Hibsago

Hibsago (bepirovirsen) is a prescription injection used to treat chronic hepatitis B (CHB) in adults without cirrhosis (advanced liver disease). It is used together with hepatitis B antiviral medicines called nucleos(t)ide analog reverse transcriptase inhibitors (NrtIs), such as entecavir or tenofovir.

Hibsago is for adults who have taken an NrtI for at least 6 months, have undetectable hepatitis B virus (HBV) DNA, and have low levels of hepatitis B surface antigen (HBsAg of 3,000 IU/mL or less).

Hibsago is an antisense oligonucleotide (ASO). It works by targeting the genetic material (RNA) of HBV in liver cells. This lowers the amount of virus and viral proteins your liver makes, including HBsAg.

Hibsago is injected under the skin (subcutaneous) twice a week for the first 2 weeks, then once a week for 22 weeks, for a total of 24 weeks. Each 300 mg dose is given as 2 injections. Your first dose is given under the supervision of a healthcare provider. After that, your provider may decide that you or a caregiver can give the injections at home, after you have been shown how.

Hibsago at a glance

• Drug class: antisense oligonucleotide (ASO)
• Used with: NrtI medicines for hepatitis B
• How it is given: 2 injections under the skin of the thigh or abdomen, per dose
• How often: twice a week for weeks 1 and 2, then once a week for weeks 3 to 24
• Treatment length: no longer than 24 weeks
• Who can use it: adults only
• FDA approved: October 2026

Hibsago can be used by adults with chronic (long-term) hepatitis B virus (HBV) infection without advanced liver disease (cirrhosis) who:

• have been on NrtI treatment for at least 6 months and have undetectable HBV deoxyribonucleic acid (DNA), and
• have low levels of HBV surface antigen (HBsAg less than or equal to 3,000 IU/mL), measured with an FDA-authorized test.

Your healthcare provider will perform tests to make sure this medicine is right for you.

It is not known if Hibsago is safe and effective in children younger than 18 years of age.

It is not known if Hibsago is safe and effective in people who also have hepatitis C virus (HCV) or hepatitis D virus (HDV) infection. Hibsago is not recommended in people with HDV infection, as it may increase the chance of flare-ups in liver enzymes.

Hibsago is an antisense oligonucleotide (ASO), a short, man-made strand of genetic material. It attaches to a specific section of hepatitis B virus messenger RNA (mRNA), the instructions the virus uses to make copies of itself and its proteins. Once Hibsago attaches, the viral RNA is broken down. This lowers the levels of HBV DNA and viral proteins, including HBsAg.

Hibsago also activates parts of the immune system. It is not yet known how much this immune effect adds to how well Hibsago works.

NrtI medicines work differently. They block an enzyme the virus needs to copy its DNA. This is why Hibsago is used together with an NrtI.

In clinical trials, about 1 in 5 adults (19%) who received Hibsago with their NrtI had undetectable hepatitis B surface antigen (HBsAg) and HBV DNA too low to measure 24 weeks after stopping all hepatitis B treatment. None of the people who received a placebo (an inactive injection) reached this result.

Results were better in people who started with lower HBsAg levels. In people with HBsAg of 1,000 IU/mL or less, 26% reached this goal.

Hibsago clinical trial results

Hibsago was approved based on 2 clinical trials, B-Well 1 (NCT05630807) and B-Well 2 (NCT05630820). The trials included 1,834 adults with chronic hepatitis B and HBsAg of 3,000 IU/mL or less who were already taking an NrtI. People received Hibsago or a placebo for 24 weeks, along with their NrtI. People whose blood tests met set criteria could then stop their NrtI.

In the trials, HBsAg was considered undetectable when it was below 0.05 IU/mL, and HBV DNA was considered too low to measure when it was below 20 IU/mL.

How long do Hibsago results last?

Of the people who reached this goal, 91% still had undetectable HBsAg and HBV DNA too low to measure 48 weeks after stopping all hepatitis B treatment.

Who does Hibsago work best for?

Hibsago worked better in people who:

• had lower HBsAg levels before starting treatment
• were hepatitis B e-antigen (HBeAg) negative
• were younger than 65

People whose HBsAg dropped below 1 IU/mL by week 12 of treatment were much more likely to reach the goal (34%) than people whose HBsAg did not (2%). This is why your healthcare provider may stop Hibsago early if your HBsAg has not dropped enough by week 12.

Use Hibsago exactly as your healthcare provider tells you to. Read the Instructions for Use that come with Hibsago each time you get a new carton.

• You will receive your first dose of Hibsago under the guidance and supervision of your healthcare provider.
• Your healthcare provider will decide if you or your caregiver may inject Hibsago at home, and will show you how.
• Keep taking your NrtI medicine during treatment and for at least 24 weeks after you finish Hibsago.
• Treatment with Hibsago usually lasts 24 weeks. Do not use Hibsago for longer than 24 weeks.
• You will need regular blood tests during treatment. Based on the results, your provider may lower your dose to 1 injection, pause your treatment, or stop it.

