Pyrazole compound BPR1P0034 with potent and selective anti-influenza virus activity

Abstract

BackgroundInfluenza viruses are a major cause of morbidity and mortality around the world. More recently, a swine-origin influenza A (H1N1) virus that is spreading via human-to-human transmission has become a serious public concern. Although vaccination is the primary strategy for preventing infections, influenza antiviral drugs play an important role in a comprehensive approach to controlling illness and transmission. In addition, a search for influenza-inhibiting drugs is particularly important in the face of high rate of emergence of influenza strains resistant to several existing influenza antivirals.MethodsWe searched for novel anti-influenza inhibitors using a cell-based neutralization (inhibition of virus-induced cytopathic effect) assay. After screening 20,800 randomly selected compounds from a library from ChemDiv, Inc., we found that BPR1P0034 has sub-micromolar antiviral activity. The compound was resynthesized in five steps by conventional chemical techniques. Lead optimization and a structure-activity analysis were used to improve potency. Time-of-addition assay was performed to target an event in the virus life cycle.ResultsThe 50% effective inhibitory concentration (IC50) of BPR1P0034 was 0.42 ± 0.11 μM, when measured with a plaque reduction assay. Viral protein and RNA synthesis of A/WSN/33 (H1N1) was inhibited by BPR1P0034 and the virus-induced cytopathic effects were thus significantly reduced. BPR1P0034 exhibited broad inhibition spectrum for influenza viruses but showed no antiviral effect for enteroviruses and echovirus 9. In a time-of-addition assay, in which the compound was added at different stages along the viral replication cycle (such as at adsorption or after adsorption), its antiviral activity was more efficient in cells treated with the test compound between 0 and 2 h, right after viral infection, implying that an early step of viral replication might be the target of the compound. These results suggest that BPR1P0034 targets the virus during viral uncoating or viral RNA importation into the nucleus.ConclusionsTo the best of our knowledge, BPR1P0034 is the first pyrazole-based anti-influenza compound ever identified and characterized from high throughput screening to show potent (sub-μM) antiviral activity. We conclude that BPR1P0034 has potential antiviral activity, which offers an opportunity for the development of a new anti-influenza virus agent.

Preclinical Activity of VX-787, a First-in-Class, Orally Bioavailable Inhibitor of the Influenza Virus Polymerase PB2 Subunit

“…Other investigators have examined PB2 as a target (47,48), but no cellular or animal antiviral activity was reported to our knowledge. We initiated a search for new anti-influenza agents using a phenotypic-based approach (28), aware that this represented a high bar for screening because influenza produces a rapid and clear CPE followed by cell death in vitro (49)(50)(51)(52)(53). As the screen employed measured protection from cell death, compounds that were directly cytotoxic were eliminated.…”

Identification of BPR3P0128 as an Inhibitor of Cap-Snatching Activities of Influenza Virus

“…The most potent compound, BPR3P0128, was identified biochemically as having potent anti-cap-snatching activity, and its chemical structure was distinct from that of two compounds identified previously in this screening ( Fig. 1) (52,53,62) and two other viral polymerase inhibitors, T-705 (favipiravir) and compound A3 (19,27). Here, we characterized BPR3P0128 and identified its underlying antiviral mechanism.…”

“…We conducted a drugscreening study using a large-scale anti-influenza virus cell-based assay based on the inhibition of the virally induced cytopathic effect (CPE) (52,53,62). An initial hit, CSV0C019002, with a 50% effective (inhibitory) concentration (EC 50 ) of 4.27 M toward A/WSN/33 was identified after screening 20,800 randomly selected small compounds (molecular masses, Ͻ500 Da) from a library.…”

Pandemic Influenza A H1N1 (2009) Virus: Lessons from the Past and Implications for the Future

“…A new pyrazole-based compound BPR1P0034, which acts during viral uncoating or viral RNA import into the nucleus has shown promising results as an antiviral drug [29]. DAS181 is a sialidase fusion protein which in early clinical development with in vitro and in vivo preclinical activity against a variety of seasonal influenza strains and highly pathogenic avian influenza strains (A/H5N1), has also shown satisfactory results with the recent pandemic H1N1 strain [33].…”