Figure 5.

Sangivamycin inhibits EBOV RNA transcription/replication. Briefly, EBOV minigenome plasmids were first transfected in HEK 293T/17 cells. Cells were initially treated with (A) sangivamycin (300 to 9.4 nM) and (B) remdesivir (3000 to 94 nM) and cytotoxicity and luciferase activity were measured at 24 h. Based on the calculated IC₅₀ values from the single drug tests in A and B, constant ratios of sangivamycin to remdesivir (S:R = 1:2.5, 1:5, 1:10, 1:20, 1:40) were set up for drug combination studies (C–E). The constant ratios were plotted relative to (C) sangivamycin concentration (1:0 represents sangivamycin alone from A) and (D) remdesivir concentration (0:1 represents remdesivir alone from B). (E) The isobologram shows the IC₅₀ values calculated from the curves in C and D plotted on the y axis (values from C) and x axis (values from D) to assess the constant ratios relative to the additive line (dotted line) drawn between the IC₅₀ values for sangivamycin and remdesivir alone calculated from curves A and B, respectively. All of the constant ratios are along the additive line within the 95% confidence interval for each point. Data for percent inhibition and cytotoxicity were determined based on a comparison to untreated negative control cells. Data represent means ± standard deviations (SD) of results from triplicate samples for the constant ratios and an n of 9 for sangivamycin- and remdesivir-alone treatments.