key: cord-0982952-vw28rf4d
authors: Drożdżal, Sylwester; Rosik, Jakub; Lechowicz, Kacper; Machaj, Filip; Kotfis, Katarzyna; Ghavami, Saeid; Łos, Marek J.
title: FDA approved drugs with pharmacotherapeutic potential for SARS-CoV-2 (COVID-19) therapy
date: 2020-07-15
journal: Drug Resist Updat
DOI: 10.1016/j.drup.2020.100719
sha: 1c9b3aa2252e7d57adf0503f71d57f5bc17d49df
doc_id: 982952
cord_uid: vw28rf4d

In December 2019, a novel SARS-CoV-2 coronavirus emerged, causing an outbreak of life-threatening pneumonia in the Hubei province, China, and has now spread worldwide, causing a pandemic. The urgent need to control the disease, combined with the lack of specific and effective treatment modalities, call for the use of FDA-approved agents that have shown efficacy against similar pathogens. Chloroquine, remdesivir, lopinavir/ritonavir or ribavirin have all been successful in inhibiting SARS-CoV-2 in vitro. The initial results of a number of clinical trials involving various protocols of administration of chloroquine or hydroxychloroquine mostly point towards their beneficial effect. However, they may not be effective in cases with persistently high viremia, while results on ivermectin (another antiparasitic agent) are not yet available. Interestingly, azithromycin, a macrolide antibiotic in combination with hydroxychloroquine, might yield clinical benefit as an adjunctive. The results of clinical trials point to the potential clinical efficacy of antivirals, especially remdesivir (GS-5734), lopinavir/ritonavir, and favipiravir. Other therapeutic options that are being explored involve meplazumab, tocilizumab, and interferon type 1. We discuss a number of other drugs that are currently in clinical trials, whose results are not yet available, and in various instances we enrich such efficacy analysis by invoking historic data on the treatment of SARS, MERS, influenza, or in vitro studies. Meanwhile, scientists worldwide are seeking to discover novel drugs that take advantage of the molecular structure of the virus, its intracellular life cycle that probably elucidates unfolded-protein response, as well as its mechanism of surface binding and cell invasion, like angiotensin converting enzymes-, HR1, and metalloproteinase inhibitors.

For the time being, there is neither a vaccination or a specific SARS-CoV-2 targeted antiviral treatment available. Multiple countries have attempted varying pharmacologic strategies to combat the disease, involving currently established antivirals, different modes of oxygen therapy or mechanical ventilation. COVID-19 pandemic requires rapid development of efficacious therapeutic strategies, in the pursuit of which three concepts are being applied: (i)

The first approach relies on testing currently known antiviral agents and verifying their clinical usefulness [5, 6] . (ii) Another modality is based on molecular libraries and databases, allowing for high computing power and simultaneous verification of millions of potential agents [6, 7] .

(iii) Lastly, the third strategy involves targeted therapy, intended to disrupt the genome and functioning of the virus. Precisely designed particles would disrupt the crucial steps of viral infection, such as cell surface binding and internalization. Unfortunately, in vitro activity does not necessarily translate into efficacy in the in vivo setting, due to differing pharmacodynamic and pharmacokinetic properties [6, 8] . The main groups of therapeutic agents that can be useful in COVID-19 treatment involve antiviral drugs, selected antibiotics, antimalarials, and immunotherapeutic drugs. In the present paper, we aim to summarize current progress and insights that have emerged from the use of pharmaceuticals in COVID-19.

In one of the newest dissertations published by a French team of doctors, a positive influence of hydroxychloroquine (HCQ) in patients infected by SARS-CoV-2 was observed [9] . Furthermore, another in vitro trial showed that both chloroquine (CQ) and its hydroxylated derivative, HCQ, possess beneficial properties. HCQ, an agent with universally established antimalarial, anti-inflammatory, and analgesic properties, is widely used in the treatment of malaria. The US Food and Drug Administration (FDA) and Centers for Disease Control and Prevention (CDC) are currently working on establishing randomized clinical trials that aim to confirm the usefulness of CQ and its derivatives in combating CoV-2 virus infection [10, 11] .

In the beginning of February 2020, China included CQ with its derivatives as one of the therapeutic options in SARS-CoV-2 treatment, with South Korea soon following this path [12, 13] . The mechanism of action of antimalarial agents has not been well elucidatedit is believed to be pleiotropic, affecting T-cells, cytokine production, and others. Graphical representation of HCQ action can be seen in Fig. 1 . Additional anti-inflammatory effect can be attributed to the inhibition of extracellular matrix metalloproteinases [14] [15] [16] . In this case, the potential mechanism of action of CQ and its hydroxylated derivative is attributed to the blockade of viral infection via an alkalization of endosomal (and lysosomal) pH; it should be emphasized that J o u r n a l P r e -p r o o f the above acidic pH is required for virus-host cell fusion [17] [18] [19] . Furthermore, the agents are believed to disrupt SARS-CoV cell receptor glycosylation [20] .

It has been shown that HCQ presents in vitro antiviral properties against SARS-CoV [21] . Its clinical safety profile is superior to that of CQ (in a long-term setting), which allows for higher daily dose, and results in fewer drug-drug interactions [22, 23] . A clinical trial aiming to assess the influence of HCQ on the outcome of patients infected with SARS-CoV-2 by Gautret et al., compared patients receiving HCQ and controls, concentrating on viral load reduction [9] (all clinical trials are summarized in Table 1 and Fig. 2 ). The study enrolled hospitalized patients with confirmed COVID-19. Patients were stratified into three categories: asymptomatic (16.7%); upper respiratory tract infection (URTI; 61.1%), presenting as rhinitis, pharyngitis, or isolated fever and muscle pain; lower respiratory tract infections (LRTI; 22.2%), who suffered from symptoms of pneumonia or bronchitis. Twenty patients were administered HCQ sulfate orally, and 16 served as the control group. Among patients treated with HCQ, 6

were also treated with azithromycin, in order to prevent superimposed bacterial infection. The percentage of patients with absence of viral loads on nasopharyngeal swab sample RT-PCR was significantly higher in the treatment group than in controls, on days 3, 4, 5 and 6 of followup. On day 6, which was considered the endpoint, in 70% of patients treated with HCQ viral load disappearance was observed, in comparison with 12.5% in the control group (p=0.001) [9] .

Another study compiling the results of over 100 patients showed that the addition of CQ phosphate is superior to standard supportive care and hence contributing to prevention of the deterioration of pneumonia. Investigators observed improved lung imaging findings, improved negative conversion, and shortening of the disease course. No severe adverse events were noted in the study. CQ phosphate was recommended to be introduced into the next edition of National Health Commission of the People's Republic of China guidelines on prevention, diagnosis, and treatment of pneumonia caused by COVID-19 [12] .

In February 2020, a randomized clinical trial on 62 patients was established in Renmin Hospital of Wuhan University to determine the efficacy of HCQ in patients with COVID-19.

The trial involved 5-day HCQ treatment (400 mg/day), during which patients were examined 3 times a day, including temperature measurement and assessment of cough. CT was performed at baseline and once again after 5 days. In the HCQ arm, significantly shorter body temperature normalization and cough remission times were noted. In addition, radiological improvement in pneumonia was observed more frequently in patients from the HCQ group (80.6% vs 54.8%).

Despite the rather limited sample size, the trial demonstrated that the use of HCQ can improve patient prognosis, accelerate remission, and improve clinical status [24] .

Teng et al., showed that administration of HCQ in patients with persistent mild to moderate COVID-19 did not improve the probability of negative conversion, in comparison with standard of care alone. One hundred and fifty patients were included in this study, with 75 assigned to HCQ plus standard of care, whereas the remaining 75 patients were treated with standard of care only. Results of HCQ group did not differ significantly from the results of the standard of care group [25] .

