What are hemophilia inhibitors, and how might these affect hemophilia treatment?
Learn about hemophilia inhibitors, their impact on hemophilia A and B treatments, risk factors, diagnosis, and alternative treatment options for effective care.
What are inhibitors in hemophilia?
Hemophilia is caused by a lack of or dysfunction of clotting factors—proteins in the blood that help form blood clots—such as Factor VIII or IX, in the body. To should we update to: address this, people with hemophilia are often treated with clotting factor concentrates (CFCs), which temporarily increase clotting factor levels to help prevent or control bleeding episodes. However, hemophilia inhibitors (also known as neutralizing antibodies) can develop when a person's immune system mistakenly identifies these CFCs as something foreign to be attacked. The immune system then produces antibodies to these CFCs, preventing them from working effectively.
Who is at risk of developing
hemophilia inhibitors?
For people with hemophilia, there are several factors that can increase the risk of developing inhibitors to CFCs. People with severe hemophilia A are more likely to develop inhibitors than people with hemophilia B. Additionally, genetic, racial, and environmental factors can all contribute to inhibitor development. Let's explore more about each of these variables!
Rates of inhibitor development in hemophilia A versus hemophilia B
Although inhibitor development is a risk factor for all people taking CFCs, it is far more common in severe hemophilia A than in hemophilia B. Around 25% to 40% of people with severe hemophilia A develop inhibitors, whereas only 1% to 5% of people with hemophilia B develop inhibitors.
Inhibitor development is less prevalent in people with moderate/mild hemophilia A, with <5% to 15% developing inhibitors.
As a final note, people with severe hemophilia A and B are both more likely to develop inhibitors early in their treatment. In hemophilia A, 79% of those who developed inhibitors did so within their first 20 exposures. In hemophilia B, most inhibitor development occurred after a median of 9 to 11 exposures.
Genetic risk factors for hemophilia inhibitors
People with specific types of genetic mutations are more likely to develop inhibitors. A family history of inhibitors in those with hemophilia could increase the risk of developing inhibitors.
People from certain ethnic backgrounds, such as Black or Hispanic, may be more likely to develop inhibitors.
Environmental risk factors for hemophilia inhibitors
Along with genetic risk factors, there are also environmental risk factors—related to a person's lifestyle and environment—that can affect the risk of developing inhibitors. For example, using large amounts of factor replacement or being treated more often, especially during early childhood, may increase the chance of developing inhibitors due to greater exposure.
Other environmental factors, such as surgery, inflammation, and infections, can also increase the likelihood of developing inhibitors.
How do I know if I have
developed hemophilia inhibitors?
Inhibitors may be detected during routine inhibitor screening or when a person with hemophilia does not respond to factor treatment. Blood tests are used to detect inhibitors and measure their levels; this level is known as an inhibitor titer. A person with a high inhibitor titer has more inhibitors in the blood compared with someone with a low inhibitor titer. Those diagnosed with low—titer inhibitors are often closely monitored as a first step, depending on the situation. For people with hemophilia who have high levels of inhibitors in their blood, immediate treatment changes may be needed to prevent and manage bleeds. Doctors may need to use different treatments to manage the condition effectively.
How do hemophilia inhibitors
impact my treatment options?
Inhibitors can make hemophilia treatments, such as CFCs, work less effectively or sometimes not work at all. This can lead to more frequent bleeding episodes. If inhibitors are detected, it's important to create a management plan as soon as possible to make sure you get the best care. This is most effective when done at a hemophilia treatment center that has experience in treating people with inhibitors. Treatment for patients with hemophilia with inhibitors includes in bypassing agents and nonfactor therapies.
Bypassing agents
Bypassing agents are used to treat bleeding episodes in people with high levels of inhibitors in the blood. Instead of replacing the missing factor, they go around (or bypass) the factors blocked by the inhibitor to help the body form a normal clot.
Nonfactor therapies
Nonfactor agents are treatments that help promote blood clotting without having to replace missing clotting factors with CFCs. These agents work by either boosting your body’s natural ability to clot or improving how well existing clotting factors work together.
Deciding on the best option for
you if you develop hemophilia inhibitors
All people with hemophilia who are treated with CFCs are at risk of developing inhibitors. If you develop inhibitors during your hemophilia treatment, it's important to discuss all available options with your healthcare provider, as this will help tailor the most effective approach to your specific needs.
It is not known if Qfitlia is safe and effective in children younger than 12 years of age.
Qfitlia can cause SERIOUS SIDE EFFECTS, including:
Abnormal blood clotting (thrombotic events): Serious blood clots have occurred in people treated with Qfitlia. Qfitlia can cause blood clots to form in the blood vessels in your arms, legs, lungs, heart, brain, eyes, or head. Your risk of blood clots is greater if your antithrombin (AT) blood level is persistently less than 15% or if you have certain other conditions. Your healthcare provider (HCP) will check your AT blood levels before and during treatment with Qfitlia
Gallbladder disease: Qfitlia can cause gallstones and inflammation of your gallbladder, which might require surgery to remove your gallbladder. Tell your HCP right away if you develop stomach pain, indigestion, nausea, or vomiting. Your HCP may temporarily or permanently stop Qfitlia if you develop any of these symptoms
What is the most important information I should know about Qfitlia?
Qfitlia helps your blood form clots. Do not stop using Qfitlia without talking to your HCP. If you miss doses or stop using Qfitlia, you may no longer be protected against bleeding.
Use of a clotting factor concentrate (CFC) or bypassing agent (BPA) to help protect against bleeding must be stopped within 7 days after your first dose of Qfitlia.
Your HCP may prescribe on-demand CFC or BPA if you bleed during treatment with Qfitlia. Carefully follow your HCP’s instructions regarding when to use on-demand treatment with CFC or BPA, including the prescribed dose and timing of the CFC or BPA.
Get medical help right away if you get any of these signs or symptoms of blood clots during or after treatment with Qfitlia:
- Swelling, pain, or redness in arms or legs
- Coughing up blood
- Shortness of breath
- Severe chest pain or tightness of the chest
- Fast heart rate
- Feeling faint or passing out
- Severe or persistent headache
- Difficulty speaking or understanding language
- Feeling confused
- Numbness or weakness in your face, arms, or legs
- Sudden loss or changes in your vision, eye pain, or swelling
What are the possible side effects of Qfitlia?
Qfitlia can cause other serious side effects, including an increase in your blood liver enzymes. Your HCP will do blood tests to check your liver function before and during treatment with Qfitlia
The most common side effects of Qfitlia include viral infection, common cold symptoms, and bacterial infection
These are not all the possible side effects of Qfitlia.
What should I tell my HCP before using Qfitlia?
Tell your HCP about all of your medical conditions, including if you have liver problems, a history of gallbladder disease, are pregnant or plan to become pregnant, or are breastfeeding or plan to breastfeed
Females who are able to become pregnant: Hormonal birth control may increase your risk of blood clots if used during treatment with Qfitlia. Talk to your HCP about effective forms of non-hormonal birth control you can use before starting and during treatment with Qfitlia
Tell your HCP about all of the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements
