AB-506 (Capsid Inhibitor)

HBV core protein, or capsid, is required for viral replication and core protein may have additional roles in cccDNA function. Current nucleot(s)ide analog therapy significantly reduces HBV DNA levels in the serum but HBV replication continues in the liver, thereby enabling HBV infection to persist. Effective therapy for patients requires new agents which will effectively block viral replication.


We are developing capsid inhibitors as oral therapeutics for the treatment of chronic HBV infection. By inhibiting assembly of the viral capsid, the ability of hepatitis B virus to replicate is impaired, resulting in reduced cccDNA.


AB-423 is Arbutus' first-generation capsid inhibitor, which was generally safe and well tolerated in Phase 1 healthy volunteer studies.


AB-506 is Arbutus' next-generation capsid inhibitor, which showed striking potency and improved PK in preclinical studies.  Arbutus will continue to focus on rapidly advancing AB-506 into clinical testing before proceeding with additional clinical evaluation of AB-423.  Arbutus plans to file an Investigational New Drug (IND)/Clinical Trial Application (CTA) in mid-2018 (pending successful IND/CTA-enabling studies) for AB-506, which has the potential to be a 'best-in-class' capsid inhibitor based on its favorable drug-like properties and potent inhibition of HBV replication. This molecule has the potential for once-daily oral dosing, making it an ideal candidate for inclusion in a combination regimen. Results from additional preclinical studies of AB-506 drug combinations with compounds acting through different mechanisms, will be presented in 2018.


Based on comparative clinical data, Arbutus will select one of its capsid inhibitors for development as part of a proprietary drug combination.