What Is Hibsago and How Does It Work?
The FDA has approved Hibsago (bepirovirsen) for adults with long-term hepatitis B virus infection who do not have liver scarring, also called cirrhosis. It is meant for patients who have already been taking daily antiviral pills for at least six months, have low levels of virus in their blood, and have low amounts of a viral protein called surface antigen. Hibsago must be used alongside a patient's existing antiviral pills.
Hepatitis B is a virus that causes a lasting infection in the liver. Over time, it can harm the liver and lead to liver cancer or severe liver damage. Current treatments usually involve taking antiviral medicine daily for many years or even for life to keep the virus quiet.
Hibsago works in a new way compared to older drugs. It targets the genetic signals that the hepatitis B virus uses to copy itself and build viral proteins. By blocking these signals, Hibsago lowers the amount of virus and viral proteins in the body. This may help the patient's immune system control the infection on its own, allowing some patients to safely stop all hepatitis B medicines.
Why Was Hibsago Approved?
The FDA approved Hibsago based on results from two large clinical trials called B-Well 1 and B-Well 2. The studies looked at more than 1,800 adults with chronic hepatitis B who were taking daily antiviral pills. Patients received either Hibsago injections or a placebo (an inactive treatment with no medicine) for 24 weeks while continuing daily treatment with their hepatitis B pills.
In these studies, Hibsago significantly helped more patients achieve viral control than placebo. Overall, 19% of patients who took Hibsago were able to stop all hepatitis B treatments and keep the virus at undetectable levels 24 weeks after stopping treatment. In comparison, none of the patients who took the placebo reached this goal. Among patients who started with lower levels of the hepatitis B surface antigen protein, 26% achieved this viral response.
While Hibsago helped control the virus, it also showed important safety risks during the trials. Some patients had sudden drops in blood platelets, which are cells that help stop bleeding. Others had temporary spikes in liver enzymes, which can happen as the immune system fights the virus. Healthcare providers closely track these safety signs through blood tests during treatment.
What Do I Need to Know About Hibsago?
Hibsago is given as an injection under the skin of the thigh, stomach, or upper arm. Patients receive doses twice a week for the first two weeks, and then once a week through week 24. A healthcare provider gives the first injection and teaches the patient or caregiver how to give doses at home. Each weekly dose usually requires two separate injections given at least 2 inches apart. Patients must continue taking their daily antiviral pills during Hibsago treatment and for at least 24 weeks after completing treatment before a healthcare provider decides if it is safe to stop pills.
Before starting Hibsago and while taking it, patients need regular blood tests to monitor their liver enzymes, platelet counts, and kidney function. You should not take Hibsago if you have cirrhosis, active liver failure, or very low blood platelet counts. Tell your healthcare provider if you have kidney problems, a history of autoimmune disease, or if you also have HIV, hepatitis C, or hepatitis D.
The most common side effects of Hibsago are mild to moderate injection site reactions, such as redness, pain, bruising, or swelling where the shot was given. Other common side effects include fever, fatigue, headache, and muscle aches. Contact your healthcare provider immediately if you develop signs of liver problems (such as yellowing skin or eyes, dark urine, or stomach pain) or signs of low platelets (such as unusual bruising, bleeding gums, nosebleeds, or blood in your urine or stool).
It is not known if Hibsago is safe for a fetus or if it passes into breast milk. If you are pregnant, planning to become pregnant, or breastfeeding, talk to your healthcare provider to discuss the risks and benefits. Taking Hibsago also does not prevent you from spreading the hepatitis B virus to others, so you should continue taking precautions to protect sexual partners and family members.