Comments
Abstract
The rapid global spread and significant mortality associated with the coronavirus disease (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral infection has spurred an urgent race to find effective treatments. Repurposing existing drugs is a particularly attractive approach as pharmacokinetic and safety data already exist; thus, development can leapfrog straight to clinical trials of efficacy, generating results far more quickly than de novo drug development. This review summarizes the state of play for the principle drugs identified as candidates to be repurposed for treating COVID-19 grouped by broad mechanism of action: antiviral, immune enhancing, and antiinflammatory or immunomodulatory. Patient selection, particularly with regard to disease stage, is likely to be key. To date, only dexamethasone and remdesivir have been shown to be effective, but several other promising candidates are in trials.
Coronavirus disease (COVID-19) is the illness resulting from syndrome coronavirus 2 (SARS-CoV-2), a highly pathogenic coronavirus showing some similarities with Middle East respiratory syndrome (MERS)-CoV and SARS-CoV. Unlike the previous MERS and SARS outbreaks, the 2019/20 outbreak has been declared a pandemic by the World Health Organization owing to high infectivity and case fatality rates. Most countries have introduced unprecedented emergency measures to support the medical response, at significant cost to their citizens and economies. Efficacious treatment, prevention of spread, and vaccine development are global imperatives.
Vaccines and antiviral therapies developed de novo for SARS-CoV-2 are likely to take at least 12–18 months to become clinically available. Repurposing existing pharmacological therapies that already have safety data can be achieved far more quickly and is therefore a major focus of current research. This review discusses the principal therapies that are targets of repurposing efforts for COVID-19, summarizing the theoretical basis and available evidence for each. Where it exists, we focus on human clinical data in SARS-CoV-2 infection, but in the absence of those data, evidence is drawn from the other epidemic respiratory viruses including influenza, SARS-CoV, and MERS-CoV. The volume of literature and research on COVID-19 is such that it is not possible to discuss all existing drugs that have been proposed as treatment options; thus, we have focused on agents where there was clear supportive evidence to draw from. Treatment of complications such as fever, thromboses, acute respiratory distress syndrome, and secondary bacterial infections are outside the scope of this review and are not directly addressed.
Studies of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) suggest that most cases are initiated by relatively low virus loads and have a benign course, with symptoms ranging from asymptomatic to mild or moderate disease of variable duration. More severe disease is associated with higher viral load at presentation (1, 2), with fever and cough the most typical symptoms (3). This is followed by a second phase likely characterized by virus-load–driven inflammatory response and manifests as pneumonia, hypoxemia, and fever, occurring 7–8 days from symptom onset, when most patients present to the hospital (4, 5). A subgroup progress to a third phase with an overwhelming proinflammatory response (again likely virus-load driven, with severe disease associated with delayed viral clearance up until at least Day 10) (1) resulting in acute respiratory distress syndrome (ARDS), usually around Day 10 (4). Nasopharyngeal viral load peaks in the early stages in mild disease, but tends to be higher in severe disease and to persist for longer (1), suggesting that antiviral or immune-boosting therapies are likely to be most beneficial in this early phase (it is well established from previous studies of antiviral therapies in respiratory disease that early intervention results in better outcomes). However, recent results with the antiviral remdesivir indicate that antivirals administered even as late as at hospitalization can be effective (6, 7). Equally immunosuppressive therapies may have deleterious effects if given when viral loads are high and the magnitude of the inflammatory response is appropriate. A suggestion that this is the case is seen in the trend toward increased mortality in patients not receiving oxygen therapy treated with dexamethasone (risk ratio [RR], 1.22; 95% confidence interval [95% CI], 0.93–1.61) (8). As the disease progresses to its most severe form, hyperinflammation is undoubtedly present, and thus, in those who develop ARDS, therapeutics aimed at attenuating the inflammatory response may be effective. Correspondingly dexamethasone improves survival in those requiring oxygen and particularly in those requiring mechanical ventilation, with a greater mortality benefit in those with a longer duration of symptoms (Figure 1) (8).
Figure 1. Possible timing of drug treatments by disease phase. Following infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), respiratory viral load is likely to increase over the first 7 days before stabilizing or starting to decrease. Interferon responses and airway inflammatory response is delayed, with early symptoms typically occurring 5 days following infection. In 80% of people affected, symptoms are mild and patients recover without further medical intervention. However, a subgroup of patients experience symptoms of an excessive and dysregulated inflammatory response to viral infection presenting with breathlessness, hypoxia, and symptoms of viral pneumonia at Day 7. This excessive inflammatory response may continue to progress to acute respiratory distress syndrome, leading to the need for mechanical ventilation or death. Treatments aimed at preventing viral replication such as exogenous interferons, hydroxychloroquine, azithromycin, or specific antivirals are most likely to be effective in the early stages of disease, when viral load is increasing, before hospital admission. In contrast, treatments aiming to reduce the excessive inflammatory response to viral infection such as corticosteroids and immunomodulatory drugs are more likely to be effective in the later stages of disease following hospital admission. COVID-19 = coronavirus disease.
[More] [Minimize]Remdesivir was developed to treat Ebola, another single-stranded RNA virus, during the recent epidemic in West Africa. It acts as an adenosine analog to interfere with viral RNA-dependent RNA-polymerase (RdRp) and induce premature or delayed RNA chain termination (9), while evading viral exoRNase activity (10). In vitro, it has antiviral activity against respiratory viral pathogens including SARS-CoV-2 (11). Similar protective effects are seen in vivo in SARS-CoV– and Middle East respiratory syndrome (MERS-CoV)–infected mice with reduced airway inflammation and lung function decline (12, 13). Importantly, the efficacy of postexposure treatment depends on when the drug is given relative to peak viral replication and airway epithelial damage (11, 12).
A case series of 61 hospitalized patients treated with remdesivir off license reported a clinical improvement in 36 out of 53 patients with sufficient data to analyze, although without a control group it is difficult to interpret these findings (14). An initial randomized controlled trial (RCT) was inconclusive, with a nonsignificant trend toward reduced time to clinical improvement favoring remdesivir (15). However, this trial was underpowered, with recruitment ending prematurely at 237 out of an intended 453 patients following the end of the outbreak in Wuhan. A subsequent RCT enrolling 1,063 patients found accelerated recovery in patients receiving remdesivir (median time to recovery 11 d vs. 15 d on placebo; P < 0.001) (7). In addition, there was a trend toward improved survival at Day 14 (7.1% with remdesivir vs. 11.9% placebo; hazard ratio [HR], 0.7; 95% CI, 0.47–1.04). Subgroup analysis found no benefit in those on high-flow oxygen or noninvasive ventilation, or invasive ventilation, suggesting that antivirals such as remdesivir will be of limited efficacy in late disease where the pathology is likely inflammatory in origin. It should be noted the study was reported early and full outcomes (e.g., 28-d mortality) were therefore only available for 731/1,063 (69%) patients; further follow-up data are awaited.
