Explained | Pfizer v/s Merck: New anti COVID pill and its comparison

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In order to further strengthen fight against COVID-19, Pfizer Inc and Merck & Co Inc developed an experimental antiviral pills that have shown promising efficacy in trials of adults who are at high risk of serious illness.

While Merck was the first to roll out its anti-COVID therapy, called molnupiravir, Pfizer has announced promising results of its own pill, called Paxlovid.

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Here are the differences between the two pills

Pfizer Inc. said on November 5 said that its experimental antiviral pill for COVID-19 cut rates of hospitalization and death by nearly 90 percent.

Pfizer released preliminary results of its study of 775 adults. The study participants were unvaccinated, with mild-to-moderate COVID-19, and were considered high risk for hospitalization due to health problems like obesity, diabetes or heart disease.

Patients taking the company’s drug along with another antiviral had an 89 percent reduction in their combined rate of hospitalization or death after a month, compared to patients taking a dummy pill. Fewer than 1 percent of patients taking the drug needed to be hospitalized and no one died. In the comparison group, 7 percent were hospitalized and there were seven deaths.
Merck’s pill, known as Molnupiravir reported in September that its drug cut rates of hospitalization and death by 50 percent 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.

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.

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.

Why are they important?

If the efficacy of these drugs is confirmed, it will be a major step forward in the fight against COVID-19. They would add to vaccines to bolster the world's fight against the virus. Though treatments already exist, a pill like these can be quickly prescribed to a patient who will then take it easily at home.Safety

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.

Pfizer said about 20 percent of patients who received either the pill or a placebo experienced adverse events, mostly mild. Serious side effects were reported by 1.7 percent of patients receiving the drug and 6.6 percent of placebo patients.

Merck said 12 percent of patients receiving its drug and 11 percent 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.

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 US 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.

Supplies of the drugs and will it be available in the Indian market?

Pfizer and Merck have said they are making efforts to expand global access to the drugs.

After molnupiravir received the green light in UK, Merck said it has been producing the pill at risk in anticipation of positive results and 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.

It has already agreed to supply 1.7 million courses of the pill to the US government after it receives the go-ahead from American regulators and said it “has entered into supply and advance purchase agreements for molnupiravir with governments worldwide."

Also, a draft document seen by Reuters said that a World Health Organization-led programme to ensure poorer countries get fair access to COVID-19 vaccines, tests and treatments aims to secure antiviral drugs for patients with mild symptoms for as little as $10 per course. While, Merck & Co’s experimental pill molnupiravir is likely to be one of the drugs, and other drugs to treat mild patients are being developed.
When India was grappled with the second wave of COVID-19 pandemic, Merck had entered into non-exclusive voluntary licensing agreements for molnupiravir with established Indian generic manufacturers to increase availability of the poll in more than 100 low- and middle-income countries following approvals by local agencies.

The agreements have been signed with Cipla Limited, Dr. Reddy’s Laboratories Limited, Emcure Pharmaceuticals Limited, Hetero Labs Limited and Sun Pharmaceutical Industries Limited – five generics manufacturers with World Health Organization (WHO) Pre-Qualified Manufacturing facilities and experience as major suppliers to global and key LMIC procurers.

As per the agreement, Merck would provide licenses to these manufacturers to supply molnupiravir to India and more than 100 LMICs.

Pfizer, on the other hand is in discussions with 90 countries over supply contracts for its experimental Covid-19 pill, its Chief Executive Officer Albert Bourla said in an interview on November 6. He said Pfizer expects to price its treatment, called Paxlovid, close to where rival Merck & Co Inc has priced its oral antiviral drug candidate. The company 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.

(With inputs from Reuters)