Roche’s Xofluza (baloxavir marboxil) is a first-in-class, single-dose oral medicine that is used to treat influenza virus (flu). 

It works differently from currently available drugs, such as oseltamivir (Tamiflu), zanamivir (Relenza), and peramivir (Rapivab), by inhibiting polymerase acidic endonuclease, the enzyme responsible for influenza virus replication, whereas older agents inhibit a viral enzyme called neuraminidase. 

Given how frequently flu viruses mutate and the potential for influenza viruses to develop resistance or reduced susceptibility to one or more influenza antiviral drugs, it is good to have as many therapeutic options as possible. With Tamiflu sales declining due to generic competition, Roche now depends on Xofluza to regain its dominance in the influenza market, however, resistance and mutation strains identified in Japan could make this an uphill battle for the pharma giant.

It’s been just over a year since Xofluza was approved in the US and Japan for the treatment of acute, uncomplicated influenza, in people aged 12 years and older, and more recently in those who pose a ‘high’ risk of developing flu-related complications. Roche intends to broaden Xofluza’s market share by targeting the pediatric population, and clinical trials are currently underway in a Phase III development programme consisting of infants and children up to 12 years of age. 

As mentioned, drug resistance can be a major drawback to any antiviral therapy, and endonuclease inhibitors are not excluded from this. Researchers at the University of Wisconsin and the University of Tokyo took strains from patients in Japan who had received Xofluza and found that some contained mutations to the strands that are also targeted by baloxavir. These mutations were primarily seen in a small group of the pediatric patients (n = 101), whereas no mutations were found in adults (n = 40). 

Barry Clinch, Ph.D, group clinical science director and global head of influenza and infectious disease product development at Genentech, suggests that emergence of viral variants such as the one described in the study was quite normal and that similar mutations also emerged with its predecessor Tamiflu.

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By GlobalData

The Phase III trial, CAPSTONE-2, met its primary objective and demonstrated the efficacy of Xofluza when compared with oseltamivir. For this reason, along with the improved single-dosing regimen, GlobalData believes Xofluza can withstand the competitive market that is currently occupied with generic and more cost-effective alternatives such as Tamiflu. Xofluza will see gradual growth; however, the rate of resistance and mutation strains remains elusive and could be a limiting factor in its development. Further studies are needed to elucidate this trend, which may well be presented in the Phase III FDA submission early on in 2020. 

Related Reports

GlobalData (2018). Expert Insight: Will Single-Dose Xofluza Be Able to Compete Against Tamiflu Generics?, October 2018, GDHC2096EI

GlobalData (2019). IDWeek 2019: New Clinical Studies Promise More Treatment Options for Influenza Infections, October 2019, GDHC2712EI