Chinese researchers yesterday reported promising results in a phase 2 trial of a novel antiviral called onradivir for treating seasonal flu. The team reported its findings yesterday in The Lancet Infectious Diseases.
The drug, developed by Zhongsheng Pharmaceutical, inhibits the flu virus's polymerase basic protein -2 (PB2) subunit, which prevents replication. The researchers note that onradivir is currently the only antiviral candidate making its way through clinical trials that targets PB2 and that more flu antiviral options are needed, given the ongoing threat of antiviral resistance with other flu drugs.
For the study, they enrolled 205 healthy adults ages 18 to 65 from multiple clinical sites who had a confirmed flu infection between December 7, 2019, and May 18, 2020. Researchers noted that the COVID-19 pandemic and related restrictions reduced the study's enrollment. Participants were randomized to one of four groups: 200 milligram (mg) twice a day, 400 mg twice a day, 600 mg once a day, and placebo. They took the medication within 48 hours of symptom onset.
All treatment groups had decreased median time to symptom alleviation, but only the 600-mg group showed statistical significance compared with the placebo group. Diarrhea was the most common side effect and was seen in 40% of participants.
The team concluded that onradivir shortened symptoms and reduced viral load in patients with uncomplicated flu, especially at the 600-mg dose. A phase 3 trial of the drug is under way with a larger study group to compare the 600-mg onradivir dose with oseltamivir and a placebo.
Practical challenges remain
In a related commentary, two experts with the University of Maryland School of Medicine Center for Vaccine Development and Global Health—Lynda Coughlan, PhD, and Kathleen Neuzil, MD, MPH—wrote that the results for onradivir are promising. But they noted practical challenges regarding clinical use, including early flu identification, for optimal treatment benefit.
They also said the results need to be replicated in groups at higher risk for flu complications, including older people and those with underlying health conditions.