What are the symptoms of Hemophilia B?

The most common symptoms of Hemophilia B include Easy bruising and bleeding, Hemarthrosis (joint bleeds) causing pain and swelling, Muscle hematomas, Spontaneous bleeding in severe forms, Bleeding after trauma or surgery, among others. Hemophilia B affects approximately 1 in 25,000 to 33,000 males; very rare in females. Symptoms can range from mild to severe and may vary between individuals. Early diagnosis through genetic testing and clinical evaluation is important for management and treatment planning.

How can I find clinical trials for Hemophilia B?

Trial Friend lists all active clinical trials for Hemophilia B from ClinicalTrials.gov, with eligibility criteria translated into plain English. Patients can filter by trial phase and recruitment status, search by location, and use the Match Me tool to score trials against their profile. Factor IX replacement therapy (plasma-derived prothrombin complex concentrate [PCC] containing factors II, VII, IX, X or recombinant factor IX) is the standard treatment, tailored to severity and bleeding event. Recombinant factor IX products with extended half-life through Fc fusion or albumin fusion significantly reduce treatment frequency.

Are there FDA-approved treatments for Hemophilia B?

Yes. As of September 2026, Trial Friend lists 4 FDA-approved drugs used to treat Hemophilia B: Hemgenix (etranacogene dezaparvovec), first approved in 2022; Alhemo (concizumab), first approved in 2024; Hympavzi (marstacimab), first approved in 2024; and Qfitlia (fitusiran), first approved in 2025. Each has its own page with what the label covers, side effects and how it is given, and the Treatments section of this page adds any further approved drugs found in FDA labeling data.

What phase are Hemophilia B clinical trials in?

Hemophilia B clinical trials span multiple development stages: Phase 1 tests safety in small groups, Phase 2 evaluates effectiveness, Phase 3 compares to existing treatments in larger populations, and Phase 4 monitors long-term effects after approval. Trial Friend shows each trial's phase, recruitment status, timeline, and estimated completion date, updated in real time from ClinicalTrials.gov.

Is genetic testing available for Hemophilia B?

Yes. Genetic testing for Hemophilia B looks at the F9 gene. Females with skewed X-inactivation can be symptomatic carriers. It is X-linked, so it mainly affects boys, and a mother who carries the variant has a 1 in 2 chance of passing it to each son. A confirmed variant establishes the diagnosis and is often required to enroll in gene-specific trials. The labs currently offering the test are listed in the Genetic Testing section of this page, pulled live from the NIH Genetic Testing Registry. A genetic counselor can help interpret the result and decide which relatives should be tested.

What causes Hemophilia B?

Hemophilia B is caused by variants in the F9 gene. Females with skewed X-inactivation can be symptomatic carriers. It is X-linked, so it mainly affects boys, and a mother who carries the variant has a 1 in 2 chance of passing it to each son. The condition affects approximately 1 in 25,000 to 33,000 males; very rare in females. Genetic testing confirms the diagnosis.

Am I eligible for Hemophilia B clinical trials?

Eligibility for Hemophilia B clinical trials depends on factors like age, diagnosis, treatment history, and overall health. Each trial sets its own inclusion and exclusion criteria. Trial Friend translates these requirements from medical language into plain English so patients can review them more easily. The Match Me tool can score your profile against active Hemophilia B trials to help identify studies that may be a fit. Always confirm eligibility with the study team before enrolling.

What should I expect in a Hemophilia B clinical trial?

Participating in a Hemophilia B clinical trial typically involves scheduled visits, medical tests, and close monitoring by a research team. Depending on the study phase, you may receive an investigational treatment, a placebo, or the current standard of care. Trials may last from a few weeks to several years. Study participation is voluntary and you can withdraw at any time. Trial Friend provides details on each study's design, timeline, and estimated completion date to help you plan ahead.

Blood & Immune

Hemophilia B Clinical Trials and Treatments

Also called Factor IX deficiency, Christmas disease, X-linked hemophilia, Hemophilia Type B, Haemophilia B

View 39 active trials Match me to a trial

About Hemophilia B

Hemophilia B is an X-linked recessive inherited bleeding disorder caused by deficiency or dysfunction of clotting factor IX (Christmas factor). Pathophysiology involves reduced or abnormal factor IX protein affecting the intrinsic tenase complex essential for coagulation amplification. Clinically, hemophilia B is indistinguishable from hemophilia A, with manifestations strictly dependent on factor IX activity levels.

