The words had hardly left President Trump’s mouth when FDA Commissioner Stephen Hahn strode to the podium and politely walked back Trump’s claim that a drug that is effective in the treatment of COVID-19 would be made available almost immediately. Not so, said the Commissioner. The President had been referring to chloroquine and hydroxychloroquine, a pair of drugs that have been used in the treatment of malaria since the 1940s. They were subsequently found useful in the treatment of some forms of autoimmune disease such as lupus. Trump was right about one thing, “these drugs are not going to kill anybody.” That, though, is not enough for approving a drug. Unfortunately, the President has no idea about what is involved in demonstrating that a drug works for a specific condition.
Malaria is an infection by a parasite transmitted by mosquito bites, while COVID-19 is a viral disease. The malaria drugs kill the malaria parasites during their development stage in the liver and red blood cells. This mechanism, however, has no relation to any possible anti-viral effect. It seems that chloroquine and hydroxychloroquine may work through a totally different mechanism when it comes to reducing viral effects. The theory is that these drugs interfere with the ability of the virus to attach to receptors on cells, which is a prelude to invading the cell and hijacking the cell’s machinery to replicate. A virus cannot replicate by itself and has to use a cell's machinery to do so. If it cannot enter a cell, it cannot replicate.
Both chloroquine (Aralen) and hydroxychloroquine (Plaquenil) show some promise based on preliminary laboratory evidence and small scale trials on humans who are symptomatic. There is no published literature yet other than some evidence that in the test tube these compounds can interfere with the way a virus attaches to cells. There is feverish activity to try to pin down whether these compounds can really have a significant effect, especially after a small trial in France showed somewhat speedier recovery with hydroxyquinoline in infected patients. The FDA is initiating larger trials to see what anti-malarials can do in the treatment, and perhaps the prevention, of COVID-19, but for now that is all we have. President Trump’s comment that this could be a “game changer” is at best premature. While there is no approval yet for either chloroquine or hydroxychloroquine specifically for COVID-19, physicians are free to prescribe the drug off-label since it is approved for other conditions.