Celgosivir is more effective (IC50: 20 μM) than the parent molecule (IC50: 254 μM) at causing the accumulation of glucosylated oligosaccharides in HIV-infected cells by inhibition of glycoprotein processing. Celgosivir exhibits potent antiviral activity against HIV-1 (IC50: 2.0 μM) [1]. BVDV is a closely related virus of hepatitis C virus (HCV). Celgosivir inhibits BVDV with IC50 values of 16 and 47 μM in plaque assay and cytopathic effect assay, respectively [2]. Celgosivir inhibits DENV2 replication with an EC50 of 0.2 μM. The EC50 values against DENV1, 3, and 4 are less than 0.7 μM [3].

During primary infection with a mouse-adapted DENV strain S221, mice show increased viremia on day 3, yet 80% survived day 10 with a virus completely cleared by day 8 [3]. Celgosivir (50 mg/kg, BID for 5 days) fully protects AG129 mice from lethal infection with a mouse-adapted dengue virus and is effective even after 48 h delayed treatment. The protection by celgosivir is dose- and schedule-dependent and that a twice-a-day regimen of 50, 25, or 10 mg/kg is more protective than a single daily dose of 100 mg/kg. Pharmacokinetics studies of celgosivir in mice show that it rapidly metabolizes to castanospermine [4].