Too good to be true? Pfizer is working on a pill that could potentially treat COVID-19-Health News , Firstpost
Usually, the trials take years, but as the pandemic rages on Pfizer will conduct them in a matter of months.
While the focus has been largely on vaccines, you might have also heard Pfizer is trialling a pill to treat COVID-19
Where most antiviral agents we’ve tried to treat COVID-19
Mounting our defence against the virus
Much of the illness associated with COVID-19
Taken early in the disease, the inhaled corticosteroid budesonide has been shown to reduce the development of more severe disease.
In people hospitalised with COVID-19
In the most severe cases — COVID patients admitted to ICU — the anti-inflammatory tocilizumab administered intravenously gives a person a better chance of survival.
But these treatments don’t target SARS-CoV-2 itself; just the consequences of infection. Directly targeting the virus has proven to be more difficult.
Targeting SARS-CoV-2
A virus like SARS-CoV-2 must enter a host cell to reproduce. It does this using its spike protein (a protein on the virus’ surface) to attach to the cell, and then it uses the cell’s own proteins to gain entry.
Once inside the cell, SARS-CoV-2 removes its outer coat and releases its viral RNA (ribonucleic acid, a type of genetic material). This acts as a template, allowing the virus to replicate, and then infect other cells. At any point of this life cycle the virus could be vulnerable to an intervention.
SARS-CoV-2 carries an enzyme, 3C-like protease (3CLpro), which plays a crucial role in the replication process. This protease is almost identical to the protease used by the SARS-CoV-1 (SARS) virus, and similar to the protease used by the Middle Eastern Respiratory Virus (MERS).
So a drug that could effectively target 3CLpro and prevent virus replication could be beneficial against multiple known coronavirus
Protease inhibitors have been successfully used to treat other viral infections, especially chronic infections such as HIV and hepatitis C.
They were put forward early in the pandemic as a possible treatment for COVID-19
Scientists also proposed a repurposed antiviral drug, remdesevir, originally developed to treat Ebola. Remdesivir delays the ability of the virus to replicate its RNA.
Initial case reports appeared promising and saw the US Food and Drugs Administration approve the drug for emergency use. But the results of randomised controlled trials in hospitalised patients with severe COVID-19
Although there was a reduction in duration of illness for patients who survived, it didn’t significantly reduce a person’s chance of dying.
Of course, neither of these agents were designed specifically to target SARS-CoV-2. But in 2020, Pfizer/BioNtech identified a small molecule — PF-00835231 — that blocks the SARS-CoV-2 3CLpro protease. It was originally designed against SARS-CoV-1, but the enzyme in the two viruses is almost identical.
PF-00835231, both alone and in conjunction with remdesevir, appears to reduce the replication of a range of coronavirus
What now?
Pfizer/BioNtech are taking two drugs to clinical trials for COVID-19
These phase 1 trials, which began in March, represent the earliest stage of drug development. These trials select healthy volunteers and use different doses of the drugs to establish their safety. They also look at whether the drugs elicit sufficient responses in the body to indicate they could be effective against SARS-CoV-2.
The next step would be phase 2 or 3 trials to see if they improve outcomes in COVID-19
The application of antiviral agents in acute COVID-19
They could also be used as a means of prevention, to contain outbreaks in exposed people. They should be effective against all the SARS-CoV-2 variants of concern, as well as against other known and possibly emergent coronavirus
The Pfizer CEO’s recent suggestion the pill could be available by the end of the year is probably a long shot. But the pandemic has shown us what’s possible in the realm of swift scientific advances, and we’ll watch this space with interest.
Peter Wark, Conjoint Professor, School of Medicine and Public Health, University of Newcastle
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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