Preparing your dose

• Make sure Hibsago has been at room temperature, up to 86°F (30°C), for at least 30 minutes before injecting. Cold medicine is more painful to inject.
• Check the medicine through the window of the syringe. It should be clear and colorless to yellow. Do not use it if it is cloudy, discolored, or has particles in it.
• Do not shake the syringe. Do not use a syringe that has been dropped or damaged.
• Air bubbles are normal. Do not try to remove them.

Choosing injection sites

• If you inject yourself, use your thighs or your stomach (abdomen). Do not inject yourself in the upper arm.
• A caregiver can inject into the outer upper arm, thigh or abdomen.
• Do not inject within 2 inches (5 cm) of your belly button.
• For a 300 mg dose, use 2 different injection sites at least 2 inches (5 cm) apart, and give the second injection right after the first.
• Change (rotate) your injection sites from one week to the next.
• Do not inject where the skin is tender, bruised, red, or hard.

Giving the injection

• Inject within 5 minutes of removing the gray needle cap. Only remove the cap from the second syringe when you are ready to use it.
• After the injection, the needle pulls back into the needle guard. Do not rub the injection site.
• Put used syringes and needle caps in an FDA-cleared sharps disposal container right away. Do not throw them in household trash.

Hibsago has a boxed warning for liver enzyme flare-ups during treatment and for low platelet counts (thrombocytopenia). A boxed warning is the strongest safety warning issued by the FDA.

Flare-ups in liver enzyme levels during treatment (boxed warning)

Hibsago may cause flare-ups in liver enzyme levels during treatment, which show up as increases in your liver function blood tests. In clinical trials, most flare-ups happened in the first 12 weeks of treatment, usually between weeks 5 and 10. Tell your healthcare provider right away if you get any of these symptoms:

• upper right stomach pain
• nausea or vomiting
• dark or “tea-colored” urine
• loss of appetite
• yellowing of your skin or the white part of your eyes

Low platelet counts (thrombocytopenia) (boxed warning)

Hibsago may cause your blood platelet levels to drop at any time during your treatment. When your platelet count is too low, your body cannot form blood clots properly. Low platelet counts can happen suddenly and without warning and can be life-threatening. Stop using Hibsago and tell your healthcare provider right away if you get any of these symptoms:

• unusual bruising or a rash of tiny reddish-purple spots
• abnormal or heavy periods (menstrual bleeding)
• bleeding from skin cuts that does not stop or oozes
• sudden severe headaches or neck stiffness
• bleeding from your gums or nose
• bleeding into the whites of your eyes
• blood in your urine or stools

Your healthcare provider will do blood tests to check your liver and platelet count before you start Hibsago, during treatment, and, if you have abnormal blood tests, for up to 24 weeks after you stop Hibsago. It is important that you make sure you get these blood tests done.

Worsening kidney function

Hibsago may cause your kidney function to get worse. Your healthcare provider will do blood tests to check your kidneys before and during treatment, and for up to 12 weeks after you stop Hibsago if you have abnormal kidney function blood tests. It is important that you make sure you get these blood tests done.

Inflammatory or immune system problems

Hibsago may cause inflammatory or immune system problems, including inflammation of the blood vessels (vasculitis). Tell your healthcare provider if you get any of these symptoms:

• flu-like symptoms
• purple rashes or spots on the legs
• scaly, raised or red patches
• swelling and itchiness
• joint pain that does not go away by itself

Serious side effects when Hibsago is not injected correctly

Injecting Hibsago in the same place too often can cause serious side effects. In clinical trials, one person who did not rotate injection sites had a serious problem inside the abdomen that needed surgery.

• Make sure the injection sites are changed (rotated) from one week to the next.
• Make sure the 2 injections in each dose are separated by at least 2 inches (5 cm).
• Do not give injections into areas where the skin is tender, bruised, red, or hard.

Hepatitis B may get worse if you stop your NrtI medicine

You must keep taking your NrtI medicine during Hibsago treatment and for at least 24 weeks after your last dose of Hibsago. Do not stop your NrtI unless your healthcare provider tells you to. If you stop taking your NrtI, your hepatitis B may come back or become severe. If your provider decides you can stop your NrtI, you will need frequent blood tests for at least 1 year afterward.

If you also have HIV

If you also have human immunodeficiency virus (HIV) and take an NrtI as part of your HIV treatment, do not stop the NrtI unless your HIV healthcare provider tells you to.

Spreading hepatitis B to others

Taking Hibsago does not stop you from passing hepatitis B to other people. Keep practicing safety habits to prevent spreading HBV.

