BAY 41-4109 racemate is a potent inhibitor of human hepatitis B virus (HBV) with an IC50 of 53 nM.

BAY 41-4109 is able to both accelerate and misdirect capsid assembly in vitro. BAY 41-4109 stabilized the preformed capsids, up to a ratio of one inhibitor molecule per two dimers[2]. BAY 41-4109 is equally effective at inhibiting HBV DNA release and the cytoplasmic HBcAg level, with IC50s of 32.6 and 132 nM in HepG2.2.15 cells, respectively. HBV DNA and HBcAg are inhibited in a dose-dependent manner, indicating that the anti-HBV mechanisms are associated with and dependent on the rate of HBcAg inhibition[3]..

BAY 41-4109 effectively diminishes viral DNA levels in both the liver and plasma in a dose-dependent fashion, showing efficacy on par with 3TC. It also decreases the hepatitis B virus core antigen (HBcAg) in the livers of HBV-transgenic mice. Pharmacokinetic evaluations reveal its rapid absorption and a bioavailability rate of 30%, with dose-proportional plasma concentrations observed, reaching approximately 60% in rats and dogs[1]. Furthermore, BAY41-4109 hampers virus production in vivo by targeting the viral capsid, demonstrating its mechanism of action[2].

Cellular metabolism is evaluated by MTT colorimetry. HepG2.2.15 cells are plated at a density of 2 × 103 cells per well in 96-well plates. After 8 d of treatment with different concentrations of each antiviral compound, 20 μL of MTT solution (5 g/L) are added to each well and incubated at 37°C for 4 h. Next, 150 μL of DMSO is added and stirred for 10 min to dissolve the crystals. Absorbance values are recorded at 490 nm by using an ELISA reader. The MTT values are calculated using the curve regression equation[3].