Severe disease (<1% factor activity) causes spontaneous bleeding into joints and muscles without provocation; moderate disease (1-5% activity) causes bleeding with minor trauma and progressive joint disease; mild disease (5-40% activity) causes bleeding only with significant trauma or surgery. Joint bleeds (hemarthrosis) cause hemarthropathy with chronic pain and joint destruction if untreated. Spontaneous intracranial hemorrhage and other serious bleeding episodes represent major morbidity.

Diagnosis requires factor IX activity assay showing reduced levels. The condition accounts for approximately 15-20% of all hemophilia cases. Factor IX deficiency results in the same bleeding phenotype as factor VIII deficiency, distinguishable only by specific factor assays. Most affected males have severe disease.

Common Symptoms of Hemophilia B

Recognizing the signs of Hemophilia B early can lead to faster diagnosis and better outcomes. Symptoms may vary in severity from person to person. If you or a loved one are experiencing any of the following, consider speaking with a specialist.

Easy bruising and bleeding
Hemarthrosis (joint bleeds) causing pain and swelling
Muscle hematomas
Spontaneous bleeding in severe forms
Bleeding after trauma or surgery
Oral and GI bleeding

Who Hemophilia B Affects

All ethnic and racial groups affected with similar incidence. No significant geographic variation in prevalence identified. Approximately 20% of hemophilia B cases represent de novo mutations. Family history crucial for carrier identification and genetic counseling.

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FDA-Approved Treatments for Hemophilia B

There are currently 4 FDA-approved medications for Hemophilia B. These therapies represent the current standard of care and may be used alongside or compared against investigational treatments in active clinical trials. Compare all 4 side by side, with dosing, trial results and warnings from the labels.

Alhemo

Drug Decoder

concizumab

Novo Nordisk

Hympavzi

Drug Decoder

marstacimab

Pfizer

Qfitlia

Drug Decoder

fitusiran

Sanofi / Alnylam

Hemgenix

Drug Decoder

etranacogene dezaparvovec

CSL Behring / uniQure

Official site

Source: openFDA drug labeling data. This list may not include all treatments. Always consult your doctor.

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Help Paying for Hemophilia B Treatment

Charity funds and drugmaker programs for Hemophilia B, checked at the source. Pick your insurance to see what fits.

Your insurance

Charity funds

From a charity · Hemophilia Federation of America
Helping Hands Program fund
Open
Apply on the foundation’s page
Pays for: Emergency living expenses ($250 prepaid card, once per year; referral through HTC or member organization; does not cover medical bills, copays or premiums), up to $250 per year.
The foundation says: “The Helping Hands program is now open on a limited basis for 2026. Due to funding constraints, a maximum of 20 requests will be approved…”
From a charity · TotalAssist (formerly PAN Foundation)
Hemophilia fund
Open
Apply on the foundation’s page
Pays for: Out-of-pocket costs for approved medications, up to $12,500 per year. Requires health insurance (any kind).
From a charity · The Assistance Fund
Hemophilia fund
Waitlist
Apply on the foundation’s page
Pays for: Copays, coinsurance, deductibles and other health-related expenses.
The foundation says: “WAITLIST — Accepting Waitlist Patients. TAF is currently accepting requests to join the enrollment waitlist for this program. Waitlists a…”

Status as each foundation showed it on September 28, 2026.

Drugmaker programs

Open a medicine for who qualifies, by insurance type.

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Side Effect Explorer

Real-world side effect reports from the FDA Adverse Event Reporting System (FAERS). Includes both FDA-approved drugs and investigational therapies from active clinical trials. Click any drug to see what patients reported.

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Genetic Testing

Genetic testing can confirm a diagnosis, guide treatment decisions, and identify family members who may be at risk.

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Trusted Hemophilia B Resources

Reputable organizations and medical references for learning more about Hemophilia B, including disease registries, foundation resources, and clinical guidelines.

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Quick facts

Active Clinical Trials for Hemophilia B

Use this Hemophilia B clinical trial finder to see the 13 studies recruiting patients and 6 opening soon in the United States and worldwide, with eligibility criteria in plain English. These studies play a critical role in advancing care for blood & immune conditions and may offer access to treatments not yet widely available. Each trial below is sourced directly from ClinicalTrials.gov, with eligibility criteria translated into plain English to help patients and caregivers evaluate whether a study may be a fit.

