Hemophilia B is an inherited bleeding disorder caused by deficiency or dysfunction of clotting factor IX, leading to prolonged and potentially life-threatening bleeding after injury or surgery, and spontaneous bleeding into joints and muscles in severe cases. It is caused by mutations in the F9 gene on the X chromosome and affects predominantly males. Regular prophylactic factor infusions have greatly improved quality of life but require frequent intravenous access.
What's actually going on in research
Extended half-life factor IX products have reduced infusion frequency for prophylaxis to once weekly or even less often in some patients. Fitusiran, an antithrombin-targeting RNA interference therapy, and concizumab, a monoclonal antibody, offer non-factor subcutaneous prophylaxis options for people with or without inhibitors. Most transformatively, gene therapy using AAV-based delivery has achieved long-term factor IX expression in clinical trials: etranacogene dezaparvovec is now approved and demonstrated sustained high-level factor IX activity after a single infusion.
Gene therapy approval
Etranacogene dezaparvovec is now approved for severe hemophilia B and has demonstrated durable factor IX expression over years after a single infusion, offering potential freedom from ongoing prophylaxis.
Non-factor subcutaneous prophylaxis
Fitusiran and concizumab offer subcutaneous injection prophylaxis that does not require factor replacement, benefiting patients — including those with inhibitors — who find intravenous access difficult.
Inhibitor treatment
Emicizumab, approved for hemophilia A with inhibitors, and new agents are being studied in hemophilia B patients who develop inhibitors against factor IX replacement therapy.
What to know before you search
Eligibility depends on factor IX activity level, inhibitor status, prior treatment history, and liver health for gene therapy trials.
What types of trials are currently open
- Gene therapy trials — Follow-up and new-generation AAV gene therapy programs for hemophilia B with improved vectors and expression.
- Non-factor prophylaxis trials — Testing fitusiran, concizumab, and related agents for bleeding prevention without factor IX infusions.
- Extended half-life factor trials — Evaluating next-generation long-acting factor IX products for reduced-frequency prophylaxis.
- Inhibitor management trials — Studying immune tolerance induction and bypass agents for hemophilia B patients with inhibitors.
- Quality-of-life and joint health studies — Assessing joint outcomes and daily functioning in patients switching from standard to novel prophylaxis.
Recently added Hemophilia B trials
Safety of KN057 Prophylaxis in Patients With Haemophilia A or B
The purposes of this open-label, multicenter III clinical trial are to evaluate the safety and efficacy of long-term preventive treatment with KN057 in Haemophilia A or B patients with or without inhibitors, and to assess the pharmacokinetic characteristics of the new and old processes KN057. The participants in Part PK will be randomly assigned to Old process Group or New process Group in a 1:1 ratio. The participants in Old process Group will receive old process KN057 prophylaxis for the first 26 weeks and new process KN057 prophylaxis for the following 26 weeks. The participants in New process Group will receive new process KN057 prophylaxis for both the first 26 weeks and the last 26 weeks. The participants in Part non-PK will be non-randomized and treated with new process KN057 for 52 weeks prophylaxis after enrollment. Priority screening and enrollment of participants who have participated in the KN057-A-301 or KN057-A-302 study.
A Study to Investigate the Efficacy and Safety of Fitusiran Prophylaxis in Male Participants Aged 1 to Less Than 12 Years With Hemophilia A or B
This is a parallel, Phase 3, two-arm, open-label study to evaluate the efficacy and safety of treatment with fitusiran prophylaxis administered to male pediatric participants (aged 1 to \<12 years) who have severe hemophilia A or B, with or without inhibitory antibodies to FVIII or FIX. Number of participants: Approximately 85 participants will be enrolled into the study: * Approximately 60 fitusiran-naïve participants with severe hemophilia A or B, with or without inhibitors (fitusiran-naïve arm), and * Approximately 25 participants with severe hemophilia A or B with inhibitors rolling over from the EFC15467\* dose confirmation study (roll-over arm). * Fitusiran has been investigated in the pediatric population in study EFC15467, which enrolled male participants aged 1 to \<12 years with hemophilia A or B with inhibitors to examine the safety and tolerability of fitusiran in the pediatric population. Participants will be enrolled into 1 of 2 arms: * Fitusiran-naïve: these participants have not previously received fitusiran, and they will undergo screening and study eligibility assessments. Once enrolled, they will go through a 24-week standard of care (SOC) period before starting fitusiran prophylaxis. * Roll-over participants from the EFC15467 study: only participants who are still on active treatment in study EFC15467 and consenting to study EFC17905 will be eligible to roll over. They will not need to undergo screening or further eligibility assessments. They will directly enroll into the fitusiran treatment period and continue treatment on their current fitusiran dose. The duration of fitusiran treatment will be up to 160 weeks for the fitusiran-naïve arm and up to 60 weeks for the roll-over arm.
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