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HBV Cure Going Back to the Drawing Board, Researchers Say
Sara Freeman
July 05, 2022
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LONDON – Achieving a functional cure for hepatitis B virus (HBV) is not going to be easily achieved with the drugs that are currently in development, according to a presentation at the annual International Liver Congress sponsored by the European Association for the Study of the Liver.
"Intriguing results have been presented at ILC 2022 that must be carefully interpreted," said Jean-Michel Pawlotsky, MD, PhD, of Henri Mondor Hospital in Créteil, France, during the viral hepatitis highlights session on the closing day of the meeting.
"New HBV drug development looks more complicated than initially expected and its goals and strategies need to be redefined and refocused," he added
"This is really something that came from the discussions we had during the sessions but also in the corridors," Pawlotsky added. "We know it's going to be difficult; we have to reset, restart – not from zero, but from not much – and revise our strategy," he suggested.
There are many new drugs under investigation for HBV, Pawlotsky said, noting that the number of studies being presented at the meeting was reminiscent of the flurry of activity before a functional cure for hepatitis C had been found. "It's good to see that this is happening again for HBV," he said.
Indeed, there are many new direct-acting antiviral agents, immunomodulatory, or other approaches being tested, and some of the more advanced studies are "teaching us a few things and probably raising more questions than getting answers," Pawlotsky said.
The B-CLEAR Study
One these studies is the phase 2b B-CLEAR study presented during the late-breaker session. This study involved bepirovirsen, an antisense oligonucleotide, and tested its efficacy and safety in patients with chronic hepatitis B virus infection who were either on or off stable nucleos(t)ide analogue (NA/NUC) therapy.
A similar proportion (28% and 29%, respectively) of patients achieved an hepatitis B surface antigen (HBsAg) level below the lower limit of quantification at the end of 24 weeks treatment. However, the effect on HBsAg varied according to the treatment arm, with changes to the dosing or switching to placebo indicating that the effect might wane when the treatment is stopped or if the dose is reduced.
"Interestingly, ALT elevations were observed in association with most HBsAg declines," Pawlotsky pointed out. "I think we still have to determine whether this is good flare/bad flare, good sign/bad sign, of what is going to happen afterward."
The REEF Studies
Another approach highlighted was the combination of the silencing or small interfering RNA (siRNA) JNJ-3989 with the capsid assembly modulator (CAM) JNJ-6379 in the phase 2 REEF-1 and REEF-2 studies.
REEF-1, conducted in patients who were either hepatitis B e antigen (HBeAg) positive or negative who were not treated with NA/NUC or were NA/NUC suppressed, showed a dose-dependent, but variable effect among individual patients as might be expected at the end of 48 weeks' treatment. This was sustained at week 72, which was 24 weeks' follow-up after stopping treatment.
However, pointed out Pawlotsky "I think the most important part of this is that if you add a CAM on top of the siRNA, you do not improve the effect on HBsAg levels."
Then there is the REEF-2 study, testing the same combination but in only patients who were NA suppressed or HBeAg negative alongside standard NA/NUC therapy. As well as being the first novel combination treatment trial to report, this was essentially a stopping trial, Kosh Agarwal, BMedSci (Hons), MBBS, MD, one of the study's investigators explained separately at a media briefing.
Patients (n = 130) were treated for 48 weeks, then all treatment – including NA/NUC – was discontinued, with 48 weeks of follow-up after discontinuation, said Agarwal, who is a consultant hepatologist based at the Institute of Liver Studies at King's College Hospital, London. He presented data from the first 24 week period after treatment had ended.
At the end of treatment, the combination had resulted in a mean reduction in HBsAg of 1.89 log10 IU/mL versus a reduction of 0.06 for the NA/NUC-only group, which acted as the control group in this trial. But "no patient in this study lost their surface antigen, i.e., were cured of their hepatitis B in the active arm or in the control arm," Agarwal said.
"We didn't achieve a cure, but a significant proportion were in a 'controlled' viral stage," said Agarwal. Indeed, during his presentation of the findings, he showed that HBsAg inhibition was maintained in the majority (72%) of patients after stopping the combination.
While the trial's primary endpoint wasn't met, "it's a really important study," said Agarwal. "This [study] was fulfilled and delivered in the COVID era, so a lot of patients were looked after very carefully by sites in Europe," he observed.
Further follow-up from the trial is expected, and Agarwal said that the subsequent discussion will "take us back to the drawing board to think about whether we need better antiviral treatments or whether we need to think about different combinations, and whether actually stopping treatment with every treatment is the right strategy to take."
Both Agarwal and Pawlotsky flagged up the case of one patient in the trial who had been in the control arm and had experienced severe HBV reactivation that required a liver transplant.
"This patient is a warning signal," Pawlotsky suggested in his talk. "When we think about NUC stopping, we have to think about the potential benefit in terms of HbsAg loss but also the potential risks."
While Agarwal had noted that it highlights that "careful design of retreatment criteria is important in studies assessing the NA/NUC-stopping concept".
Monoclonal Antibody Shows Promise
Other combinations could involve an siRNA and an immunomodulatory agent and, during the poster sessions at the meeting, Agarwal also presented data from an ongoing phase 1 study with a novel, neutralizing monoclonal antibody called VIR-3434.
This monoclonal antibody is novel because it is thought to have several modes of action, first by binding to HBV and affecting its entry into liver cells, then by presenting the virus to T cells and stimulating a 'vaccinal' or immune effect, and then by helping the with the clearance of HBsAg and delivery of the virus to dendritic cells.
In the study, single doses of VIR-3434 were found to be well tolerated and to produce rapid reductions in HBsAg, with the highest dose used (300 mg) producing the greatest and most durable effect up to week 8.
VIR-3434 is also being tested in combination with other drugs in the phase 2 MARCH trial. One of these combinations is VIR-3434 together with an investigational siRNA dubbed VIR-2218. Preclinical work presented at ILC 2022 suggests that this combination appears to be capable of reducing HBsAg to a greater extent than using either agent alone.
Rethinking the Strategy to Get to a Cure
Of course, VIR-3434 is one of several immunomodulatory compounds in development. There are therapeutic vaccines, drugs targeting the innate immune response, other monoclonal antibodies, T-cell receptors, checkpoint inhibitors and PD-L1 inhibitors. Then there are other compounds such as entry inhibitors, apoptosis inducers, and farnesoid X receptor agonists.
"I finish this meeting with more questions than answers," Pawlotsky said. "What is the right target to enhance specific anti-HBV immunity? Does in vivo induction of immune responses translate into any beneficial effect on HBV infection? Will therapeutic vaccines every work in a viral infection?"
Moreover, he asked, "how can we avoid the side effect of enhancing multiple and complex nonspecific immune responses? Are treatment-induced flares good flares or bad flares? All of these are questions that are really unanswered and that we'll have to get answers to in the near future."
The B-CLEAR study was sponsored by GlaxoSmithKline. The REEF-2 study was sponsored by Janssen Research & Development. The VIR-3434 studies were funded by Vir Biotechnology. Pawlotsky has received grant and research support, acted as a consultant, adviser, or speaker, and participated in advisory boards for multiple pharmaceutical and biotechnology companies. This news organization was unable to verify Agarwal's ties to Vir Biotechnology, but he presented one of the posters on VIR-3434 at the meeting and has been involved in the phase 1 study that was reported.
This article originally appeared on MDedge.com, part of the Medscape Professional Network. |
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发表于 2022-7-7 20:46
