Hydroxychloroquine and chloroquine
Among the published hydroxychloroquine studies is a “promising” 36-patient open-label nonrandomized French study, in which the antimalarial agent given every 8 hours improved virologic clearance by day 6 versus controls (70% vs. 12.5%, respectively), the review authors said. Moreover, viral clearance was 100% for 6 patients who received hydroxychloroquine plus azithromycin, compared to 57% (8 of 14) for patients treated with hydroxychloroquine alone. However, that study had several important limitations, including the small sample size, variable viral loads at baseline between groups, and a lack of safety and clinical outcomes reporting, according to the investigators. Moreover, six patients in the hydroxychloroquine group were taken out of the analysis because of early treatment stoppage due to medical intolerance or critical illness, the authors noted.
One prospective study including 30 patients in China demonstrated no difference in virologic outcomes for patients randomized to hydroxychloroquine plus standard of care versus standard of care alone, they added. There is also a case series of more than 100 patients with COVID-19 that reportedly improved viral clearance and reduced disease progression, though they said results haven’t been published or presented beyond a news briefing in China.
Randomized, controlled trials of chloroquine and hydroxychloroquine for COVID-19 treatment are underway, and studies are planned or enrolling to look at chloroquine prophylaxis in health care personnel and hydroxychloroquine for postexposure prophylaxis, authors said.
In results from one of those randomized trials, just reported, a higher dose of chloroquine was associated with a cardiac adverse event and an increased mortality risk, leading to the closure of that study arm. In the parallel, double-blinded, phase IIb clinical trial, patients in Brazil with SARS-CoV-2 infection received low or high doses of chloroquine plus ceftriaxone and azithromycin. According to the preprint publication, a higher rate of heart rate–corrected QT interval (QTc) prolongation and a “trend toward higher lethality” was observed in the high-dose group, leading investigators to “strongly recommend” the higher dose be abandoned.
“No apparent benefit of chloroquine was seen regarding lethality in our patients so far, but we will still enroll patients in the low chloroquine dose group to complete the originally planned sample size,” said investigators of the study, which at the time of the report had enrolled 81 out of an anticipated 440 patients.