Introduction: Baloxavir marboxil, a cap-dependent endonuclease inhibitor, has proven efficacy against influenza. There are limited comparative data between baloxavir and oseltamivir in Japanese pediatric patients with influenza. We evaluated the clinical and virologic outcomes and assessed safety of baloxavir compared with oseltamivir for treating influenza in Japanese patients aged 6 to < 12 years.

Methods: In this open-label, randomized (2:1) trial, patients received oral administration of either a single dose of baloxavir or a twice-daily 5-day course of oseltamivir. The primary efficacy endpoint was time to illness alleviation (TTIA). Other efficacy and safety endpoints were also assessed.

Results: Of 199 enrolled patients (mean age: 9 years), 195 were randomized (baloxavir, n = 128; oseltamivir, n = 67). Of these, 50.8% had influenza A/H3N2, 37.4% influenza B, and 10.3% influenza A/H1N1pdm. Median (95% confidence interval) TTIA was 44.8 (41.5, 69.7) h and 72.2 (50.9, 96.9) h in the baloxavir group and the oseltamivir group, respectively. The median time to first cessation of virus shedding was shorter in the baloxavir vs. oseltamivir group (48.0 vs. 192.0 h). Before treatment, one patient had PA/I38X virus infection at baseline. After treatment, PA/I38X viruses were observed in 12 patients (11 A/H3N2 and 1 A/H1N1pdm). No serious adverse events, including death, were observed in either group.

Conclusion: In this study, baloxavir showed the potential for shortening of symptom duration compared with oseltamivir, which suggests baloxavir as an important treatment option for patients with influenza aged 6 to < 12 years.