In a recent study, HCQ administration resulted in earlier recovery, without affecting overall mortality. The study was conducted on a group of 522 patients, 127 of which were symptomatic, while the remaining 395 patients had no clinical manifestations at baseline. Their COVID-19 status was confirmed by RT-PCR. Asymptomatic patients treated with HCQ recovered earlier (average recovery time = 5.4 days) compared to asymptomatic patients who did not receive any treatment (average recovery time = 7.6 days) [26] .

In conclusion: CQ is a cheap and relatively safe drug that has been in clinical use for over 70 years [27, 28] , therefore can be a potential candidate for SARS-CoV-2 treatment [29] .

Despite promising results, it is essential to consider all safety measures and treat with this medication only as a supplementary form of treatment. Moreover, the initial enthusiasm surrounding HCQ and CQ was curbed after both were discontinued from SOLIDARITY trial due to the lack of benefit [30] . This, along with other promising treatment schemes that have emerged in the recent months, are summarized in Table 2 .

The antiparasitic agent ivermectin is another drug worth exploring further. In an in vitro study, it showed a 99.98% reduction in viral load after 48 hours of treatment [31] . The drug is not toxic at a standard dose, and is safe for pregnant women, which makes it a strong candidate for evaluation in clinical trials [31] . So far, one study has been established to verify its clinical efficacy, in combination with HCQ (NCT04343092) [32] .

The WHO states in his recommendations that systemic steroids should not be routinely administered in treatment of viral pneumonia or acute respiratory distress syndrome (ARDS), unless recommended for other medical reasons, or as part of a clinical trial [33] . In a systemic review of observational studies that focused on the effects of corticoid administration to patients with SARS, no clinical benefit was noted in terms of overall survival. In the case of influenza, steroid administration was associated with higher mortality rate and superimposed infections J o u r n a l P r e -p r o o f [34] . General quality of evidence advocating for the use of steroids is considered weak. Another study, adjusted for confounding factors, did not present any association of steroid therapy with lower mortality rates. Finally, the latest study on steroids administration in patients with MERS, no effect on survival was disclosed, but steroids may have been responsible for halting the disease progression in severe forms of LRTI. The use of steroids was associated with delayed clearance of viral RNA from the respiratory tract [35] and blood [36] . Given the evidence presently available, it is recommended to avoid the routine administration of steroids, unless recommended for the treatment of another comorbidity, e.g. shock or as continuation of treatment [37, 38] .

There are several studies that present potential benefits of antibiotic therapy in coronavirus infection. It is challenging to elucidate the potential underlying mechanism of action that might be of benefit in monotherapy, therefore most researchers turn their attention to combination therapy. Azithromycin, a macrolide antibiotic, in combination with HCQ, might yield clinical benefit as an adjunctive. The insights from the French study (described in the section concerning CQ) presents the thesis that azithromycin potentiates the effects of therapy [9] .

Among patients treated with HCQ, 6 of them were given azithromycin (500 mg initially, then 250 mg per day for the next 4 days), in order to prevent superimposed bacterial infections.

When comparing HCQ monotherapy to combination therapy with azithromycin, the percentage of patients who presented with negative PCR viral load was significantly different, at 3, 4, 5 and 6 days of follow-up, in the favor of dual therapy. On day 6, 100% of patients were declared viral load-negative, in comparison with 57.1% in HCQ monotherapy group and 12.5% in control group (p<0.001). The effect of treatment was significantly more pronounced in patients with URTI and LRTI in comparison with asymptomatic patients (p<0.05) [9] .

Teicoplanin is a glycopeptide antibiotic routinely used in the treatment of bacterial infections. In an in vitro setting it exerts anti-SARS-CoV activity. Therefore, it might be used as one of potential therapeutic agents against COVID-19. While it is most commonly used in [39] . Latest studies carried out by the same researchers, suggested that it is likewise effective against SARS-CoV-2 (as the target sequence, the molecular target for cathepsin L is identical to that of SARS-CoV). The teicoplanin concentration that is required to inhibit viral replication by 50% (IC50; 50% inhibitory concentration) in vitro was 1.66 μM, a value significantly lower than that reached in human blood (8.78 μM for a daily dose of 400 mg). These results require further confirmation in randomized clinical trials [39] .

