Broad-Spectrum Inhibitors against 3C-Like Proteases of Feline Coronaviruses and Feline Caliciviruses

Abstract

Feline infectious peritonitis and virulent, systemic calicivirus infection are caused by certain types of feline coronaviruses (FCoVs) and feline caliciviruses (FCVs), respectively, and are important infectious diseases with high fatality rates in members of the Felidae family. While FCoV and FCV belong to two distinct virus families, the Coronaviridae and the Caliciviridae, respectively, they share a dependence on viral 3C-like protease (3CLpro) for their replication. Since 3CLpro is functionally and structurally conserved among these viruses and essential for viral replication, 3CLpro is considered a potential target for the design of antiviral drugs with broad-spectrum activities against these distinct and highly important viral infections. However, small-molecule inhibitors against the 3CLpro enzymes of FCoV and FCV have not been previously identified. In this study, derivatives of peptidyl compounds targeting 3CLpro were synthesized and evaluated for their activities against FCoV and FCV. The structures of compounds that showed potent dual antiviral activities with a wide margin of safety were identified and are discussed. Furthermore, the in vivo efficacy of 3CLpro inhibitors was evaluated using a mouse model of coronavirus infection. Intraperitoneal administration of two 3CLpro inhibitors in mice infected with murine hepatitis virus A59, a hepatotropic coronavirus, resulted in significant reductions in virus titers and pathological lesions in the liver compared to the findings for the controls. These results suggest that the series of 3CLpro inhibitors described here may have the potential to be further developed as therapeutic agents against these important viruses in domestic and wild cats. This study provides important insights into the structure and function relationships of 3CLpro for the design of antiviral drugs with broader antiviral activities. IMPORTANCE Feline infectious peritonitis virus (FIPV)is the leading cause of death in young cats, and virulent, systemic feline calicivirus (vs-FCV) causes a highly fatal disease in cats for which no preventive or therapeutic measure is available. The genomes of these distinct viruses, which belong to different virus families, encode a structurally and functionally conserved 3C-like protease (3CL-pro) which is a potential target for broad-spectrum antiviral drug development. However, no studies have previously reported a structural platform for the design of antiviral drugs with activities against these viruses or on the efficacy of 3CLpro inhibitors against coronavirus infection in experimental animals. In this study, we explored the structure-activity relationships of the derivatives of 3CLpro inhibitors and identified inhibitors with potent dual activities against these viruses. In addition, the efficacy of the 3CLpro inhibitors was demonstrated in mice infected with a murine coronavirus. Overall, our study provides the first insight into a structural platform for anti-FIPV and anti-FCV drug development. F eline coronaviruses (FCoVs) and feline ...

Characterization of amino acid substitutions in feline coronavirus 3C-like protease from a cat with feline infectious peritonitis treated with a protease inhibitor

“…These findings indicate that A252S and K260 N mutations do not affect the susceptibility of 3CLpro against GC376. NPI52 is a tripeptidyl compound that shares a similar backbone structure with GC376 and has a similarly potent activity against feline coronavirus as GC376 in the FRET assay and cell culture (Kim et al, 2015). However, unlike those of GC376, there was no difference in the IC 50 values of 3CLpro with WT, single, double or triple mutations against NPI52 (Fig.3A and B).…”

“…The https://doi.org/10.1016/j.vetmic.2019.108398 Received 10 July 2019; Received in revised form 21 August 2019; Accepted 21 August 2019 released viral proteins form the replicase-transcriptase complex, which is required for RNA replication and transcription of the subgenomic RNAs, thus inhibition of viral proteases blocks viral replication. We have previously reported the synthesis of protease inhibitors for feline coronavirus (Kim et al, 2012a(Kim et al, , 2013Kim et al, 2015), and showed the efficacy of one of the inhibitors, GC376, in cats with experimentally induced FIP (Kim et al, 2016) and naturally-occurring FIP in a field trial (Pedersen et al, 2018). We have also reported the amino acid changes (N25S, A252S and K260 N) in the 3CLpro of feline coronavirus collected from a patient who was treated with GC376 but did not show clinical resistance to multiple rounds of treatment in the field trial (Pedersen et al, 2018).…”

Lopinavir; A Potent Drug against Coronavirus Infection: Insight from Molecular Docking Study

“…In this context, many reports showed that Mpro is an ideal target for drug design and development (34)(35)(36). The well-characterized inhibitors of Mpro can be classified into 2 classes based on their chemical structures.…”

“…Anti-protease inhibitors approved for viral infection treatment are interesting examples in this connection. Recently, these inhibitors are screened for their capability to inhibit Mpro and treat SARS infection using in vivo, in vitro, and in silico experiments (34)(35)(36)(37)(38)(39). The clinical trial of LPV showed a significant decrease in virus titer, reduced rate of death, and improved clinical recovery (40)(41)(42).…”

The future of antivirals

“…Rupintrivir for instance is an irreversible 3C-protease inhibitor that was originally developed for the treatment of human rhinovirus infections [22] and antiviral activity has also been shown against other picornaviruses, coronaviruses, and norovirus [23][24][25]. Other inhibitors of 3C-like proteases were reported with broad-spectrum antiviral activity against both feline coronaviruses and caliciviruses [26]. Therefore, the design of BSAA targeting proteases of different virus families appears feasible and could be a good strategy to develop broader-spectrum antivirals.…”