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 Enanta Pharmaceuticals, Pardes Biosciences, Japan's Shionogi & Co
Ltd and Novartis AG said they have designed antivirals that
specifically target the coronavirus while aiming to avoid potential
shortcomings such as the need for multiple pills per day or known
safety issues.
Infectious disease experts stressed that preventing COVID-19 through
wide use of vaccines remains the best way to control the pandemic.
But they said the disease is here to stay and more convenient
treatments are needed
https://www.reuters.com/business/
healthcare-pharmaceuticals/inside-race-find-covid-19-treatment-pill-2021-05-21.
"We need to have oral alternatives for suppression of this virus. We
have people who aren't vaccinated getting sick, people whose vaccine
protection is waning, and people who can't get vaccinated," said Dr.
Robert Schooley, an infectious diseases professor at UC San Diego
School of Medicine.
Pfizer and Merck, as well as partners Atea Pharmaceuticals and Roche
AG have all said they could seek emergency approval for their
COVID-19 antiviral pills this year.
Rivals are at least a year behind. Pardes began an early-stage trial
last month, Shionogi plans to start large-scale clinical trials by
year-end, Enanta aims to start human trials early next year and
Novartis is still testing its pill in animals.
Enanta Chief Executive Jay Luly said re-purposing drugs originally
developed for other viral infections is not an unreasonable
approach. But it is not known how potent they will be against
COVID-19 or how well they can target lung tissue, where the virus
takes hold.
The risk is "if it's not a great effort ...you'll end up losing
time," Luly said.
Antivirals are complex to develop because they must target the virus
after it is already replicating inside human cells without damaging
healthy cells. They also need to be given early to be most
effective.
Currently, intravenous and injected antibodies are the only approved
treatments for non-hospitalized COVID-19 patients.
An effective, convenient COVID-19 treatment could reach annual sales
of over $10 billion, according to a recent Jefferies & Co estimate.
Merck has a contract with the U.S. government that implies a price
of $700 for a course of treatment with its antiviral molnupiravir.
SEARCH FOR AN EASY TREATMENT
Several classes of antiviral drugs are being explored. Polymerase
inhibitors such as Atea's drug - first developed for hepatitis C -
aim to disrupt the ability of the coronavirus to make copies of
itself. There are also protease inhibitors, like Pfizer's pill,
which are designed to block an enzyme the virus needs in order to
multiply earlier in its lifecycle.
[to top of second column] |
 We are trying to halt the
processes "that allow the virus to set up a
replication factory," said Uri Lopatin, CEO at
Pardes, which is also developing a COVID-19
protease inhibitor.
Merck's molnupiravir, developed with Ridgeback
Therapeutics, was at one point envisioned as a
flu drug and works by introducing errors into
the genetic code of the virus.
"The broad spectrum activity of molnupiravir
against RNA viruses, including other respiratory
viruses, suggests that it should be a durable,
useful molecule," said Jay Grobler, who oversees
infectious disease and vaccines at Merck.
Merck said data shows the drug is not capable of
inducing genetic changes in human cells, but men
in its trials have to abstain from heterosexual
intercourse or agree to use contraception.
Until reproductive toxicology study results are
available, "we don't know if there's any
potential effect of drug on sperm," said Merck
research executive Nicholas Kartsonis.
Both molnupiravir and Pfizer's pill are taken
every 12 hours for five days. Pfizer's drug must
be combined with older antiviral ritonavir,
which boosts the activity of protease inhibitors
but can cause gastrointestinal side effects and
interfere with other medications.
"It is a nuisance to add a drug you don't need
to have a drug you want to take be effective,"
Schooley said.
Pfizer said a low dose of ritonavir will help
its protease inhibitor remain in the body longer
and at higher concentrations.
Enanta, which gets most of its revenue from a
hepatitis C deal with AbbVie Inc, scanned its
library of antiviral compounds early in 2020. It
instead chose to design a new protease inhibitor
that targets an enzyme vital to the ability of
the coronavirus, and its variants, to replicate.
The drug will be tested at once daily dosing
with no ritonavir boosting, Luly said.
Lopatin said Pardes is assessing once- and
twice-a-day dosing and whether its drug needs to
be combined with ritonavir. "We do not
anticipate that we will need to use a booster,"
he said.
Pardes received funding from Gilead Sciences,
which gave up on an inhaled version of its
remdesivir, an intravenous polymerase inhibitor
approved for hospitalized COVID-19 patients.
Gilead is still working an oral remdesivir,
which was also first developed for hepatitis C
and is currently the only antiviral approved for
treating COVID-19.
(Reporting By Deena Beasley; Editing by Caroline
Humer and Bill Berkrot)
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