In our effort to develop agents for the treatment of influenza, a phenotypic screening approach utilizing a cell protection assay identified a series of azaindole based inhibitors of the cap-snatching function of the PB2 subunit of the influenza A viral polymerase complex. Using a bDNA viral replication assay (Wagaman, P. C., Leong, M. A., and Simmen, K. A. Development of a novel influenza A antiviral assay. J. Virol. Methods 2002, 105, 105-114) in cells as a direct measure of antiviral activity, we discovered a set of cyclohexyl carboxylic acid analogues, highlighted by VX-787 (2). Compound 2 shows strong potency versus multiple influenza A strains, including pandemic 2009 H1N1 and avian H5N1 flu strains, and shows an efficacy profile in a mouse influenza model even when treatment was administered 48 h after infection. Compound 2 represents a first-in-class, orally bioavailable, novel compound that offers potential for the treatment of both pandemic and seasonal influenza and has a distinct advantage over the current standard of care treatments including potency, efficacy, and extended treatment window.

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JNJ-63623872 (2) is a first-in-class, orally bioavailable compound that offers significant potential for the treatment of pandemic and seasonal influenza. Early lead optimization efforts in our 7-azaindole series focused on 1,3-diaminocyclohexyl amide and urea substitutions on the pyrimidine-7-azaindole motif. In this work, we explored two strategies to eliminate observed aldehyde oxidase (AO)-mediated metabolism at the 2-position of these 7-azaindole analogues. Substitution at the 2-position of the azaindole ring generated somewhat less potent analogues, but reduced AO-mediated metabolism. Incorporation of a ring nitrogen generated 7-azaindazole analogues that were equipotent to the parent 2-H-7-azaindole, but surprisingly, did not appear to improve AO-mediated metabolism. Overall, we identified multiple 2-substituted 7-azaindole analogues with enhanced AO stability and we present data for one such compound (12) that demonstrate a favorable oral pharmacokinetic profile in rodents. These analogues have the potential to be further developed as anti-influenza agents for the treatment of influenza. KEYWORDS: Influenza, PB2 subunit, 7-azaindole, aldehyde oxidase, metabolic stability S easonal influenza causes high morbidity and mortality around the globe annually. The impact of influenza epidemics is estimated to be approximately 3.5 million cases for severe illness and 300,000 to 500,000 deaths annually. 1 Transmission of novel strains of influenza from other species (mammals and birds) can cause human pandemics, such as the 2009 H1N1 swine flu pandemic as well as the H5N1 avian flu outbreaks. 2 Influenza is caused by three orthomyxoviridae family viruses, influenza A, B, and C. 3 The current antiviral standard of care (SOC) for treatment of influenza cases in the United States are the neuraminidase inhibitors, oseltamivir 1 (Figure 1) and zanamivir. While these agents can be effective against a variety of type A and B influenza viruses, they suffer from two main limitations. First, the neuraminidase inhibitors have only a moderate impact on the severity of symptoms as well as duration of sickness, and they must be administered within 24−48 h of the infection. 4 Second, resistance to this class of antivirals has generated significant concern, 5 especially with the report that the H5N1 influenza virus has shown resistance to oseltamivir, 6 reinforcing the critical need for new anti-influenza therapeutics with novel mechanisms of action.We have previously reported a series of potent 7-azaindolebased influenza inhibitors, highlighted by JNJ-63623872 (2) (formerly known as VX-787). 7 The molecular target for these compounds was identified as the PB2 subunit of the influenza viral polymerase. The PB2 subunit contains a cap binding domain for 7-methyl GTP (m7-GTP) on the 5′-end of the host pre-mRNA. Once bound to PB2, the polymerase acidic protein (PA) endonuclease subunit cleaves the host RNA strand, leaving a 10−13 nucleotide primer. The PB1 subunit contains the conserved polymerase domain and utilizes the pr...