In the BLOCKSTONE phase III, randomized, post-exposure prophylaxis study, a single dose of Roche’s Xofluza compared with placebo appears to be highly effective as a preventive treatment for household adults and children who are living with someone with an influenza infection confirmed by a rapid influenza diagnostic test (the ‘index patient’).
Participants enrolled in the study, conducted by Shionogi & Co., Ltd. during the 2018-2019 flu season in Japan, were randomized to receive a single dose of Roche’s Xofluza (dose according to body weight) or placebo as a preventive measure against developing influenza. The primary endpoint of the study was to evaluate the proportion of participants who tested positive for the influenza virus and had fever, and one or more respiratory symptoms between day one and 10. Secondary endpoints included:
· clinical efficacy, pharmacokinetics
· safety
· tolerability
Roche said the phase III BLOCKSTONE study showed preventive treatment with Xofluza (baloxavir marboxil) after exposure to an infected household member significantly reduced the risk of people developing flu by 86 percent versus placebo.
The results show just 1.9 percent of Xofluza-treated household members had flu compared with 13.6 percent in the placebo-treated group. The BLOCKSTONE study showed fewer people testing positive for flu, with fever and at least one respiratory symptom, when treated with Xofluza versus placebo. This benefit with Xofluza remained statistically significant versus placebo regardless of influenza A subtype.
It was also observed in household contacts who are at high risk of flu-associated complications and children under 12 years of age who are more vulnerable to developing flu. Xofluza had a comparable safety profile to placebo, with an overall incidence of adverse events being 22.2 percent for Xofluza and 20.5 percent for placebo. No serious adverse events were reported for Xofluza.
Full results of the study were presented as a late-breaking abstract during the OPTIONS X 2019 congress in Singapore on September 1, 2019.
The BLOCKSTONE study also demonstrated that even when fewer criteria for flu were applied (proportion of participants with flu, with fever OR one or more respiratory symptom), there was still a significant 76 percent reduction in the risk of household members developing flu with Xofluza versus placebo.
According to the release, Xofluza is the first and only one-dose oral medicine approved to treat flu in otherwise healthy patients, and the first new flu medicine with a novel proposed mechanism of action approved by the FDA in nearly 20 years.
Xofluza is a first-in-class, one-dose oral medicine with a novel proposed mechanism of action that has demonstrated efficacy in a wide range of influenza viruses, including in vitro activity against oseltamivirresistant strains and avian strains (H7N9, H5N1) in non-clinical studies. Xofluza is the first in a new class of antivirals designed to inhibit the CAP-dependent endonuclease protein, which is essential for viral replication.
