All four clinical trials above showed that remdesivir cannot significantly reduce the mortality of 23 but have a positive effect on clinical improvement of mild COVID-19. Therefore, remdesivir was permitted 24 to be applied in severe COVID-19 patients by the U.S. Food and Drug Administration (Administration, 25 2020) . In June and July 2020, remdesivir was approved conditionally in several other countries / regions 26 around the world. On August 10, 2020, a new drug application for remdesivir for the treatment of 27 COVID-19 was submitted to the US FDA (Lamb, 2020) . Remdesivir has become one of the most promising 28 drugs for the treatment of COVID-19. But the side effects of remdesivir need to be noted. The most common 29 adverse events in 10% of patients taking remdesivir are nausea and liver damage (Grein et al., 2020; Wang et 30 al., 2020c) . However, it is not clear whether these effects are due to the drug itself or the virus. At present, 31 there are too few data on the adverse reactions of remdesivir used in humans, and more phase 3 clinical trials 32 and 14 as the secondary end event. We cannot evaluate which trial design is more reasonable; however, 84 currently the clinical application of CQ and HCQ remains controversial. In addition, the number of patients 85 included in previous studies was relatively small. Large-scale clinical trials are needed for further research. 86 (Table 3 ) 87
Although there are still controversies in CQ-related clinical studies, the latest published cell experiment 88 results suggested that CQ cannot effectively protect against the spread of SARS-CoV-2 in and between 89 patients (Hoffmann et al., 2020b) . The conclusion of this study is diametrically opposed to the results of 90 previous study in vitro, which are the theoretical basis for subsequent clinical studies of CQ or HCQ (Wang 91 et al., 2020b) . The cell type used in two cell experiments may be one of the reasons for the difference. The 92 cells used in the previous study were the African green monkey kidney cell line (Vero E6 Cells). There must 93 be some differences between these cells and human lung epithelial cells. In recent study, German scientists 94 discovered that the TMPRSS2 protease, which is essential for SARS-CoV-2 infection, exists in human lung 95 epithelial cells instead of Vero cells (Hoffmann et al., 2020b) . Previously, they discovered that the activation 96 of SARS-CoV-2 spike protein by TMPRSS2 protease is the prerequisite for SARS-CoV-2 to bind to ACE2 97 and invade human cells (Hoffmann et al., 2020a) . Researchers found that if Vero cells express TMPRSS2 98 protease, the effect of CQ on inhibiting SARS-CoV-2 from invading cells almost disappears. They also 99 verified in the human Calu-3 lung cell line that highly expresses TMPRSS2 and found that CQ cannot 00 protect lung cells against SARS-CoV-2 infection (Hoffmann et al., 2020b) . Further experiments have shown 01 that cathepsin L (CatL) in Vero cells can process spike protein, which is similar to TMPRSS2. CQ affects the 02 intracellular pH, inhibits the function of CatL, and indirectly prevents the invasion of SARS-CoV-2, which 03 can explain the protective effect of CQ on Vero cells in the previous study (Hoffmann et al., 2020b; Rolain 04 et al., 2007) . These results suggested that CQ does not exert anti-SARS-CoV-2 effects in the lung. The 05
research team also pointed out that it is very important to select cell lines that are closer to respiratory 06 epithelial cells in cell experiments. 07
In another study, French scientists also found that the antiviral effect of HCQ in Vero cells cannot be 08 transformed into reconstructed human respiratory epithelial cells that are closer to the real situation of the 09 human body (Maisonnasse et al., 2020) . They used primate experimental animals to further explore the 10 effectiveness of HCQ against SARS-CoV-2 infection. In order to comprehensively evaluate the effects of 11 prevent At the beginning of the pandemic, CQ and HCQ were used to prevent SARS-CoV-2 infection by some 19
people. However, recent evidence showed that HCQ cannot reduce the rate of confirmed infection after 20 exposure to Covid-19, suggesting that there is no effective preventive effect of HCQ (Boulware et al., 2020) . 21
In the current COVID-19 pandemic, isolation, quarantine, social distancing, and community containment 22 appear to be the only preventive measures that have proven to be effective (Wilder-Smith and Freedman, 23 2020). Furthermore, the use of CQ and HCQ will cause some patients to suffer from rare but potential side 24 effects, including severe skin reactions (Murphy and Carmichael, 2001) , fulminant liver failure (Makin et al., 25 1994) , and ventricular arrhythmias (especially when prescribed with azithromycin) (Mercuro et al., 2020; 26 Saleh et al., 2020) . Moreover, an overdose is dangerous and difficult to treat (Gunja et al., 2009 ). The 27 clinical efficacy of CQ and HCQ in the treatment of COVID-19 still remains controversial. The results of 28 cell and animal experiments further indicate that CQ cannot effectively treat and prevent Recently, FDA revoked the emergency use authorization for CQ and HCQ in COVID-19 due to lack of 30 evidence to prove the efficacy, and the serious adverse reactions (FDA, 2020) . In addition, the WHO and 31 other authoritative organizations have stopped clinical researches on CQ/HCQ in the treatment of 32 COVID-19. The clinical usage of CQ and HCQ in COVID-19 is now not suggested. 33
