SARS-CoV-2 is the coronavirus that is responsible for the disease Covid-19. Are antiviral drugs effective against the disease? So far, apparently not. For example, the lopinavir-ritonavir antiviral combination, used against HIV/AIDS, was found to be of little to no benefit in a large clinical trial of patients with COVID-19.
Surprisingly, two antimalarial drugs, chloroquine and hydroxychloroquine, hold promise. The research started in a laboratory, when a Chinese team found that chloroquine was able to inhibit SARS-CoV-2 infection in cultured cells. In a later study, also conducted in cultured cells, this team reported that hydroxychloroquine, which is safer and better tolerated than chloroquine, was also effective against the virus. Another laboratory study, again by a Chinese team, confirmed the findings.
If benefit is observed in cultured cells in a laboratory, it does not automatically mean that benefit will be observed in humans with the disease. There are hundreds of examples of drugs that work in the laboratory, and even in animal models of an illness, but not in humans with that illness. So, clinical trials are necessary.
In this context, it appears that many preliminary clinical trials have been conducted in China, and the results from more than 100 patients with the disease have shown that chloroquine prevents worsening of COVID-19 pneumonia, improves lung imaging findings, hastens the conversion of patients to a virus negative status, and shortens the course of the disease.
Does this mean that there has been a breakthrough? Not yet. The problem is that these results are so far only hearsay. The data are yet to be published in scientific journals after due scrutiny for research quality. However, if the findings are confirmed, and if chloroquine and hydroxychloroquine are truly found to reduce illness severity, illness complications, and death rates in COVID-19 patients, then the global impact will be great. Greater clarity on the subject is expected in the coming weeks.
In the meantime, on March 23, the National Task Force for Covid-19, Indian Council of Medical Research, recommended the use of hydroxychloroquine for the prevention of contraction of the disease in health workers and adult patient contacts who are at high risk of the disease. The recommendation is presumptive, and the guidance may change when better evidence becomes available.
(Dean, National Institute of Mental Health and Neurosciences, Bengaluru)