Angiotensin converting enzyme 1 (ACE1) is a monocarboxypeptidase, which is responsible primarily for the conversion of angiotensin I (ATI) into angiotensin II (ATII), while angiotensin converting enzyme 2 (ACE2) is an enzyme that catalyzes the conversion of ATII into Angiotensin 1-7 that possesses vasodilatory properties. Type 2 pneumocytes present in the alveoli belong to the group of ACE2 expressing cells [40] . Full-length ACE2 contains a structural transmembrane domain, which anchors its extracellular domain to the plasma membrane. The extracellular domain has been demonstrated as a receptor for the spike (S) protein of SARS-CoV-2 ( Fig. 3 ) [41] .

ACE inhibitors (ACE-I) are the basis for the treatment of heart failure with impaired left ventricular systolic function (ejection fraction <40%) of classes II-IV according to the New York Heart Association [42] . They owe their popularity in clinical practice to well-established effects on reducing all-cause mortality and heart failure hospitalization rate [42] [43] [44] . An alternative to ACE-I, mainly used in the case of side effects associated with inhibition of bradykinin degradation -including persistent dry cough, are AT1 receptor antagonists (AT1-A). Both groups belong to the most basic drugs used in the treatment of hypertension, which makes them two of the most commonly used medications in the world, especially in the elderly population.

Recent analysis of SARS-CoV-2 infected populations presents a relationship between increased age of the population and more severe disease course [45] . Some researchers associate this phenomenon with the universal use of drugs that affect the renin-angiotensinaldosterone system (RAA). In the early stages of the pandemic, a hypothesis was proposed where chronic use of ACE-I and AT1-A could lead to an increase in ACE2 in the pulmonary circulation, which in turn increases the number of receptors available for the virus [46] , thus the risk of severe COVID-19 increases [47, 48] . However, the results of the recent animal and human studies do not support this theory [49] [50] [51] [52] [53] .

On the other hand, a hypothesis has been proposed that the attachment of the virus to ACE2 during the development of pneumonia disrupts the homeostasis by violating the RAA system, which further aggravates the patient's condition. Thus, when used in patients developing fully-blown COVID-19, ACE-I and AT1-A can reduce symptoms and even reduce mortality [54, 55] . A trial on 651 patients (NCT04335786) aiming to verify whether the antihypertensive agent valsartan influences COVID-19 treatment outcomes is currently in progress [56] . The knowledge gained thus far does not allow stating that long-term therapy with drugs inhibiting the cascade of reactions in the renin-angiotensin-aldosterone (RAA) system is associated with worse patient prognosis, while their immediate supply can save the patient.

There is no reason to discontinue therapy with these groups of drugs after the infection is diagnosed [49] [50] [51] [52] [53] 57] .

The information obtained from mechanistic studies concerning the entry of the virus into cells, as well as the presumed association between the use of ACE-I and AT1-A with the cases, leads to the hypothesis implying potential effectiveness of controlling the virus by supplying the soluble form of ACE2. Soluble ACE2 would competitively compete for SARS-CoV attachment with receptors present on cell surfaces, preventing virion invasion of pneumocytes. In vitro studies support the above assumptions -soluble ACE2 limited the proliferation of SARS-CoV on the Vero-E6 cell line [58, 59] . In in vitro tests, ACE2 combined with the Fc fragment of the antibody neutralized the virus [60] . The method described is currently not feasible, with numerous obstacles that need to be removed before this therapy can enter human testing phase. The development of bioinformatics sparks hope that the analysis of protein data banks will allow for faster discovery of a receptor for which SARS-CoV-2 proteins will be a high-affinity ligand [61] . Currently, studies on an animal model are not being carried out, however, transgenic mice expressing the human form of ACE2 are achievable and it is likely a matter of time before research in this model begins [41] .

The inhibitor for transmembrane serine protease 2 (TMPRSS2) would act similarly to the described soluble ACE2. The enzyme, together with the virus receptor (ACE2) is responsible for the virion's entry into the cell (Fig. 3 ) [62] .

Another point of focus for COVID-19 treatment associated with the mechanism of SARS-CoV-2 entry into the cell may be HR1 -a fragment of the S protein that is important for the virus in order to attach to the cell. For now, the results of in vitro and animal model tests are encouraging. OC43-HR2P peptide successfully inhibits coronavirus invasion. Its modified form -EK1 possesses even more desirable properties. Intranasal peptide administration has been shown to be effective in a murine model, while not causing any organ dysfunction [63] .

This group of drugs has been routinely used in the treatment of viral infections for many years [64] [65] [66] [67] [68] [69] . It is characterized by high affinity to viral enzymes and low affinity to human enzymes.

Because of that feature, nucleotide and nucleoside analogs are capable of inhibiting viral DNA replication, reverse transcription, and virion protein biosynthesis. This effect is possible due to many mechanisms, of which premature termination and inhibition of nitrogenous bases synthesis are most notable [6, 70] .

SARS-CoV and SARS-CoV-2 RNA-dependent RNA polymerases are structurally similarthey share 95% identity in amino acid sequence [61] . This fact accelerates research, as some substances previously tested during SARS epidemic might be found equally effective against COVID [61] .

Remdesivir (GS-5734) is widely known from trials on patients infected with Ebola virus [71] [72] [73] . This adenosine analog binds to viral RNA, leading to premature termination [74, 75] .

Its effectiveness has already been proven in vitro [20] . Remdesivir was used in the rhesus macaque model of MERS infection. It was effective if administered either before or after MERS-CoV infection. Remdesivir restricted lung injury, inhibited viral replication and improved medical condition [76, 77] . It was more effective than combined therapy lopinavir/ritonavir and interferon-1β in the animal model [72] . Remdesivir was further introduced into clinical trials. Preliminary results suggest that it is safe for humans [6, 78] . The The risk ratio for patients receiving invasive ventilation compared to patients receiving noninvasive oxygen support was 2.78 (95% CI: 0. 33 -23.19) . Clinical improvement was seen in 36 of 53 patients (68%) [80] . However, other researchers have raised concerns regarding the methodology of this study and question its results [81] .

Beigel et al., verified the effectiveness of remdesivir in a randomized trial involving a group of 1063 patients (NCT04280705). Their preliminary results are promising, as patients receiving this agent recovered significantly sooner than those who received placebo [82] .

Moreover, remdesivir has a positive recommendation of The European Medicines Agency in the treatment of COVID-19 [83] . However, not all trials (NCT04257656) reported such favorable resultsin 237 patients, remdesivir was not associated with any clinical benefits [84] . favipiravir than the group treated with lopinavir/ritonavir [85] . Additionally, less side effects were noted in the treatment group [85, 86] . Pharmacokinetics of favipiravir are a cause of concern. This agent reaches significantly lower serum concentrations in critically ill patients than in healthy individuals [87] . Nevertheless, favipiravir seems to be a safe therapeutic option [88] . Other nucleotide analogs, which are under investigation for their potential effectiveness against SARS-CoV-19 include triazavirin, emtricitabine, and tenofovir (Table 1 ) [89] .

