Flu: Novel Oral Single Dose Antiviral Baloxavir Marboxil Reduced Symptoms in High Risk Patients

MedicalResearch.com Interview with:

Mark Eisner MD MPH Vice President and Global Head of Respiratory Actemra, ID, and Metabolism Clinical Development at Genentech Professor of Clinical Medicine University of California, San Francisco

Dr. Mark Eisner

Mark Eisner MD MPH

Mark D. Eisner, MD, MPH
Vice President, Product Development Immunology, Infectious Disease, and Ophthalmology


MedicalResearch.com: What is the background for this study?
Would you briefly explain how 
baloxavir marboxil differs from other flu treatments? 

Response: CAPSTONE-2 is a Phase III multicenter, randomized, double-blind study that evaluated a single dose of baloxavir marboxil compared with placebo and oseltamivir in people 12 years and older who are at a high risk of complications from the flu. The high risk inclusion criteria in CAPSTONE-2 were aligned with the Centers for Disease Control and Prevention (CDC), which defines people at high risk for serious flu complications to include adults 65 years of age or older, or those who have conditions such as asthma, chronic lung disease, diabetes or heart disease. For these people, flu can lead to hospitalization or even death. Participants enrolled in the study were randomly assigned to receive a single dose of 40 mg or 80 mg of baloxavir marboxil (according to body weight), placebo or 75 mg of oseltamivir twice a day for five days.

The FDA recently accepted a New Drug Application (NDA) and granted Priority Review to baloxavir marboxil as a single-dose, oral treatment for acute, uncomplicated influenza in people 12 years and older. The NDA was based on results from the Phase III CAPSTONE-1 study of a single dose of baloxavir marboxil compared with placebo or oseltamivir 75 mg, twice daily for five days, in otherwise healthy people with the flu. Results from a placebo-controlled Phase II study in otherwise healthy people with the flu were included as supporting data in the NDA. The FDA is expected to make a decision on approval by December 24, 2018.

Baloxavir marboxil is a first-in-class, single-dose investigational oral medicine with a novel proposed mechanism of action designed to target the influenza A and B viruses, including oseltamivir-resistant strains and avian strains (H7N9, H5N1). Unlike other currently available antiviral treatments, baloxavir marboxil is the first in a new class of antivirals designed to inhibit the cap-dependent endonuclease protein within the flu virus, which is essential for viral replication. By inhibiting this protein, baloxavir marboxil prevents viral replication earlier in the flu virus life cycle.

MedicalResearch.com: What are the main findings of this Phase III study?

Response: The Phase III CAPSTONE-2 study assessing the safety and efficacy of baloxavir marboxil in people 12 years and older who are at high risk of complications from the flu met the study’s primary objective and showed superior efficacy in the primary endpoint of time to improvement of flu symptoms versus placebo. Baloxavir marboxil also demonstrated superior efficacy compared to placebo and oseltamivir for important secondary endpoints, including reducing the time that the virus continued to be released (viral shedding) and reducing viral levels in the body. Furthermore, baloxavir marboxil significantly reduced the incidence of influenza-related complications compared to placebo. Baloxavir marboxil was well tolerated and no safety signals were identified. Full results of the study will be presented at upcoming medical meetings.

MedicalResearch.com: What should readers take away from your report?

Response: Baloxavir marboxil is the first investigational flu medicine with a novel proposed mechanism of action in nearly 20 years and is expected to be the first approved medicine to demonstrate significant efficacy in high risk populations. It has the potential to offer an improved treatment for one of the most common, yet serious infectious diseases worldwide, in both otherwise healthy and high-risk populations. 

MedicalResearch.com: What are the next steps in the development process?

Response: The CAPSTONE-2 study assessed the safety and efficacy of baloxavir marboxil in people at high risk of complications from the flu, including older people and those living with certain medical conditions. These data are not included in the NDA pending FDA approval. We plan to submit the results of the CAPSTONE-2 study to the FDA and look forward to discussing next steps since there are no current antiviral medicines approved to specifically treat this high-risk population.

Baloxavir marboxil will also be studied in a Phase III development program including pediatric and severely ill hospitalized populations with influenza. 

MedicalResearch.com: Is there anything else you would like to add? 

Response: Influenza, or “flu,” is one of the most common infectious diseases and represents a serious threat to public health. Current treatments, including vaccines and antivirals, have limitations as are flu viruses are constantly changing and new antiviral medicines are necessary. We are committed to addressing this unmet need through our agreement with Shionogi & Co., Ltd., and are working with the FDA to bring baloxavir marboxil to people in the United States as soon as possible.


Genentech: CAPSTONE-2 Study With Baloxavir Marboxil For Flu Meets Primary Goal

July 17 2018


Jul 26, 2018 @ 6:24 pm 

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