Favipiravir acts as a purine analog to also disrupt RdRp and is licensed to treat influenza in Japan (16). It is effective in vitro against a range of RNA viruses including SARS-CoV-2 (11). In mice, favipiravir improves survival in influenza A infection (17).
An open-label nonrandomized trial in China found a significantly shorter time to viral clearance (4 d [interquartile range (IQR), 2.5–9] vs. 11 d [IQR, 8–13]) and greater improvement in chest radiographic appearances in patients with SARS-CoV-2 treated with favipiravir/interferon (IFN)-α (n = 35) compared with lopinavir/ritonavir/IFN-α (n = 45) (18).
Lopinavir (LPV) and ritonavir (RTV) are protease inhibitors that are prescribed in combination form (Kaletra; AbbVie) for the treatment of human immunodeficiency virus. Lopinavir is thought to inhibit coronavirus proteases that cleave viral polyprotein to lead to the formation of RdRp; ritonavir boosts the bioavailability of lopinavir by inhibiting cytochrome P450. Ribavirin is a guanosine analog, terminating RdRp-mediated viral RNA chain elongation (19). In murine MERS-CoV infection, prophylactic LPV/RTV-IFN-β modestly reduced viral load compared with remdesivir, but treatment after infection showed no significant effect on viral load, lung hemorrhage, or acute lung injury (13).
Numerous human studies have assessed LPV/RTV, with or without ribavirin, as a treatment for COVID-19. A retrospective cohort study observed no difference in viral shedding or survival for 41/191 patients treated with LPV/RTV (20). Similarly, a larger (n = 199) open-label RCT found LPV/RTV did not affect time to clinical improvement (HR for clinical improvement, 1.24; 95% CI, 0.90–1.72) (21). However a modified intention-to-treat analysis that excluded three patients who died within 24 hours of randomization found time to clinical improvement was a median 1 day shorter in the treatment group (15 d vs. 16 d; HR, 1.39; 95% CI, 1.00–1.91). There was no difference in viral loads, with 42% of patients positive for SARS-CoV-2 at Day 28 suggesting at best incomplete antiviral effects, and higher gastrointestinal adverse effects in the treatment group. Several limitations may have impacted the results including higher baseline viral loads in the treatment group, the possibility of confounding from additional clinical interventions (e.g., corticosteroids), and delayed time to intervention (enrollment was a median 13 d after symptom onset). A smaller (n = 86) open-label RCT comparing LPV/RTV, umifenovir, and a control group on no antiviral found no evidence of benefit in terms of time to viral clearance, antipyresis, cough alleviation, or improvement of chest computed tomography (22).
To date, only one open-label RCT has assessed the combination of ribavirin with LPV/RTV, with IFN-β additionally given if patients had a symptom history of <7 days (23). Triple therapy was associated with reductions in time to viral clearance, normalization of vital observations, and length of hospital stay compared with LPV/RTV. In a subgroup analysis, these findings were only true of those treated within 7 days of symptom onset. This trial only enrolled patients with mild or moderate disease (there was no mortality in either group, n = 127), so it is unclear whether the findings apply to severe patients.
Chloroquine has long been used as an antimalarial agent. The emergence of chloroquine-resistant strains of Plasmodium prompted the development of chloroquine analogs including hydroxychloroquine. Hydroxychloroquine, owing to its immunomodulatory properties, is used in the treatment of autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis. It is less toxic in animals than chloroquine (24) (Table 1).
| • Vaccines and antiviral therapies developed de novo for SARS-CoV-2 are likely to take at least 12–18 mo to become clinically available. |
| • Repurposing licensed drugs with existing safety data can be achieved far more quickly. |
| • Timing of treatment is likely to be key: antivirals should be more effective if given early; antiinflammatory treatments if given later in the disease course. |
| • Currently, the only drugs with RCT data supporting their use in COVID-19 are: |
| dexamethasone, which reduced mortality in patients requiring oxygen and/or mechanical ventilation; and |
| remdesivir, which shortened time to recovery particularly in milder cases (probably earlier in the disease course). |
| • It is important that, despite the urgency, clinical trial research is conducted in line with accepted scientific principles. Poorly designed trials consume research resources and time without advancing our understanding, therefore unethically exposing patients to unproven therapies. |
| • A large number of clinical trials are currently in progress; readers are advised to consult the most up-to-date guidelines given the pace of change. |
Various mechanisms may underlie the antiviral properties of chloroquine and its analogs. Following protonation and subsequent accumulation of these drugs inside lysosomes, there is a rise in lysosomal pH, which interferes with subsequent intracellular viral trafficking (25). Chloroquine impairs autophagosome fusion with lysosomes (26) and inhibits terminal glycosylation of angiotensin-converting enzyme 2 on the cell surface, required for viral entry (27). Additionally, hydroxychloroquine interferes with both Toll-like receptor signaling (due to endosomal pH changes) (28) and cyclic guanosine monophosphate–adenosine monophosphate synthase (29), both of which result in diminished downstream production of type-I IFNs (30) and other cytokines, which may reduce the risk of a “cytokine storm.” (31) In vitro, hydroxychloroquine has superior activity against SARS-CoV-2 infection compared with chloroquine, when administered either before or after infection (32). Thus, it was hypothesized that chloroquine or hydroxychloroquine might be effective both early and late in the disease owing to their antiviral and antiinflammatory effects, respectively.
