Pfizer said Tuesday the drug’s main component, nirmatrelvir, worked in three separate laboratory studies. Patients take two tablets of nirmatrelvir with one tablet of another antiviral called ritonavir twice a day for five days.
The company issued the results by news release. The research hasn’t been published in a peer-reviewed medical journal.
Pfizer is working to increase supply of Paxlovid.
PHOTO: YONHAP/SHUTTERSTOCK “These data suggest that our oral Covid-19 therapy can be an important and effective tool in our continued battle against this devastating virus and current variants of concern, including the highly transmissible Omicron,” said Mikael Dolsten, Pfizer’s chief scientific officer.
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The Food and Drug Administration last month authorized Paxlovid’s use in people at high risk of severe Covid-19. Health authorities, doctors and patients say the pill is a valuable addition to the Covid-19 medicine chest because unlike other available therapies, people who are newly infected can easily take it at home to avoid becoming hospitalized.
Yet the emergence of Omicron raised questions of whether Paxlovid, as well as other Covid-19 drugs, would remain effective because the new variant carries many more mutations compared with earlier strains, especially to the spike protein that juts from the surface of the virus and plays a crucial role infecting cells.
Because of the changes, some Covid-19 antibody drugs don’t appear to work as well against Omicron.
Many researchers suspected Paxlovid and another new antiviral pill from Merck MRK +0.26% & Co. and partner Ridgeback Biotherapeutics LP would work against Omicron because both target the virus’s ability to replicate, rather than the spike protein.
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In one lab study, Pfizer researchers tested nirmatrelvir against an enzyme called protease that the virus needs to generate copies of itself. Nirmatrelvir blocked the protease target in Omicron to the same degree it blocked the enzyme in the original strain, Pfizer said.
In a second lab study, the resulting antiviral activity against Omicron was in line with activity Pfizer observed in several other variants of concern, including Beta and Delta.
The third study, performed by researchers at the Icahn School of Medicine at Mount Sinai in New York City with Pfizer, measured nirmatrelvir’s efficacy against Omicron and other strains and found a similar concentration of the drug was needed to block infection.
Supply remains limited even as monthly shipments of Paxlovid have begun to reach pharmacies and hospitals for dispensing. Pfizer isn’t due to finish delivering until June at least half of the 20 million courses of treatment purchased by the U.S.
FDA Authorizes Merck’s Covid-19 Pill: Here’s How It Works
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FDA Authorizes Merck’s Covid-19 Pill: Here’s How It Works
The FDA has cleared Merck’s new Covid-19 therapy, molnupiravir, the latest antiviral that adults can take at home to avoid severe disease. WSJ’s Daniela Hernandez explains the science behind the new drug. Photo: Merck Pfizer is scaling up manufacturing capabilities, but the end-to-end process, from raw ingredients to finished dosages, can take about nine months, according to the company.
The drugmaker expects to produce about seven million courses globally this quarter en route to making 120 million courses by the end of the year, Chief Executive Albert Bourla said during a recent investor conference.
“Any decent manufacturer of medicines can make it but the chemistry, it is complicated,” Mr. Bourla said.
Biden administration officials last week said that they worked with Pfizer to shave about seven months from the drug’s clinical trials, so that the pill is available months before the original time line.