A first-of-its-kind drug for hepatitis B is allowing some patients to stop treatment without showing signs of the dangerous liver virus, in what is called a “functional cure”, researchers reported on Thursday.

In two international studies, about one in five patients given the experimental drug saw their virus reduced to levels low enough for the immune system to keep it in check.

“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, who helped lead the GSK-funded studies, told reporters before presenting the findings at a scientific meeting in Barcelona, Spain.