FDA approves GSK's Hibsago for chronic hepatitis B treatment

GSK plc (NYSE: GSK) announced that the US Food and Drug Administration (FDA) has approved Hibsago (bepirovirsen) for the treatment of chronic hepatitis B (CHB) virus infection in adult patients without cirrhosis, according to a company press release.

The drug is indicated for use in combination with nucleos(t)ide analogue reverse transcriptase inhibitor (NrtI) therapy in patients who have been on NrtI therapy for at least six months, have suppressed HBV DNA, and have hepatitis B surface antigen (HBsAg) levels of 3,000 IU/ml or below, as determined by an FDA-authorized test. The approval was granted under FDA Priority Review and Breakthrough Therapy Designation.

Bepirovirsen is an antisense oligonucleotide (ASO) licensed by GSK from Ionis. The drug is administered over a six-month course, with the option of self-administration after the first dose.

The approval was supported by pooled data from the B-Well phase III trials, which were conducted across 29 countries. The trials showed a functional cure response rate of 19% in adults with HBsAg levels of 3,000 IU/ml or below (233 of 1,220 participants), compared to zero in the placebo group. Current standard of care typically achieves a functional cure rate of less than 1% after one year of treatment. In participants with HBsAg levels of 1,000 IU/ml or below, the functional cure rate reached 26%.

The most common adverse reactions reported included injection site reactions, fever, fatigue, and headache. The drug carries a boxed warning for on-treatment hepatic flares and thrombocytopenia. Hibsago is contraindicated in patients with cirrhosis, acute hepatic impairment, or a platelet count below 100 x 10⁹/L.

CHB affects approximately 1.7 million people in the US. Hibsago is also approved in Japan, and GSK said it is advancing regulatory submissions in additional markets, with decisions anticipated in the coming months.

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