The described preconceptions led quickly to studies in China. On February 15, 2020, the Chinese government recommended that antimalarials should be included in the guidelines for prevention, diagnosis, and treatment of COVID-19 pneumonia, issued by the National Health Commission of the People’s Republic of China [3, 31], but it should be noted that all the positive reports available until March 31, 2020 were anecdotal reports and open-label studies without control groups. On that date, a report of a blinded, randomized, controlled trial of HCQ from Wuhan was published. It analyzed 31 patients in the treatment group (HCQ 400 mg per day for 5 days) and 31 in the control group [32]. The median age was 44.7 years, the male-female ratio was even, and all patients had pneumonia by computed tomography (CT) scan. Both groups received a not well-defined standard-of-care (oxygen therapy, antiviral drugs, antibiotics and even immunoglobulin, with or without corticosteroids). At presentation, more patients in the treatment group had fever and cough as compared to the control group. The treatment group showed significant improvements in comparison to the control group in fever, in cough, and in pneumonia by CT scan. Although this was the first controlled study to show any benefit from HCQ, it should be noted that the original registered trial informed a design for 100 control patients, 100 patients to receive a low dose of HCQ, and 100 more to receive a higher dose. The trial design also mentions as endpoints results for viral RNA, and for T cell recovery time [33]. This was not shown in the final publication. A previous Chinese controlled, pilot, study showed no benefit when 30 treatment-naïve patients were randomized 1:1 to HCQ 400 mg per day for 5 days or conventional treatment only [34]. Neither trial reported serious adverse events, but both excluded patients with cardiac arrhythmias, as high doses of hydroxychloroquine can induce QT interval prolongation.
In a French Clinical trial, 20 patients that received 600 mg of HCQ per day were compared with a group of untreated patients from another center. Viral load in nasopharyngeal swabs was tested daily. Azithromycin was added in 6 patients of the HCQ group. Results showed that the virus was not found after 6 days in all the patients treated with HCQ and azithromycin, in 57.1% of the patients treated with HCQ only, and in 12.5% of the control group patients (p < 0.001). No side effects or clinical evolution of patients were described. The authors said that azithromycin was added by clinical decision to treat a possible bacterial infection, but they also mention in their discussion that azithromycin may have an antiviral effect based on in vitro studies [35]. This study was questioned by a multinational team that reanalyzed its statistics performing a Bayesian A/B test and reported that for the original data, there was a strong statistical evidence for the positive effect of HCQ monotherapy on viral reduction, but that the level of evidence dropped to moderate when the deteriorated patients were included in the analysis, and to anecdotal evidence when the patients that were not tested on the day of the primary outcome (day 6) were excluded [36].
The same group recently reported the results of a cohort of 80 patients that received HCQ 600 mg per day for 10 days, and azithromycin 500 mg the first day, and 250 mg per day for the next 4 days. Only 2 patients, according to their report, did not improve (an 86-year-old patient who died and a 74-year-old patient still in intensive care unit [ICU] at the time of the report). In 83% of the patients, the virus was not found at the nasopharyngeal sample tested by PCR at Day 7 (93% at Day 8). Virus cultures from patient respiratory samples were negative in 97.5% at day 5. The mean length of hospital stay was 5 days [37]. These results support the original report in that between 5 and 7 days of treatment, few patients had detectable virus by nasopharyngeal swab. The lack of comparison (hydroxychloroquine monotherapy, or standard of care) is problematic.
In contrast to these results, another French study evaluated 11 consecutive patients treated with the same combination (HCQ 600 mg per day and azithromycin, 500 mg the first day, and 250 mg per day thereafter). The mean age was 58.7 years, and 8 had significant comorbidities (2 obese, 5 with cancer, 1 with HIV). In this group, the combination was ineffective as 1 patient died, 2 had to be admitted to the ICU, and 8 (of 10) were still positive for the virus by nasal swab on day 5 or 6 after treatment. One patient had to discontinue therapy on day 4 because of prolongation of the QT interval [38].
Also, a multicenter, open-label, randomized controlled trial from China analyzed 75 patients receiving standard of care, and 75 receiving 1200 mg of HCQ per day for the first 3 days and then 800 mg per day for 2 weeks or 3 weeks (mild/moderate or severe disease, respectively). Specimens from the upper or lower respiratory tract were analyzed for viral RNA at screening, and then at days 4, 7, 10, 14, 21, and 28. The number of negative tests was similar between the two groups after 28 days (85.4% in the HCQ group, 81.3% in the standard of care group). Post hoc analysis did not identify any subgroups that showed a difference in these results. The alleviation of symptoms was also similar, but the adverse events were more frequent in the HCQ group (30% vs 9%), being diarrhea the most frequent [39].
Regarding the need to be admitted to ICU, a retrospective study from France analyzed 181 patients who were receiving oxygen therapy. Eighty-four received HCQ (600 mg per day) and the rest did not receive HCQ. The composite primary endpoint was transfer to an ICU within 7 days or death from any cause, and the secondary endpoint was the development of acute respiratory distress syndrome (ARDS). There were no statistical differences between the two groups. Eight of the patients in the HCQ group had electrocardiogram changes that required to stop the medication [40].
In relation to the cardiovascular risk, it is worth mentioning a study from the USA where 84 patients were treated with HCQ plus azithromycin combination. A notable QT interval prolongation was found in 30% of the patients, and in 11%, the interval increased to > 500 ms, with a high risk for arrhythmia. The mean age was 63, 74% of the patients were male, 65% had hypertension, and 20% were diabetic. The development of renal failure while on the drug combination was a strong predictor of QT interval prolongation [41]. Also, a multinational collaboration presented data from health care systems in Germany, Japan, Netherlands, Spain, UK, and the USA where the safety of HCQ and azithromycin combination versus HCQ and amoxicillin combination was compared. In users of the HCQ and azithromycin combination, a 15% increased risk of angina/chest pain, 22% increased risk of heart failure, and 2 times increased risk of cardiovascular mortality at 30 days of treatment was found in 323,122patients [42]. Finally, a study from Brazil analyzed 81 patients in two treatments arms, CQ 1200 mg per day for 10 days or low dose (900 mg on the first day, 450 mg for the next 4 days). All patients also received azithromycin and ceftriaxone. The high-dose arm showed more QT interval prolongation (> 500 ms) and a trend toward higher mortality (17%) than the lower dose group. The overall mortality rate was 13.5%, similar with their historical rate of patients not receiving CQ. The authors had to stop recruiting patients for the high-dose arm due to the cardiovascular events. The authors mention that they did not use a placebo control group as the use of placebo in Brazil in severe cases of COVID-19 infections was not considered ethically acceptable by national regulatory health agencies [43].