Monoclonal antibody shows promise
Other combinations could involve an siRNA and an immunomodulatory agent and, during the poster sessions at the meeting, Dr. 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,” Dr. 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. Dr. 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 Dr. 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.