UPDATE 1-GSK to pay $1 bln for exclusive license to J&J's hepatitis B therapy

(Adds details on the agreement in paragraph 5)

Oct 31 (Reuters) - GSK will pay about $1 billion for exclusive rights to further develop and commercialize Johnson & Johnson's hepatitis B therapy, the British drugmaker said on Tuesday.

JNJ-3989 was initially developed by Arrowhead Pharmaceuticals and licensed to Johnson & Johnson-owned Janssen in 2018.

Exclusive rights to the therapy will fuel the expansion of GSK's own hepatitis B treatment, bepirovirsen, which is currently in late-stage development, the company said.

Hepatitis B, which affects an estimated 300 million people, is a life-threatening viral infection that attacks the liver and patients risk death from cirrhosis and liver cancer.

Under the terms of the deal, GSK will make upfront and potential milestone-based payments to both Janssen and Arrowhead totalling about $1 billion.

(Reporting by Eva Mathews in Bengaluru; Editing by Shinjini Ganguli)