T-705 (Favipiravir) Inhibition of Arenavirus Replication in Cell Culture

T he family Paramyxoviridae contains a number of viruses causing respiratory tract illnesses in humans, which together have a large clinical impact (1). Human metapneumovirus (HMPV), respiratory syncytial virus (RSV), and parainfluenza virus (PIV) infections are responsible for severe acute respiratory illnesses mainly in young children, but also in immunocompromised and elderly individuals, and are-together with the influenza viruses (family Orthomyxoviridae)-the primary viral causes of hospitalizations for severe respiratory tract disease (2-5). No licensed vaccines or effective antiviral treatments are available for these viruses. Measles virus, yet another paramyxovirus, is responsible for a devastating disease which the WHO committed to eradicate with the aid of effective vaccines. However, due to suboptimal immunization levels, resurgences in infections have been detected, and there is no effective antiviral treatment available for measles virusinfected patients (6-8). Paramyxoviruses are well known for their zoonotic potential: avian pneumovirus (AMPV) is the proposed avian ancestor of HMPV, and the avian Newcastle disease virus (NDV) can cause disease-primarily conjunctivitis-in humans (9-11). Multiple novel paramyxoviruses have been detected in bats, including close relatives of human viruses (12, 13), and henipaviruses continue to cause infections in humans in . No licensed vaccines or effective antiviral treatments are available for any of these viruses. The continuous burden of disease associated with human and zoonotic paramyxoviruses argues for the development of antiviral therapies with broad-spectrum activity against all paramyxoviruses.Favipiravir (T-705; 6-fluoro-3-hydroxy-2-pyrazinecarboxamine) is a pyrazine derivative that has demonstrated potent antiviral activity against multiple RNA viruses (18,19). Intracellular host enzymes act upon T-705, converting it to its active form, T-705-4-ribofuranosyl-5-triphosphate (T-705RTP) (20). T-705RTP functions as a purine nucleotide analog that selectively inhibits the RNA-dependent RNA polymerase (RdRp) or causes lethal mutagenesis upon incorporation into the viral RNA (21-24). T-705 is presently in clinical development as an influenza virus inhibitor in Japan (new drug application filed) and the United States (phase 3 clinical trial) (18). Antiviral activity has been demonstrated against a broad range of negative-strand RNA viruses, such as members of the Picorna-, , and positive-strand RNA viruses, such as the Noro-and Flavivirus genera (31, 32). Here we evaluated the activity of T-705 against a broad range of paramyxoviruses in vitro and against HMPV in hamsters. MATERIALS AND METHODS Cells

Section: Discussionmentioning

confidence: 80%

Antiviral Activity of Favipiravir (T-705) against a Broad Range of Paramyxoviruses In Vitro and against Human Metapneumovirus in Hamsters

Jochmans

Nieuwkoop

Smits

et al. 2016

“…T-705 was shown to have different characteristics from amantadine and neuraminidase inhibitors. T-705 strongly inhibits the replication of influenza virus types A, B, and C and has broad-spectrum activities against various RNA viruses, such as arenaviridae, bunyaviridae, flaviviridae, picornaviridae, and paramyxoviridae (4,(7)(8)(9)(10)(11). T-705 is currently undergoing phase II clinical trials for the treatment of influenza virus infections in the United States.…”

mentioning

confidence: 99%

Mechanism of Action of T-705 Ribosyl Triphosphate against Influenza Virus RNA Polymerase

Sangawa

Komeno

Nishikawa

et al. 2013

Self Cite

170

152

T-705 (favipiravir; 6-fluoro-3-hydroxy-2-pyrazinecarboxamide) selectively and strongly inhibits replication of the influenza virus in vitro and in vivo. T-705 has been shown to be converted to T-705-4-ribofuranosyl-5-triphosphate (T-705RTP) by intracellular enzymes and then functions as a nucleotide analog to selectively inhibit RNA-dependent RNA polymerase (RdRp) of the influenza virus. To elucidate these inhibitory mechanisms, we analyzed the enzyme kinetics of inhibition using Lineweaver-Burk plots of four natural nucleoside triphosphates and conducted polyacrylamide gel electrophoresis of the primer extension products initiated from 32 P-radiolabeled 5=Cap1 RNA. Enzyme kinetic analysis demonstrated that T-705RTP inhibited the incorporation of ATP and GTP in a competitive manner, which suggests that T-705RTP is recognized as a purine nucleotide by influenza virus RdRp and inhibited the incorporation of UTP and CTP in noncompetitive and mixed-type manners, respectively. Primer extension analysis demonstrated that a single molecule of T-705RTP was incorporated into the nascent RNA strand of the influenza virus and inhibited the subsequent incorporation of nucleotides. These results suggest that a single molecule of T-705RTP is incorporated into the nascent RNA strand as a purine nucleotide analog and inhibits strand extension, even though the natural ribose of T-705RTP has a 3=-OH group, which is essential for forming a covalent bond with the phosphate group.

“…T-705, an RNA-dependent RNA polymerase inhibitor, was also reported to have antiviral activity against a variety of RNA viruses. It is under development as a therapeutic candidate; however, its potency (50% inhibitory concentration [IC 50 ]) falls in the few hundred micromolar range for most viruses, with the exception of influenza viruses (7).…”

mentioning

confidence: 99%

Discovery of a Broad-Spectrum Antiviral Compound That Inhibits Pyrimidine Biosynthesis and Establishes a Type 1 Interferon-Independent Antiviral State

Chung

Golden

Adcock

et al. 2016

Viral emergence and reemergence underscore the importance of developing efficacious, broad-spectrum antivirals. Here, we report the discovery of tetrahydrobenzothiazole-based compound 1, a novel, broad-spectrum antiviral lead that was optimized from a hit compound derived from a cytopathic effect (CPE)-based antiviral screen using Venezuelan equine encephalitis virus. Compound 1 showed antiviral activity against a broad range of RNA viruses, including alphaviruses, flaviviruses, influenza virus, and ebolavirus. Mechanism-of-action studies with metabolomics and molecular approaches revealed that the compound inhibits host pyrimidine synthesis and establishes an antiviral state by inducing a variety of interferon-stimulated genes (ISGs). Notably, the induction of the ISGs by compound 1 was independent of the production of type 1 interferons. The antiviral activity of compound 1 was cell type dependent with a robust effect observed in human cell lines and no observed antiviral effect in mouse cell lines. Herein, we disclose tetrahydrobenzothiazole compound 1 as a novel lead for the development of a broad-spectrum, antiviral therapeutic and as a molecular probe to study the mechanism of the induction of ISGs that are independent of type 1 interferons.