The protease inhibitor lopinavir and its booster ritonavir were verified in trial ChiCTR2000029308 on 199 patients with laboratory-confirmed COVID-19 infection. Cao et al., did not observe any benefit of lopinavir/ritonavir treatment in comparison with standard care [90] . Adverse effects, such as nausea, vomiting, and hypokalemia might lead to deterioration of the clinical condition, consequently causing discontinuation of treatment [90] [91] [92] . Nevertheless, it is too soon to reject lopinavir/ritonavir altogether [93, 94] . This drug might be by far more effective if combined with ribavirin or interferon-1β to reduce side effects and increase therapeutic potential [95] . The first of aforementioned combinations has proven its effectiveness against SARS [96] . The second led to better results than no antiviral treatment in an animal model [97] . It is also under scrutiny in the MIRACLE J o u r n a l P r e -p r o o f trial, which seeks for an effective medication against highly fatal MERS [54, 70] . A phase 2 trial (NCT04276688) including 127 COVID-19 patients showed superiority of triple therapy (lopinavir/ritonavir, ribavirin and interferon-β1b) over lopinavir/ritonavir. The combined therapy alleviated symptoms sooner and accelerated viral clearance [98] . Most recently, the WHO has announced that it will be discontinuing its lopinavir/ritonavir arm of SOLIDARITY trial, due to no clinical benefit in terms of mortality reduction [30] .

Since the beginning of 2020 another HIV protease inhibitor -darunavir has been in the process of verification, with early results being promising [86] .

Umifenovir (arbidol) has been investigated in the past as a potential drug for SARS and MERS [6] . Its mechanism of action is similar to Imatinib, an Abelson kinase inhibitor (Abl), the anchor drug in the treatment of Chronic Myeloid Leukemia. Both of these molecules prevent virus binding to the cell membrane [86, 99] .

A trial on 33 adults with laboratory proven COVID-19, who had not been invasively ventilated has reached encouraging favorable resultsjoint therapy of umifenovir and lopinavir/ritonavir was more efficacious than lopinavir/ritonavir only [100] . Patients treated not only with protease inhibitor, but also with umifenovir became sooner SARS-CoV-19-negative (nasopharyngeal specimens) and more of them were found to improve radiologically, according to CT scans [100] . As reported by Deng et al., umifenovir might decrease both the risk of SARS-CoV-19 transmission and the risk of acute respiratory distress syndrome (ARDS) [100] .

Other studies on the effectiveness of umifenovir showed its superiority in comparison with lopinavir/ritonavir [101] , potency to reduce COVID-19 symptoms and accelerate the recovery time [102] , but also underlined the lack of significant differences between umifenovir combined with IFN-α2b and IFN-α2b alone [103] or lack of SARS-CoV-2 clearance acceleration [104] .

However, meta-analysis of 12 studies with 1052 patients reached statistical significance only in higher negative rate of PCR after 14 days of treatment (RR = 1.27, 95% CI = 1.04 -1.55).

Huang et al., concluded that there is no evidence that umifenovir improves COVID-19 outcomes [105] .

SARS-CoV-2 infection depends on ACE2 and TMPRSS2 host cell factors (Fig. 3) [106] .

TMPRSS2 is believed to be involved in the process of S protein priming, a vital step in SARS-CoV-2 viral entry [62, 107] . This cellular protease can be blocked by the clinically proven J o u r n a l P r e -p r o o f protease inhibitor camostat mesylate. This drug is theoretically capable of preventing viral infection of the host cell. Thus, it should be considered as a potential therapeutic agent for COVID-19 infection [60] . Camostat mesylate is approved in Japan for the treatment of pancreatitis. During a study on SARS-CoV-2 isolated from a patient, camostat mesylate managed to prevent the virus from entering lung cells [107] and lung epithelial cells (Fig. 3 ) [113] . In the study, 17 patients were given 10 mg meplazumab intravenously on day 1, 2 and 5, while 11 patients served as the control group. Patients treated with meplazumab, were discharged significantly faster and the severity of the disease was decreased. The time to negative viral load was also reduced. No side effects were noted during the study. Due to the small group, this drug requires further research, but the initial results are promising [114] .

The use of interferon α and β is heavily disputed [115] . Both substances are associated with serious side effects. While their administration in the early stages of the disease is associated with the expected positive effect, a delayed administration may intensify the cytokine storm, causing inflammation and consequentially worsening the patient's condition [76] .

