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PubMed This is a summary of 20 peer-reviewed journal articles Updated
Hematology

Can a Hemophilia A Inhibitor Be Eradicated? ITI Explained

At a Glance

A Hemophilia A inhibitor can sometimes be eliminated with immune tolerance induction, which uses repeated Factor VIII infusions to retrain the immune system. Treatment may take months or years, does not cure Hemophilia A, and requires ongoing monitoring because the inhibitor can return.

In this answer

4 sections

01

What is Immune Tolerance Induction (ITI)?

02

What Does the Protocol Involve?

03

What Are the Chances of Success?

04

Protection During ITI and Important Safety Warnings

While an inhibitor diagnosis can be frightening, it is not always permanent. In many patients, the inhibitor can be eliminated using a specialized treatment called Immune Tolerance Induction (ITI). However, ITI treats only the inhibitor, not the underlying Hemophilia A. If successful, it allows the patient to return to using standard Factor VIII replacement to prevent bleeds, though it is not guaranteed to work for everyone and requires a significant time commitment [1][2].

What is Immune Tolerance Induction (ITI)?

ITI is the established clinical approach for attempting to eradicate an inhibitor [1]. The broad concept is similar to how the immune system is retrained during allergy therapy [3]. By giving the body repeated, controlled exposure to Factor VIII (the clotting protein the body is missing), the immune system can gradually learn to accept it and stop producing inhibitor antibodies [1].

What Does the Protocol Involve?

No single ITI protocol is universally considered the best. Regimens are tailored by your hemophilia treatment center and generally involve:

  • Frequent Infusions: Patients typically receive Factor VIII infusions from three times a week up to every single day [4][5].
  • Variable Dosing: Depending on the specific protocol, doses can be low or high, but the total exposure to Factor VIII is significant [4][6].
  • Long Duration: ITI is a slow process, often taking many months or even over two years to achieve immune tolerance [5][7].

Because of the frequent intravenous (IV) needle sticks, a surgically implanted port (central venous access device) is often considered for young children. While ports make infusions easier, they carry risks such as infection or blood clots, which should be discussed carefully with your care team.

What Are the Chances of Success?

In several large studies of people with severe Hemophilia A, ITI successfully eradicated the inhibitor in roughly 70% to 72% of participants [3][8]. Clinical “success” is usually defined as having a negative inhibitor test along with adequate Factor VIII recovery (meaning infused Factor VIII reaches expected levels in the blood and lasts a normal amount of time) [7][9].

An individual’s chances of success vary based on:

  • Inhibitor Levels: Patients whose inhibitor levels—measured in Bethesda Units (BU)—remained lower at their historical peak tend to have better outcomes [10].
  • Genetics: Certain mutations, such as large deletions in the F8 gene, are associated with a harder time achieving tolerance, though they do not mean ITI is impossible [11][12].

Tolerance can also be lost over time. One study estimating recurrence found that roughly 30% of successfully treated patients experienced a return of their inhibitor within five years [13]. Because of this risk, ongoing monitoring of inhibitor levels and Factor VIII recovery is critical even after ITI is completed [7][9].

Protection During ITI and Important Safety Warnings

Because it takes time for ITI to work, the patient remains vulnerable to bleeds during the process [14]. Doctors prescribe other medications to prevent or treat bleeding while waiting for tolerance to build:

  • Emicizumab: A non-factor injection that can significantly reduce bleeding risk while the body undergoes ITI [15][16]. Emicizumab does not eliminate the inhibitor itself; it only provides bleeding protection [17].
  • Bypassing Agents: Medications that bypass the need for Factor VIII to form a clot.

CRITICAL SAFETY WARNING: If a patient is taking emicizumab, extreme caution must be used with bypassing agents. Using a bypassing agent called activated prothrombin complex concentrate (aPCC, brand name FEIBA) alongside emicizumab can cause severe and dangerous blood clots or damage to small blood vessels (thrombotic microangiopathy) [18][19]. Because of this, recombinant factor VIIa (rFVIIa) is generally preferred for treating acute bleeds in patients on emicizumab. You must have a clear emergency bleed plan, and every emergency medical provider must be told that your child takes emicizumab [20].

Additionally, emicizumab interferes with several standard laboratory tests. Your care team must use specialized assays to accurately monitor your child’s inhibitor levels and Factor VIII recovery, as standard test results may be misleading [9][17]. Do not stop, change, or pause any treatments without consulting your hemophilia treatment center.

Common questions in this guide

Can a Hemophilia A inhibitor go away permanently?
It can sometimes be eliminated with immune tolerance induction (ITI), but treatment does not cure the underlying Hemophilia A. If ITI works, the person may be able to use standard Factor VIII replacement again, although the inhibitor can return and requires ongoing monitoring.
What does immune tolerance induction involve?
ITI uses repeated Factor VIII infusions to help the immune system stop attacking the protein. Infusions may be needed three times a week or every day, and treatment can last many months or more than two years.
How likely is ITI to eliminate a Hemophilia A inhibitor?
In large studies of people with severe Hemophilia A, ITI eliminated the inhibitor in about 70% to 72% of participants. Higher historical peak inhibitor levels and some F8 gene changes are linked with lower success, but they do not make treatment impossible.
How are bleeding risks managed while ITI is working?
People remain at risk of bleeding during ITI, so clinicians may use emicizumab or a bypassing medicine for protection or treatment. Emicizumab reduces bleeding but does not remove the inhibitor, and the hemophilia team should provide a written emergency plan.
Can FEIBA be used with emicizumab during a bleed?
Activated prothrombin complex concentrate (aPCC, also called FEIBA) can cause dangerous blood clots or small-vessel injury when used with emicizumab. Recombinant factor VIIa is generally preferred for an acute bleed in someone receiving emicizumab, but the treating hemophilia center should direct emergency care.
How is a Hemophilia A inhibitor monitored during and after ITI?
Clinicians monitor inhibitor levels and how well infused Factor VIII reaches and remains in the blood. Emicizumab can interfere with standard laboratory tests, so specialized assays may be needed; monitoring continues after successful ITI because inhibitors can recur.

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References

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This page is for education about Hemophilia A inhibitors and immune tolerance induction, not medical advice. Your hemophilia treatment center must create your individualized bleed and treatment plan, especially if emicizumab is being used.