Oral, Single-Dose Antiviral Significantly Reduces Symptoms In High-Risk Influenza Patients

Genentech has announced that baloxavir marboxil met the primary objective and showed superior efficacy in the primary endpoint of time to improvement of influenza symptoms compared with placebo in the phase 3 CAPSTONE-2 study assessing the safety and efficacy in individuals with a high risk of complications from the flu.

Individuals at high risk for flu complications include those with asthma, chronic lung disease, diabetes or heart disease, and adults over age 65. In fact, the Centers for Disease Control and Prevention (CDC) estimate that 71% to 85% of seasonal flu-related deaths have occurred in people 65 years of age and older with 54% to 70% of seasonal flu-related hospitalizations having occurred in this population as well.

“Baloxavir marboxil is the first antiviral to show a clinically meaningful benefit in people who are most susceptible to complications from the flu, including older people and those living with certain medical conditions,” said Sandra Horning, MD, chief medical officer and executive vice president of Global Product Development at Genentech in a statement.

Baloxavir marboxil has a novel proposed mechanism of action designed to target influenza A and B viruses, including oseltamivir-resistant strains and avian strains. It is an antiviral designed to inhibit the cap-dependent endonuclease protein within the flu virus, which is essential for viral replication.

The phase 3 randomized, double blind study evaluated a single dose of baloxavir marboxil compared with placebo and oseltamivir in individuals aged 12 and older. In the study, participants were randomly assigned to receive a single dose of 40 mg or 80 mg of baloxavir marboxil (based off of body weight), placebo, or 75 mg of oseltamivir twice a day for the duration of 5 days.

The drug was found to have superior efficacy compared with placebo and oseltamivir for secondary endpoints, which included reducing the time of viral shedding and decreasing viral levels in the body. Additionally, baloxavir marboxil reduced the incidence of influenza-related complications significantly in comparison with placebo. The researchers also report that the drug was well tolerated in the patients and no safety signals were identified. Results of the study will be presented at an upcoming meeting.

Baloxavir marboxil proved to have clinically significant benefit over placebo in healthy individuals who had been enrolled in the phase 3 CAPSTONE-1 study. Because of this, in June, the US Food and Drug Administration (FDA) accepted a New Drug Application (NDA) and granted Priority Review for for the drug for the treatment of acute, uncomplicated influenza in individuals aged 12 and older. A decision by the FDA is expected by December 24, 2018.

If approved, baloxavir marboxil would be the first single-dose oral antiviral and the first medicine with a novel proposed mechanism of action to treat the flu in nearly 20 years.

“We plan to submit the results of this second positive Phase III study for baloxavir marboxil to healthcare authorities and look forward to discussing next steps since there are no current antiviral medicines approved to specifically treat this high-risk population,” concluded Dr Horning.

Future steps for baloxavir marboxil include a phase 3 development program, which will include pediatric and severely ill hospitalized populations with influenza.