Will an old malaria drug help fight the coronavirus?

Hydroxychloroquine has been used for around 70 years to treat malaria, rheumatic conditions and other ailments. Now its potential use in the fight against coronavirus has become a source of hope for many, following encouraging results from a clinical trial in France on Monday. But experts caution that there is still uncertainty about its effectiveness.

A very old drug is coming back to the fore. The successful testing of hydroxychloroquine for use against the coronavirus in France’s second city Marseille on March 16 created high expectations amid this surging epidemic – especially in light of Donald Trump’s announcement on Thursday that the US Food and Drug Administration has approved its use for this purpose

Didier Raoult, director of a university hospital institute in  Marseille, explained that he had conducted a clinical trial in which he treated 25 Covid-19 patients with hydroxychloroquine. After six days, he said, only 25 percent of patients who took this drug still had the virus in their body. By contrast, 90 percent of those who had not taken hydroxychloroquine continued to carry the Covid-19.

In the wake of this announcement, French pharmaceutical giant Sanofi offered to donate millions of Plaquenil (a trade name for hydroxychloroquine) to continue the tests, while the French government’s spokesperson Sibeth Ndiaye hailed the “promising results” and promised to expand clinical trials for this treatment.

Well-known and inexpensive

In France, some pharmacies have reportedly been overwhelmed by demand for the drug over the past few days. However, many voices soon pointed out that people should not jump to the conclusion that hydroxychloroquine is a proven miracle cure. “This study seems promising, but we have to be really careful before raising hope when it comes to a virus as new as this one, for which we don’t yet have a lot of data,” said Sarah D’Alessandro, a professor of molecular medicine at the University of Milan and a malaria specialist who has worked on hydroxychloroquine.

This drug is regularly touted as a potential solution whenever a new virus appears. One “possibility is that chloroquine may alter the ability of the virus to bind to the outside of a host cell in the first place (which is an essential first step for entry) ”, noted Robin May, a professor of infectious disease at Birmingham University.

Seeing as it has been available and used for decades, hydroxychloroquine is “very well known, inexpensive and can be rapidly produced in large quantities”, D’Alessandro added. In light of these qualities, 25 clinical trials have been conducted or are underway in China to see whether or not this treatment should be used to treat Covid-19 patients. That’s while research was carried out into hydroxychloroquine’s effectiveness against SARS, MERS and Zika when these diseases first flared.

It was a Chinese study published on March 9 which first put the spotlight on this anti-malaria drug in the context of the current pandemic. Researchers at the University of Beijing demonstrated its effectiveness in an in vito trial – that is to say, an experiment on cells in a laboroatory.

‘Difficult’ to interpret results

But when it comes to human trials, the picture is foggier. “Tests on human patients [except for malaria] have so far produced contrasting results that are difficult to interpret,” D’Alessandro observed.

Hence the interest in Didier Raoult’s work in Marseille: he is the first scientist to have carried out trials with human patients that seem to have produced conclusive results. But there are still doubts: the precise data from the clinical trial have not yet been published in a scientific journal, and so have not yet been subject to peer review, noted MedScape, a specialist publication for healthcare professionals.

Another reason for caution is that the trial was “only carried out on a few patients”, D’Alessandro emphasised. The Chinese study on March 9 was criticised by many in the scientific community because it was carried out on a group of “only” 100 patients – four times more than the experiment conducted in Marseille. The French government’s spokesperson highlighted this point, stressing the importance of carrying out trials on a larger scale before trying to reach conclusions on hydroxychloroquine’s effectiveness.

A European programme of large-scale clinical trials was launched on March 12, aiming to test the effectiveness of four treatments which have already proven themselves against other viruses, such as Ebola. Hydroxychloroquine was not chosen.

A particular risk is that it does not work well with other medicines which may be necessary for certain patients with pre-existing health problems, particularly some autoimmune conditions. Hydroxychloroquine also presents risks of poisoning, and can be fatal if incorrectly dosed. Even if this danger is rigorously controlled in a hospital, the risk of an accident cannot be completely ruled out.

However, the French National Institute of Health and Medical Research, which is piloting the European clinical trial programme, has said that there is additional proof in human patients of hydroxychloroquine’s effectiveness, it could be added to the list of drugs used in Europe’s large-scale clinical trials.

Photo: A packet of Nivaquine tablets containing chloroquine ( Julien Gerard, AFP)

This article was adapted from the original in French.