Both chloroquine and hydroxychloroquine are being assessed as treatments for SARS-CoV-2 in various clinical trials. There are no published data on chloroquine, despite reports in the media and inclusion in various national guidelines. However, published trials of hydroxychloroquine have been the subject of some controversy, with a small (n = 26) but well-publicized open-label trial in France suggesting benefit (33), although many have questioned these results because of major methodological flaws, including exclusion of six patients in the treatment arm, a lack of randomization, possible confounders including variable viral loads at enrollment, and selection bias in the administration of azithromycin to a subset of patients. A separate pilot study of 30 patients randomized to hydroxychloroquine or conventional treatment found no significant differences in time to viral clearance, resolution of fever, or radiological progression (34). A further open-label RCT of 150 hospitalized patients comparing hydroxychloroquine with standard of care showed no difference in viral clearance at 28 days but did show an improvement in symptom burden and reduction in C-reactive protein at 28 days (35). However, this was offset by a significantly higher risk of adverse events—30% in the hydroxychloroquine group versus 8.8% in the standard of care group (P = 0.001).
A retrospective analysis of 368 patients treated with hydroxychloroquine monotherapy, hydroxychloroquine and azithromycin, or standard care found no difference in the need for mechanical ventilation but an increased risk of all-cause mortality in the hydroxychloroquine group (HR, 2.61; 95% CI, 1.10–6.17; P = 0.03) (36). A very large (n = 96,032) observational study of chloroquine and hydroxychloroquine with or without a macrolide was published in The Lancet, reporting an increase in mortality with treatment, but has since been retracted over concerns regarding the integrity of the source data (37). A press release from the RECOVERY (Randomised Evaluation of COVid-19 thERapY) trial has reported no benefit of hydroxychloroquine (28-d mortality 25.7% vs. 23.5% usual care; HR, 1.11; 95% CI, 0.98–1.26; P = 0.10); full results are awaited (38). Treatment is not without risk: serious adverse effects including QT prolongation with potentially fatal cardiac arrhythmia have been reported in patients treated with both drugs (39). More robust data are now needed before these drugs can be given in COVID-19.
IFNs, specifically type-I (IFN-α and-β) and -III (IFN-λ), are a key component of the host innate defense against viruses. Upon viral infection, specific molecular patterns that are frequently expressed by viruses are detected by host pattern recognition receptors to induce secretion of IFNs. These then mediate a gene expression program via hundreds of IFN-stimulated genes with pleiotropic antiviral effects (40). Both SARS-CoV-2 and SARS-CoV can delay and/or reduce type-I IFN signaling and thus replicate to high viral titers (41, 42). This impaired IFN response is a direct consequence of strategies evolved by the virus to evade host immune defenses. These include mechanisms to counteract IFN induction, for example, sequestering viral dsRNA within double membrane vesicles to escape detection, and to disrupt IFN signaling, for example, proteolytic degradation of the type-I IFN receptor, blocking STAT1 phosphorylation (43).
IFN deficiencies may partly explain the striking high mortality in the elderly in COVID-19 (44). Researchers comparing SARS-CoV infection in aged and young adult macaques found more pathology in the older animals despite similar viral titers, with decreased expression of IFN-β and increased expression of inflammatory genes in lung tissue (45). Treating aged macaques with IFN-α 1 and 3 d after infection significantly improved lung pathology and outcomes, with corresponding differences in proinflammatory gene transcripts. Prophylactic or early-disease-phase treatment with IFN has therefore been proposed.
Although IFNs were discovered in 1957, when Lindenmann and Isaacs observed that chicken embryos stimulated with heat-killed viruses released a soluble product that “interfered” with influenza virus replication, it took the advent of recombinant DNA production techniques to enable sufficient IFNs to be produced to assess their therapeutic potential. Initial studies found intranasal IFN-α reduced infection rates, symptoms, and viral loads both following experimental infection with respiratory viruses (rhinoviruses, coronaviruses, and influenza) and when given as prophylaxis for naturally occurring infections (46). However, treatment was associated with nasal erosions and bleeding, which led to these therapies being abandoned, although IFNs were subsequently licensed for the treatment of chronic hepatitis B and C.
More recently, investigators assessed whether inhaled IFN-β given to patients with asthma within 24 hours of cold symptoms would improve their asthma control (47). Although the primary endpoint was not met, a prespecified subgroup analysis found reduced symptom scores and improved lung function in those with moderately severe asthma. Timing may be key: a recent ex vivo study found effects only when treating macrophages and bronchial epithelial cells with IFN-β before, but not after, stimulation with influenza (48).
In vitro and in vivo studies of SARS-CoV and MERS-CoV have found high-dose type-I and -III IFN to be effective (43). A single pilot clinical trial in SARS with 22 patients indicated that the addition of IFN‐α to corticosteroids was associated with improved oxygen saturations, resolution of lung abnormalities on imaging, and a trend toward reduced need for mechanical ventilation (49). However, the IFN-α group also received higher doses of corticosteroids and the numbers are too small to draw firm conclusions. IFN-α was given at a median 8 days after symptom onset, implying beneficial effects even when given relatively late after infection, consistent with a study of SARS-infected macaques treated with IFN-α2β (50). This is of particular interest because it suggests that exogenous IFNs may still be beneficial at the time patients present to the hospital.
A recent in vitro study suggests SARS-CoV-2 may be more susceptible to IFN-α treatment than SARS-CoV, which the authors attributed to differences in two of the viral proteins that antagonize IFN (51). Several trials of recombinant IFN therapy are in progress. IFN treatment will need to be carefully balanced against the potential for these drugs to promote pulmonary vascular disease (52).
Azithromycin is a macrolide antibiotic that possesses additional properties that may support its use in viral infections, including induction of antiviral IFNs. Azithromycin doubles levels of antiviral type-I and type-III IFN released from virus-infected bronchial epithelial cells, a property not seen with the macrolides erythromycin and telithromycin or roughly half of 225 novel macrolides studied (53, 54). Macrolides also possess antiinflammatory properties (55) that could ameliorate COVID-19 and are antibiotic and thus could help prevent secondary bacterial infection. A drug screen preprint has suggested azithromycin possesses antiviral activity against SARS-CoV-2 (56), although this has not been seen in other drug screening studies (57).
Two studies assessing the effectiveness of azithromycin when added to oseltamivir in patients with influenza showed evidence of clinical benefit (58, 59). Conversely, analysis of a retrospective multicenter cohort of patients with MERS treated with macrolides found no improvement in 90-day mortality or viral clearance (60). However, this study only included critically ill patients with MERS, the majority of whom were not treated with a macrolide until after admission to intensive care, and 39% of whom received a macrolide other than azithromycin. As with chloroquine and hydroxychloroquine, azithromycin is associated with serious adverse effects, also including QT prolongation and cardiac arrhythmias, and in the absence of evidence of benefit, should not be given outside of a clinical trial.
