Dichloro-Phenyl-Benzotriazoles: A New Selective Class of Human Respiratory Syncytial Virus Entry Inhibitors.

Sandra Piras,Maurizio Fermeglia,Giuseppina Sanna,Roberta Loddo,Roberta Ibba,Suzana Aulic,Paola Caria,Sabrina Pricl,Paola Corona,Antonio Carta,Erik Laurini,Silvia Madeddu

doi:10.3389/fchem.2019.00247

Abstract

Human Respiratory Syncytial Virus (RSV) is the primary cause of bronchopneumonia in infants and children worldwide. Clinical studies have shown that early treatments of RSV patients with ribavirin improve prognosis, even if the use of this drug is limited due to myelosuppression and toxicity effects. Furthermore, effective vaccines to prevent RSV infection are currently unavailable. Thus, the development of highly effective and specific antiviral drugs for pre-exposure prophylaxis and/or treatment of RSV infections is a compelling need. In the quest of new RSV inhibitors, in this work we evaluated the antiviral activity of a series of variously substituted 5,6-dichloro-1-phenyl-1(2)H-benzo[d][1,2,3]triazole derivatives in cell-based assays. Several 1- and 2-phenyl-benzotriazoles resulted fairly potent (μM concentrations) inhibitors of RSV infection in plaque reduction assays, accompanied by low cytotoxicity in human highly dividing T lymphoid-derived cells and primary cell lines. Contextually, no inhibitory effects were observed against other RNA or DNA viruses assayed, suggesting specific activity against RSV. Further results revealed that the lead compound 10d was active during the early phase of the RSV infection cycle. To understand whether 10d interfered with virus attachment to target cells or virus-cell fusion events, inhibitory activity tests against the RSV mutant strain B1 cp-52—expressing only the F envelope glycoprotein—and a plasmid-based reporter assay that quantifies the bioactivity of viral entry were also performed. The overall biological results, in conjunction with in silico modeling studies, supported the conclusion that the RSV fusion process could be the target of this new series of compounds.

Highlights

Viral pneumonia is an increasing health problem worldwide, and the incidence and number of viruses known to induce respiratory diseases have expanded in recent years (Lee and Qureshi, 2013)
Given the beneficial role of the alogen substituent and with the aim of further potentiating the anti-Respiratory Syncytial Virus (RSV) activity of benzotriazole compounds, in this paper we report the design and synthesis of 5,6-dichloro-1-phenyl1H-benzotriazole amides (5a-d and 7a-h) (Scheme 1) and 5,6dichloro-2-phenyl-2H-benzotriazole derivatives 6a-f, 8a-h and 10a-k (Schemes 2, 3) as potential RSV inhibitors
These findings demonstrate that pretreatment with 10d does not protect cells from RSV infection

Summary

INTRODUCTION

Viral pneumonia is an increasing health problem worldwide, and the incidence and number of viruses known to induce respiratory diseases have expanded in recent years (Lee and Qureshi, 2013). A prophylactic strategy based on a humanized neutralizing antibody against RSV is available to protect newborn babies at high-risk, such as preterm infants and those suffering from cardiovascular diseases and immunodeficiencies (Feltes et al, 2003; Cardenas et al, 2005) This approach is costly and unaffordable for most public health systems worldwide. Since F is essential for RSV infection, humans elicit neutralizing antibodies that target it, with the most potent recognizing the prefusion conformation This conformation of F is considered to be the ideal vaccine antigen, and antibodies and small molecules that disrupt its structure and function constitute a very active field of current research. Results of the antiviral selectivity of these dichloro-phenyl-benzotriazoles, their cytotoxicity and antiviral activity against representative DNA, ± single-stranded RNA, and double-stranded genome (dsRNA) viruses families obtained in cell-based assays are reported (see Supplementary Material)

MATERIALS AND METHODS

AND DISCUSSION

Findings

CONCLUSION