Antiviral pills for Covid-19 — not a cure, but a great tool

By Maggie Fox, CNN

A pill to treat Covid — Pfizer and Merck both generated excitement with news they have pills that could help keep people out of the hospital if they catch coronavirus.

Pfizer says its pill, which it proposes to sell under the brand name Paxlovid if it gets authorized, reduced the risk of death or hospitalization by 89% in people who got it within three days of symptoms starting. Merck says its capsule molnupiravir reduced the risk by about 50%.

Neither is a cure, and they don’t work like antibiotics do against bacterial infections. But doctors say easy-to-take antivirals can be important additions to hospital-based treatments such as monoclonal antibodies, the infused antiviral remdesivir and immune system modulators. They might help cut death rates from a virus that’s killed 750,000 people in the United States alone.

“I see them as a one-two punch. Vaccines are prevention. These antivirals are early treatment. Both have utility,” Dr. William Schaffner, professor of medicine in the Division of Infectious Diseases at the Vanderbilt University School of Medicine, told CNN. “Neither one is a substitute for the other.”

Having two possible treatments adds a lot, said Dr. Amesh Adalja, senior scholar at the Johns Hopkins Center for Health Security.

“It makes the landscape a lot more promising because what these antivirals represent is more evidence of the ability to tame the virus,” Adalja told CNN. “It gives us a big toolbox, makes it a more treatable infection. It brings it down from the level of being a five-alarm fire.”

Currently, if someone gets sick with Covid-19, the options include quick treatment with monoclonal antibodies to boost immune response. If that is not available — and monoclonals must be infused by a professional — or if it doesn’t work and patients are hospitalized, there’s no single specific treatment. Patients might get infusions of the antiviral remdesivir, which can reduce the length of time someone is ill but doesn’t lower the risk of death.

They’re also likely to get blood thinners to stop the out-of-control blood clotting that killed many patients early in the pandemic, as well as steroids or other immune modulating drugs to control inflammation.

There’s nothing to specifically attack the virus.

The pills are designed to do that — each by stopping different stages of its replication.

Not a lot is known about either pill yet. Merck has applied for emergency use authorization for molnupiravir with the US Food and Drug Administration. Pfizer, which announced its interim results on Friday, says it is preparing to do so.

That means what is known is the bare-bones information given by a news release. According to Pfizer, researchers gave its pills to volunteers within either three days or five days of their symptoms showing, and these are people who agreed to take part in clinical trials because they were considered at high risk of hospitalization or death from Covid-19 if they became infected. That means doctors will have been paying close attention to them and to their symptoms. Molnupiravir was started within five days of symptom onset.

“We haven’t seen the safety data,” Schaffner noted. Side effects he’d be on the lookout for include any evidence the drug may cause kidney or bone marrow damage. “We’d want to know a little bit more about the mechanism of action,” he said — how the drug is working. “And there is always the issue of pregnancy,” he said.

These are all questions the FDA will want answered, and it means neither drug will be available quickly. Both companies will be asked to provide safety and efficacy data and now that there are three highly effective vaccines available, the pressure is off to authorize anything too quickly.

Nonetheless, the US and the world are hungry for antivirals to treat Covid-19.

“Effective, early, oral medicines will be fundamental to ending Covid-19. Health agency Unitaid welcome additional small molecule antivirals — supported by evidence — and with meaningful commitments to access in all countries, including low and middle income countries,” Herve Verhoosel, a spokesperson for the World Health Organization sponsored nonprofit, said in a statement.

Raising expectations

Some people may have unrealistic expectations of an antiviral.

“There’s a group of people who are really vaccine averse. They will see this as a port in a storm,” Schaffner said. “They’ll say to themselves, ‘Oh, I don’t like the vaccine but in case I get sick, I can get treated.’ They may have too many expectations of this treatment.”

Antivirals aren’t magic bullets in the same way antibiotics can be. One easy analogy is flu. Four prescription antivirals are available for flu in the US: Tamiflu, or oseltamivir; Relenza, known generically as zanamivir; peramivir, sold under the name Rapivab; and baloxavir, sold as Xofluza.

Tamiflu and baloxavir can be given as pills and work best if started immediately after someone tests positive — or even, in the case of Tamiflu, to prevent infection in people who have been exposed. Zanamivir is inhaled and peramivir is injected.

Adalja said it looks like the Merck and Pfizer drugs for Covid-19 work more effectively than any of the influenza drugs.

“I think that when you have oral antivirals that can decrease complications and decrease hospitalizations, that makes Covid-19 a much more manageable respiratory infection, and that’s always been the goal,” Adalja said.

Down the road, if either or both drugs are authorized, an important question will be how they are delivered.

Speed will be of the essence, Schaffner said.

“There will be delivery mechanism. Can you get this at a pharmacy? Will there be some central mechanism to send it out to people at their homes?” he asked.

Plus, there will be the issue of making sure people take the drugs as directed. Molnupiravir is given as a batch of four pills taken twice a day for five days. “That sounds easy. But that’s not so easy for a lot of people,” Schaffner said. “I think there are a lot of people who won’t take all the pills.”

Adalja hopes having Covid-19 antivirals will kickstart a system that should have already existed, with tests available for a range of infections, from flu to strep. “People should have the ability to test themselves at home and have that linked to antiviral treatment,” Adalja said.

“I envision a kind of a world where someone has a cough or cold and they walk into their bathroom or their kitchen and they put a swab in their nose and they stick it in the machine and it spits out rhinovirus or flu or strep or whatever it might be,” he said.

And that test result could be sent to a pharmacy that would then deliver any appropriate medication to the patient’s home. The infected person would get treatment without wasting time standing in lines first to see a caregiver and then for a prescription, and best of all, would know to stay home from school or work.

“So the faster that antiviral gets into someone once they know they’re infected, the better the impact will be,” Adalja said.

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