Trials Site map Pipeline timeline

Note: Trial recruitment statuses on ClinicalTrials.gov may not immediately reflect recent FDA decisions, sponsor announcements, or enrollment changes. Always confirm a trial's current status directly with the study coordinator before making plans.

39 active trials worldwide

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RECRUITINGPHASE3Recently updatedNCT05568719

Safety and Effectiveness of Giroctocogene Fitelparvovec or Fidanacogene Elaparvovec in Patients With Hemophilia A or B Respectively

Intervention: Testing of hepatic AAV Vector integration

Sponsor: Pfizer

A study to learn about the long-term safety and efficacy of giroctocogene fitelparvovec or fidanacogene elaparvovec in patients with hemophilia A or hemophilia B respectively, who have received treatment through prior participation in a Pfizer-sponsored clinical trial. Data colle...

Ages 18 Years+39 locations

Started Dec 2022Updated yesterdayEst. Feb 2040 (~13y 4m)

RECRUITINGPHASE3Recently updatedNCT05611801

A Clinical Trial of Study Medicine (Marstacimab) in Pediatric Patients With Hemophilia A or Hemophilia B

Intervention: marstacimab

Sponsor: Pfizer

The purpose of this clinical trial is to learn about the safety and effects of the study medicine (called marstacimab) for the potential treatment of hemophilia in pediatric patients.

Ages 1 Year – 17 Years63 locations

Started Dec 2022Updated 1 week agoEst. Sep 2028 (~1y 11m)

NOT YET RECRUITINGRecently updatedNCT05932914

Liver Biopsy Following Gene Therapy For Hemophilia

Intervention: Liver Biopsy

Sponsor: St. Jude Children's Research Hospital

This observational study will obtain liver biopsy samples and evaluate the long-term effect of adeno-associated virus (AAV)-mediated gene therapy on the liver tissue in adult patients with hemophilia A or hemophilia B who have previously been treated with a factor VIII or factor ...

Ages 18 Years – 80 Years1 location

Started Oct 2026Updated 2 weeks agoEst. Jan 2030 (~3y 4m)

RECRUITINGPHASE3Recently updatedNCT07080905

Phase 3, Open-label, Single-dose Study of CSL222 in Adolescent Male Subjects (≥ 12 to < 18 Years of Age) With Severe or Moderately Severe Hemophilia B

Intervention: CSL222 (Adeno-associated viral vector serotype 5 [AAV5]-hFIXco-Padua)

Sponsor: CSL Behring

This is a phase 3, prospective, open-label, single-arm, single-dose, multicenter study investigating the efficacy, safety, and tolerability of CSL222 (AAV5-hFIXco-Padua) in adolescent male participants with severe or moderately severe hemophilia B.

Ages 138 Months – 206 Months14 locations

Started Jul 2025Updated 2 weeks agoEst. Oct 2033 (~7 years)

RECRUITINGPHASE1, PHASE2Recently updatedNCT06379789

A Study to Investigate the Safety and Effectiveness of a Coagulation Factor IX Gene Insertion Therapy (REGV131-LNP1265) in Pediatric, Adolescent and Adult Participants With Hemophilia B

Intervention: REGV131, LNP1265

Sponsor: Regeneron Pharmaceuticals · Intellia Therapeutics

Participants in this study have a genetic mutation, specifically in the coagulation (blood clotting) Factor 9 gene that causes severe or moderately severe hemophilia B. This study is researching an experimental gene insertion therapy (the adding of a gene into your DNA) called RE...

Ages 2 Years+49 locations

Started Sep 2024Updated 3 weeks agoEst. Aug 2034 (~7y 10m)

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Active trial locations78 cities in the US

+70 more

Trial Pipeline

Jan 2021 to Oct 2031

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Data from ClinicalTrials.gov, U.S. National Library of Medicine.
Always talk to your doctor before considering a clinical trial.

Patient Communities

Connect with other Hemophilia B patients, caregivers, and advocacy groups across Facebook groups, Reddit communities, and YouTube channels. These patient communities offer peer support, shared experiences, caregiver resources, and real-time discussion about Hemophilia B treatments, clinical trial participation, and day-to-day disease management.

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Related Blood & Immune Conditions

Other rare diseases in the blood & immune category. Patients with Hemophilia B may find relevant research, shared treatment pathways, or overlapping clinical trials among these related conditions.