Abelson Kinase Inhibitors Are Potent Inhibitors of Severe Acute Respiratory Syndrome Coronavirus and Middle East Respiratory Syndrome Coronavirus Fusion

Abstract

The highly pathogenic severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) cause significant morbidity and morality. There is currently no approved therapeutic for highly pathogenic coronaviruses, even as MERS-CoV is spreading throughout the Middle East. We previously screened a library of FDA-approved drugs for inhibitors of coronavirus replication in which we identified Abelson (Abl) kinase inhibitors, including the anticancer drug imatinib, as inhibitors of both SARS-CoV and MERS-CoV in vitro. Here we show that the anti-CoV activity of imatinib occurs at the early stages of infection, after internalization and endosomal trafficking, by inhibiting fusion of the virions at the endosomal membrane. We specifically identified the imatinib target, Abelson tyrosine-protein kinase 2 (Abl2), as required for efficient SARS-CoV and MERS-CoV replication in vitro. These data demonstrate that specific approved drugs can be characterized in vitro for their anticoronavirus activity and used to identify host proteins required for coronavirus replication. This type of study is an important step in the repurposing of approved drugs for treatment of emerging coronaviruses. T he severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) coronaviruses (CoVs) are two highly pathogenic viruses that infect humans. These viruses undergo a distinct replication cycle, involving virion entry, RNA genome replication and transcription of viral mRNAs, protein translation, virion assembly in the endoplasmic reticulum (ER)-Golgi intermediate complex, and egress by exocytosis of assembled virions (reviewed in reference 1). Coronavirus entry can be further subdivided into virion binding, receptor-mediated endocytosis, intracellular trafficking, and protease-dependent cleavage of spike (S) protein, leading to fusion of the virion membrane to the endosomal membrane. The SARS-CoV virion is endocytosed following S binding to angiotensin-converting enzyme 2 (ACE2) and trafficking to the late endosome, where the virion membrane fuses with the endosomal membrane in a cathepsin L-dependent manner (2). The MERS-CoV virion is endocytosed following S binding to dipeptidyl peptidase 4 (DPP4) and trafficking to the early endosome, where the virion membrane fuses with the endosomal membrane in a furin-dependent manner (3). IMPORTANCE Both SARS-CoV and MERS-The outbreaks of SARS-CoV and MERS-CoV highlight the need to find treatments for these and potential future coronavirus outbreaks. The drug development process from novel compound to approved drug generally takes over 10 years, making it impractical to develop novel anticoronavirus drugs once an outbreak begins. For SARS-CoV, drugs that inhibit the viral protease (4-7), replicase (8-10), or helicase (10, 11) in vitro have been identified;

A Systematic Review of therapeutic agents for the treatment of the Middle East Respiratory Syndrome Coronavirus (MERS-CoV)

“…Chlorpromazine reduced MERS-CoV by 2 log10 and had a narrow therapeutic window and a high toxicity [41]. Chloroquine, Chloropromazine, and loperamide were tested on Huh7 cells [43]. The cells were treated 1-h prior to infection.…”

Drug Repurposing for Viral Infectious Diseases: How Far Are We?

“…In this case, the approved drug can be exploited also as an antiviral therapeutic agent (new indication). The case is exemplified by the anticancer drug imatinib that inhibits cellular Abelson (ABL) kinase and was found to be also active against pathogenic coronaviruses [3].…”

“…However, they did not progress further in preclinical studies. The DR approach also allowed identification of the ABL tyrosine kinase oncogene pathway as essential for the entry of CoVs [3,46]. Indeed, the ABL kinase inhibitor imatinib, approved as an oral anticancer agent, inhibited the replication of both MERSand SARS-CoV by preventing the fusion of the virus with the endosomal membrane.…”

Repurposing approved drugs on the pathway to novel therapies

“…Given the rising number of strains found to be resistant to drugs that affect pathways specific to infectious agents, many repurposing studies are now looking for more broad‐spectrum agents that block or activate host pathways, such as those targeted in cancer therapy . Drugs developed to inhibit intracellular kinases, phosphatases, or reduce inflammation may indeed have multivalent activity against several different infectious organisms. For example, drugs approved for different indications, chosen from a 400 compound library, inhibited the ability of several pathogenic bacteria to grow in macrophages.…”