An experimental pill developed by Pfizer was found to reduce hospitalizations and deaths from Covid-19 by almost 90% when given within three days of symptom onset—suggesting the pill could be a major boon in the fight against the coronavirus.
The most promising Covid-19 drugs in development—beyond vaccines
The pill, which is called Paxlovid, is a protease inhibitor that blocks a key enzyme that the coronavirus needs to replicate. The drug is intended to be taken alongside ritonavir, a drug currently used in combination treatments for HIV infection. According to Pfizer, ritonavir slows the breakdown of Paxlovid and so extends the duration of its effectiveness in the body.
In a trial of more than 750 people, Paxlovid was found to reduce the risk of hospitalization and death from Covid-19 by 89% when given within three days of symptoms starting.
In particular, in the group of trial participants who received a placebo, there were 10 deaths from Covid-19, while no one in the Paxlovid group died during the trial.
According to Pfizer, Paxlovid was also found to be active against multiple variants of the coronavirus, including the delta variant, in lab testing.
Paxlovid is the second oral antiviral drug to show strong evidence of efficacy against Covid-19. On Thursday, the United Kingdom became the first country to approve a separate antiviral, molnupiravir, which was developed by Merck and Ridgeback Biotherapeutics and reduced hospitalizations and deaths by about 50% in a clinical trial.
Nahid Bhadelia, founding director of the Center for Emerging Infectious Diseases Policy & Research at Boston University, said that oral antiviral pills are "incredibly important" because current treatments for Covid-19, including monoclonal antibodies, must be given intravenously.
"With an oral antiviral, patients have more time and greater access to a treatment that will keep them out of the hospital," Bhadelia said. "But the promise of oral antivirals will only be recognized if they're available at your local pharmacy, and you can afford it, and you can get the test that tells you that you're positive for Covid, so you can actually take advantage of this drug. So, the promise is there, but the rest of the pieces need to come together."
Pfizer CEO Albert Bourla in a statement said the results of the Paxlovid study marked "a real game-changer in the global efforts to halt the devastation of this pandemic."
"The results are really beyond our wildest dreams," said Annaliesa Anderson, an executive at Pfizer who led Paxlovid's development. She added that she's hopeful the drug "can have a big impact on helping all our lives go back to normal again and seeing the end of the pandemic."
"It's stunning data," said Mikael Dolsten, Pfizer's chief scientific officer. "I feel very optimistic on a day like this. For everyone living in this pandemic, a new light of hope has turned on."
Pfizer said it will submit its findings to FDA for emergency use authorization "as soon as possible."
Paxlovid could become available within the next few months, the New York Times reports, but supplies could be limited at first, as the drug is primarily geared toward high-risk patients.
Angie Rasmussen, a vaccine researcher at the Vaccine and Infectious Disease Organization-International Vaccine Centre in Canada, expressed concerns about ensuring Paxlovid is available equitably worldwide.
"Without question, having new antivirals to add to the mix is a 'game-changer,' but the utility in the global efforts to halt the devastation of this pandemic remains to be seen," Rasmussen said.
According to Dolsten, "It is Pfizer's ambition to make this medicine accessible to as many patients as possible on the globe. We'll find the best way to do that." (Robbins, New York Times, 11/5; Falconer, Axios, 11/5; Herper, STAT News, 11/5; Hopkins, Wall Street Journal, 11/5; Weintraub, USA Today, 11/5)
It's not common to see clinical trials stop early for results being so overwhelmingly positive, especially when creating novel treatments in a global pandemic. But we have now seen it twice, first with the Merck antiviral pill and now with Pfizer's antiviral pill. With 89% efficacy at cutting risk of hospitalization or death, there is an exciting opportunity for Pfizer's drug to help provide some calm and confidence in the fight against Covid-19—adding another critical tool to our pandemic toolbox.
The remarkable results from the clinical trial studying Pfizer's Covid-19 pill resonate a clear message: we are experiencing a paradigm shift from focusing on Covid-19 prevention to focusing on mitigation, and it is a big deal. As Pfizer's Paxlovid joins the waiting line for approval in the United States behind Merck's Molnupiravir (which the FDA is meeting to discuss in late November), there are some key considerations to highlight in this promising turning point in the pandemic response.
Pfizer's Paxlovid can be taken orally, while other treatments have required hospitals or infusion centers to administer an IV-based treatment in a narrow time window after diagnosis. With the option to simply take a pill in the few days after symptom onset, patients will have more time and ease with a treatment that could keep them out of the hospital. And that is critically important to move Covid-19 treatment into the comfort of one's own home, especially for the high-risk population the clinical trial analyzed.
Many pieces still need to come together to ensure access. For one, it will be essential that this treatment is affordable and available at local pharmacies. But patients need to know they have tested positive for Covid-19 in the first place, so ensuring people have access to low-cost rapid tests is a necessary aspect of the mitigation phase we are moving towards.
Additionally, open questions about initial supply of Pfizer's antiviral—and exactly what number of doses will be available and whom—will create critical turning points about distribution and access. For example:
Whether public and private insurers will fully cover this treatment or demand cost-sharing—and whether they restrict access based on patients' vaccination status, pre-existing conditions, age, demographics, or other risk factors—will play a critical role in determining the treatment's reach. To better inform these decisions, it will be essential for the manufacturers and regulators to collect data to understand the drug's success in a broader range of use cases.
Because the pandemic is global, it is worth questioning how Pfizer plans to make the drug available to nations that are still struggling to vaccinate their populations. While Merck has allowed manufacturers to access patents to their drug to reach less wealthy nations, this second treatment option must also be made available in the global fight against Covid-19. We should pay close attention to the 'tiered pricing approach' they discussed for roll out. The key decision makers, such as manufacturers, insurers, and federal regulators, among others, have an opportunity to prevent inequities upon roll out. Ultimately, if we are not careful, the new antiviral oral treatments for Covid-19 could exacerbate disparities and health inequities.
We now have two promising oral antiviral treatments against Covid-19, and with an expected authorization on the near horizon, there is reason to be excited. In the coming weeks, many pieces still need to come together, and we will need more information to determine the future success of the treatment. For example: what does the data show about efficacy in various subpopulations (e.g. age, demographic, comorbidity, vaccination history)? How will regulators and public health experts view Pfizer versus Merck's antiviral pills? What will we learn from the recent authorization of Merck's antiviral in the UK? We continue to assess data, open questions, and challenges.
As we progress forward, if you are a health care leader, now is the time to proactively think about the new frontier of Covid-19 treatment and its impact on your pandemic response.
Andrew Mohama contributed to this piece.
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