The U.S. Food and Drug Administration (FDA) on Tuesday approved GSK plc’s (NYSE:GSK) Hibsago (bepirovirsen) injection to treat adult chronic hepatitis B patients without cirrhosis.
FDA Clears First-In-Class Treatment
Under FDA priority review and Breakthrough Therapy Designation, regulators cleared the weekly subcutaneous injection for adults who have received antiviral therapy for at least six months, maintain suppressed viral DNA, and exhibit surface antigen (HBsAg) levels of 3,000 IU/mL or less.
The agency also cleared the Roche Elecsys HBsAg II quant II RxDx assay as a companion diagnostic to select and monitor patients.
Chronic hepatitis B causes long-term liver infection, which increases the risk of cirrhosis and liver cancer.
As a first-in-class antisense oligonucleotide, Hibsago disables the genetic instructions that the hepatitis B virus uses to replicate and generate viral proteins, decreasing circulating virus and antigen levels.
Phase 3 Trials Show Significant Cure Rates
The approval is based on data from the B-Well 1 and B-Well 2 phase 3 trials.
Across these studies, a 24-week Hibsago regimen alongside existing antiviral medicine enabled 24% of participants to stop baseline medication, compared to zero in the placebo group.
Twenty-four weeks after halting all therapies, 19% of Hibsago patients (233 of 1,220) sustained a functional cure, meaning viral DNA and HBsAg remained undetectable.
In contrast, placebo achieved zero responses, while standard care alone typically achieves less than 1% after one year.
Among participants with baseline antigen levels at or below 1,000 IU/mL—a group representing about 45% of global cases—functional cure rates reached 26% (200 of 768).
Exploratory data at week 72 showed 49% of overall participants reduced surface antigen levels to 100 IU/mL or less.
Safety Profile And Boxed Warnings
Hibsago carries a boxed warning for serious liver reactions and low platelet counts that increase bleeding risks. Regulators also warned of kidney decline, inflammatory reactions like vasculitis, and improper administration risks.
GSK Price Action: Gsk shares were down 0.75% at $50.25 at the time of publication on Wednesday, according to Benzinga Pro data.
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