Examining Evolving Treatment Paradigms in the Hemophilia B Space - Episode 1
Steven Pipe, MD, defines Hemophilia B and its standard of care.
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Steven Pipe, MD: Hemophilia A and B are both X-linked inherited bleeding disorders that result from deficiency of the clotting factors, factors 8 and 9 respectively. In their severe forms, this deficiency results in risk for recurrent spontaneous and traumatic bleeding, primarily into joints. This ultimately leads to painful and debilitating chronic joint disease. This is found in about 1 in 5,000 male births, and hemophilia A is about 4 times more common than hemophilia B. With respect to bleeding and outcomes, [as well as] general approach to treatment, they are similar.
Worldwide, there are approximately 33,000 people with hemophilia B. Two-thirds of these are classified as moderate-to-severe deficiency. This is determined by their residual factor 9 activity. It's those with moderate-to-severe deficiency who are at the highest risk for recurrent bleeding.
The standard of care for treatment for hemophilia B is aimed at preventing bleeding because if we can prevent bleeding, we can prevent the long-term adverse outcomes related to joint disease. Prophylactic intravenous factor 9 replacement therapy is the current standard of care, but these regular infusions are a major treatment burden, and they're expensive. We also [must be aware of] poor adherence to the treatment, limited access to treatment, individual variations and required doses, and the low factor 9 trough levels following infusion. This means that arthropathy and other complications, although they're reduced, cannot be completely prevented over the long-term. Previously, our targets for prophylaxis had been aimed to maintain factor 9 levels at a trough of at least 1% or higher. Severe disease is defined as < 1%. Going back multiple decades, we know that people who have a minimum of at least 1% or higher have a moderation of their bleeding phenotype. Recent global guidelines now recognize that maintaining higher trough levels of at least 3%–5% or even higher are associated with improved clinical outcomes. For patients with established joint disease, higher levels may be required. Estimates are that levels maintained above 10%–15% are likely required to prevent breakthrough joint bleeding.
As far as who is actually on prophylaxis on a sustained basis, month after month or year after year, this would primarily be individuals with severe disease [with] < 1% residual factor 9 activity. However, patients with moderate hemophilia B, which is a level of 1%–5% percent, have enough bleeding that, over time, also contributes to the development of joint disease. However, the burden of the prophylactic treatment becomes weighed in the balance for whether they're committed to being maintained on a prophylactic regimen. Unfortunately, there are a number of patients with moderate and then those with mild disease who aren't typically on prophylactic therapy even though they would benefit from committing to it.
This transcript has been edited for clarity.