BF738735 is a selective inhibitor of phosphatidylinositol 4-kinase III beta (PI4KIIIβ, IC50 = 5.7 nM) showing higher activity over α(IC50 = 1.7 μM). BF738735 exhibits a broad spectrum of antiviral activity.

PI4KIIIα:1.7 μM, PI4KIIIβ:5.7 nM

BF738735 effectively inhibits all viruses tested, with EC50s ranging between 4 and 71 nM. The cytotoxicity of BF738735, determined in parallel with the EC50 and using the same culture conditions for 3 to 4 days, is low, with CC50 values ranging from 11 to 65 μM, resulting in high selectivity indices. BF738735 exhibits a broad spectrum of antiviral activity, as it inhibits all tested species of enteroviruses and rhinoviruses, with 50% effective concentrations ranging between 4 and 71 nM. BF738735 also impairs PI4KIIIα, but only at an ~300-fold-higher concentration (IC50 of 1.7 μM). The activity of BF738735 is analyzed on a set of 150 cellular kinases, including 13 lipid kinases at a concentration of 10 μM. For all kinases, the inhibition is less than 10%, indicating that BF738735 specifically inhibits PI4KIIIβ in vitro. Low concentrations of BF738735 decrease the amount of luciferase to GuaHCl-treated levels, suggesting that the BF738735 blocks viral RNA replication. The EC50 of BF738735 in this assay is 77 nM, which is comparable to the inhibition observed in the multicycle assay for coxsackievirus serotype B3 (CVB3)[1].

BF738735 demonstrates favorable tolerability in test subjects, achieving effective plasma concentrations of the antiviral. Notably, a complete inhibition of the target activity is achieved at a dosage of 25 mg/kg, while a partial inhibition is observed with a 5 mg/kg dose[2].