Breakthrough Antiviral Offers Functional Cure for 20% of Hepatitis B Patients

Chronic hepatitis B has long been managed with daily oral medication that suppresses the virus but rarely removes it. New data from two international clinical studies show that the experimental drug bepirovirsen, also known as “bepi,” can allow a subset of patients to discontinue therapy altogether.

In the trials, 1,838 participants received either bepi or a placebo shot once a week for six months while continuing their standard pills. After the injection phase, patients whose viral levels fell below detection stayed off the shots. If they remained undetectable for an additional six months, they were also allowed to stop their oral medication. Approximately 20% of those who received bepi maintained undetectable virus levels, a result described by researchers as a “functional cure.”

Bepi works by binding to the hepatitis B virus’s genetic material, halting new copies from forming, and decreasing the release of the surface (S) protein. This dual action not only curtails viral replication but also appears to reinforce the patient’s immune response. Patients who began the study with lower levels of the S protein were slightly more likely to reach a functional cure, indicating that baseline viral markers may predict response.

Side effects were mild, including local soreness, redness at the injection site, and temporary elevations in liver enzymes. Early long‑term follow‑up suggests that the functional cure can last at least three years, although larger studies are needed to confirm durability and to identify why only a minority of patients respond.

The findings were published in the New England Journal of Medicine and have prompted fast‑track review by the FDA, with a decision anticipated in October. Regulators in Japan, China, and Europe are also evaluating the drug. Although the current studies excluded patients with advanced liver disease, ongoing research aims to broaden eligibility and determine the drug’s impact on those with cirrhosis or high S protein levels.

Hepatitis B remains a global threat, responsible for over a million deaths annually from liver cancer or failure. A therapy that offers lasting remission could lighten the physical, psychological, and financial burden on millions worldwide and marks a significant step toward truly curative treatment options.