SAN FRANCISCO – Most years, when it comes to research to treat hepatitis viral infections, hepatitis C has been front and center at the annual meeting of the American Association for the Study of Liver Diseases. But things have changed in the past couple of years, with hepatitis C curative treatment maturing and altering the therapeutic landscape.
“Hepatitis C has been where all the action is, but that’s clearly changed in the last few years,” said, who summed up the hepatitis B findings during a wrap-up session on the final day of the conference. Dr. Feld is a clinician-scientist at the Toronto Western Hospital Liver Clinic and the McLaughlin-Rotman Centre for Global Health.
An analysis () of a mixed North American and Asian cohort of more than 10,000 untreated patients showed just a 1.3% annual clearance rate of surface antigen, with little guidance for risk stratification. “This leaves us really needing new therapies,” said Dr. Feld.
Fortunately, the hepatitis B virus (HBV) life cycle offers various opportunities for therapeutic intervention, including blocking entry, targeting assembly and export of the virus, targeting HBV RNA, and targeting the capsid protein and viral packaging.
One study () examined a hepatitis B entry inhibitor’s effect on hepatitis D virus (HDV), which requires coinfection with HBV to replicate. A phase 2 clinical trial found that treatment with alone or in combination with interferon led to a decline in HDV RNA, but the result was most pronounced in patients who received the combination therapy. The combination was also associated with a greater probability of surface antigen decline. “I think that’s really important, that we see this synergistic effect. This is really promising phase 2 data that raises the possibility of curative therapy for this troubling infection,” said Dr. Feld.
Another study () looked at an RNA inhibitor that targets both integrated and covalently closed circular DNA (cccDNA)–derived HBV RNA. The drug was given to 11 HBV patients who were positive for HBeAg (hepatitis B e-antigen) and 13 HBV patients who were HBeAg negative. It had similar effects in reducing HBV surface antigens and other correlated antigens in both groups of patients, and no evidence of a dose-response relationship. “Seeing a similar effect is quite important and suggests that it’s targeting both cccDNA-derived and integrated HBV DNA, and although there were some mild injection reactions, it generally seemed to be safe and pretty well tolerated,” said Dr. Feld.
Further down the life cycle, capsid assembly modulators (CAMs) have the potential to counter HBV by two mechanisms; blocking encapsulation of pregenomic RNA, and degrading capsids, which could prevent the replenishment of cccDNA. The latter effect could be important for achieving a cure, according to Dr. Feld.
A novel CAM, JNJ-6379 (), was tested at three different doses, and was well tolerated at higher doses, but it had limited dose response at the higher dose with respect to HBV DNA suppression. However, it could be that the two CAM mechanisms may require different doses. “These two things are hard to tease apart, and hopefully, we’ll see more data to separate them in the future,” said Dr. Feld.
Another CAM, ABI-HO731 (), had a potent effect on HBV DNA and HBV RNA, showing that it blocks encapsulation of both pregenomic RNA related to reverse transcription and pregenomic RNAs within the capsid. Stopping the medication led to some HBV DNA rebound, though no alanine aminotransferase flares, which Dr. Feld found reassuring. One patient had baseline resistance but was nevertheless able to achieve some suppression on the drug.
Another therapeutic approach used a nucleic acid polymer to block subviral particle release (). The study treated immunosuppressed patients with the polymer alone or in combination with interferon or tenofovir disoproxil, and led to “striking reductions in hepatitis B surface antigen quantities during therapy,” said Dr. Feld. An alanine aminotransferase flair did occur, which may signify an immune response, and it will be important to determine if this is indeed the case, he said. After stopping therapy there was a gain of anti–hepatitis B antibodies, which suggests that functional clearance of surface antigen is occurring.
Researchers also are recruiting the immune system to combat HBV. The novel agent inarigivir is a retinoic acid-inducible gene-1 agonist, which has both a direct antiviral effect and an indirect effect via the intrahepatic innate immune response, which it accomplishes by activating the interferon signaling pathway. It also directly interferes with the interaction between pregenomic RNA and the HBV polymerase, preventing replication. In the, the researchers noted greater reduction in HBV RNA and DNA at higher doses ( ). “This is certainly an interesting molecule and an interesting proof of concept that you can potentially target HBV using two different pathways, and we’ll be interested to see more data with this approach,” said Dr. Feld.
Dr. Feld wrapped up the discussion of novel therapies with an animal model study () that suggests future strategies for a cure. In it, the researchers combined a therapeutic vaccine with a stabilized, liver-targeted small interfering RNA to suppress surface antigen. Animals that received only the vaccine saw little benefit, but the combined approach led to viral clearance. The treatment also restored the immune response. “It gives us an inkling that we may need to both reduce the antigen load and stimulate immunity,” said Dr. Feld.
Dr. Feld has consulted for AbbVie, Gilead, ContraVir, MedImmune, and Merck. He has received funding from AbbVie, Gilead, Merck, and Janssen.