Hemophilia B is a rare, inherited bleeding disorder caused by low levels (or a lack) of a blood clotting protein called factor IX. Without enough factor IX, blood doesn’t clot the way it should. This can lead to bleeding that’s harder to stop, including bleeding inside the body, such as in the joints or muscles, sometimes without any obvious injury. Hemophilia B mostly affects males because the gene involved sits on the X chromosome.
One treatment option for hemophilia B is Alprolix (eftrenonacog alfa). Alprolix is a lab-made version of factor IX that’s joined to a small piece of an antibody. That extra piece helps the medicine stay active in the body longer than standard factor IX products, so it can be used less often. The FDA approved Alprolix in 2014. It was the first medicine in its category, known as an extended half-life factor IX product, approved for hemophilia B.
This article covers how Alprolix works, who it’s approved for, how it’s given, and what clinical studies found. You may also be interested in reading about Alprolix side effects.
How Does Alprolix Work for Hemophilia B?
Normally, the body clears proteins such as factor IX from the bloodstream fairly quickly. That’s why older, standard factor IX products need to be given two to three times a week to keep enough factor IX in the blood to help prevent bleeding.
Alprolix is built differently. It’s made of a factor IX molecule fused to a piece of an antibody called an Fc domain. This Fc piece lets Alprolix tap into a natural recycling system in the body, called the neonatal Fc receptor (FcRn) pathway. Instead of being broken down and cleared quickly, some of the medicine gets pulled back into the bloodstream and reused rather than discarded.
This recycling extends how long Alprolix stays active in the body. In studies, its half-life (the time it takes for half the medicine to clear from the blood) was many times longer than that of standard factor IX. That means people using Alprolix may be able to go longer between infusions while still keeping their factor IX levels high enough to help prevent or control bleeding.
Is Alprolix Right for Me?
Alprolix is approved for adults and children with hemophilia B for:
- On-demand treatment and control of bleeding episodes
- Managing bleeding around the time of surgery (perioperative management)
- Routine prophylaxis, meaning regular use to lower how often bleeding episodes happen
Alprolix is not approved for immune tolerance induction, a specific approach used for people who develop inhibitors (antibodies that block factor IX from working).
Your health care provider will consider things such as how severe your hemophilia B is, your bleeding history, your age, and how often you’re willing or able to get infusions when deciding whether Alprolix is right for you.
How Do I Use Alprolix?
Alprolix is given as an IV infusion. It’s not a pill, and it’s not injected under the skin. Many people or their caregivers learn to give the infusion themselves at home after training from a health care provider, though it can also be given at a clinic or hospital.
How it’s dosed depends on why you’re using it:
To treat a bleeding episode. Your health care provider will choose a dose based on how severe the bleed is and may have you repeat doses over the following days, as the dose and how often you need it depends on the type and severity of the bleed.
Around surgery. You’ll likely get a dose beforehand to reach a target factor IX level, then your health care provider may continue dosing for several days afterward while you heal.
For routine prevention. Alprolix is usually given once every 7 or 10 days. Your health care provider will determine your dose and dosing schedule based on your age, your weight, and how well the medicine controls bleeding. Children, especially those under 6 years of age, sometimes need more frequent or higher doses because their bodies process the medicine faster than adults do.
Don’t change your dose or schedule on your own. If you think you need it more or less often, talk to your health care provider first.
How Was Alprolix Studied for Hemophilia B?
The main study of Alprolix in adults and adolescents, called B-LONG, enrolled 123 males aged 12 or older with severe hemophilia B who had already been treated with factor IX products in the past. At the start of the study, the participants’ average age was 30 years (ranging from 12 to 71), and many had frequent bleeding before joining the study.
This was an open-label study, meaning everyone knew they were getting Alprolix. There was no placebo group, as withholding factor IX replacement from people with hemophilia B wouldn’t be considered ethical. Instead, participants were assigned to one of many approaches based on their usual care: weekly prophylaxis, prophylaxis with a longer, adjustable interval between doses, on-demand treatment for bleeds as they happened, or use around surgery. A smaller group within the study also had their factor IX levels measured over time after getting a standard factor IX product and, separately, after getting Alprolix to directly compare how long each stayed active in the body.
A related study, called Kids B-LONG, looked at Alprolix in 30 boys younger than 12 years who had also been treated with factor IX products before. Half were younger than 6 years. All of them used weekly prophylaxis and were followed for about a year.
What Are the Main Benefits of Alprolix Based on Studies?
In the B-LONG study, people using weekly prophylaxis had their annualized bleeding rate (the number of bleeding episodes expected per year) drop by 83%. People using the longer, adjustable-interval regimen had theirs drop by 87%, compared with people using on-demand treatment only.
Alprolix also worked well to stop bleeding episodes once they started. About 90% of bleeding episodes were resolved with a single infusion. During major surgeries, health care providers rated how well Alprolix controlled bleeding as excellent or good every time.
Alprolix’s half-life was significantly longer than that of standard factor IX (about 82 hours, compared with about 34 hours). Because of this, more than half of the people in the adjustable-interval group were able to space their doses 14 days or more apart during the last few months of the study.
Your results may differ from what was seen in clinical studies.
Are There Additional Benefits of Alprolix Based on Studies?
In Kids B-LONG, no children developed factor IX inhibitors, and their annualized bleeding rate was low, with a median of about two bleeding episodes a year. About a third of the children had no bleeding episodes at all during the study, and about two-thirds had no bleeding into a joint. Alprolix’s half-life in children was shorter than in adults (at about 69 hours) but still much longer than standard factor IX.
How Long Were the Studies? Is There Longer-Term Data?
The main comparison periods in B-LONG and Kids B-LONG lasted less than two years. To learn more about long-term use, 120 people who completed either study (93 from B-LONG and 27 from Kids B-LONG) went on to an extension study called B-YOND. Some participants stayed in B-YOND for up to five years, adding up to a cumulative treatment time of as long as 6.5 years across both studies.
During B-YOND, no one developed a factor IX inhibitor. Bleeding rates stayed low, and most people kept the longer dosing intervals they’d reached in the earlier studies. On average, adults using the adjustable-interval regimen were able to space doses about every two weeks, while children using that same approach averaged about every 10 days.
Other Considerations
Alprolix has also been studied in children with hemophilia B who had never been treated with any factor IX product before, in a study called PUPs B-LONG. Most of these children were under 1 year old at the start. Alprolix helped prevent and control bleeding in this group as well, though one child developed a low-level factor IX inhibitor during the study. Inhibitors and other side effects are covered in detail in the companion article on Alprolix side effects and interactions.
How Do I Get Alprolix? Is Cost Assistance Available?
Alprolix requires a prescription, typically from a hematologist or a health care provider at a hemophilia treatment center.
A copay savings program may be available from the manufacturer to help lower what you pay out of pocket. Whether you qualify may depend on the type of insurance you have. Visit the manufacturer’s website for current details on cost-assistance options, or ask your health care provider’s office if they can help you get connected.