' self-assessed severity of seven influenza symptoms on a 4-point ordinal scale, and the treatment-emergent adverse events in all patients. This trial is registered with ClinicalTrials.gov, number NCT04024137.

Findings: Between Dec 7, 2019, and May 18, 2020, a total of 205 patients were screened; of whom, 172 (84%) were randomly assigned to receive onradivir (n=43 in the 200 mg twice per day group; n=43 in the 400 mg twice per day group; and n=43 in the 600 mg once per day group), or placebo (n=42). Median age was 22 years (IQR 20-26). All three onradivir groups showed decreased median time to alleviate influenza symptoms (46·92 h [IQR 24·00-81·38] in the 200 mg twice per day group, 54·87 h [23·67-110·62] in the 400 mg twice per day group, and 40·05 h [17·70-65·82] in the 600 mg once per day) compared with the placebo group (62·87 h [36·40-113·25]). The median difference between the onradivir 600 mg once per day group and the placebo group was -22·82 h (p=0·0330). The most frequently reported treatment-emergent adverse event was diarrhoea (71 [42%] of 171), ranging from 33-65% of the patients in onradivir-treated groups compared with 10% in the placebo group; no serious adverse events were observed.

Interpretation: Onradivir showed a safety profile comparable to placebo, as well as higher efficacy than placebo in ameliorating influenza symptoms and lowering the viral load in adult patients with uncomplicated influenza infection, especially the onradivir 600 mg once per day regimen.

Funding: National Multidisciplinary Innovation Team Project of Traditional Chinese Medicine, National Natural Science Foundation of China, Guangdong Science and Technology Foundation, Guangzhou Science and Technology Planning Project, Emergency Key Program of Guangzhou Laboratory, Macao Science and Technology Development Fund, and Guangdong Raynovent Biotech.