Editorial of Special Column "Research on Emerging COVID-19 (Target, Mechanism, and Therapeutics)".

Coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a global crisis,. Infection from SARS-CoV-2 can result in severe lymphopenia, prolonged coagulation profiles, lethal acute respiratory distress syndrome (ARDS), watery diarrhea, cardiac disease, multiorgan dysfunction, and sudden death,. Due to its high infectivity and pathogenicity, to date, more than 100,000,000 positive cases and 500,000 deaths were reported, taking away thousands of lives each day. However, there are no specific drugs or vaccines proven effective against this viral infectious disease. Drug development with conventional discovery pipelines will not meet the immediate needs. Therefore, effective prevention and treatment (drugs and vaccines) against the highly pathogenic coronaviruses is in urgent need. Identification of readily available drugs or natural products for repositioning in COVID-19 therapy avails a relatively rapid way to clinical treatment,.

The title of this special issue is the research on emerging COVID-19 (target, mechanism, and therapeutics). In this issue, there are several original researches, reviews, and letters in these areas. As the guest editors, we would like to appreciate Acta Pharmaceutica Sinica B for providing us the opportunity to share the information and thank all authors for their contributions to this special issue.

Firstly, three reviews summarized the potential agents including drugs and vaccines against COVID-19. Hongzhuan Chen and colleagues reviewed over 100 registered clinical studies on TCM/integrated traditional Chinese and Western medicine in China. Pharmacological studies suggested three Chinese medicines such as Lianhua Qingwen Keli/Jiaonang, Jinhua Qinggan Keli, and Xuebijing Injection were effective for COVID-19 probably through its host-directed regulation and certain antiviral effects. Xian and colleagues provided a comprehensive review about the potential use of the natural compounds for the treatment of COVID-19, SARS, and MERS. Xun Sun and colleagues summarized recent advances in the development of coronavirus vaccines, and highlighted current adjuvants for improving the efficacy of coronavirus vaccines. Fortunately, five vaccines (40% of the world's total) have entered clinical trials in China, and most of them have shown remarkable prospects.

Secondly, the original articles related to drug targets and potential agents against COVID-19 were presented. Shoudeng Chen and colleagues determined the 2.7 Å crystal structure of the N-terminal RNA binding domain of SARS-CoV-2 nucleocapsid protein and revealed potential unique drug targeting sites, which helps to guide the rational design of novel agents targeting SARS-CoV-2. Based on several crystal structures of important drug targets related to SARS-CoV-2, Weiliang Zhu and Zhijian Xu developed a molecular docking-based web server D3Targets-2019-nCoV to accelerate drug discovery against COVID-19 with two functions. One is to predict targets for active compounds, and the other is to identify potent compounds via virtual screening.

To date, more than tens of thousands of people in the world had used chloroquine (CQ) to treat this disease12., 13., 14., but the conclusions are different and controversial. The main problem is its cardiovascular safety since it is easy to cause QT prolongation. Dongyang Liu and colleagues developed a physiologically-based pharmacokinetic model for predicting tissue distribution of CQ and apply it to optimize dosage regimens for patients with COVID-19 to improve CQ's clinical applicability.

Several works have demonstrated that hypercoagulability related to the COVID-19 severity,16., 17., 18., 19.. Hai-Bin Luo and colleagues rapidly identified a potential agent targeting main protease (Mpro) from existing drug database against the epidemic via anticoagulant and antiviral effects (see a story for the front cover). In an analysis of a randomly collected cohort of 124 patients with COVID-19, they found that hypercoagulability as indicated by elevated concentrations of D-dimers was associated with disease severity. They further identified that the anticoagulant dipyridamole bound to the SARS-CoV-2 protease Mpro via the virtual screening and bioassay validation, and thus suppressed viral replication in vitro. In a proof-of-concept trial involving 31 cases with COVID-19, dipyridamole supplementation markedly improved clinical outcomes (87.5% vs. 33.3%) of severely ill patients in comparison to the control patients. This work suggests drug repurposing effort for the treatment of COVID-19 could be a truly promising approach to combat this disease.

Traditional Chinese medicine (TCM) was used in 91.50% of the COVID-19 cases in China, showing encouraging results in improving symptom management and reducing the deterioration, mortality, and recurrence rates. Thus, Shilin Chen and colleagues analyzed 26 officially published protocols of herbal treatment for COVID-19 in China, containing a total of 179 individual herbs and 166 formulae with 1212 chemical components (see a story for the backup cover). Most of the TCMs are anti-inflammatory, antiviral, immunomodulatory, antitumor, antipyretic, antispasmodic, and antiasthmatic. Scaffold analysis, self-organizing mapping (SOM) and cluster analysis, 12 clusters of molecules yielded 8 pharmacophore families of structures that were further screened as pharmacological targets in human metabolic pathways for inhibiting coronavirus. This article aims to aid the international COVID-19 researcher community to accelerate the journey in finding effective natural medicines and containing the global spread of COVID-19.

Thirdly, the two letters to editors relate to clinical treatment of two important complications (hypertension and diabetes) of patients with COVID-19. Many patients are accompanied by basic diseases, such as diabetes, hypertension, hyperlipidemia, tumor, etc. Treatment of those patients represents additional complexities. Since glucagon-like peptide-1 (GLP-1)-based drugs for the treatment of diabetes possess the strong anti-inflammatory effect in the lung and elsewhere, Tianru Jin and colleagues suggested to repurpose these drugs for COVID-19. In addition, they also suggested to conduce large scale retrospective studies to reveal whether administration of these drugs have beneficial effects on clinical outcomes of type 2 diabetes patients with COVID-19. Zijian Li and colleagues suggested that no clear evidence of anti-RAS drugs (ACEIs and ARBs) increase the risk of SARS-CoV-2 infection, as well as organ injury. Furthermore, they did not recommend the discontinuation of ACEIs/ARBs for hypertensive patients with COVID-19, or the change to other antihypertensive drugs.

We hope this special column would provide valuable information for our readers to realize the wisdom and effort of Chinese experts during combating COVID-19 and gain more knowledge in the fields of drug targets and potential agents against SARS-CoV-2.