The transfer of antibodies from a recovered patient to a diseased one, so-called passive immunity, received revived interest during the Ebola epidemic. Convalescent plasma or sera are attractive options but logistically challenging to source at scale. A single RCT found no benefit in the primary outcome of time to clinical improvement, although a statistically significant reduction was seen in a subgroup with severe but non–life-threatening disease (61). There was also a trend toward significantly reduced 28-day mortality that requires further corroboration. However, this study was underpowered, terminating early with 103 out of the planned 200 patients owing to containment of COVID-19 in China. The only other evidence comes from isolated reports of the use of convalescent plasma in COVID-19, with a meta-analysis finding seven case series and one prospective single-arm study with a total of 32 participants (62). With small numbers, a lack of control groups, and a high risk of bias, no conclusions could be drawn about efficacy, and although serious adverse events were infrequent, they were not absent. Forty-seven studies are ongoing, including 22 RCTs.
The rationale for using immunomodulatory therapies in SARS-CoV-2 is to target hyperinflammation in the later stages of COVID-19. In clinical studies of SARS-CoV infection, serum levels of proinflammatory cytokines (IFN-γ, IL-1, IL-6, IL-12, and TGFβ) and chemokines (CCL2, CXCL8, CXCL9, and CXCL10) were significantly higher in plasma from patients with severe disease compared with those with moderate disease (63, 64). High levels of the proinflammatory cytokines IL-6, IL-8, and IL-1β and chemokines CCL2, CCL5, CXCL10, and CCL3 were associated with an increased risk of ARDS (64, 65). Accordingly, an early study of patients infected with SARS-CoV-2 with ARDS requiring ICU admission exhibited higher serum levels of IL-2, IL-7, IL-10, G-CSF, MCP-1, MIP-1a, TNF, and CXCL10 compared with patients not requiring ICU care (4), while an elevated ferritin and serum IL-6 have been associated with increased risk of mortality (20). This cytokine profile has been likened to secondary hemophagocytic lymphohistiocytosis, a hyperinflammatory syndrome that can be caused by viral infections and frequently results in ARDS (66). In addition, many of the clinical features and laboratory findings of patients with severe COVID-19 meet the criteria for cytokine storm syndrome (CSS) (67). Consequently, immunomodulators and compounds targeting specific inflammatory cytokines are being pursued as potential treatments. However, it should be noted that no report discussing CSS in SARS, MERS, or COVID-19 has actually measured virus load in the lung, so whether CSS is purely driven by high lung virus loads has not been properly investigated to date.
Blockade of IL-6 with the humanized monoclonal antibody tocilizumab is currently U.S. Food and Drug Administration approved for use in cytokine release syndrome as well as rheumatoid arthritis and systemic juvenile idiopathic arthritis. As a result, there is substantial interest in IL-6 blockade as a treatment in COVID-19 resulting in off-license use.
Numerous case series of patients treated with tocilizumab off license have been published with mixed results (68–75). Certainly tocilizumab is effective in reducing fever and inflammatory markers, but whether clinical outcomes are meaningfully different will require an RCT, of which several are in progress. Another anti–IL-6 monoclonal antibody, siltuximab, has been used in 21 ventilated patients with COVID-19 on compassionate use grounds. An improvement was seen in seven patients, with nine patients stabilizing. However, five (24%) experienced worsening in their condition (76).
Binding of SARS-CoV-2 also activates pro–IL-1β, leading to inflammasome activation and production of IL-1β (77), which in turn mediates influx of inflammatory cells, resulting in lung inflammation and eventually fibrosis. Anti–IL-1 therapy with the recombinant IL-1RA (IL-1 receptor antagonist) protein anakinra has previously been shown to reduce mortality in patients with sepsis-related hyperinflammation (78). Three small case series in COVID-19 from Greece, France, and Italy with between five and nine patients have now been published (79–81), but as for anti–IL-6 therapies, it is hard to draw conclusions in the absence of a control group randomized to placebo. RCTs are ongoing.
The use of systemic corticosteroids to suppress SARS-CoV-2–induced lung inflammation has been advocated to prevent and/or treat ARDS, but there is a risk that they inhibit immune responses and impair pathogen clearance. Indeed, in severe influenza, corticosteroids are associated with increased mortality (82). Initial World Health Organization guidance on COVID-19 cautioned against the routine use of systemic corticosteroids, except for specific indications, such as septic shock or an exacerbation of underlying airways disease (83).
That has changed with the recent results of a large (n = 6,425) RCT of dexamethasone (8). Twenty-eight day mortality was reduced with dexamethasone in the overall cohort (21.6% vs. 24.6% usual care; RR, 0.83; 95% CI, 0.74–0.92; P < 0.001). Strikingly, dexamethasone reduced mortality by 35% in those on mechanical ventilation (29.0% vs. 40.7%; RR, 0.65; 95% CI, 0.48–0.88; P = 0.003) and by 20% in those treated with oxygen (21.5% vs. 25.0%; RR, 0.80; 95% CI, 0.67–0.96; P = 0.0021) but with a trend toward worse survival in mild cases not requiring oxygen (17.0% vs. 13.2%; RR, 1.22; 95% CI, 0.93–1.61; P = 0.14). As well as demonstrating the benefit of dexamethasone, this result reinforces the importance of RCTs: previous observational studies in COVID-19 had found associations between corticosteroid use and disease severity and/or death, which now appears to reflect a greater propensity to treat with corticosteroids in severe disease (84–86).
Currently, there is only RCT evidence in COVID-19 to support dexamethasone in patients requiring at least oxygen therapy, and remdesivir for shortening time to recovery, although remdesivir appears only to be beneficial if given early in the disease process. A large number of clinical trials are currently in progress assessing a variety of existing antiviral, immune-enhancing, immunomodulatory, and immunosuppressive treatments. Early results are expected in the coming weeks, months ahead of vaccines and newly developed antivirals. Readers are advised to consult the most up-to-date guidelines given the pace of change.
