Clinical and virological responses to a broad-spectrum human monoclonal antibody in an influenza virus challenge study

Influenza A infections cause significant seasonal morbidity and mortality as well as periodic pandemic infections. Currently, no approved therapies exist for patients hospitalized with influenza. The efficacy of VIS410, a broadly neutralizing human immunoglobulin IgG1 monoclonal antibody engineered to bind to the stem region of group 1 and 2 influenza A hemagglutinins, was explored in experimental human influenza infection. Healthy volunteers were inoculated with influenza A/California/07/2009 (H1N1) and received a single dose of VIS410 or placebo 24 h later. Subjects were monitored for symptoms, viral shedding, and safety, including cytokine measurements. The primary efficacy endpoint was the area under the curve (AUC) of viral load (VL) in the VIS410 group versus placebo. VIS410 treatment was associated with a 76% reduction in median VL AUC as measured by qRT-PCR (p = 0.024). Similar VIS410 antiviral activity was observed by virus culture, with a 91% reduction in median VL AUC by TCID50 (p = 0.019) compared to placebo-treated volunteers. Influenza symptoms were generally mild or moderate, with a trend toward faster resolution in VIS410-treated subjects. Treatment with VIS410 was generally safe, with an increase in gastrointestinal events that were largely mitigated by pre-treatment with oral diphenhydramine (50 mg) in combination with 600 mg of ibuprofen. Transient elevation of specific cytokines (IL-8 and TNF alpha) were associated with gastrointestinal adverse events. Treatment with VIS410 did not interfere with the endogenous immune response to influenza A. These data indicate that VIS410 may provide therapeutic benefit in influenza A infection.