‘When will we have drugs to treat Covid, doc?’

Muiris Houston: Barriers remain before potential coronavirus disease treatments become available

The MSD and Pfizer medications are for adults who are in the early stages of Covid-19 with mild to moderate symptoms at risk of hospitalisation

The MSD and Pfizer medications are for adults who are in the early stages of Covid-19 with mild to moderate symptoms at risk of hospitalisation

 

More than 18 months into the pandemic, we’re still hunting for effective antiviral treatments for Covid-19 – medicines that target the coronavirus itself and stop it from developing in the body.

The intravenous anti-viral drug Remdesivir has been authorised for use, but the latest research shows it doesn’t improve outcomes for Covid patients. And we know that treatment with the steroid, dexamethasone, improves survival for a subgroup of critically- ill hospital patients infected with Sars-CoV-2.

For patients who started taking the drug within three days of the onset of symptoms, the hospitalisation rate was 89 per cent lower

So recent announcements from pharmaceutical companies Merck, Sharpe and Dohme (MSD) and Pfizer about the preliminary results of trials into two new oral medications for Covid are a major step forward. Vaccination is still the primary and most effective defence against the novel coronavirus, but having oral medication to save lives and prevent hospitalisation, among people who become infected, will be an important string to our therapeutic bow.

Both the MSD and Pfizer medications are for adults who are in the early stages of Covid-19 with mild to moderate symptoms and who are at risk of deteriorating into severe illness, requiring hospitalisation. Those at risk could include people who are older or who have underlying conditions, such as obesity, diabetes or heart disease.

Pfizer’s preliminary results from its clinical trial of the drug combination Lopinavir/ ritonavir showed a reduction of between 85 and 89 per cent in the combined rate of hospitalisation and death among those who got the drug, compared to those who got a placebo pill. For patients who started taking the drug within three days of the onset of symptoms, the hospitalisation rate was 89 per cent lower.

The reduction in hospitalisation was slightly less (85 per cent) among those who took the pills a day or two later (but within five days of symptoms developing). Lopinavir is a protease inhibitor and is from the same family of drugs used to treat HIV/AIDS and hepatitis C. It works by blocking an enzyme that the virus needs to multiply. The new medication is taken with an older protease inhibitor called ritonavir, which boosts the level of lopinavir in the body.

Molnupiravir, MSD’s new medication, reduced the rate of hospitalisation by 50 per cent among recipients, compared to those who got a placebo pill. That was among patients who started taking the medication within five days of symptoms beginning.

The new antiviral medication was approved for use by regulators in the UK earlier this month, who said molnupiravir (Lagevrio) is safe and effective at reducing the risk of hospitalisation and death in people with mild to moderate Covid-19 symptoms, who have at least one risk factor for developing serious illness.

The researchers did not give the drugs to people who were already vaccinated so further trials to cover this group are needed

Molnupiravir works by targeting an enzyme that the coronavirus uses to reproduce itself, by inserting errors into its genetic code, thereby disrupting the virus’s ability to spread among cells.

But before we get over-excited about these landmark Covid-19 treatments, a number of potential barriers remain: the trial results of the two new antiviral drugs have yet to be peer reviewed and so must be regarded as preliminary at this point. The EU medicines regulator (EMA) has yet to approve the drugs for use in the Republic (and the rest of Europe). The researchers did not give the drugs to people who were already vaccinated so further trials to cover this group are needed. And the fact that they have to be taken within the first 5 days of Covid-19 symptoms emerging is a problem; many of us feel relatively well in the early days of infection and may miss the window of prescribing opportunity.

On the other hand, think back to this time last year as we anxiously awaited results of the first Covid-19 vaccine trials: If we can make the same progress with these new anti-Covid drugs as we did with vaccines, then we could expect to see medication on pharmacists shelves within months.

mhouston@irishtimes.com

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