Coronaviruses require two proteases for successful protein biosynthesis: 3CLpro and PLpro [116] . Without them, replication and generation of virions is impossible. These proteins, like RNA polymerases, are characterized by great sequence similarity between the forms found in SARS-CoV and SARS-CoV-2 [61] . The use of inhibitors to these proteases, previously tested in the context of SARS, is currently under consideration [117, 118] . Summary of research into the most important drugs is presented in Table 3 .

Statins are some of the most commonly prescribed drugs, especially in elderly patients.

CoV-2 infection. Zhang et al., conducted a retrospective study in which they showed that the risk for 28-day all-cause mortality was 5.2% and 9.4% in the matched statin and non-statin groups of COVID-19 patients, respectively, with an adjusted hazard ratio of 0.58 [119] .

In March 2020, the pharmaceutical company PharmaMar announced that Aplidine (Plitidepsin), a medicine commonly used to treat multiple myeloma, has antiviral activity [120] .

In vitro studies showed that Plitidepsin affects EF1A (eukaryotic translation elongation factor 1 alpha 1), which is key to multiplication and spread of the virus [120] . The antiviral activity of plitidepsin was initially analyzed in a human hepatoma cell line infected with the HCoV-229E-GFP virus, which is similar to SARS-CoV-2. The preliminary results are promising, but a multicenter, randomized proof of concept (Phase 1) clinical trial is ongoing and patients are currently being recruited (NCT04382066) [121] .

Scientists are beginning to consider utilizing immunomodulatory therapies to treat COVID-19 infection [89] . The use of drugs that increase the inflammatory response and reactivity of leukocytes can, on one hand, aid in combating the infection, but, on the other hand, could expose the body to the negative effects due to exacerbation of the inflammatory response.

There are numerous clinical trials investigating drugs such as anti-PD1 antibodies, recombinant IL-2, recombinant human granulocyte colony-stimulating factor (rhG-CSF), all of which are summarized in Table 1 . Previously used in cancer therapy, they can alter the inflammatory response, thereby reducing the negative effects of infection such as pulmonary fibrosis or sepsis.

In addition to the drugs discussed in the current review, many antiviral drugs have been explored for COVID-19 treatment for several months, without any positive effect.

Neuraminidase inhibitors, known from influenza therapy: baloxavir marboxil, oseltamivir, paramivir, and zanamivir were used, especially in the first weeks of the epidemic [89, 122] .

Other drugs tested to date include thymidine kinase inhibitors (acyclovir and ganciclovir), translation-inhibiting mRNA encapsulation inhibitor -ribavirin, nafamostat -successful in the treatment of MERS, nitazoxanide -used to control helminthiasis and currently tested for viability in viral infections, another nucleotide analogpenciclovir, as well as drugs known from HCV therapy (azvudine, danoprevir/ritonavir, sofosbuvir/daclatasvir, and J o u r n a l P r e -p r o o f sofosbuvir/ledipasvir) [20, 54, 89] . None of the above drugs is currently recommended for the treatment and support of treatment in SARS-CoV-2 infection [122] . Due to the lack of an effective COVID-19 therapeutic protocol, prevention of infection is pivotal.

In addition to isolating the sources of infection and following thorough hygienic The complex aspects of SARS-CoV-2 infection mandates collaboration of scientists from different disciplines including basic, clinical and engineering fields to enhance the probability of success against this life-threatening pandemic [126] . As viral infection hijacks fundamental mechanisms of mammalian cell physiology [127, 128] , besides potential vaccine development strategy, combination of antiviral treatment in the presence of targeting these pathways could have the highest rate of success on overcoming this COVID-19 pandemic.

