FDA Approves Hibsago for Chronic Hepatitis B Treatment

• The FDA has approved Hibsago (bepirovirsen) injection for chronic hepatitis B in specific adult patients without cirrhosis.
• Hibsago is the first FDA-approved antisense oligonucleotide for chronic HBV, administered in combination with existing antiviral therapy.
• Eligibility requires patients to have suppressed HBV, HBsAg levels of 3,000 IU/mL or less, and prior antiviral treatment for at least six months.
• The drug carries a boxed warning for serious liver reactions and low platelet counts, necessitating careful patient monitoring.
• Clinical trials showed 19% of Hibsago patients maintained viral control with undetectable HBsAg 24 weeks after stopping all treatment.

Hibsago introduces a new treatment paradigm, offering certain patients the potential to maintain viral control even after discontinuing all chronic HBV therapy.

The U.S. Food and Drug Administration (FDA) recently granted approval for Hibsago (bepirovirsen) injection, a novel therapeutic option developed by GSK plc. This medication is specifically indicated for the treatment of chronic hepatitis B virus (HBV) infection in certain adult patients who do not have cirrhosis. Its administration is designed to be in combination with existing antiviral therapy.

This approval marks a significant advancement in the fight against chronic HBV, as Hibsago is the first FDA-approved antisense oligonucleotide to address this condition. The introduction of this drug offers a distinct and innovative therapeutic approach for a disease that frequently necessitates prolonged medication regimens to manage viral load and prevent progression.

Eligibility for Hibsago treatment is precisely defined, targeting a specific subset of the chronic HBV population. Patients must be adults who have not developed cirrhosis, and they must have been receiving HBV antiviral therapy for a minimum of six months. Furthermore, their blood tests must indicate suppressed levels of the hepatitis B virus.

A crucial criterion for patient selection is that their hepatitis B surface antigen (HBsAg) levels must be 3,000 IU/mL or less. This specific HBsAg level must be accurately determined using an FDA-authorized test, for which the Roche Elecsys HBsAg II quant II RxDx assay was also authorized as a companion diagnostic device. This assay plays a dual role, assisting not only in initial patient selection but also in ongoing monitoring throughout the treatment course. Hibsago's expedited path to market was facilitated by several FDA designations, including Fast Track, Breakthrough Therapy, and Priority Review, underscoring the urgent medical need it aims to fulfill. The drug's mechanism involves targeting the virus's genetic instructions, thereby impeding its ability to replicate and produce viral proteins, which ultimately leads to a reduction in both viral load and HBsAg levels in the body.

The efficacy and safety profile of Hibsago were rigorously evaluated through two distinct clinical trials, where the drug was compared against a placebo. Participants received Hibsago via subcutaneous injection for a period of up to 24 weeks, concurrently with their ongoing hepatitis B medication. Following the completion of the Hibsago course, patients continued their existing antiviral therapy for at least an additional 24 weeks.

A notable outcome from these trials was that 24% of patients treated with Hibsago successfully met the predefined criteria to discontinue their existing medication, a significant achievement not observed in the placebo group. Furthermore, 24 weeks after all hepatitis B treatment had ceased, 19% of the Hibsago-treated patients maintained effective viral control, evidenced by undetectable levels of the hepatitis B surface antigen in their blood.

However, the treatment is associated with substantial risks, prominently highlighted by a boxed warning. This warning specifically cautions healthcare providers and patients about the potential for serious liver reactions and the occurrence of low platelet counts, a condition that can significantly increase the risk of potentially life-threatening bleeding. Additional warnings include the possibility of worsening kidney function, serious inflammatory adverse reactions such as vasculitis, and specific risks linked to improper injection administration. Consequently, patients undergoing Hibsago therapy necessitate regular blood tests and close follow-up with their healthcare providers, both prior to and throughout the treatment period, to diligently monitor for these serious adverse events. The most commonly reported side effects, excluding laboratory abnormalities, include reactions at the injection site, fever, fatigue, and headache.

The recent FDA approval of Hibsago represents a pivotal development in the long-term management of chronic hepatitis B, a persistent liver infection caused by the hepatitis B virus. This condition is known to progress to severe liver disease, including cirrhosis, and substantially elevates an individual's risk of developing liver cancer.

Dr. Wendy Carter, who serves as the Acting Director of the Office of Infectious Diseases within the Center for Drug Evaluation and Research, underscored the enduring challenge posed by chronic HBV. She noted that for many individuals, treatment has historically involved years of continuous antiviral medication simply to keep the virus suppressed. Dr. Carter highlighted that Hibsago introduces a new treatment paradigm, offering certain patients the potential to maintain viral control even after discontinuing all chronic HBV therapy. This advancement is therefore considered a crucial step forward for individuals grappling with this serious and often debilitating disease, potentially altering the long-term treatment landscape and offering a new pathway for sustained viral remission.

Lawyers advising pharmaceutical companies should analyze the regulatory pathway and implications of the boxed warning for product liability and market access. Compliance officers must ensure adherence to specific prescribing criteria, companion diagnostic use, and patient monitoring protocols given the serious adverse events.

Source: Original reporting via FDA press release