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FDA authorized emergency use of Pfizer’s oral antiviral drug Paxlovid on December 22, 2021, skipping the advisory committee review to make the drug available as quickly as possible. This decision was followed on December 23 with FDA providing similar authorization for Merck’s Molnupiravir, with certain restrictions due to questions raised as to its safety and efficacy during its examination by FDA’s expert panel last month.1 These actions by FDA offer patients a take-at-home pill that can keep them out of the hospital at a time when the U.S. is being devastated by the spreading Omicron variant.
Pfizer’s Paxlovid (nirmatrelvir/ritonavir) gained emergency use authorization (EUA) from FDA for patients over age 12 experiencing mild-to-moderate COVID-19 infection as a way to prevent progression to more severe illness or hospitalization.2 The treatment is specified for use at early stage of infection, and involves taking a packet of three pills taken twice daily for five days, adding up to 30 pills overall.
Being able to treat COVID-19 with a drug taken orally at home is “a major step forward in the fight against this global pandemic,” said Patrizia Cavazzoni, director of the Center for Drug Evaluation and Research (CDER). And the approval, she added, comes “at a crucial time in the pandemic as new variants emerge.” At the same time, FDA continued to emphasize the importance of vaccination in protecting individuals from COVID infection.
Despite concerns that the antiviral drug molnupiravir developed by Merck and Ridgeback Biotherapeutics may be less effective and more risky than the Pfizer treatment, FDA granted an EUA for the product to provide an additional option for treating patients (over 18 only) with early symptoms and in need of treatment quickly to prevent hospitalization or more serious disease. Cavazzoni stated that molnupiravir use should be limited to situations where other authorized treatments “are inaccessible or are not clinically appropriate.”
Merck’s drug ran into trouble at the Nov. 30, 2021 meeting of FDA’s Antimicrobial Drugs Advisory Committee, where concerns were raised about possible birth defects if used by pregnant women and potential damage to patients’ DNA. The drug suffered from data released just before the meeting that showed only a 30% decrease in hospitalizations, compared to 50% in preliminary results, a drop that the sponsors had difficulty explaining. Consequently the panel recommended approving the drug by only a very slim margin.
However, scientists involved with the drug’s development and testing made the case for molnupiravir being a useful weapon in combatting COVID-19. An article in the New England Journal of Medicine Dec. 16, 2021 emphasizes that molnupiravir is an effective treatment that can reduce the risk of hospitalization or death in patients infected with COVID-19.3 The authors provide details on the clinical trials and analysis, including safety issues. A companion editorial summarizes these issues, noting that the drug has been licensed in the United Kingdom and may be particularly valuable in other markets.4
Merck’s drug may be particularly helpful in the lesser developed countries where access to new therapies is limited. Merck has said it plans to make its patents available to the World Health Organization patent pool and to generic drug manufacturers so that it can be produced for developing countries at low cost. Similarly, Pfizer stated that it will provide the new drug through a tiered pricing program, where high-income countries will pay more than lower income countries. And the company has signed a voluntary license agreement with the Medicines Patent Pool to expand access to its oral antiviral treatment to 95 low- and middle-income countries.
The main factor clouding the immediate impact of these new drugs is limited supplies. Pfizer said that it planned to provide 10 million treatment courses “between 2021 and 2022,” as per a $5.3 billion advance purchase agreement with the U.S. government. The company also aims to produce 120 million courses of treatment in 2022 through expansion of its own manufacturing and agreements with contract manufacturers.5 But analysts count less than 200,000 courses of the pills now available, raising questions about how quickly the firm will be able to meet what is expected to be widespread demand.
Similarly, Merck has said it is ramping up production to expand its supply. The United Kingdom, where the drug was already authorized, is purchasing more than 2 million courses of treatment, and the company has an agreement to supply some 3 million courses of treatment to the U.S. Merck says it expects to produce 10 million courses of treatment by the end of 2021 and at least 20 million in 2022.