Among these mechanisms, autophagy and unfolded protein response (UPR) received the attention of many research groups and important commentary papers and suggestions have been recently published [129] [130] [131] [132] . SARS-CoV-2 infection probably involves autophagy pathway like many other respiratory viral infections [133, 134] . Some useful adjuvant therapy strategies like chloroquine or statins has common effects including regulation of cytokine storm and inflammation and inhibition of autophagy flux [129, 130, 135] . On the other hand, SARS-CoV-J o u r n a l P r e -p r o o f [132] . UPR is involved in regulation of autophagy and in the cellular secretome [136, 137] . Therefore, simultaneous targeting of autophagy/UPR pathway using FDA-approved compounds including chloroquine, statins, or drugs that are on their Phase-I or Phase-II clinical trials (MKC8866 to target IRE1 RNase activity) and antiviral therapy regimens could be an ideal strategy to control COVID-19 pandemic and help high risk patients to increase survival. This strategy will also potentially decrease significant amount of cost for taking care of COVID-19 patients in ICU units and decrease the demand for ventilators. The COVID-19 pandemic is likely to be controlled in the future with close collaboration of different science disciplines.

The WHO SOLIDARITY trial is ongoing and the results of this trial are anxiously expected by both researchers and clinicians. This large international multicenter study with thousands of COVID-19 patients will have the statistic power to finally prove or reject many hypotheses about COVID-19 therapy [138] . This SOLIDARITY trial will test remdesivir, lopinavir/ritonavir, lopinavir/ritonavir combined with interferon-, HCQ/CQ. As of 5 th of July 2020, two of those arms have been discontinuedlopinavir/ritonavir and HCQ/CQ, due to the lack of benefit [30] .

[9] -One of the first clinical trials in the world that evaluated HCQ in the treatment of COVID by limiting the release of proinflammatory cytokines and increasing the endosomal and lysosomal pH. Its combination with azithromycin may become one of pivotal therapeutic strategies.

[86] -Excellent review providing insight into the use of drugs, in the early stages of the pandemic, that rely on inhibition of receptors that are utilized by the virus to enter the host cell (ACE2, TMPRSS2, and CD147).

J o u r n a l P r e -p r o o f [39] -The antibiotic teicoplanin that displays activity against other coronaviruses retained its activity against SARS-CoV-2 in vitro. This study presents the principles, which suggest that this agent has a potential to succeed in clinical trials. lopinavir/ritonavir III/IV phase [90] hydroxychloroquine III phase [9] remdesivir III phase [75] favipiravir II phase [86] chloroquine research on cell lines [10, 11] ribavirin research on cell lines [54] cepharanthine research on cell lines [141] mefloquine research on cell lines [141] J o u r n a l P r e -p r o o f It is believed that most important pathways involve lysosomal enzyme stabilization, antigen presentation suppression, T-cell stimulation inhibition, or cytokine cascade blockade. HCQ inhibits the proliferation of T-cells and monocytes, and decreases the production of proinflammatory cytokines (Il-6, Il-17, IFN-α, IFN-λ, TNF-α). Additionally, it inhibits antibody and prostaglandin (PG) production. It decreases thrombocyte aggregation, lipid levels, insulin secretion, as well as oxidative stress [14] . Another mechanism that contributes to its antimalarial properties involves the inhibition of toll-like-receptors, namely TLR-3, TLR-7, and TLR-9, in response to microbial antigens that under normal conditions induce inflammatory response. Furthermore, antimalarial drugs inhibit PG production and lipid peroxidation.

Decreasing PG production involves the inhibition of phospholipase A2 activity.

J o u r n a l P r e -p r o o f [113] .

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-CTR) 3000 compared to IFN β-1a and remdesivir

-CTR) 2000 compared to dexamethasone and IFN β-1a

60 -Lopinavir/Ritonavir ChiCTR20000 29496 90 compared to IFN-α

Lopinavir/Ritonavir ChiCTR20000 29548 30 compared to baloxavir marboxil and favipiravir

90 compared to favipiravir

Lopinavir/Ritonavir NCT04291729 11 compared to darunavir/ritonavir, IFN-α and peginterferon α-2a