A Randomized Double-Blind Phase 2 Study of Combination Antivirals for the Treatment of Influenza

BACKGROUND: Influenza continues to have a significant socioeconomic and health impact despite a long established vaccine program and approved antivirals. Preclinical data suggest combination antivirals might be more effective than oseltamivir alone in the treatment of influenza. METHODS: We conducted a randomized, double-blinded, multicenter phase 2 trial of combination antivirals versus monotherapy for the treatment of influenza. Participants ≥18 years with influenza at increased risk of complications from influenza were randomized by an online computer-generated randomization system to receive either oseltamivir, amantadine, and ribavirin or oseltamivir alone for 5 days, and followed for 28 days. The primary endpoint was the percentage of participants with virus detectable by polymerase chain reaction in nasopharyngeal swab at Day 3. Among the secondary outcomes, there were safety and time to alleviation of influenza clinical symptoms. ClinicalTrials.gov Identifier: NCT01227967. FINDINGS: Between March 2011 and April 2016 we randomized 633 participants. Seven participants were excluded from analysis: 3 were given treatment without randomization, 3 withdrew before taking any medication, and 1 was lost to follow-up. The primary analysis included 394 participants, excluding 47 in the pilot phase, 172 without confirmed influenza, and 13 without an endpoint sample. 80 of 200 (40.0%) participants in the combination arm had virus detectable at Day 3 compared to 97 of 194 (50.0%) (95%C.I. 0.2–19.8%, p=0.046) in the control arm. There was no benefit, however, in multiple clinical secondary endpoints, such as median duration of symptoms (4.5 days in the combination arm vs 4.0 days in the oseltamivir arm; p = 0.21). INTERPRETATION: Although oseltamivir, amantadine, and ribavirin showed a statistically significant decrease in viral shedding at Day 3 relative to oseltamivir, this difference was not associated with improved clinical benefit. More work is needed to understand the lack of clinical benefit when a difference in virologic outcome was identified. FUNDING: National Institute of Allergy and Infectious Diseases, National Institutes of Health, United States.