Do not use Hibsago if you have:

• a condition where your liver is currently not working as well as it should (acute liver impairment)
• advanced liver disease (cirrhosis) of any severity
• low platelet blood counts (below 100 x 109/L before starting treatment)

Talk to your healthcare provider if you are not sure if you have any of these conditions.

Before using this medicine, tell your healthcare provider about all of your medical conditions, including if you:

• have bleeding problems or a history of bleeding problems
• have kidney problems
• have received an organ transplant
• have problems with your immune system (autoimmune disease), or have a history of blood vessel inflammation (vasculitis)
• have hepatitis D
• have hepatitis C
• have HIV

Pregnancy

Tell your healthcare provider if you are pregnant or plan to become pregnant. It is not known if this medicine will harm your unborn baby.

Breastfeeding

Tell your healthcare provider if you are breastfeeding or plan to breastfeed. Hibsago may pass into your breast milk. Talk to your healthcare provider about the best way to feed your baby during treatment with this medicine.

Common Hibsago side effects

The most common Hibsago side effects include:

• injection site reactions, such as redness, pain, itching, bruising, swelling or hardness, and skin discoloration (57%)
• fever (20%)
• tiredness (16%)
• headache (14%)

Other side effects reported in clinical trials include muscle pain, nausea or vomiting, skin redness, itching, flu-like illness, rash and bruising.

Hibsago can also cause changes in blood test results, including higher liver enzyme levels, lower platelet counts, lower white blood cell (neutrophil) counts and lower kidney function. Most of these changes returned to near normal after treatment ended.

Injection site reactions usually became less frequent and less severe over time, and almost all were mild to moderate.

Serious Hibsago side effects

Hibsago may cause serious side effects, including:

• Increased liver laboratory tests: see “Flare-ups in liver enzyme levels during treatment” above.
• Bleeding because of low platelet counts: see “Low platelet counts (thrombocytopenia)” above.
• Worsening kidney function: see “Worsening kidney function” above.
• Inflammatory or immune system problems: see “Inflammatory or immune system problems” above.
• Serious side effects if not injected correctly: see “Serious side effects when Hibsago is not injected correctly” above.

Tell your healthcare provider if you have any side effect that bothers you or that does not go away.

This is not a complete list of side effects, and others may occur. Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Notes:

• Hibsago must be used in combination with an NrtI.
• The maximum treatment length is 24 weeks.
• Your healthcare provider may lower your dose to 150 mg (1 injection) once a week, or pause or stop treatment, based on your liver, platelet and kidney blood tests.
• Your healthcare provider may consider stopping Hibsago early if your HBsAg level is not below 1 IU/mL by week 12 of treatment.

Hibsago injection: 150 mg/mL in a single-dose prefilled syringe, in cartons of 2 syringes.

• If you miss a dose and your next dose is due in 3 days or more, inject the missed dose as soon as you remember. Then continue your treatment as before.
• If you miss a dose and your next dose is due in less than 3 days, skip the missed dose and inject your next dose at your usual time. Then continue your treatment as before.

In case of overdose, call the poison control helpline at 1-800-222-1222. If the victim has collapsed, had a seizure, has trouble breathing, or can’t be awakened, immediately call emergency services at 911.

Do not inject more than your prescribed dose.

Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements. Using Hibsago with certain other medicines may increase the risk of side effects. Especially tell your healthcare provider if you take:

• medicines that prevent your blood from clotting (anticoagulants or antiplatelet medicines) or that lower your blood platelet count, as these may increase your risk of bleeding
• medicines that may lower your kidney function
• peginterferon alfa-2a. Using it with Hibsago is not recommended because it may increase the risk of liver enzyme increases, low platelet counts and immune system side effects.

Know the medicines you take. Keep a list of them to show your healthcare provider and pharmacist when you get a new medicine.

Other drugs may interact with this medicine, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

• Your pharmacy stores Hibsago in a refrigerator at 36°F to 46°F (2°C to 8°C).
• After you receive Hibsago, store it at room temperature up to 86°F (30°C) for up to 12 weeks. Do not store above 86°F (30°C).
• Do not freeze.
• Store in the original carton to protect from light. If your dose is 150 mg, keep the unused syringe in the carton.
• Inject Hibsago within 6 hours after you take it out of the carton. Throw away syringes not used within 6 hours.
• Throw away Hibsago in an FDA-cleared sharps disposal container if the expiration date has passed or it has been 12 weeks since you received the carton, whichever comes first.
• Throw away any unused syringes when your healthcare provider tells you your treatment is complete.

Keep out of reach of children.

Active ingredient: bepirovirsen sodium

Inactive ingredients: water for injection, hydrochloric acid or sodium hydroxide to adjust to pH 8.

GlaxoSmithKline, Durham, NC 27701