FDA Approves GSK's Hibsago for Chronic Hepatitis B

The US Food and Drug Administration has approved Hibsago (bepirovirsen), a GSK drug for some adults with chronic hepatitis B. The FDA said on Oct. 20 that it is the first antisense oligonucleotide it has approved for the disease. GSK developed the drug with Ionis Pharmaceuticals, which licensed it to GSK in 2019.

What happened

Hibsago is used together with standard antiviral therapy known as nucleos(t)ide analogues. The approval covers adults without cirrhosis who have taken that therapy for at least six months. Their virus must be suppressed in the blood. Their hepatitis B surface antigen (HBsAg) level must also be 3,000 IU/mL or lower on an FDA-authorized test.

The decision rests on two phase 3 trials, B-Well 1 and B-Well 2. GSK said 19% of treated patients across both trials (233 of 1,220) reached functional cure. None of the 614 patients on placebo did. GSK defines functional cure as HBV DNA and HBsAg staying undetectable for at least 24 weeks after all treatment stops.

In patients who started with HBsAg of 1,000 IU/mL or less, the rate was 26% (200 of 768), against none of 393 on placebo, the company said.

The drug is given as injections under the skin over a six-month course. GSK said patients can inject it themselves after the first dose.

The label carries a boxed warning for serious liver reactions and low platelet counts. The FDA said the most common side effects were injection site reactions, fever, fatigue and headache. The agency gave the drug Fast Track, Breakthrough Therapy and Priority Review status.

Why it matters

The FDA said Hibsago gives some patients a chance to keep the virus under control after they stop treatment. GSK said standard care alone typically reaches functional cure in less than 1% of patients after one year.

GSK said about 1.7 million people in the US live with chronic hepatitis B, and more than 240 million people are affected worldwide. The FDA also authorized a Roche HBsAg test to help select patients and monitor them during treatment.

The drug is also approved in Japan, according to GSK. Ionis said it is eligible for more milestone payments and tiered royalties of 10 to 12% on net sales.

What it means for people in the industry

GSK said quantitative HBsAg testing will help identify patients suited to the drug. The FDA said patients need regular blood tests before and during treatment.

GSK said it is continuing regulatory filings in other countries, with key decisions expected in the coming months. Its release did not give a US launch date.

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Sources

• FDA Approves First-of-Its-Kind Chronic Hepatitis B Treatment, US Food and Drug Administration
• Hibsago (bepirovirsen) approved in the US for the treatment of chronic hepatitis B (CHB), GSK
• Ionis partner GSK announces Hibsago (bepirovirsen) approved in the U.S. for the treatment of chronic hepatitis B (CHB), Ionis Pharmaceuticals via BioSpace