How a New Hepatitis B Drug Could Change Treatment for Millions

A new drug called bepirovirsen has shown results that could reshape hepatitis B treatment. In clinical trials, about one in five patients achieved what doctors call a "functional cure" — meaning the virus became undetectable and stayed that way even after stopping treatment. This is a significant shift from today's standard therapy, which requires taking medication indefinitely.

To put this in perspective: roughly 300 million people worldwide carry chronic hepatitis B, and current treatments keep the virus in check but don't clear it. The B-clear trial showed that bepirovirsen achieved this functional cure at a rate of about 9–10% in the overall patient group, with some subsets reaching roughly 20%, according to analysis published in PMC.

What "Functional Cure" Actually Means

This term gets used loosely, so it helps to be precise. A functional cure for hepatitis B means the virus becomes undetectable in the blood at a specific timepoint — specifically 24 weeks after stopping treatment — and stays undetectable. The virus isn't completely eradicated; a dormant version of it persists in liver cells. But it remains quiet and inactive long-term, according to the World Hepatitis Alliance.

This is different from what current standard treatments do. Medications called nucleos(t)ide analogues suppress the virus while you take them, but the virus bounces back if you stop. A functional cure, in principle, doesn't require lifelong treatment.

The only approved drug that can achieve this level of virus clearance is interferon-alpha (IFN-α), and it does so in roughly 10% of patients. Published data shows that many doctors stop prescribing it because the side effects are harsh and hard to tolerate. A drug that clears the virus in twice as many patients, with fewer side effects, would be a genuine advance.

How Bepirovirsen Works and What's Coming Next

Bepirovirsen is an antisense oligonucleotide — a type of drug that works by targeting viral RNA and blocking the production of all hepatitis B viral proteins, including the surface antigen (HBsAg) that allows the virus to be detected. Most current medications can't drive HBsAg that low, which is why bepirovirsen represents something new.

The drug has now advanced to Phase 3 trials, the final stage before seeking approval, based on these B-clear results. But bepirovirsen won't be alone for long. A Chinese company, AusperBio, has received permission to test its own candidate drug, AHB-137, in Phase 3 trials in China. China carries a disproportionate share of the global hepatitis B burden, and there is real financial and political incentive to develop a treatment domestically.

Combination Therapy: The More Likely Path Forward

Even more interesting is the work on combination treatments. Brii Biosciences, Vir Biotechnology, and VBI Vaccines have launched a Phase 2 trial combining two drugs: one (BRII-835) that suppresses the virus, and another (BRII-179) designed to wake up the immune system. The rationale is straightforward: in chronic hepatitis B, the immune response gets exhausted over time. The virus suppressor tackles viral load while the immune activator tries to restore the body's ability to fight the infection on its own.

The working hypothesis across the field is that no single drug will be the full answer. Instead, a cocktail of agents — hitting the virus from multiple angles while simultaneously restoring immune function — is probably necessary. This mirrors what happened with HIV and hepatitis C: single-drug approaches plateaued, but combinations of drugs targeting different mechanisms broke through to high cure rates.

One important caveat: hepatitis B's persistence problem is uniquely stubborn. The virus hides in a form called cccDNA that sits inside liver cells, and it can also integrate into the host genome. Clearing integrated viral sequences remains beyond what current or near-term drugs can do. But the convergence of multiple drug classes — each with different mechanisms — suggests the toolbox is getting more complete.

What Happens Next

As of now, bepirovirsen leads the field with actual human efficacy data. The combination trials are in Phase 2, meaning their results won't be ready for a year or two, but those readouts will be crucial in understanding whether adding immune reconstitution on top of viral suppression makes a meaningful difference.

A complete, widely applicable functional cure for hepatitis B is not here yet. But the clinical research community has a clear target and multiple pathways to reach it. The biggest questions now are practical rather than scientific: Will the Phase 3 trials go smoothly. Will regulators approve these drugs. And critically, will patients in the regions carrying the heaviest disease burden — Southeast Asia, sub-Saharan Africa — actually gain access to whatever gets approved.

The latter part deserves emphasis. Roughly 150 million people with chronic hepatitis B live in Asia and the Pacific, and another 100 million in sub-Saharan Africa. If a new treatment is approved in wealthy countries but costs thousands of dollars per course, the math works out to zero for most of the world's patients. That's not a scientific problem; it's a distribution, manufacturing, and policy problem.