A Proposed MOA That Stops Viral Replication Across a Broad Range of Flu Strains1

Active even against key oseltamivir-resistant and avian strains of the flu*

XOFLUZA® (baloxavir marboxil) is effective against a broad range of A & B flu strains including A/H1N1, Avian A/H5N1 and others.

Influenza A and B viruses with treatment-emergent amino acid substitutions at positions associated with reduced susceptibility to baloxavir occurred at higher frequencies in pediatric subjects 5 to <12 years of age compared to subjects ≥12 years of age. The most common substitution emerging during baloxavir treatment is PA-I38X.1,14

Consider available information on influenza virus types or subtypes and on drug susceptibility patterns for circulating influenza virus strains when deciding whether to prescribe XOFLUZA.1

*Antiviral activity was determined against laboratory strains and clinical isolates in vitro. The relationship between antiviral activity in cell culture and clinical response to treatment in humans has not been established.1

Single-Dose XOFLUZA Interrupts the Flu Viral Life Cycle Early, Helping Prevent Replication1,25

First-in-its-class XOFLUZA has a proposed mechanism of action (MOA) that works differently to stop the flu at its source1,24

XOFLUZA® (baloxavir marboxil) MOA - Mechanism of Action
  1. Viral entry25
    • The flu virus enters the host cell.
  2. Uncoating26,27
    • M2 ion channel blockers/adamantanes target viral uncoating; however, they are no longer recommended by the CDC due to high resistance.
  3. Viral replication25
    • The novel MOA of single-dose XOFLUZA works by inhibiting polymerase acidic (PA) endonuclease to prevent viral replication.1,24*
  4. Viral assembly and budding25
    • Neuraminidase inhibitors, such as oseltamivir, target viral release.28
  5. Viral release from the host cell25,28
    • Once targeted, the already-replicated viruses are prevented from leaving the host cell.

ER = endoplasmic reticulum.

Important Safety Information & Indication


XOFLUZA is an influenza virus polymerase acidic (PA) endonuclease inhibitor indicated for:

  • Treatment of acute uncomplicated influenza in patients who have been symptomatic for no more than 48 hours and who are:
    • otherwise healthy adults and pediatric patients 5 years of age and older, OR
    • adults and pediatric patients 12 years of age and older who are at high risk of developing influenza-related complications
  • Post-exposure prophylaxis (PEP) of influenza in patients 5 years of age and older following contact with an individual who has influenza.


Limitations of Use
Influenza viruses change over time, and factors such as the virus type or subtype, emergence of resistance, or changes in viral virulence could diminish the clinical benefit of antiviral drugs. Consider available information on drug susceptibility patterns for circulating influenza virus strains when deciding whether to use XOFLUZA.

Important Safety Information

XOFLUZA is contraindicated in patients with a history of hypersensitivity to baloxavir marboxil or any of its ingredients. Serious allergic reactions have included anaphylaxis, angioedema, urticaria, and erythema multiforme.


Warnings and Precautions

 Cases of anaphylaxis, urticaria, angioedema, and erythema multiforme have been reported in postmarketing experience with XOFLUZA.  Appropriate treatment should be instituted if an allergic-like reaction occurs or is suspected.

Increased Incidence of Treatment-Emergent Resistance in Patients Less Than 5 Years of Age: XOFLUZA is not indicated in patients less than 5 years of age due to increased incidence of treatment-emergent resistance in this age group. In clinical trials, the incidence of virus with treatment-emergent substitutions associated with reduced susceptibility to baloxavir (resistance) was higher in pediatric subjects younger than 5 years of age (43%, 36/83) than in pediatric subjects ≥5 years to <12 years of age (16%, 19/117) or subjects ≥12 years of age (7%, 60/842). The potential for transmission of resistant strains in the community has not been determined.

Risk of bacterial Infections: There is no evidence of the efficacy of XOFLUZA in any illness caused by pathogens other than influenza viruses. Serious bacterial infections may begin with influenza-like symptoms or may coexist with, or occur as, a complication of influenza. XOFLUZA has not been shown to prevent such complications. Prescribers should be alert to potential secondary bacterial infections and treat them as appropriate.

Adverse Reactions

  • The most common adverse reactions (≥1%) in adult and adolescent patients (≥12 years of age) in clinical studies for acute uncomplicated influenza were diarrhea (3%), bronchitis (3%), nausea (2%), sinusitis (2%), and headache (1%).
  • The most frequently reported adverse reactions (≥5%) in pediatric patients (5 to <12 years of age) in clinical studies for acute uncomplicated influenza were vomiting (5%) and diarrhea (5%).
  • The safety profile reported in a clinical study for post-exposure prophylaxis was similar in pediatric patients ages 5 to <12 years old as that reported in adults and adolescents 12 years of age and older.

Drug Interactions

Polyvalent cations:
 Coadministration with polyvalent cation-containing products may decrease plasma concentrations of baloxavir, which may reduce XOFLUZA efficacy. Avoid coadministration of XOFLUZA with dairy products, calcium-fortified beverages, polyvalent cation-containing laxatives, antacids, or oral supplements (e.g., calcium, iron, magnesium, selenium, or zinc).


Vaccines: The concurrent use of XOFLUZA with intranasal live attenuated influenza vaccine (LAIV) has not been evaluated. Concurrent administration of antiviral drugs may inhibit viral replication of LAIV and, thereby, decrease the effectiveness of LAIV vaccination. Interactions between inactivated influenza vaccines and XOFLUZA have not been evaluated.

For additional Important Safety Information, please see the XOFLUZA full Prescribing Information.

You are encouraged to report side effects to Genentech by calling 1-888-835-2555 or to the FDA by visiting www.fda.gov/medwatch or calling 1-800-FDA-1088.