Xofluza Garners FDA Approval for Influenza Prevention Following Contact with Infected Patients
On November 24th, Roche announced that the USFDA approved a supplemental New Drug Application (sNDA) for Xofluza® (baloxavir marboxil). This previously FDA approved drug is now authorized to prevent the development of influenza in those 12 years of age and older following contact with an influenza-infected person (known as post-exposure prophylaxis). Xofluza is the first single-dose influenza medicine approved for post-exposure prophylaxis.
Xofluza is only intended to fight influenza viruses and is the first in a class of antivirals designed to inhibit the cap-dependent endonuclease protein necessary to initiate viral transcription. This endonuclease is very common throughout human strains of influenza. Xofluza interrupts viral transcription by cleaving capped mRNA bound to PB2.
This first-in-class, single-dose oral medicine has demonstrated efficacy in a wide range of influenza viruses, including in vitro activity against oseltamivir-resistant strains and avian strains (H7N9, H5N1) in non-clinical studies. Now that it is approved for the prevention of flu, Roche has the benefit of another use for Xofluza that is now having to compete against generic versions of other Roche products like Tamiflu.
Xofluza is approved by the FDA to treat influenza types A and B in otherwise healthy people older than 12. The patients must have been symptomatic for no more than 48 hours as well as post-exposure prophylaxis of influenza. Xofluza’s FDA approval was the first one for a new antiviral in 20 years.
Post-exposure prophylaxis with single-dose Xofluza was evaluated in the Phase III BLOCKSTONE study during the 2018-2019 flu season. This double-blind, multicenter, randomized, placebo-controlled, post-exposure study was published in The New England Journal of Medicine. BLOCKSTONE evaluated Xofluza compared to placebo as a preventive treatment for both adults and children who were living with someone with influenza. The study was conducted by Shionogi & Co., Ltd. in Japan.
Those diagnosed with influenza must have had onset of symptoms for less than 48 hours and participants were required to have lived with infected people for more than 48 hours. Each participant was randomly administered a single dose of Xofluza or placebo as a preventive measure against developing influenza.
Xofluza showed a statistically significant prophylactic effect on influenza after a single oral dose in people exposed to an infected household contact. The proportion of household members 12 years of age and older who developed influenza was 1% in participants treated with Xofluza and 13% in the placebo-treated group. The treatment is being further studied in a Phase III development program with children below age 1 (NCT03653364) as well as to assess the potential to reduce flu transmission from an infected person to healthy people (NCT03969212). Xofluza was well tolerated, with the most frequently reported adverse events (occurring in at least 1% of adult and adolescent influenza patients treated with Xofluza) were:
- diarrhea (3%)
- bronchitis (3%)
- nausea (2%)
- sinusitis (2%)
- and headache (1%)
Shionogi & Co., Ltd., the original discoverer of Xofluza’s compound, partnered with the Roche Group to commercialize it for the global market. Under the terms of this agreement, Roche has global rights to Xofluza excluding Japan and Taiwan, which are retained exclusively by Shionogi.
Despite these approvals, Xofluza is still not tested for risks in unborn children as the medication can be passed on to infants via breast milk. As such, it is advised that pregnant women and new mothers must not take this medication. Therefore, the drug sales might be somewhat lower amongst new families, and the Roche group will likely need to account for that in their calculations.
Seasonal epidemics result in 3-5 million cases of severe disease and up to 650,000 deaths every year worldwide. While the COVID-19 pandemic still rages and millions are infected, the usual seasonal viruses are of no less a threat to human health. It is overall a positive thing that the flu virus is still receiving attention despite the events of the past year.
By Eduardo Longoria
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