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.