Baloxavir Marboxil Appears Safe and Effective for Treatment of Acute Influenza

By Matt Silver

SAN FRANCISCO -- October 10, 2018 -- Baloxavir marboxil (BXM), an oral selective cap-dependent endonuclease inhibitor, is safe and effective for treating acute influenza in otherwise healthy patients, according to a study presented here at ID Week 2018, the 56th Annual Meeting of the Infectious Diseases Society of America (IDSA).

“The biggest take away, which may be a surprise to many but [was predictable] from prior studies, is that antiviral therapy is associated with a clinically and statistically significant improvement,” said Michael G. Ison, MD, MS, FIDSA, Northwestern University, Chicago, Illinois, on October 6. “This should drive clinicians to use antiviral drugs more often to prevent complication, [which is] something all clinicians should want to do for their patients.”

In this phase 3 study, researchers investigated the safety and efficacy of BXM in 2,184 patients, 53% of whom had confirmed influenza.

As part of the inclusion criteria, all patients were at least 12 years of age, had fever and influenza symptoms for <48 hours, and had at least 1 higher risk factor according to US Centers for Disease Control and Prevention criteria. Asthma or chronic lung disease and age ≥65 years were the most common risk factors (39.2% and 27.4%, respectively).

Patients were randomised 1:1:1 to a single oral dose of BXM 40 mg for body weight <80 kg or 80 mg for body weight ≥80 kg, placebo, or oseltamivir 75 mg twice daily for 5 days.

The median time to improvement of influenza symptoms, the primary endpoint, was 73.2 hours in patients who received BXM versus 102.3 hours in those who received placebo (P< .0001) and 81.0 hours in those who took oseltamivir (P = .8347).

Median time to cessation of viral shedding was 48 hours in patients receiving BXM, which was significantly less than the 96 hours in patients receiving placebo and oseltamivir.

Also, patients on BXM had significantly less systemic antibiotic use and less influenza-related complications than patients getting placebo. No significant difference was found in the incidence of any adverse events (25.1%-29.7%) or serious adverse events (0.7%-1.2%).

“The major next steps are to extend what we learned from this study to other populations, including kids and hospitalised patients,” said Dr. Ison. “Studies are needed to understand the implications of faster clearance of virus with BXM; if this reduces transmission, it could result in favouring this class of drugs for future pandemics and routing therapy in patients with exposures to others.”

Finally, Dr. Ison added, “More needs to be understood about resistance to BXM. Are there ways to prevent emergence, such as combining oseltamivir and BXM or giving a second dose of the medication, and what does BXM resistance mean?”

BXM is being developed by Shionogi Co., a Japanese pharmaceutical company, for treatment of influenzas A and B, in collaboration with Roche AG. It was approved for sale in Japan on 23 February 2018. The US Food and Drug Administration granted it priority review in June and is expected to decide by December.

[Presentation title: Phase 3 Trial of Baloxavir Marboxil in High Risk Influenza Patients (CAPSTONE-2 Study). Abstract LB16]
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