Fig 1.
Plasma concentrations (ng/mL + SD) of BXM and BXA in ferrets compared to humans.
Administration to ferrets was either via an oral (BXM) or subcutaneous (BXA) route. BXM was prepared at a concentration of 2 mg/ml and delivered to ferrets via an intragastric tube at a concentration of 10 mg/5 mL/kg. Subcutaneous injections were made using BXA in suspension (1 mg/mL) and administered to four sites on the dorsal region of the ferret (1 mL at each site). Human PK data was derived from population pharmacokinetics and exposure-response analyses in adults and adolescents [20]. Blood samples were collected at various time points and the plasma concentration of BXA was determined by LC-MS/MS. BXA-treated ferrets were sampled at 48 and 144 hours post-treatment in London (Lon) IC model experiments, or at 48 or 72 hours post-treatment in Melbourne (Mel) DC model experiments.
Fig 2.
Effect of BXA treatment on indirect transmission (London).
(A) Experimental setup. Donor ferrets were intranasally inoculated with 104 PFU of A/England/195/2009. Antiviral treatment of infected donor ferrets commenced 24 hours post-infection. OST was administered a total of ten times across a five-day period; BXA was delivered as a single dose. Influenza-naïve sentinel DC ferrets were co-housed immediately following treatment. In addition, naïve sentinel IC ferrets were housed immediately after treatment in separate cages from those of the donor and DC sentinel ferrets. Nasal washes were collected from all donor and sentinel ferrets to assess shedding of infectious virus from 1 DPE to 11 DPE. (B) Nasal wash infectious viral titres in donor and sentinel ferrets. Donor ferrets were either untreated (upper panel), treated with oseltamivir (OST, middle) or treated with baloxavir (BXA, lower). Virus replication curves (plaque assay) for each donor and their corresponding DC and IC sentinels are graphed.
Fig 3.
Effect of BXA treatment on direct contact transmission after immediate co-housing of sentinel ferrets (Melbourne study).
(A) Experimental setup. Donor ferrets were intranasally inoculated with 103 TCID50 of influenza A/Perth/265/2009. Antiviral treatment of infected donor ferrets commenced 24 hours post-infection, and influenza-naïve sentinel ferrets were co-housed with donor ferrets immediately following treatment. OST was administered to donors a total of four times across a two-day period until sacrifice. BXA and placebo (methyl cellulose solution) were each delivered subcutaneously as a single dose. Nasal washes were collected from sentinel ferrets to assess shedding of infectious virus from 1 DPE to 10 DPE. A terminal bleed was not collected for this experiment. (B) Nasal wash infectious viral titres in donor and sentinel ferrets. Donor ferrets were either treated with placebo (upper panel), treated with oseltamivir (OST, middle) or treated with baloxavir (BXA, lower). Virus replication curves (TCID50) for each donor/DC sentinel pair are graphed.
Fig 4.
Effect of BXA treatment on direct contact transmission after delayed co-housing of sentinel ferrets (Melbourne study).
(A) Experimental setup. Donor ferrets were intranasally inoculated with 103 TCID50 of influenza A/Perth/265/2009. Antiviral treatment of infected donor ferrets commenced 24 hours post-infection, and influenza-naïve sentinel ferrets were co-housed with donor ferrets 24 hours post-treatment. OST was administered to donors a total of six times across a three-day period until sacrifice. BXA and placebo (methyl cellulose solution) were each delivered subcutaneously as a single dose. Nasal washes were collected from sentinel ferrets to assess shedding of infectious virus from 1 DPE to 10 DPE, and a terminal bleed was collected for serology at 16 DPE. (B) Nasal wash infectious viral titres in donor and sentinel ferrets. Donor ferrets were either treated with placebo (upper panel), treated with oseltamivir (OST, middle) or treated with baloxavir (BXA, lower). Virus replication curves (TCID50) for each donor/DC sentinel pair are graphed.
Fig 5.
Effect of delayed BXA treatment on direct contact transmission (Melbourne study).
(A) Experimental setup. Donor ferrets were intranasally inoculated with 103 TCID50 of influenza A/Perth/265/2009. Antiviral treatment of infected donor ferrets commenced 48 h post-infection, and influenza-naïve sentinel ferrets were co-housed with donor ferrets immediately following treatment. OST was administered to donors a total of four times across a two-day period until sacrifice. BXA and placebo (methyl cellulose solution) were each delivered subcutaneously as a single dose. Nasal washes were collected from sentinel ferrets to assess shedding of infectious virus from 1 DPE to 10 DPE, and a terminal bleed was collected for serology at 16 DPE. (B) Nasal wash infectious viral titres in donor and sentinel ferrets. Donor ferrets were either treated with placebo (upper panel), treated with oseltamivir (OST, middle) or treated with baloxavir (BXA, lower). Virus replication curves (TCID50) for each donor/DC sentinel pair are graphed.