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Hemophilia is an inherited bleeding disorder in which the blood lacks a working clotting factor: factor VIII in hemophilia A and factor IX in hemophilia B. The gene sits on the X chromosome, so the disease mostly affects males, about 1 in 5,000 at birth, and hemophilia A is about four times as common as B. Female carriers can have low factor levels and bleeding problems of their own, and about a third of cases appear in families with no history of it. Severe hemophilia causes spontaneous bleeding into joints and muscles that damages joints over time.
Standard care is prophylaxis: regular infusions of clotting factor or injections of newer non factor medicines, coordinated through specialized hemophilia treatment centers. Some people develop inhibitors, antibodies that neutralize infused factor and make treatment harder. Gene therapies for hemophilia A and B were approved between 2022 and 2024.
New to research? Read how informed consent works for long term studies.
Gene therapy trials. One time infusions that deliver a working factor gene to the liver, including the first studies in adolescents; see gene therapy clinical trials.
Non factor prophylaxis trials. Antibodies and small interfering RNA medicines given weekly to every few months that prevent bleeds without replacing factor.
Inhibitor trials. New approaches for people whose antibodies make factor treatment ineffective.
Long term follow up studies. Years of tracking after gene therapy, required to learn how long the effect lasts.
Joint and bone health studies. Imaging, ultrasound, and bone density research in people with severe disease.
Women and carriers. Studies of bleeding in female carriers, a long neglected group.
Most treatment trials enroll males with moderate or severe hemophilia A or B, often 12 or 18 and older, who are on prophylaxis and have a documented bleeding history. Gene therapy trials add strict rules: no antibodies to the viral vector used, healthy liver function, no history of inhibitors, and years of follow up visits. Inhibitor trials enroll the opposite group. Observational studies often include children, carriers, and people with mild disease, and many studies run through hemophilia treatment centers. Eligibility always varies by study.
Gene therapy is the closest thing: approved products for hemophilia A and B can raise factor levels for years after a single infusion, though levels vary and may decline. It is not suitable for everyone, and trials are testing newer versions and younger patients.
Mild (6 to 40 percent of normal factor). Bleeding mainly after injury or surgery; few treatment trials, some observational studies.
Moderate (1 to 5 percent). Occasional spontaneous bleeds; eligible for many prophylaxis and gene therapy trials.
Severe (under 1 percent). Frequent spontaneous bleeds, especially into joints; the main target of gene therapy and non factor trials.
With inhibitors. Any severity plus antibodies against factor; a separate set of trials.
Identify your trial. Use the filters; titles state hemophilia A or B, severity, and whether people with inhibitors are included.
Select your preferred location. Enter your city or state; many trials run through hemophilia treatment centers.
Explore study details. Click "Learn More" for factor level, inhibitor, and liver test requirements, and the length of follow up.
Complete the health profile. Click "Get started" to begin the 5-step application. Have ready your hemophilia type and severity, your current prophylaxis and recent bleed history, and whether you have ever had inhibitors.
Submit the application. A clinical trial coordinator reviews it and contacts you. Nothing is decided until informed consent, and participation is voluntary at every step.