Lopinavir is a human immunodeficiency virus 1 (HIV-1) protease inhibitor approved by FDA. Lopinavir is 35 mainly eliminated in the intestine and liver through CYP3A4 (the main enzyme involved in the metabolism 36 of most protease inhibitors) (Kappelhoff et al., 2004) . Ritonavir is an effective CYP3A4 inhibitor, which 37 forms the basis for the enhancement of lopinavir administered at the same time (Hsu et al., 1998) . Ritonavir 38 can increase the plasma concentration of lopinavir by improving its bioavailability or increasing its 39 elimination half-life in plasma (Hill et al., 2009) . Therefore, lopinavir is recommended to be used in 40 combination with ritonavir (Hammer et al., 2008) . Early reports had different opinions on LPV/r for 41 COVID-19 treatment. Ye et al. reported that compared with the control group, LPV/r can effectively reduce 42 body temperature and restore normal physiological function, with no obvious toxicity and side effects (Ye et 43 al., 2020) . However, another study showed that LPV/r did not promote the negative conversion or clinical study suggested that LPV/r treatment cannot improve the clinical condition and prognosis of COVID-19. 48 (Table 4 ) 49
Although there was no clear evidence supporting the treatment with LPV/r for COVID-19, abandoning the 50 use of LPV/r is considered a premature action. We cannot ignore the significantly reduced time to clinical 51 improvement in patient with LPV/r, although no statistical difference was found (Dalerba, 2020). LPV/r is 52 still the current recommended antiviral treatment in countries such as China (China, 2020). However, when 53 using LPV/r, adverse effects including nausea, diarrhea, and hepatotoxicity should be considered (Cao et al., 54 2020; Young et al., 2020) . Liver dysfunction was also reported in patients treated with LPV/r (Wu et al., 55 2020a). The application conditions and methods of LPV/r require more researches and guidance. 56
( Crotty et al., 2002) . Ribavirin can also enhance the antiviral response of the immune system to indirectly 59 exert antiviral properties (Hultgren et al., 1998) . Its activity against other coronaviruses showed its potential 60 in treating COVID-19 (Ferron et al., 2018) . A retrospective study suggested that treatment with IFN-α 61 + LPV/r + ribavirin might be beneficial for COVID-19 patients . A recently terminated 62 clinical trial (NCT04276688) reported that the group treated with combined IFN-1b, LPV/r, and ribavirin 63 had a significantly shorter time to negative conversion than the control group treated with LPV/r (Hung et al., arbidol/IFN-2b therapy was suggested to be an effective method to improve COVID-19 pneumonia in mild 79 patients, although it does not accelerate virus clearance (Xu et al., 2020) . However, there is a different 80 opinion about treatment with arbidol. Arbidol was reported to have nothing to do with the prognosis or virus 81 clearance of COVID-19 patients (Lian et al., 2020; Wen et al., 2020) . The different results may be because 82 the above studies were all retrospective studies, the inclusion and exclusion criteria of patients were different, 83 the number of patients was small, and the observation indicators were different. Currently, the improvement 84 by arbidol still has no clear proof, and further study is warranted. (Table 4 ) 85
Interferons are cytokines with spectral antiviral properties (de Weerd et al., 2007) . Early retrospective 87 studies found that IFN-α + LPV/r + ribavirin might be beneficial for the treatment of COVID-19 (Yuan et al., 88 2020) . A recent clinical trial reported that COVID-19 patients receiving treatment of combined IFN-1b, 89 LPV/r, and ribavirin had a shorter time to clinical improvement and negative conversion than patients with 90 LPV/r treatment alone (Hung et al., 2020) . This report may support the recommendation of IFN as an 91 alternative to combination therapy in Chinese guidelines (Authority, 2020). Multiple antiviral therapy based 92 on IFN is worthy of further study to find a more appropriate treatment strategy. In addition, when applying 93 interferon, it is also important to consider adverse reactions, including flu-like symptoms, leukopenia, 94 lymphopenia, autoimmune hepatitis, and thyroid disease (Sulkowski et al., 2011) . (Table 4 ) 95 treatment of COVID-19 (Ding et al., 2020) . It has been reported to have the putative inhibitory potential for 07 SARS-CoV-2 (Adeoye et al., 2020). Case reports showed an improved prognosis in COVID-19 patients 08 treated with oseltamivir (Ghiasvand et al., 2020; Xiong et al., 2020) . However, the efficacy of oseltamivir 09
