> Chloroquine and hydroxychloroquine are other potential but controversial drugs that interfere with the entry of SARS-CoV-2. They have been used in the prevention and treatment of malaria and autoimmune diseases, including systemic lupus erythematosus and rheumatoid arthritis. They can inhibit the glycosylation of cellular receptors and interfere with virus–host receptor binding, as well as increase the endosomal pH and inhibit membrane fusion. Currently, no scientific consensus has been reached for their efficacy in the treatment of COVID-19. Some studies showed they can inhibit SARS-CoV-2 infection in vitro, but the clinical data are insufficient. Two clinical studies indicated no association with death rates in patients receiving chloroquine or hydroxychloroquine compared with those not receiving the drug and even suggest it may increase the risk of dying as a higher risk of cardiac arrest was found in the treated patients130,131. On 15 June 2020, owing to the side effects observed in clinical trials, the US Food and Drug Administration (FDA) revoked the emergency use authorization for chloroquine and hydroxychloroquine for the treatment of COVID-19
The in vitro studies that showed HCL efficacy were using vero lines, basically kidney cells. Those cells don't express the TMPRSS2 receptor, which is expressed on lung cells though. Studies have shown since that if you modify vero lines to express TMPRSS2, or use lung cells instead of kidney cells, HCL has no effect. It's kinda understandable that the earlier studies have used vero lines, because it's a standard cell line. But research has moved on since. The newer study has come out in July and should have been known to the authors of this review.