BAY 41-4109 has multiple effects on Hepatitis B virus capsid assembly

Abstract

Here we report the effect of a heteroaryldihydropyrimidine (HAP) antiviral compound, BAY 41-4109, on Hepatitis B virus (HBV) capsid assembly and on preformed HBV capsids. The HBV capsid is an icosahedral complex of 120 capsid protein dimers. BAY41-4109 inhibits virus production in vivo by a mechanism that targets the viral capsid. We found that BAY 41-4109 was able to both accelerate and misdirect capsid assembly in vitro. As little as one HAP molecule for every five HBV dimers was sufficient to induce formation of non-capsid polymers. Unlike the related molecule HAP-1 (Stray et al., Proc. Natl. Acad. Sci. USA 102:8138-43, 2005), no stable assembly intermediates were observed in assembly reactions with BAY 41-4109, indicating that accelerated assembly by BAY 41-4109 was still kinetically regulated by the nucleation rate. Preformed capsids were stabilized by BAY 41-4109, up to a ratio of one inhibitor molecule per two dimers. However, at BAY 41-4109:dimer ratios of 1:1 and greater, capsids were destabilized to yield very large non-capsid polymers. These data suggest the existence of two functionally distinguishable classes of drug-binding sites on HBV capsids. Occupation of the first class of site stabilizes capsid, while binding at the second class requires or induces structural changes that cannot be tolerated without destabilizing the capsid. Our data suggest that HAP compounds may inhibit virus replication by inducing assembly inappropriately and, when in excess, by misdirecting assembly decreasing the stability of normal capsids.

Emerging therapeutics and relevant targets for chronic Hepatitis B

“…Heteroaryldihydropyrimidines (HAPs), a family of nucleocapsid assembly effectors, have been identified as potent non-nucleosidic inhibitors of HBV replication in preclinical studies (24,25). Bay 4104109 (26)(27)(28) and GLS4 (29) HBsAg secretion is known to contribute to the suppression of the host immune system as well as the infection of neighboring hepatocytes. REP 9 AC (32), an amphipathic DNA polymer, inhibited HBsAg secretion from infected hepatocytes in patients with chronic HBV infection, which resulted in the recovery of innate immunity and cytotoxic T cell response in a phase I clinical study.…”

Structure-based design and biochemical evaluation of sulfanilamide derivatives as hepatitis B virus capsid assembly inhibitors

“…Assembly domain is a structural domain which interacts with other HBcAgs to construct an icosahedral capsid structure 3 . Assembly begins with a binding of three HBcAg dimers, and this trimer works as a nucleus, promoting further nucleation without leaving an observable population of intermediates 4 .…”

“…Also, purification of Cp149 is simpler than process involves HBcAg. Also, it is able to form capsidlike particle spontaneously in vitro and in vivo, so it could be used as an alternative to full-length HBcAg 3 . Cp exists in dimer form naturally, and dimers interact with each other to form hexameric structure.…”

“…Lamivudine, Adefovir) and α-interferon is used as first-line treatments, and these agents quite efficiently decrease virus titer. Nevertheless, long-term use of nucleoside analogs could develop drug resistance 3 . Therefore, it needs to research novel mechanism to inhibit virus proliferation and the establishment of chronic infection.…”

“…HBcAg consists of 183-185 AAs and is divided into assembly domain (1-149 AA) and protamine domain (150-183/185 AA) 3 . Protamine domain interacts with…”