Although there is a place for the use of drugs on compassionate grounds and experience sharing through reports of case series, it is important that, despite the urgency, clinical trial research is conducted in line with accepted scientific principles (as set out in various guidelines) (87, 88). Poorly designed trials consume research resources and time without advancing our understanding of whether a treatment is effective and as such represent unethical exposure of patients to unproven therapies. National and international coordination of trials will also be important, both to ensure a unified effort and to rationalize the number of trials, thereby reducing the risk of a type-I error. Governments and health service providers must also maintain a focus on preventive measures, both nonpharmacological and vaccines. Ultimately, treatments will be needed as social distancing measures, which cannot go on indefinitely, are finally lifted.
| 1 . | Liu Y, Yan LM, Wan L, Xiang TX, Le A, Liu JM, et al. Viral dynamics in mild and severe cases of COVID-19. Lancet Infect Dis 2020;20:656–657. |
| 2 . | Adura PT, Reed E, Macintyre J, Del Rosario A, Roberts J, Pestridge R, et al. Experimental rhinovirus 16 infection in moderate asthmatics on inhaled corticosteroids. Eur Respir J 2014;43:1186–1189. |
| 3 . | Channappanavar R, Perlman S. Pathogenic human coronavirus infections: causes and consequences of cytokine storm and immunopathology. Semin Immunopathol 2017;39:529–539. |
| 4 . | Huang C, Wang Y, Li X, Ren L, Zhao J, Hu Y, et al. Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China. Lancet 2020;395:497–506. |
| 5 . | Peiris JS, Chu CM, Cheng VC, Chan KS, Hung IF, Poon LL, et al.; HKU/UCH SARS Study Group. Clinical progression and viral load in a community outbreak of coronavirus-associated SARS pneumonia: a prospective study. Lancet 2003;361:1767–1772. |
| 6 . | NIAID. NIH clinical trial shows remdesivir accelerates recovery from advanced COVID-19. Bethesda, MD: National Institute of Allergy and Infectious Diseases; 2020 [accessed 2020 Apr 30]. Available from: https://www.niaid.nih.gov/news-events/nih-clinical-trial-shows-remdesivir-accelerates-recovery-advanced-covid-19. |
| 7 . | Beigel JH, Tomashek KM, Dodd LE, Mehta AK, Zingman BS, Kalil AC, et al. Remdesivir for the treatment of Covid-19 - preliminary report. N Engl J Med [online ahead of print] 22 May 2020; DOI:https://doi.org/10.1056/NEJMoa2007764. |
| 8 . | RECOVERY Collaborative Group. Dexamethasone in hospitalized patients with Covid-19—Preliminary Report. N Engl J Med [online ahead of print] 17 Jul 2020; DOI: 0.1056/NEJMoa2021436. |
| 9 . | Tchesnokov EP, Feng JY, Porter DP, Götte M. Mechanism of inhibition of Ebola virus RNA-dependent RNA polymerase by remdesivir. Viruses 2019;11:326. |
| 10 . | Agostini ML, Andres EL, Sims AC, Graham RL, Sheahan TP, Lu X, et al. Coronavirus susceptibility to the antiviral Remdesivir (GS-5734) is mediated by the viral polymerase and the proofreading exoribonuclease. mBio [online ahead of print] 6 Mar 2018; DOI:https://doi.org/10.1128/mBio.00221-18. |
| 11 . | Wang M, Cao R, Zhang L, Yang X, Liu J, Xu M, et al. Remdesivir and chloroquine effectively inhibit the recently emerged novel coronavirus (2019-nCoV) in vitro. Cell Res 2020;30:269–271. |
| 12 . | Sheahan TP, Sims AC, Graham RL, Menachery VD, Gralinski LE, Case JB, et al. Broad-spectrum antiviral GS-5734 inhibits both epidemic and zoonotic coronaviruses. Sci Transl Med 2017;9:eaal3653. |
| 13 . | Sheahan TP, Sims AC, Leist SR, Schäfer A, Won J, Brown AJ, et al. Comparative therapeutic efficacy of remdesivir and combination lopinavir, ritonavir, and interferon beta against MERS-CoV. Nat Commun 2020;11:222. |
| 14 . | Grein J, Ohmagari N, Shin D, Diaz G, Asperges E, Castagna A, et al. Compassionate use of remdesivir for patients with severe covid-19. N Engl J Med 2020;382:2327–2336. |
| 15 . | Wang Y, Zhang D, Du G, Du R, Zhao J, Jin Y, et al. Remdesivir in adults with severe COVID-19: a randomised, double-blind, placebo-controlled, multicentre trial. Lancet 2020;395:1569–1578. |
| 16 . | Sangawa H, Komeno T, Nishikawa H, Yoshida A, Takahashi K, Nomura N, et al. Mechanism of action of T-705 ribosyl triphosphate against influenza virus RNA polymerase. Antimicrob Agents Chemother 2013;57:5202–5208. |
| 17 . | Sidwell RW, Barnard DL, Day CW, Smee DF, Bailey KW, Wong MH, et al. Efficacy of orally administered T-705 on lethal avian influenza A (H5N1) virus infections in mice. Antimicrob Agents Chemother 2007;51:845–851. |
| 18 . | Cai Q, Yang M, Liu D, Chen J, Shu D, Xia J, et al. Experimental treatment with favipiravir for COVID-19: an open-label control study. Engineering (Beijing) [online ahead of print] 18 Mar 2020; DOI:https://doi.org/10.1016/j.eng.2020.03.007. |
| 19 . | Dixit NM, Perelson AS. The metabolism, pharmacokinetics and mechanisms of antiviral activity of ribavirin against hepatitis C virus. Cell Mol Life Sci 2006;63:832–842. |
| 20 . | Zhou F, Yu T, Du R, Fan G, Liu Y, Liu Z, et al. Clinical course and risk factors for mortality of adult inpatients with COVID-19 in Wuhan, China: a retrospective cohort study. Lancet 2020;395:1054–1062. [Published erratum appears in Lancet 395:1038.] |
| 21 . | Cao B, Wang Y, Wen D, Liu W, Wang J, Fan G, et al. A trial of lopinavir-ritonavir in adults hospitalized with severe covid-19. N Engl J Med 2020;382:1787–1799. |
