FDA Authorizes Second Oral Antiviral for COVID-19

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The U.S. Food and Drug Administration has greenlit Merck's and Ridgeback Biotherapeutic’s molnupiravir under Emergency Use Authorization for the treatment of mild to moderate COVID-19 infections in adults who are at high risk of progression to severe disease.

The FDA authorization limits the use of molnupiravir to situations where other treatment options for COVID-19 are not available or clinically appropriate, the FDA said in its announcement. 

The authorization marks the second oral antiviral treatment against COVID-19 in the United States. The Emergency Use Authorization for the Merck drug comes one day after the FDA granted EUA to Pfizer’s oral COVID-19 therapy, Paxlovid, which data shows provide an 89% reduction of risk of hospitalization or death in mild to moderate COVID-19 patients who have not been hospitalized. 

Early in the fight against COVID-19, the FDA approved Gilead Sciences’ antiviral treatment, remdesivir, marketed under the brand name Veklury. However, unlike the Merck and Pfizer assets, the Gilead Sciences medication is an infused treatment. The Merck and Pfizer treatments can be taken at home. 

The authorization for molnupiravir comes about three weeks after the FDA’s Antimicrobial Drugs Advisory Committee voted 13 to 10 to recommend authorization of the medication. The narrow nod by the FDA advisory committee came hot on the heels of the two companies providing disappointing diminished efficacy data than what was originally expected. 

Initially, interim data from a clinical study first announced in October showed that molnupiravir provided a 50% efficacy in treating COVID-19. However, in late November, Merck and Ridgeback released updated clinical trial results that showed molnupiravir only offered a relative risk reduction of 30%

The FDA granted EUA based on the Phase III MOVe-OUT clinical trial data. In its letter to Merck announcing the authorization, the FDA said “it is reasonable to believe that molnupiravir may be effective for the treatment of mild-to-moderate COVID-19 in adults who are at high-risk for progression to severe COVID-19, including hospitalization or death, and for whom alternative COVID-19 treatment options authorized by FDA are not accessible or clinically appropriate.”

Patrizia Cavazzoni, director of the FDA's Center for Drug Evaluation and Research, said the authorization of molnupiravir provides an additional treatment option for COVID-19, which is in the midst of another surge due to the Omicron variant. 

"Molnupiravir is limited to situations where other FDA-authorized treatments for COVID-19 are inaccessible or are not clinically appropriate and will be a useful treatment option for some patients with COVID-19 at high risk of hospitalization or death," Cavazzoni said in a statement. "As new variants of the virus continue to emerge, it is crucial to expand the country's arsenal of COVID-19 therapies using emergency use authorization, while continuing to generate additional data on their safety and effectiveness."

Molnupiravir is an orally administered form of a potent ribonucleoside analog that is designed to inhibit the replication of SARS-CoV-2. The recommended dose for the Merck/Ridgeback medication is 800 mg taken twice daily for five days. Molnupiravir is expected to be taken within five days of the display of symptoms following exposure to the virus.

The United Kingdom was the first to authorize molnupiravir as a treatment for adults with mild-to-moderate COVID-19 and at least one risk factor for severe disease. Earlier this week, the U.K. government announced plans to secure 1.75 million courses of treatment of the antiviral medicine. 

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