Hemophilia B is a rare bleeding disorder that causes blood to clot more slowly than usual. If you have this condition, you may have prolonged bleeding or oozing after an injury or surgery. In severe cases, you may have prolonged bleeding after a minor injury or even with no injury.

Hemophilia B is caused by genetic mutations in the F9 gene. This gene gives your body instructions for producing factor IX. This is one of multiple clotting factors that help your blood to clot. If you have hemophilia B, your body does not produce enough factor IX.

The first-line treatment is factor IX replacement therapy. Your doctor will give you high doses of factor IX concentrate to stop bleeding episodes. They may also prescribe factor IX prophylactic therapy, which involves taking regular doses of factor IX concentrate to help prevent bleeds.

You might find factor IX prophylactic therapy is inconvenient, especially if you need multiple infusions per week to prevent bleeds. Some people with hemophilia B also develop neutralizing antibodies that block the action of factor IX. These are known as inhibitors, which make factor IX therapy less effective.

To improve treatment options, researchers have been developing new factor IX products and other therapies.

Read on to learn about the latest research findings and novel treatments for this condition.

The earliest factor IX products were derived directly from human blood or plasma.

Later on, scientists developed recombinant factor IX (rFIX) products, which are genetically engineered in a lab.

The Food and Drug Administration (FDA) approved the first rFIX product in the 1990s.

In more recent years, scientists have modified rFIX to create products with an extended half-life. These products last longer in your body than rFIX products with a standard half-life. This means you need less frequent doses.

The FDA has approved multiple rFIX products with an extended half-life, including:

  • eftrenonacog alfa (Alprolix; rFIX-Fc), approved in 2014
  • albutrepenonacog alfa (Idelvion; rFIX-FP), approved in 2016
  • nonacog beta pegol (Rebinyn; N9-GP), approved in 2017

All these products are infused into a vein through an intravenous (IV) line.

Researchers are continuing to study the long-term effects of these products, according to a 2021 review.

Scientists are also developing and testing other rFIX products with an extended half-life, including dalcinonacog alfa (DalcA). This product is injected under your skin.

A small phase 1/2a clinical trial found that daily injections of DalcA were safe and effective for increasing factor IX in people with hemophilia B. More research is needed to evaluate this treatment.

Factor IX isn’t the only protein that helps your blood to clot. Some treatments for hemophilia B increase the availability or action of other clotting factors to help stop bleeding without factor IX.

These include recombinant factor VIIa (rFVIIa). Your doctor may prescribe rFVIIa to treat and prevent bleeding episodes if you have factor IX inhibitors.

The FDA has approved two rFVIIa products to treat hemophilia B:

  • NovoSeven RT, approved in 1999
  • eptacog beta (SEVENFACT), approved in 2020

SEVENFACT is currently approved only for adults and adolescents ages 12 years and older, but recent research suggests it may also be safe and effective for younger people.

In a phase 3 clinical trial, 25 children with hemophilia A or B under age 12 received SEVENFACT to treat a mild to moderate bleeding episode. The treatment was successful within 24 hours for at least 97% of children who received it. No participants experienced serious side effects.

Researchers are also developing rFVIIa products with an extended half-life that last longer in your body than NonoSeven RT or SEVENFACT. These products include MOD-5014 and marzeptacog alfa.

Research on these products is ongoing.

Antithrombin is a protein that blocks the action of factor Xa, as well as factor IXa.

Fitusiran is an experimental drug that lowers levels of antithrombin. This promotes blood clotting and limits bleeding.

In 2022, researchers reported the results of two phase 3 clinical trials on fitusiran at a conference of the International Society on Thrombosis and Haemostasis. They found that monthly doses of fitusiran were linked to fewer bleeding episodes in people with hemophilia A or B. Those who took fitusirin also required fewer doses of clotting factor to treat bleeds.

Studies have shown that fitusirin works in people with factor IX inhibitors, as well as those without.

The FDA has not yet approved fitusirin for treating hemophilia A or B.

Researchers are continuing to study it to learn more about its efficacy, safety, and ideal dosing.

The tissue factor pathway inhibitor (TFPI) is another protein that limits the action of clotting factor Xa.

Concizumab is an injectable monoclonal antibody that blocks TFPI. Blocking TFPI allows your body to produce more Xa, which helps your blood to clot even without factor IX.

Phase 1 and 2 clinical trials found that concizumab was effective for reducing bleeds in people with hemophilia A or B, report the authors of a 2022 review.

Concuzimab may provide a treatment option for people with factor IX inhibitors, as well as those without.

Phase 3 clinical trials on concizumab are ongoing.

Researchers are also studying other anti-TFPI antibodies, including:

  • befovacimab (BAY-1093884)
  • marstacimab (PF-06741086)
  • MG1113

More research is needed to evaluate the safety and efficacy of these medications.

Gene therapy corrects genetic mutations that cause certain diseases.

In this treatment approach, a doctor uses a modified virus to deliver nonfaulty genes into your body’s cells. They may also remove or inactivate faulty genes.

Successful gene therapy for hemophilia B could provide long-term or potentially permanent benefits by replacing your faulty F9 gene with a nonfaulty gene. This would allow your body to produce enough factor IX on its own, with fewer or no infusions of factor IX.

Scientists have been studying multiple gene therapy approaches for treating hemophilia B. Some of these approaches have shown promise in clinical trials.

For example, researchers found gene therapy increased circulating factor IX levels to 1 to 6% of the normal level for at least 3 years. People who received the highest dose of the therapy had more than 90% fewer bleeding episodes. They also required fewer treatments with factor IX concentrates.

Gene therapy is not yet available to treat hemophilia outside of clinical trials.

More research is needed to study its long-term safety and efficacy.

Getting treatment for hemophilia B is important for preventing and managing bleeding episodes, lowering your risk of complications, and improving your quality of life.

Factor IX replacement and prophylactic therapy are the main treatments for this condition. Some people develop inhibitors that make these treatments less effective.

New and experimental therapies may help improve treatment options, including for people with and without inhibitors.

Talk with your doctor to learn more about current and emerging treatment options. In some cases, they might encourage you to take part in a clinical trial to receive an experimental treatment that has not yet been approved.

Your doctor can help you learn more about the potential benefits and risks of different treatments for hemophilia B, including experimental treatments.