key: cord-275037-sji0u8nu
authors: Cavalli, Giulio; Dagna, Lorenzo
title: Large-scale use of hydroxychloroquine for COVID-19 confirms safety, if not effectiveness
date: 2020-10-28
journal: Eur J Intern Med
DOI: 10.1016/j.ejim.2020.10.023
sha: 
doc_id: 275037
cord_uid: sji0u8nu

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In this issue of the Journal, Di Castelnuovo and colleagues report the findings of the observational multicentre Italian CORIST Study on the use of hydroxychloroquine (HCQ) in hospitalised COVID-19 patients [1] . In this large, retrospective cohort of 3,451 COVID-19 inpatients from 33 clinical centers, the use of HCQ was associated with a significant increase in survival. Specifically, the Authors reported an in-hospital death rate of 8.9 per 1,000 person-day for patients receiving HCQ, and of 15.7 for patients not receiving HCQ. Using an inverse probability weighting approach for propensity matching, and adjusting for various possible confounders, the Authors report a 30% reduction in the mortality risk in patients receiving HCQ. While these findings may provide clinical evidence in support of the use of HCQ therapy in patients with COVID-19, the study findings ought to be considered with caution, in light of several limitations, which are inherent to the retrospective, observational design of this study. These include bias by indication (why did some patients receive HCQ in addition to standard management, whereas others did not?), a possible immortal time bias (patients who died before treatment administration tend to be included as controls in retrospective studies), and of the fact that residual confounders typically remain even after stringent propensity matching is applied (not all clinically relevant variables are included in or captured by covariate analyses). However, these inherent limitations should not discourage large, real-world observational studies, which are particularly informative on the safety, rather than the efficacy of medications. In these regards, the study by Di Castelnuovo and colleagues holds clear value.

Hydroxychloroquine (HCQ) is broadly used for the treatment of autoimmune and rheumatologic conditions such as lupus and rheumatoid arthritis [2] . It is orally administered, well tolerated, and safe, as there are no common adverse events typically limiting its use. A feared but utterly rare long-term side effect is retinal deposition leading to progressive visual impairment, whereas theoretical risks of arrhythmic disturbances are clinically negligible (i.e., no cardiac screening is required prior to initiation of HCQ treatment). Before use in autoimmune patients, HCQ was effectively used as an antimalarial agent. Of note, evidence accumulating since the late 1960 ′ s also indicates in vitro antiviral activity [2] . Specifically, HCQ interferes with a key step of the infection lifecycle of different viruses, by inhibiting endosomal acidification and viral entry into the host cell. In vitro, this effect prevented infection of target cells by clinical isolates of SARS-CoV-2 [3] . Following these and other reports, empirical, large-scale use of HCQ began with the wishful aim of preventing development of COVID-19 or escalation to severe disease states. HCQ was one of many agents used to treat rheumatologic conditions, which were repurposed for use in COVID-19 patients. Other notable examples include biologic cytokine inhibitors such as the interleukin IL-1 blocker anakinra [4] , the IL-6 blockers tocilizumab and sarilumab [5, 6] , and the GM-CSF blocker mavrilimumab [7, 13, 14] .

In general, published studies as well as direct physician experience indicate that HCQ is marginally or not effective for the treatment of COVID-19, regardless of the disease stage and the dose administered [8] [9] [10] . However, a controversial, and later retracted publication raised concerns that HCQ might be associated with an increase in the risk of death due to arrhythmia and cardiac events [11] . This finding, which was in stark contrast with clinical experience with HCQ in immune-rheumatologic conditions, was later debased by a retraction [12] and refuted by subsequent, separate studies. In these regards, the study by Di Castelnuovo and colleagues is particularly valuable, as included patients had an acute, severe disease, were on concomitant therapies with other drugs, and had pre-existing comorbidities such as ischemic heart disease, cancer and severe chronic kidney disease. Controlled, prospective investigations will determine the efficacy of HCQ in COVID-19. Properly conducted real-world, retrospective investigations can reassure physicians that this old-used medication is generally safe and well tolerated.

Of chloroquine and COVID-19

Therapeutic options for the 2019 novel coronavirus (2019-nCoV)

Interleukin-1 blockade with high-dose anakinra in patients with COVID-19, acute respiratory distress syndrome, and hyperinflammation: a retrospective cohort study

Interleukin-6 blockade with sarilumab in severe COVID-19 pneumonia with systemic hyperinflammation: an open-label cohort study

Efficacy and safety of tocilizumab in severe COVID-19 patients: a single-centre retrospective cohort study

GM-CSF blockade with mavrilimumab in severe COVID-19 pneumonia and systemic hyperinflammation: a single-centre, prospective cohort study

Observational Study of Hydroxychloroquine in Hospitalized Patients with Covid-19

Association of Treatment With Hydroxychloroquine or Azithromycin With In-Hospital Mortality in Patients With COVID-19 in New York State

Effect of Hydroxychloroquine in Hospitalized Patients with COVID-19: Preliminary results from a multi-centre, randomized

Hydroxychloroquine or chloroquine with or without a macrolide for treatment of COVID-19: a multinational registry analysis

Retraction-Hydroxychloroquine or chloroquine with or without a macrolide for treatment of COVID-19: a multinational registry analysis [retraction of: Lancet

Targeting GM-CSF in COVID-19 Pneumonia: Rationale and Strategies

Targeting IL-1, IL-6 or GM-CSF in COVID-19