The in vitro testing in this study was performed using a standard fluorometric furin activity assay (Anaspec: Fremont, CA). This assay uses a fluorometric substrate to measure the enzymatic activity of recombinant human furin. When the enzyme is active, it breaks the substrate in such a way that a chemical compound is released that will fluoresce when exposed to light at the proper wavelength. The assay includes appropriate quantities of the reagents for microplate studies and is designed to be suitable for screening substances for furin inhibition as part of a medication discovery process.