| 22 . | Li Y, Xie Z, Lin W, Cai W, Wen C, Guan Y, et al. Efficacy and safety of lopinavir/ritonavir or arbidol in adult patients with mild/moderate COVID-19: an exploratory randomized controlled trial. Med [online ahead of print] 19 May 2020; DOI:https://doi.org/10.1016/j.medj.2020.04.001. |
| 23 . | Hung IF, Lung KC, Tso EY, Liu R, Chung TW, Chu MY, et al. Triple combination of interferon beta-1b, lopinavir-ritonavir, and ribavirin in the treatment of patients admitted to hospital with COVID-19: an open-label, randomised, phase 2 trial. Lancet 2020;395:1695–1704. |
| 24 . | McChesney EW. Animal toxicity and pharmacokinetics of hydroxychloroquine sulfate. Am J Med 1983;75:11–18. |
| 25 . | Al-Bari MAA. Chloroquine analogues in drug discovery: new directions of uses, mechanisms of actions and toxic manifestations from malaria to multifarious diseases. J Antimicrob Chemother 2015;70:1608–1621. |
| 26 . | Mauthe M, Orhon I, Rocchi C, Zhou X, Luhr M, Hijlkema K-J, et al. Chloroquine inhibits autophagic flux by decreasing autophagosome-lysosome fusion. Autophagy 2018;14:1435–1455. |
| 27 . | Vincent MJ, Bergeron E, Benjannet S, Erickson BR, Rollin PE, Ksiazek TG, et al. Chloroquine is a potent inhibitor of SARS coronavirus infection and spread. Virol J 2005;2:69. |
| 28 . | Kuznik A, Bencina M, Svajger U, Jeras M, Rozman B, Jerala R. Mechanism of endosomal TLR inhibition by antimalarial drugs and imidazoquinolines. J Immunol 2011;186:4794–4804. |
| 29 . | An J, Woodward JJ, Sasaki T, Minie M, Elkon KB. Cutting edge: antimalarial drugs inhibit IFN-β production through blockade of cyclic GMP-AMP synthase-DNA interaction. J Immunol 2015;194:4089–4093. |
| 30 . | van den Borne BE, Dijkmans BA, de Rooij HH, le Cessie S, Verweij CL. Chloroquine and hydroxychloroquine equally affect tumor necrosis factor-alpha, interleukin 6, and interferon-gamma production by peripheral blood mononuclear cells. J Rheumatol 1997;24:55–60. |
| 31 . | Zhou D, Dai S-M, Tong Q. COVID-19: a recommendation to examine the effect of hydroxychloroquine in preventing infection and progression. J Antimicrob Chemother 2020;75:1667–1670. |
| 32 . | Yao X, Ye F, Zhang M, Cui C, Huang B, Niu P, et al. In vitro antiviral activity and projection of optimized dosing design of hydroxychloroquine for the treatment of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Clin Infect Dis 2020;71:732–739. |
| 33 . | Gautret P, Lagier J-C, Parola P, Hoang VT, Meddeb L, Mailhe M, et al. Hydroxychloroquine and azithromycin as a treatment of COVID-19: results of an open-label non-randomized clinical trial. Int J Antimicrob Agents 2020;56:105949. |
| 34 . | Chen J, Liu D, Liu L, Liu P, Xu Q, Xia L, et al. A pilot study of hydroxychloroquine in treatment of patients with moderate coronavirus disease-19 (COVID-19) [in Chinese]. Zhejiang Da Xue Xue Bao Yi Xue Ban) 2020;49:215–219. |
| 35 . | Tang W, Cao Z, Han M, Wang Z, Chen J, Sun W, et al. Hydroxychloroquine in patients with mainly mild to moderate coronavirus disease 2019: open label, randomised controlled trial. BMJ 2020;369:m1849. |
| 36 . | Magagnoli J, Narendran S, Pereira F, Cummings T, Hardin J, Sutton S, et al. Outcomes of hydroxychloroquine usage in United States veterans hospitalized with Covid-19 [preprint]. medRxiv; 2020 [accessed 2020 Apr 23]. Available from: https://www.medrxiv.org/content/10.1101/2020.04.16.20065920v2. |
| 37 . | Mehra MR, Ruschitzka F, Patel AN. Retraction-hydroxychloroquine or chloroquine with or without a macrolide for treatment of COVID-19: a multinational registry analysis. Lancet 2020;395:1820. |
| 38 . | Randomised Evaluation of COVID-19 Therapy. Statement from the Chief Investigators of the Randomised Evaluation of COVid-19 thERapY (RECOVERY) Trial on hydroxychloroquine, 5 June 2020. 2020 [accessed 2020 Jun 5]. Available from: https://www.recoverytrial.net/files/hcq-recovery-statement-050620-final-002.pdf. |
| 39 . | Giudicessi JR, Noseworthy PA, Friedman PA, Ackerman MJ. Urgent guidance for navigating and circumventing the QTc-prolonging and torsadogenic potential of possible pharmacotherapies for coronavirus disease 19 (COVID-19). Mayo Clin Proc 2020;95:1213–1221. |
| 40 . | Singanayagam A, Joshi PV, Mallia P, Johnston SL. Viruses exacerbating chronic pulmonary disease: the role of immune modulation. BMC Med 2012;10:27. |
| 41 . | Channappanavar R, Fehr AR, Vijay R, Mack M, Zhao J, Meyerholz DK, et al. Dysregulated type I interferon and inflammatory monocyte-macrophage responses cause lethal pneumonia in SARS-CoV-infected mice. Cell Host Microbe 2016;19:181–193. |
| 42 . | Blanco-Melo D, Nilsson-Payant BE, Liu WC, Uhl S, Hoagland D, Møller R, et al. Imbalanced host response to SARS-CoV-2 drives development of COVID-19. Cell 2020;181:1036–1045, e9. |
| 43 . | Kindler E, Thiel V, Weber F. Interaction of SARS and MERS coronaviruses with the antiviral interferon response. Adv Virus Res 2016;96:219–243. |
| 44 . | Wu Z, McGoogan JM. Characteristics of and important lessons from the coronavirus disease 2019 (COVID-19) outbreak in China: summary of a report of 72 314 cases from the Chinese center for disease control and prevention. JAMA [online ahead of print] 24 Feb 2020; DOI:https://doi.org/10.1001/jama.2020.2648. |
| 45 . | Smits SL, de Lang A, van den Brand JMA, Leijten LM, van IJcken WF, Eijkemans MJC, et al. Exacerbated innate host response to SARS-CoV in aged non-human primates. PLoS Pathog 2010;6:e1000756. |
