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 Here is an explanation of the differences in the two pills.
Which of the new pills works better?
Trial figures provided by the two companies suggest that Pfizer has
the more effective pill, but they have not yet offered full data.
Pfizer said on Friday
https://www.reuters.com/business/
healthcare-pharmaceuticals/pfizer-says-antiviral-pill-cuts-risk-severe-covid-19-by-89-2021-11-05
trial results showed that its pill reduced the chance of
hospitalization or death by 89% in COVID-19 patients at risk for
severe illness given the treatment within three days of the onset of
symptoms and by 85% when given within five days of onset.
Merck on Oct. 1 said
https://www.reuters.com/business/
healthcare-pharmaceuticals/mercks-covid-19-pill-cuts-risk-death-hospitalization-by-50-study-2021-10-01
its pill lowered the chance of hospitalization or death by about 50%
in patients at risk for severe illness given the treatment within
five days of onset. It did not provide figures regarding patients
getting the pill within three days of onset.
Pfizer's drug has the brand name Paxlovid. Merck's drug has the
brand name Lavgevrio in Britain, where it has won regulatory
approval
https://www.reuters.com/business/
healthcare-pharmaceuticals/britain-approves-mercks-oral-covid-19-pill-2021-11-04.
Why are these drugs important?
While a number of vaccines are available worldwide to prevent
infection including one made by Pfizer, there are limited treatment
options for people infected with COVID-19.
Currently, COVID-19 patients who are not sick enough to be
hospitalized but are at risk of serious illness can be treated with
antibody drugs, though they have to be given intravenously at
hospitals or infusion centers.
How do they work?
Both drugs are given for five days. Pfizer's regimen is three pills
in the morning and three pills at night. Merck's drug is taken as
four pills in the morning and four at night.
Pfizer's drug is part of a class known as protease inhibitors
designed to block an enzyme that the coronavirus needs to multiply.
Pfizer said that because the drug targets a part of the virus
essential to replication, the pathogen cannot become resistant to
the treatment.
Pfizer's drug is given in combination with ritonavir, an older
antiviral that boosts the activity of protease inhibitors but can
cause gastrointestinal side effects and interfere with other
medications.
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Merck's pill, developed with Ridgeback Biotherapeutics, is a
nucleoside analogue with a mechanism of action that aims to
introduce errors into the genetic code of the virus. Because the
drug generates random mutations into the virus, it is difficult for
the coronavirus to evolve and become resistant.
What do we know about safety?
Both companies have released only limited data on the treatments,
but expressed confidence in their safety.
Pfizer said about 20% of patients who received either the pill or a
placebo experienced adverse events, mostly mild. Serious side
effects were reported by 1.7% of patients receiving the drug and
6.6% of placebo patients.
Merck said 12% of patients receiving its drug and 11% of placebo
patients experienced drug-related adverse events.
Drugs in the same class as Merck's pill have been linked to birth
defects in animal studies. Merck has said similar studies of its
drug - for longer and at higher doses than used in humans - show
that it does not cause birth defects or cancer.
What do we know about supplies?
Pfizer and Merck have said they are making efforts to expand global
access to the drugs. Pfizer said it expects to produce more than
180,000 courses of its therapy by the end of this year, with
production of at least 50 million planned for 2022. Merck has said
it expects to produce 10 million courses of its drug by the end of
this year, with at least 20 million set to be manufactured in 2022.
Which costs more?
The U.S. government provides vaccines and treatments for COVID-19
for free to U.S. residents. Countries around the world are
negotiating prices with Pfizer and Merck.
President Joe Biden on Friday said the U.S. government has secured
millions of doses of Pfizer's treatment. Merck has a $1.2 billion
contract to supply the United States with 1.7 million courses of its
drug - or about $700 per course.
Britain has secured 250,000 courses of Pfizer's drug, but prices for
the British contracts have not been made public.
(Reporting by Deena Beasley; Editing by Will Dunham and Caroline
Humer)
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