COVID-19: Pfizer claims pill cuts severe infection risk by 89 per cent

The pharmaceutical giant says its experimental drug was highly effective at cutting rates of hospitalization and death.

Pfizer has published the results of a study showing a pill that it has developed is highly effective in treating coronavirus.

Pfizer said on November 5 that its experimental antiviral pill for COVID-19 cut rates of hospitalization and death by nearly 90 per cent. The announcement follows a day after the United Kingdom became the first country to authorize a pill for coronavirus treatment developed by competitor Merck & Co.

How effective is Pfizer's COVID-19 pill?

Patients taking the Pfizer-developed pill in combination with an older antiviral called ritonavir saw an 89 per cent reduction in their combined rate of hospitalization or death after a month, in a trial study of 775 patients. This was compared to patients taking a placebo. Fewer than 1 per cent of patients taking the drug needed to be hospitalized and no one died. In the comparison group, 7 per cent were hospitalized and there were seven deaths.

Study participants were not vaccinated, showed mild-to-moderate COVID-19, and were considered high risk for hospitalization due to health problems like obesity, diabetes or heart disease. Treatment began within three to five days of initial symptoms, and lasted for five days. An independent group of medical experts monitoring the trial recommended stopping it early. This is standard procedure when interim results show such a clear benefit. Pfizer provided few details on side effects but said rates of problems were similar between the groups at about 20 per cent.

The results appear to surpass those seen with Merck & Co Inc's pill, molnupiravir. Last month it was shown to halve the likelihood of dying or being hospitalized for COVID-19 patients also at high risk of serious illness. Full trial data is not yet available from either company.

Mikael Dolsten, Pfizer's chief scientific officer, praised the results of the trial as "rare." Pfizer CEO Albert Bourla said the company was in discussions with 90 countries over supply contracts for the pill. U.S. President Joe Biden said his government had secured millions of doses of the drug and that, if authorized by the Food and Drug Administration (FDA), it would "be another tool in our toolbox to protect people from the worst outcomes of COVID."

How do pills to treat COVID work?

Pfizer's drug is part of a decades-old family of antiviral drugs known as protease inhibitors, which revolutionized the treatment of HIV and hepatitis C. The drugs block a key enzyme that viruses need to multiply in the human body. The drug was first identified during the SARS outbreak originating in Asia in 2003. While Pfizer's drug has not yet been named, Pfizer's combination treatment will have the brand name Paxlovid. It consists of three pills given twice daily.

Merck's molnupiravir has a different mechanism of action designed to introduce errors into the genetic code of the virus.

The race for U.S. authorization

Currently, all COVID-19 treatments used in the U.S. require intravenous therapy or injection. Pfizer said it plans to submit interim trial results for its pill to the U.S. FDA as part of the emergency use application it opened in October. The FDA has set a public meeting later this month to review Merck's pill.

While Merck's pill is further along in the U.S. regulatory process, Pfizer's drug could benefit from a safety profile that is more familiar to regulators with fewer red flags. While pregnant women were excluded from the Merck trial due to a potential risk of birth defects, Pfizer's drug did not have any similar restrictions.

Top U.S. health officials continue to stress that vaccination will remain the best way to protect against infection.

kmm/rt (AP, Reuters)