| 46 . | Borden EC, Sen GC, Uze G, Silverman RH, Ransohoff RM, Foster GR, et al. Interferons at age 50: past, current and future impact on biomedicine. Nat Rev Drug Discov 2007;6:975–990. |
| 47 . | Djukanović R, Harrison T, Johnston SL, Gabbay F, Wark P, Thomson NC, et al.; INTERCIA Study Group. The effect of inhaled IFN-β on worsening of asthma symptoms caused by viral infections: a randomized trial. Am J Respir Crit Care Med 2014;190:145–154. |
| 48 . | Watson A, Spalluto CM, McCrae C, Cellura D, Burke H, Cunoosamy D, et al. Dynamics of IFN-β responses during respiratory viral infection: insights for therapeutic strategies. Am J Respir Crit Care Med 2020;201:83–94. |
| 49 . | Loutfy MR, Blatt LM, Siminovitch KA, Ward S, Wolff B, Lho H, et al. Interferon alfacon-1 plus corticosteroids in severe acute respiratory syndrome: a preliminary study. JAMA 2003;290:3222–3228. |
| 50 . | Haagmans BL, Kuiken T, Martina BE, Fouchier RAM, Rimmelzwaan GF, van Amerongen G, et al. Pegylated interferon-α protects type 1 pneumocytes against SARS coronavirus infection in macaques. Nat Med 2004;10:290–293. |
| 51 . | Lokugamage KG, Schindewolf C, Menachery VD. SARS-CoV-2 sensitive to type I interferon pretreatment [preprint]. bioRxiv; 2020 [accessed 2020 Mar 9]. Available from: https://www.biorxiv.org/content/10.1101/2020.03.07.982264v1. |
| 52 . | George PM, Oliver E, Dorfmuller P, Dubois OD, Reed DM, Kirkby NS, et al. Evidence for the involvement of type I interferon in pulmonary arterial hypertension. Circ Res 2014;114:677–688. |
| 53 . | Gielen V, Johnston SL, Edwards MR. Azithromycin induces anti-viral responses in bronchial epithelial cells. Eur Respir J 2010;36:646–654. |
| 54 . | Porter JD, Watson J, Roberts LR, Gill SK, Groves H, Dhariwal J, et al. Identification of novel macrolides with antibacterial, anti-inflammatory and type I and III IFN-augmenting activity in airway epithelium. J Antimicrob Chemother 2016;71:2767–2781. |
| 55 . | Menzel M, Akbarshahi H, Bjermer L, Uller L. Azithromycin induces anti-viral effects in cultured bronchial epithelial cells from COPD patients. Sci Rep 2016;6:28698. |
| 56 . | Touret F, Gilles M, Barral K, Nougairède A, van Helden J, Decroly E, et al. In vitro screening of a FDA approved chemical library reveals potential inhibitors of SARS-CoV-2 replication. Sci Rep 2020;10:13093. |
| 57 . | Weston S, Coleman CM, Haupt R, Logue J, Matthews K, Frieman MB. Broad anti-coronaviral activity of FDA approved drugs against SARS-CoV-2 in vitro and SARS-CoV in vivo [preprint]. bioRxiv; 2020 [accessed 2020 Apr 27]. Available from: https://www.biorxiv.org/content/10.1101/2020.03.25.008482v3. |
| 58 . | Kakeya H, Seki M, Izumikawa K, Kosai K, Morinaga Y, Kurihara S, et al. Efficacy of combination therapy with oseltamivir phosphate and azithromycin for influenza: a multicenter, open-label, randomized study. PLoS One 2014;9:e91293. |
| 59 . | Ishaqui AA, Khan AH, Sulaiman SAS, Alsultan MT, Khan I, Naqvi AA. Assessment of efficacy of Oseltamivir-Azithromycin combination therapy in prevention of Influenza-A (H1N1)pdm09 infection complications and rapidity of symptoms relief. Expert Rev Respir Med 2020;14:533–541. |
| 60 . | Arabi YM, Deeb AM, Al-Hameed F, Mandourah Y, Almekhlafi GA, Sindi AA, et al. Macrolides in critically ill patients with Middle East Respiratory Syndrome. Int J Infect Dis 2019;81:184–190. |
| 61 . | Li L, Zhang W, Hu Y, Tong X, Zheng S, Yang J, et al. Effect of convalescent plasma therapy on time to clinical improvement in patients with severe and life-threatening COVID-19: a randomized clinical trial. JAMA [online ahead of print] 3 Jun 2020; DOI:https://doi.org/10.1001/jama.2020.10044. |
| 62 . | Valk SJ, Piechotta V, Chai KL, Doree C, Monsef I, Wood EM, et al. Convalescent plasma or hyperimmune immunoglobulin for people with COVID-19: a rapid review. Cochrane Database Syst Rev 2020;5:CD013600. |
| 63 . | Chien JY, Hsueh PR, Cheng WC, Yu CJ, Yang PC. Temporal changes in cytokine/chemokine profiles and pulmonary involvement in severe acute respiratory syndrome. Respirology 2006;11:715–722. |
| 64 . | Zhang Y, Li J, Zhan Y, Wu L, Yu X, Zhang W, et al. Analysis of serum cytokines in patients with severe acute respiratory syndrome. Infect Immun 2004;72:4410–4415. |
| 65 . | Cameron MJ, Bermejo-Martin JF, Danesh A, Muller MP, Kelvin DJ. Human immunopathogenesis of severe acute respiratory syndrome (SARS). Virus Res 2008;133:13–19. |
| 66 . | Mehta P, McAuley DF, Brown M, Sanchez E, Tattersall RS, Manson JJ; HLH Across Speciality Collaboration, UK. COVID-19: consider cytokine storm syndromes and immunosuppression. Lancet 2020;395:1033–1043. |
| 67 . | Cron R, Chatham W. Don’t forget the host: COVID-19 cytokine storm. The Rheumatologist 2020 [accessed 2020 Apr 10]. Available from: https://www.the-rheumatologist.org/article/dont-forget-the-host-covid-19-cytokine-storm/. |
| 68 . | Xu X, Han M, Li T, Sun W, Wang D, Fu B, et al. Effective treatment of severe COVID-19 patients with tocilizumab. Proc Natl Acad Sci USA 2020;117:10970–10975. |
| 69 . | Colaneri M, Bogliolo L, Valsecchi P, Sacchi P, Zuccaro V, Brandolino F, et al.; The Covid Irccs San Matteo Pavia Task Force. Tocilizumab for treatment of severe COVID-19 patients: preliminary results from SMAtteo COvid19 REgistry (SMACORE). Microorganisms 2020;8:695. |