for the treatment of COVID-19 needs further investigation in RCTs. 10
Nitazoxanide is a broad-spectrum antiviral agent used for the treatment of influenza and other viral 11 respiratory infections (Rossignol, 2014) . It is currently recommended as a treatment for COVID-19 (Kelleni, 12 2020). However, the efficacy and safety of nitazoxanide for SARS-CoV-2 are yet to be proven by further 13 studies. 14 Nelfinavir is an anti-HIV protease inhibitor and has been reported to strongly inhibit SARS-CoV-1 15 replication and cell culture cytopathic effects in vitro (Pai and Nahata, 1999; Yamamoto et al., 2004) . Owing 16 to the performance of nelfinavir in SARS, researchers have considered exploring its effect on COVID-19. A 17 recent study showed that nelfinavir inhibits SARS-CoV-2 spike-mediated cell fusion, which is projected to 18 be an important determinant of SARS-CoV-2 infectivity, spread, and pathogenicity (Musarrat et al., 2020) . 19
There are no clinical data regarding the efficacy of nelfinavir treatment for SARS or Camostat mesylate is a protease inhibitor used to treat pancreatitis in Japan (Ikeda et al., 1988) . Camostat 21 mesylate effectively protected mice from death after fatal SARS-CoV-1 infection with a survival rate of 60% 22 (Zhou et al., 2015) . Camostat mesylate was also reported to inhibit TMPRSS2-dependent host cell entry by 23 MERS-CoV (Yamamoto et al., 2016) . Recent studies show that camostat mesylate prevents SARS-CoV-2 24 spike protein-mediated entry into primary human lung cells (Hoffmann et al., 2020a) . Camostat mesylate 25 might block the activation of SARS-CoV-2, which could provide a new treatment option for COVID-19 26 (Hoffmann et al., 2020c) . There are also some controversies about the efficacy of some drugs, such as CQ and HCQ, as treatment for 44 COVID-19 (Huang et al., 2020a; Rosenberg et al., 2020) . More clinical researches are needed to further 45 explore the effectiveness and safety of antiviral treatments for Recalling the current reports related to antiviral treatments for COVID-19, several drug studies have 47
reported controversial conclusions, such as remdesivir, CQ, and arbidol. Our further analysis of the research 48 methods of these reports revealed that there were many reasons for the different research results. 49
Considering the two currently published RCTs on remdesivir, there is no doubt that both clinical studies 50 were well designed and the trials were performed well, but the difference in the number of patients, 51 inclusion criteria, and evaluation indicators led to different results (Beigel et al., 2020; Wang et al., 2020c) . 52
First, due to the timely control of the pandemic in China, the number of patients enrolled in China's research 53 was insufficient, and the research did not reach the preset sample size, resulting in insufficient statistical 54 power. Second, the two studies are essentially different because of the differences in evaluation indicators. 55
For example, the American study included hospitalization as one of the rehabilitation standards without 56 oxygen inhalation, but this standard did not apply to China. Different outcome evaluations may lead to 57 different conclusions. Third, in terms of enrollment criteria, the Chinese trial required enrolled patients to are not optimal and may even harm the patient. Therefore, clinical trials of COVID-19 should seek the best 76 COVID-19 treatment with high-quality methods. 77
Remdesivir is currently the most potential antiviral drug for the treatment of COVID-19. Triple combination 79 of IFN-1b, LPV/r, and ribavirin was confirmed to be more effective. CQ and HCQ are not recommended for 80 the treatment of COVID-19. The efficacy and safety of other antiviral treatments still have controversy and 81 require more high-quality clinical trials. The median time to achieve an undetectable viral RNA was shorter in CQ than in non-CQ [absolute difference in medians -6 (-6 to -4) days]. The duration of fever is shorter in CQ [geometric mean ratio 0.6 (0.5-0.8)].
Abbreviation: CQ, chloroquine; HCQ, hydroxychloroquine; LPV/r, lopinavir/ritonavir; HR, hazard ratio; CI, confidence interval J o u r n a l P r e -p r o o f An open-label, randomized, phase 2 trial; 127 patients were randomly assigned (2:1) to a 14-day combination of lopinavir / ritonavir, ribavirin, IFN-β1b (combination group) or to 14 days of lopinavir / ritonavir (control group).
IFN-β1b, LPV/r, and ribavirin
The combination group had a significantly shorter median time from start of study treatment to negative nasopharyngeal swab (median 7 [5] [6] [7] [8] [9] [10] [11] Arbidol,
The duration of viral RNA of respiratory tract in the monotherapy group was not longer than that in the combined therapy group. The absorption of pneumonia in the combined group was faster than that in the monotherapy group. Patients in the umifenovir group had a longer hospital stay than patients in the control group (13 [9-17] vs 11 [9-14] d).