GSK wins FDA approval for Hibsago, a hepatitis B drug licensed from Ionis

The therapy, licensed from Ionis Pharmaceuticals in 2019, showed a 19% functional cure rate against 0% for placebo in a late-stage trial

The FDA has approved Hibsago, known chemically as bepirovirsen, to treat chronic hepatitis B in adult patients without cirrhosis who are on nucleos(t)ide analogue therapy and have suppressed HBV DNA with HBsAg levels of 3000 IU/ml or below. GSK licensed the drug from Ionis Pharmaceuticals in 2019.

The approval came under FDA priority review and Breakthrough Therapy Designation. It rests on Phase 3 B-Well trial data showing a 19% functional cure rate in patients with HBsAg levels at or below 3000 IU/ml, against 0% in the placebo group.

Under its agreement with GSK, Ionis has already received an upfront payment, a license fee and development and regulatory milestone payments. It is eligible for further regulatory and sales milestones, plus tiered royalties of 10% to 12% on net sales.

That structure lets Ionis collect on the drug's success without paying for its launch, a contrast to Revolution Medicines, which drew on a credit facility to fund the commercial rollout of its own approved therapy. GSK's reach into chronic hepatitis B, a far larger patient population than the ultra-rare diseases Mirum and BridgeBio have targeted with their own approvals this quarter, gives Hibsago a broader market than most of the period's other new drug approvals. The approval also marks a functional-cure claim for the disease that none of the season's other hepatitis or oncology approvals have matched, a point in favor of Ionis's RNA-targeting drug platform.