An experimental drug from GSK silenced hepatitis B to levels the immune system could control without daily medication in roughly one in five patients, researchers reported Thursday, offering the first glimpse of what they are calling a functional cure for a virus that has resisted eradication since the vaccine era began four decades ago.
The injectable drug, bepirovirsen, was tested in two international studies that enrolled adults with chronic hepatitis B. Among those who received the active drug, about 20 % saw the virus drop below the threshold of detection after a course of injections, and they were able to stop all antiviral therapy without the virus reappearing during the study period. The results were published Thursday in the New England Journal of Medicine and presented at a meeting in Barcelona.
“We have not had a treatment which has come to this level of cure,” Dr. Seng Gee Lim, of the National University Health System of Singapore, said at a news briefing ahead of the presentation. Lim helped lead the GSK‑funded trials.
Hepatitis B is a liver virus that, when chronic, can cause cirrhosis and liver cancer. The World Health Organization estimates that 254 million people are living with the infection, and about 1.1 million die each year, predominantly in parts of Asia and sub‑Saharan Africa where mother‑to‑child transmission remains common. A safe and effective vaccine has existed since the early 1980s, but global coverage remains incomplete, and those already infected have had only daily oral antiviral pills that suppress the virus but rarely eliminate it.
Bepirovirsen works by targeting the genetic material the virus uses to replicate. In the studies, patients received a series of injections over several months. Those whose hepatitis B surface antigen level dropped to undetectable and who remained antigen‑negative for at least 24 weeks after stopping all medication were considered to have a functional cure.
The 20 % response rate is a landmark in a field where the term “cure” has been virtually absent. Still, the effect was not universal. In some patients the virus rebounded after treatment was withdrawn, and the therapy’s durability beyond the study period is unknown. Researchers stressed that larger, longer‑term trials will be needed to confirm the findings and to identify which patients are most likely to benefit — questions that will guide GSK’s plans for a next‑stage study.
If those studies bear out, bepirovirsen could reshape the management of a disease that, despite cheap and effective tools for prevention, remains one of the world’s most stubborn infectious killers. For now, Thursday’s data represent the first clear proof that a drug can push the virus to a level where the body’s own defenses can keep it in check, a milestone researchers have been chasing for decades.