Novel Ranking System for Identifying Efficacious Anti-Influenza Virus PB2 Inhibitors.

Through antigenic drift and shifts, influenza virus infections continue to be an annual cause of morbidity in healthy populations and of death among elderly and at-risk patients. The emergence of highly pathogenic avian influenza viruses such as H5N1 and H7N9 and the rapid spread of the swine-origin H1N1 influenza virus in 2009 demonstrate the continued need for effective therapeutic agents for influenza. While several neuraminidase inhibitors have been developed for the treatment of influenza virus infections, these have shown a limited window for treatment initiation, and resistant variants have been noted in the population. In addition, an older class of antiviral drugs for influenza, the adamantanes, are no longer recommended for treatment due to widespread resistance. There remains a need for new influenza therapeutic agents with improved efficacy as well as an expanded window for the initiation of treatment. Azaindole compounds targeting the influenza A virus PB2 protein and demonstrating excellent in vitro and in vivo properties have been identified. To evaluate the in vivo efficacy of these PB2 inhibitors, we utilized a mouse influenza A virus infection model. In addition to traditional endpoints, i.e., death, morbidity, and body weight loss, we measured lung function using whole-body plethysmography, and we used these data to develop a composite efficacy score that takes compound exposure into account. This model allowed the rapid identification and ranking of molecules relative to each other and to oseltamivir. The ability to identify compounds with enhanced preclinical properties provides an opportunity to develop more-effective treatments for influenza in patients.

Improvement in Bone Mineral Density and Architecture in a Patient with Gaucher Disease Using Teriparatide.

Gaucher disease is an autosomal recessive lysosomal storage disorder caused by deficiency of the enzyme acid beta-glucosidase (glucocerebrosidase) due to mutations in the GBA gene. The most common form (type I) is associated with severe hematologic, visceral and bone disease. Disease-modifying treatments, such as enzyme replacement therapy and substrate reduction therapy, can improve the hematologic and visceral aspects of the disease but success with improving severe osteopenia, which can increase the risk of fractures, is limited. Our case involves a patient with complex disease affecting bone health including Gaucher disease (type I), Sjögren syndrome, rheumatoid arthritis and corticosteroid use who did not respond to long term use of bisphosphonates. We report an improvement in bone mineral density and bone architecture commensurate with a reduced incidence of fractures in whom we used teriparatide (human parathyroid hormone (PTH; 1-34) to treat severe osteopenia. We conclude that teriparatide should be considered for further studies as an agent to improve bone mineral density in patients with Gaucher disease.

Preclinical activity of VX-787, a first-in-class, orally bioavailable inhibitor of the influenza virus polymerase PB2 subunit.

VX-787 is a novel inhibitor of influenza virus replication that blocks the PB2 cap-snatching activity of the influenza viral polymerase complex. Viral genetics and X-ray crystallography studies provide support for the idea that VX-787 occupies the 7-methyl GTP (m(7)GTP) cap-binding site of PB2. VX-787 binds the cap-binding domain of the PB2 subunit with a KD (dissociation constant) of 24 nM as determined by isothermal titration calorimetry (ITC). The cell-based EC50 (the concentration of compound that ensures 50% cell viability of an uninfected control) for VX-787 is 1.6 nM in a cytopathic effect (CPE) assay, with a similar EC50 in a viral RNA replication assay. VX-787 is active against a diverse panel of influenza A virus strains, including H1N1pdm09 and H5N1 strains, as well as strains with reduced susceptibility to neuraminidase inhibitors (NAIs). VX-787 was highly efficacious in both prophylaxis and treatment models of mouse influenza and was superior to the neuraminidase inhibitor, oseltamivir, including in delayed-start-to-treat experiments, with 100% survival at up to 96 h postinfection and partial survival in groups where the initiation of therapy was delayed up to 120 h postinfection. At different doses, VX-787 showed a 1-log to >5-log reduction in viral load (relative to vehicle controls) in mouse lungs. Overall, these favorable findings validate the PB2 subunit of the viral polymerase as a drug target for influenza therapy and support the continued development of VX-787 as a novel antiviral agent for the treatment of influenza infection.

Discovery of a novel, first-in-class, orally bioavailable azaindole inhibitor (VX-787) of influenza PB2.

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.

In vivo bone architecture in pompe disease using high-resolution peripheral computed tomography.

Pompe disease (lysosomal acid alpha-glucosidase deficiency) in adolescents and adults presents primarily with muscle weakness. Bone weakness is an under-recognized finding in patients with Pompe disease, but there is emerging evidence that loss of muscle function and mobility can lead to loss of mineral content and a higher risk of fracture. In addition to the mineral content, architecture is also important in determining the overall strength of the bone. We present the results of the longest longitudinal duration study to date using a novel application of high-resolution peripheral quantitative computed tomography (HR-pQCT) in four patients with Pompe disease over 4 years of observation during the normal course of their disease management. The subjects varied in treatment status with recombinant human alpha-glucosidase (rhGAA), use of anti-resorptive therapy (such as bisphosphonates), mobility and weight-bearing status, and the use of side-alternating vibration therapy. Our observations were that HR-pQCT can measure trends in mineral density and architecture over a long period of observation and may be an early indicator of the response to interventional therapies. In addition, a combination of decreased loading forces due to decreased mobility likely contributes to the compromise of bone integrity in Pompe disease. These trends can be reversed by applying increased loading forces such as vibration therapy and maintaining weight-bearing and mobility. We conclude that HR-pQCT can serve as a valuable tool to monitor bone health in patients with Pompe disease.