Abstract: National Science Review 7: 1428–1436, 2020 doi: 10.1093/nsr/nwaa113 Advance access publication 28 May 2020 RESEARCH ARTICLE (Continued on next page) ∗ Corresponding authors. E-mails: pei duanqing@gibh.ac.cn; tianlin@mail.sysu.edu.cn; xiajinyu@mail.sysu.edu.cn; jiangshp@mail.sysu.edu.cn; nanshan@vip.163.com; shanhong@mail.sysu.edu.cn † Equally contributed to this work. Received 19 April 2020; Revised 8 May 2020; Accepted 10 May 2020 CLINICAL MEDICINE Special Section: SARS-CoV-2 Preliminary evidence from a multicenter prospective observational study of the safety and efficacy of chloroquine for the treatment of COVID-19 Mingxing Huang1,† , Man Li2,3,† , Fei Xiao1,2,† , Pengfei Pang2,3,† , Jiabi Liang4,† , Tiantian Tang5,† , Shaoxuan Liu6 , Binghui Chen7 , Jingxian Shu4 , Yingying You8 , Yang Li2,3 , Meiwen Tang9 , Jianhui Zhou10 , Guanmin Jiang10 , Jingfen Xiang11 , Wenxin Hong12 , Songmei He13 , Zhaoqin Wang14 , Jianhua Feng15 , Changqing Lin16 , Yinong Ye17 , Zhilong Wu18 , Yaocai Li19 , Bei Zhong20 , Ruilin Sun21 , Zhongsi Hong1 , Jing Liu22 , Huili Chen1 , Xiaohua Wang23 , Zhonghe Li24 , Duanqing Pei25,26,∗ , Lin Tian3,∗ , Jinyu Xia1,∗ , Shanping Jiang5,∗ , Nanshan Zhong27,∗ and Hong Shan2,3,∗ ABSTRACT Effective therapies are urgently needed for the SARS-CoV-2 pandemic. Chloroquine has been proved to have antiviral effect against coronavirus in vitro. In this study, we aimed to assess the efficacy and safety of chloroquine with different doses in COVID-19. In this multicenter prospective observational study, we enrolled patients older than 18 years old with confirmed SARS-CoV-2 infection excluding critical cases from 12 hospitals in Guangdong and Hubei Provinces. Eligible patients received chloroquine phosphate 500 mg, orally, once (half dose) or twice (full dose) daily. Patients treated with non-chloroquine therapy were included as historical controls. The primary endpoint is the time to undetectable viral RNA. Secondary outcomes include the proportion of patients with undetectable viral RNA by day 10 and 14, hospitalization time, duration of fever, and adverse events. A total of 197 patients completed chloroquine treatment, and 176 patients were included as historical controls. The median time to achieve an undetectable viral RNA was shorter in chloroquine than in non-chloroquine (absolute difference in medians −6.0 days; 95% CI −6.0 to −4.0). The duration of fever is shorter in chloroquine (geometric mean ratio 0.6; 95% CI 0.5 to 0.8). No serious adverse events were observed in the chloroquine group. Patients treated with half dose experienced lower rate of adverse events than with full dose. Although randomized trials are needed for further evaluation, this study provides evidence for safety and efficacy of chloroquine in COVID-19 and suggests that chloroquine can be a cost-effective therapy for combating the COVID-19 pandemic. Keywords: COVID-19, SARS-CoV-2, treatment, chloroquine