Comparison of Routes of Administration, Frequency, and Duration of Favipiravir Treatment in Mouse and Guinea Pig Models of Ebola Virus Disease

Abstract

Favipiravir is a ribonucleoside analogue that has been explored as a therapeutic for the treatment of Ebola Virus Disease (EVD). Promising data from rodent models has informed nonhuman primate trials, as well as evaluation in patients during the 2013-2016 West African EVD outbreak of favipiravir treatment. However, mixed results from these studies hindered regulatory approval of favipiravir for the indication of EVD. This study examined the influence of route of administration, duration of treatment, and treatment schedule of favipiravir in immune competent mouse and guinea pig models using rodent-adapted Zaire ebolavirus (EBOV). A dose of 300 mg/kg/day of favipiravir with an 8-day treatment was found to be fully effective at preventing lethal EVD-like disease in BALB/c mice regardless of route of administration (oral, intraperitoneal, or subcutaneous) or whether it was provided as a once-daily dose or a twice-daily split dose. Preclinical data generated in guinea pigs demonstrates that an 8-day treatment of 300 mg/kg/day of favipiravir reduces mortality following EBOV challenge regardless of route of treatment or duration of treatments for 8, 11, or 15 days. This work supports the future translational development of favipiravir as an EVD therapeutic.

Keywords: EBOV; Ebola virus; T-705; animal model; favipiravir; filovirus.

Figure 1

Groups (n = 10, 5 males, 5 females) of BALB/c mice were challenged with a 2.9 × 10² PFU dose of 1000 PFU of maEBOV at day 0 (D0) (left panel schematic). One hour post infection, treatment with 300 mg/kg of favipiravir daily given either QD (red squares, green triangles, and purple inverted triangles) or split into BID doses of 150 mg/kg (blue circles) was initiated. A control group was sham treated with vehicle only (orange diamonds). Treatment was delivered PO (orange diamonds, blue circles, red squares), SC (green triangles), or IP (purple inverted triangles). Animals were monitored for 21 days for morbidity and mortality (top right panel; p < 0.0001 by Mantel–Cox log-rank test), percent change in weight from D0 (right middle panel), and clinical score (right bottom panel).

Figure 2

Groups (n = 8, 4 males, 4 females) of Hartley outbred guinea pigs were challenged with a target dose of 1000 PFU of gpaEBOV at D0 (left panel schematic). After an hour, they were treated QD with 300 mg/kg of favipiravir delivered PO (red squares, green triangles, purple inverted triangles) or IP (black open squares, brown open triangles, navy open inverted triangles) for 8 days (red squares, black open squares), 11 days (green triangles, brown open triangles), or 15 days (purple inverted triangles, navy open inverted triangles). A control group was sham treated PO (blue circles) or IP (orange diamonds) with vehicle only QD for 11 days. Animals were followed for 21 days for survival (panel A; p < 0.0001 by Mantel–Cox log-rank test), percent change in weight from D0 (PO treatment in panel (B); IP treatment in panel (C)), (clinical score (PO treatment in panel (D); IP treatment in panel (E)). Temperatures were taken by IPTT-300 RFID transponder for guinea pigs treated PO (panel (F)) or IP (panel (G)). Blood was collected at the time of euthanasia and serum was either used for RNA extraction and qRT-PCR viral load quantification (PO panel (H), IP panel (I)) or stored frozen at −80 °C for plaque assay quantification (PO panel (J), IP panel (K). Differences in qRT-PCR GEq/μL and PFU/mL were analyzed by Kruskal–Wallis test with Dunnet’s post hoc comparison to vehicle-treated controls. * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001.

Figure 2

Groups (n = 8, 4 males, 4 females) of Hartley outbred guinea pigs were challenged with a target dose of 1000 PFU of gpaEBOV at D0 (left panel schematic). After an hour, they were treated QD with 300 mg/kg of favipiravir delivered PO (red squares, green triangles, purple inverted triangles) or IP (black open squares, brown open triangles, navy open inverted triangles) for 8 days (red squares, black open squares), 11 days (green triangles, brown open triangles), or 15 days (purple inverted triangles, navy open inverted triangles). A control group was sham treated PO (blue circles) or IP (orange diamonds) with vehicle only QD for 11 days. Animals were followed for 21 days for survival (panel A; p < 0.0001 by Mantel–Cox log-rank test), percent change in weight from D0 (PO treatment in panel (B); IP treatment in panel (C)), (clinical score (PO treatment in panel (D); IP treatment in panel (E)). Temperatures were taken by IPTT-300 RFID transponder for guinea pigs treated PO (panel (F)) or IP (panel (G)). Blood was collected at the time of euthanasia and serum was either used for RNA extraction and qRT-PCR viral load quantification (PO panel (H), IP panel (I)) or stored frozen at −80 °C for plaque assay quantification (PO panel (J), IP panel (K). Differences in qRT-PCR GEq/μL and PFU/mL were analyzed by Kruskal–Wallis test with Dunnet’s post hoc comparison to vehicle-treated controls. * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001.