WASHINGTON — An experimental drug for hepatitis B achieved a functional cure in about 20% of patients in two international clinical trials, allowing them to stop all treatment while maintaining undetectable virus levels. The findings, published in the New England Journal of Medicine on May 28, 2026, mark progress in treating a chronic infection that affects more than 250 million people worldwide and causes approximately 1.1 million deaths annually.

Bepirovirsen, developed jointly by GSK and Ionis Pharmaceuticals, works by binding to the virus’s genetic material, suppressing replication and reducing levels of the hepatitis B surface protein while stimulating the immune system. In the trials, 1,838 patients received weekly injections of bepirovirsen or a placebo for six months, in addition to their standard antiviral therapy. Patients whose virus remained undetectable for six months after stopping injections were allowed to discontinue their daily antiviral pills. About one in five bepirovirsen recipients maintained undetectable virus levels for an additional six months off all treatment—a benchmark defined as a functional cure—while no placebo recipients achieved this outcome.

"We have not had a treatment which has come to this level of cure," said Dr. Seng Gee Lim of the National University Health System of Singapore. Lim noted that patients who began treatment with lower levels of the surface protein were slightly more likely to achieve a functional cure and is conducting further research to understand why only some patients respond.

Dr. Anna Lok of the University of Michigan wrote in an accompanying editorial in the journal, "The new findings represent a major step," but cautioned that more study is needed to determine how long the remission-like state lasts. Lok also noted that the trials excluded patients with cirrhosis, high surface protein levels, or other complicating factors.

Bepirovirsen is under fast-track review by the U.S. Food and Drug Administration, with a decision expected in October 2026. Regulatory agencies in Japan, China, and Europe are also evaluating the drug. GSK reported that a small group of patients from earlier studies have maintained undetectable virus levels for up to three years. Common side effects included mild injection-site reactions and temporary increases in liver enzymes.