Clinical Efficacy of Baloxavir Marboxil in the Treatment of Seasonal Influenza in Adult Patients: A Prospective Observational Study

PURPOSE: Baloxavir marboxil, a recently developed antiviral drug, has been used to treat influenza in some countries including Japan. The aim of this study was to determine the clinical efficacy of the drug, which currently remains unclear. PATIENTS AND METHODS: Overall, 43 adult patients with seasonal influenza who visited the outpatient clinic of Teikyo University Hospital in Tokyo during the winter of 2018–2019 were enrolled. Of them, 14, 13, and 16 were prescribed baloxavir marboxil (40 or 80 mg once), oseltamivir (75 mg twice daily for 5 days), and laninamivir (40 mg once), respectively. A questionnaire was used to collect data about symptoms, and the Medical Outcome Study 8-Items Short Form Health Survey was employed to examine health-related quality-of-life (HRQOL) before and 7 days after admission. The main study endpoints included time to defervescence and the extent of improvement in HRQOL after treatment initiation. The data were analyzed with Welch’s t-test and Fisher’s exact test using StatFlex version 6. RESULTS: No significant differences in clinical background characteristics were observed among the patients. The mean time to defervescence in the baloxavir group (median [interquartile range]; 1.0 [1.0–2.0] days) was significantly shorter than that in the laninamivir group (2.0 [1.5–3.5] days; p=0.0322). No significant differences in mean time to defervescence, change in HRQOL, and time for resolution of other symptoms were observed between the groups. CONCLUSION: The results suggest that baloxavir marboxil has a better antipyretic effect than oseltamivir and laninamivir. Moreover, baloxavir marboxil might be clinically more valuable than the other two drugs owing to higher medication adherence among patients.