In vitro activity: AB-423 is a potent inhibitor of HBV capsid assembly that shows inhibitory effect on rcDNA production in AML12-HBV10 and HepDE19 cells with EC50s of ~0.260 μM. AB-423 also suppresses cccDNA formation-dependent HBeAg production in the HepBHAe82 assay with an EC50 of 0.267 μM and inhibits HBV DNA levels in culture supernatants of HepG 2.2.15 cells with an EC50 of 0.134 μM. However, AB-423 has no cytotoxicity in any of the three cell lines.

Kinase Assay:

Cell Assay: HepBHAe82 (50,000 cells/well) are plated in 96-well tissue-culture treated microtiter plates in DMEM/F12 medium supplemented with 10% fetal bovine serum, 1% penicillin-streptomycin and tetracycline (1 μg/mL), and incubated in a humidified incubator at 37°C and 5% CO2 overnight. On the next day, the cells are switched to fresh medium and treated with inhibitor A and inhibitor B, at concentration range in the vicinity of their respective EC50 values. The inhibitors are either diluted in 100% DMSO (ETV, TDF and AB-423) or growth medium (ARB-1467 and ARB-1740) and the final DMSO concentration in the assay is ≤0.5%. The two inhibitors are tested both singly as well as in combinations determine their effects on inhibition of rcDNA production. The final DMSO concentration in the assay is 0.5%. The plates are incubated for 9 days in a humidified incubator at 37°C and 5% CO2. Following a 9 day-incubation, medium is removed, and cells are subjected to RNA extraction to measure the cccDNA-dependent precore mRNA leve