International Journal of Molecular Sciences Review COVID-19: The Immune Responses and Clinical Therapy Candidates Sareh Zhand 1,2, † , Marie Saghaeian Jazi 3,4, † , Saeed Mohammadi 4,5 , Roozbeh Tarighati Rasekhi 6 , Ghassem Rostamian 7 , Mohammad Reza Kalani 8 , Aida Rostamian 9 , Jacob George 10, * and Mark W Douglas 10,11, * 1 School of Biomedical Engineering, University of Technology Sydney, Sydney, NSW 2007, Australia; sareh.zhand@uts.edu.au 2 Department of Microbiology, Faculty of Biological Sciences and technology, Shahid Beheshti University, Tehran 1983969411, Iran 3 Metabolic Disorders Research Center, Golestan University of Medcial Sciences, Gorgan 4934174515, Iran; marie.saghaeian@goums.ac.ir 4 Stem Cell Research Center, Golestan University of Medical Sciences, Gorgan 4934174515, Iran; s.mohammadi@goums.ac.ir 5 Infectious Diseases Research Center, Golestan University of Medical Sciences, Gorgan 4934174515, Iran 6 Department of Radiology and Imaging Sciences, School of Medicine, Emory University, Atlanta, GA 30322, USA; roozbeh.rasekhi@emory.edu 7 Reliance GP Super-Clinic, Gosford, NSW 2250, Australia; ghassem.rostamian@reliancehealth.com.au 8 Medical Cellular and Molecular Research Centre, Golestan University of Medical Sciences, Gorgan 4934174515, Iran; kalanimr@yahoo.com 9 Department of Clinical Sciences, Faculty of Veterinary Science, Islamic Azad University of Karaj, Alborz 3149968111, Iran; aida.rostamian@yahoo.com 10 Storr Liver Centre, Westmead Institute for Medical Research, Westmead Hospital and University of Sydney, Sydney, NSW 2145, Australia 11 Centre for Infectious Diseases and Microbiology, Marie Bashir Institute for Infectious Diseases and Biosecurity, University of Sydney at Westmead Hospital, Sydney, NSW 2145, Australia * Correspondence: jacob.george@sydney.edu.au (J.G.); mark.douglas@sydney.edu.au (M.W.D.) † The authors are considered as first author. Received: 15 July 2020; Accepted: 31 July 2020; Published: 3 August 2020   Abstract: The pandemic of coronavirus disease 2019 (COVID-19), with rising numbers of patients worldwide, presents an urgent need for effective treatments. To date, there are no therapies or vaccines that are proven to be effective against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Several potential candidates or repurposed drugs are under investigation, including drugs that inhibit SARS-CoV-2 replication and block infection. The most promising therapy to date is remdesivir, which is US Food and Drug Administration (FDA) approved for emergency use in adults and children hospitalized with severe suspected or laboratory-confirmed COVID-19. Herein we summarize the general features of SARS-CoV-2’s molecular and immune pathogenesis and discuss available pharmacological strategies, based on our present understanding of SARS-CoV and Middle East respiratory syndrome coronavirus (MERS-CoV) infections. Finally, we outline clinical trials currently in progress to investigate the efficacy of potential therapies for COVID-19. Keywords: SARS-CoV-2; COVID-19; MERS-CoV; SARS-CoV; clinical trial; anti-viral; anti-parasite; molecular immune response; immunotherapy; adjunctive therapy Int. J. Mol. Sci. 2020, 21, 5559; doi:10.3390/ijms21155559 www.mdpi.com/journal/ijms