All calculations were performed using the corresponding software tool contained in the Excel software package (Microsoft, Redmond, WA, USA). Cytotoxicity assays using uninfected confluent HFF host cells were performed by the alamarBlue assay as previously reported . Confluent HFF monolayers in 96-well plates were exposed to 0.1, 1 and 2.5 μM of each compound and incubated for 72 h at 37 °C/5% CO2. After this incubation step, the medium was removed, plates were washed once with PBS and 200 μL of resazurin (1:200 dilution in PBS) were added to each well. Plates were measured at excitation wavelength 530 nm and emission wavelength 590 nM using an EnSpire ® multimode plate reader (PerkinElmer, Inc.). Fluorescence was measured at two different time points: T0 as starting timepoint and T5h as at 5 hours later. Relative fluorescence units were calculated from time points with linear increases.