| 70 . | Klopfenstein T, Zayet S, Lohse A, Balblanc JC, Badie J, Royer PY, et al.; HNF Hospital Tocilizumab multidisciplinary team. Tocilizumab therapy reduced intensive care unit admissions and/or mortality in COVID-19 patients. Med Mal Infect 2020;50:397–400. |
| 71 . | Luo P, Liu Y, Qiu L, Liu X, Liu D, Li J. Tocilizumab treatment in COVID-19: a single center experience. J Med Virol 2020;92:814–818. |
| 72 . | Morena V, Milazzo L, Oreni L, Bestetti G, Fossali T, Bassoli C, et al. Off-label use of tocilizumab for the treatment of SARS-CoV-2 pneumonia in Milan, Italy. Eur J Intern Med 2020;76:36–42. |
| 73 . | Quartuccio L, Sonaglia A, McGonagle D, Fabris M, Peghin M, Pecori D, et al. Profiling COVID-19 pneumonia progressing into the cytokine storm syndrome: results from a single Italian Centre study on tocilizumab versus standard of care. J Clin Virol 2020;129:104444. |
| 74 . | Sciascia S, Aprà F, Baffa A, Baldovino S, Boaro D, Boero R, et al. Pilot prospective open, single-arm multicentre study on off-label use of tocilizumab in patients with severe COVID-19. Clin Exp Rheumatol 2020;38:529–532. |
| 75 . | Toniati P, Piva S, Cattalini M, Garrafa E, Regola F, Castelli F, et al. Tocilizumab for the treatment of severe COVID-19 pneumonia with hyperinflammatory syndrome and acute respiratory failure: a single center study of 100 patients in Brescia, Italy. Autoimmun Rev 2020;19:102568. |
| 76 . | Gritti G, Raimondi F, Ripamonti D, Riva I, Landi F, Alborghetti L, et al. Use of siltuximab in patients with COVID-19 pneumonia requiring ventilatory support [preprint]. medRxiv; 2020 [accessed 2020 Apr 3]. Available from: https://www.medrxiv.org/content/10.1101/2020.04.01.20048561v1.full.pdf. |
| 77 . | Conti P, Ronconi G, Caraffa A, Gallenga CE, Ross R, Frydas I, et al. Induction of pro-inflammatory cytokines (IL-1 and IL-6) and lung inflammation by Coronavirus-19 (COVI-19 or SARS-CoV-2): anti-inflammatory strategies. J Biol Regul Homeost Agents 2020;34:1. |
| 78 . | Shakoory B, Carcillo JA, Chatham WW, Amdur RL, Zhao H, Dinarello CA, et al. Interleukin-1 receptor blockade is associated with reduced mortality in sepsis patients with features of macrophage activation syndrome: reanalysis of a prior phase III trial. Crit Care Med 2016;44:275–281. |
| 79 . | Aouba A, Baldolli A, Geffray L, Verdon R, Bergot E, Martin-Silva N, et al. Targeting the inflammatory cascade with anakinra in moderate to severe COVID-19 pneumonia: case series. Ann Rheum Dis [online ahead of print] 6 May 2020; DOI:https://doi.org/10.1136/annrheumdis-2020-217706. |
| 80 . | Dimopoulos G, de Mast Q, Markou N, Theodorakopoulou M, Komnos A, Mouktaroudi M, et al. Favorable anakinra responses in severe COVID-19 patients with secondary hemophagocytic lymphohistiocytosis. Cell Host Microbe 2020;28:117–123, e1. |
| 81 . | Pontali E, Volpi S, Antonucci G, Castellaneta M, Buzzi D, Tricerri F, et al. Safety and efficacy of early high-dose IV anakinra in severe COVID-19 lung disease. J Allergy Clin Immunol 2020;146:213–215. |
| 82 . | Lansbury LE, Rodrigo C, Leonardi-Bee J, Nguyen-Van-Tam J, Lim WS. Corticosteroids as adjunctive therapy in the treatment of influenza: an updated Cochrane systematic review and meta-analysis. Crit Care Med [online ahead of print] 15 Nov 2019; DOI:https://doi.org/10.1097/CCM.0000000000004093. |
| 83 . | WHO. Clinical management of severe acute respiratory infection (SARI) when COVID-19 disease is suspected: interim guidance, 13 March 2020. 2020 [accessed 2020 Mar 26]. Available from: https://apps.who.int/iris/handle/10665/331446. |
| 84 . | Wu C, Chen X, Cai Y, Xia J, Zhou X, Xu S, et al. Risk factors associated with acute respiratory distress syndrome and death in patients with coronavirus disease 2019 pneumonia in Wuhan, China. JAMA Intern Med 2020;180:1–11. |
| 85 . | Li X, Xu S, Yu M, Wang K, Tao Y, Zhou Y, et al. Risk factors for severity and mortality in adult COVID-19 inpatients in Wuhan. J Allergy Clin Immunol 2020;146:110–118. |
| 86 . | Lu X, Chen T, Wang Y, Wang J, Yan F. Adjuvant corticosteroid therapy for critically ill patients with COVID-19. Crit Care 2020;24:241. |
| 87 . | NIH. Coronavirus disease 2019 (COVID-19) treatment guidelines. Bethesda, MD: National Institutes of Health; 2020 [updated 2020 Jun 25; accessed 2020 Jul 10]. Available from: https://www.covid19treatmentguidelines.nih.gov/. |
| 88 . | IDSA. Infectious Diseases Society of America guidelines on the treatment and management of patients with COVID-19. Arlington, VA: Infectious Diseases Society of America; 2020 [updated 2020 Jun 25; accessed 2020 Jul 10]. Available from: https://www.idsociety.org/practice-guideline/covid-19-guideline-treatment-and-management/#. |
Author Contributions: H.F. performed literature search, data analysis, and drafted the manuscript. K.K. performed literature search, data analysis, and drafted the manuscript. A.I.R. performed literature search, data analysis, figure draft, and drafted the manuscript. L.J.F. performed literature search, data analysis, figure draft, and drafted the manuscript. S.L.J. performed literature search, data analysis, and drafted the manuscript. A.S. designed the review, performed the literature search, data analysis, and drafted the manuscript. All the authors approved the final version of the manuscript for submission for publication.
Author disclosures are available with the text of this article at www.atsjournals.org.
