FDA Accepts Baloxavir Marboxil sNDA for Flu Complications

The Genentech therapy is currently the first and only single-dose oral medicine marketed for flu treatment, and was the first new flu medicine with a novel mechanism of action in 2 decades.

The US Food and Drug Administration (FDA) has accepted the supplemental New Drug Application (sNDA) for baloxavir marboxil (XOFLUZA) as a single-dose, oral treatment of high-risk influenza complications.

The Genentech drug—previously approved as an acute, uncomplicated influenza therapy in patients aged 12 years or older—has an anticipated FDA PDUFA decision date of November 4, 2019. It is currently the first and only single-dose oral medicine marketed for flu treatment, and was the first new flu medicine with a novel mechanism of action in 2 decades.

Its sNDA is supported by the results of the phase 3 CAPSTONE-2 trial, in which single-dose baloxavir marboxil was compared versus twice-daily placebo or oseltamivir 75 mg, over 5 days in people 12 years of age or older who are at high risk of complications from the flu.

The multicenter, randomized, double-blind study evaluated the therapy’s safety and efficacy in 2184 patients, with the primary objective being measured time to improvement of influenza symptoms. Key secondary endpoints included time to fever resolution, time to viral shedding cessation, infectious virus detection in nose and throat swabs, antibiotic prescriptions and flu-related complications.

Investigators reported significantly reduced time to flu symptom improvement in treated patients (median 73.2 hours vs 102.3 hours, P< .0001). Baloxavir marboxil also showed superior efficacy in this metric for patients with influenza type B (74.6 hours) versus both placebo (100.6 hours; P= .0138) and oseltamivir (101.6 hours; P= .0251). For secondary endpoints, the therapy also significantly reduced time to fever resolution, incidence of flu-related complications, patient use of systemic antibiotics, and length of time to viral shedding cessation.

Baloxavir marboxil’s proposed mechanism of action has previously shown efficacy in various influenza viruses, including in vitro activity against both oseltamivir-resistant (H7N9) and avian strains (H5N1)—though in non-clinical studies. It is the first among its class of antivirals to inhibit polymerase acidic endonuclease—an enzyme associated with viral replication.

The flu can be particularly debilitating for this higher-risk patient population, Sandra Horning MD, chief medical officer and head of Global Product Development for Genentech, said. These patients face an increased chance of serious complications, worsening of existing health problems, hospitalization, and death.

“XOFLUZA is the first antiviral medicine to demonstrate a significant and clinically meaningful benefit in people at high risk of complications from the flu, for which there are currently no approved medicines,” Horning said in a statement.