Adverse reactions of Xofluza

1. Clinical Trial Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice.

The overall safety profile of baloxavir marboxil is based on data from 2079 subjects aged 5 years and older who received baloxavir marboxil in 5 controlled clinical trials. Among these subjects, 1943 were adults and adolescents (≥12 years) and 136 were of pediatric age group (5 to<12 years).

Treatment of Acute Uncomplicated Influenza

Adult and Adolescent Subjects (≥12 years):

The safety of baloxavir marboxil in adult and adolescent subjects is based on data from 3 placebo-controlled trials in which 1640 subjects received baloxavir marboxil: 1334 (81%) subjects were 18 to 64 years of age, 209 (13%) subjects were adults 65 years and older, and 97 (6%) subjects were adolescents 12 to 17 years of age. These trials included otherwise healthy adults and adolescents (N=910) and subjects at high risk of influenza-associated complications (N=730). Among them, 1440 subjects received the recommended dose of baloxavir marboxil. Trial T0821 was a Phase 2 dose‑finding placebo-controlled trial in otherwise healthy adults 20 to 64 years of age who received a single oral dose of baloxavir marboxil or placebo. Trial T0831 was a placebo- and active-controlled trial in otherwise healthy adults and adolescents 12 to 64 years of age; subjects received a single oral dose of weight-based baloxavir marboxil or placebo, or oseltamivir twice daily for 5 days on Day 1. Trial T0832 was a randomized, double-blind, placebo- and active-controlled trial in adults and adolescents aged 12 years and older at high risk of influenza complications who received baloxavir marboxil, placebo, or oseltamivir.

The most common adverse events (regardless of causality assessment) reported in at least 1% of adult and adolescent subjects receiving the recommended dose of baloxavir marboxil in Trials T0821, T0831, and T0832 are shown.

Incidence of Adverse Events Occurring in at Least 1% of Adult and Adolescent Subjects Receiving Baloxavir Marboxil in Acute Uncomplicated Influenza Trials T0821, T0831, and T0832

Adverse Event Diarrhea: 3% in baloxavir marboxil group (N=1,440), 4% in placebo group (N=1,136).

Adverse Event Bronchitis: 3% in baloxavir marboxil group, 4% in placebo group.

Adverse Event Nausea: 2% in baloxavir marboxil group, 3% in placebo group.

Adverse Event Sinusitis: 2% in baloxavir marboxil group, 3% in placebo group.

Adverse Event Headache: 1% in baloxavir marboxil group, 1% in placebo group.

Pediatric Subjects (5 to<12 years):

In Trial CP40563, an active-controlled, double-blind trial in pediatric subjects, a total of 79 subjects aged 5 to less than 12 years received the recommended weight-based dose of baloxavir marboxil and 39 subjects received oseltamivir. Among the 118 subjects aged 5 to less than 12 years in Trial CP40563, 15 subjects in the baloxavir marboxil group and 4 subjects in the oseltamivir group were at high risk of influenza complications. The most frequently reported adverse events (≥5%) in all subjects treated with baloxavir marboxil were vomiting (5%) and diarrhea (5%). Vomiting was reported in 18% of subjects in the oseltamivir group [see Clinical Studies (14.3)]. Safety data are limited in patients aged 5 to<12 years at high risk of influenza complications.

Post‑Exposure Prophylaxis of Influenza

In Trial T0834, a placebo-controlled clinical trial in adults and pediatric subjects ≥5 years of age, a total of 360 subjects received baloxavir marboxil, of whom 291 (81%) were adults ≥18 years; 12 (3%) subjects were adolescents aged ≥12 to 17 years, and 57 (16%) were pediatric subjects aged 5 to<12 years. The safety profile in pediatric patients aged 5 to <12 years was similar to that reported in adults and adolescents aged 12 years and older [see Clinical Studies (14.4)].

2. Postmarketing Experience

The following adverse reactions have been identified during post‑approval use of baloxavir marboxil. Because these reactions are reported voluntarily from a population of uncertain size, it is not possible to reliably estimate their frequency or establish a causal relationship to baloxavir marboxil exposure.

Immune System: Anaphylaxis, anaphylactic shock, anaphylactoid reactions, hypersensitivity, angioedema (swelling of the face, eyelids, tongue, and lips).

Skin and Subcutaneous Tissue: Rash, urticaria, erythema multiforme.

Gastrointestinal: Vomiting, hematochezia, melena, colitis.

Psychiatric: Delirium, abnormal behavior, hallucinations.

FDA，2025.05