Alprolix for Hemophilia B

Alprolix is an approved recombinant DNA-derived coagulation factor IX concentrate for people with hemophilia B. Biogen initially developed Alprolix and spun off Bioverativ Therapeutics to further develop the therapy. Sanofi then acquired Bioverativ.

Alprolix is used as an on-demand treatment to control bleeding episodes, for the management of bleeding during surgery, and as a routine preventive treatment (prophylaxis) to lower the frequency of bleeding episodes.

How does Alprolix work?

Alprolix is the first recombinant clotting factor IX therapy with prolonged circulation in the body. It was developed using Fc fusion technology. Fc fusion technology combines factor IX to the Fc portion of immunoglobulin G subclass 1 (IgG1). This enables Alprolix to use a naturally occurring pathway to remain in the body longer.

Some proteins in the blood, such as clotting factors, break down with time. Alprolix uses a natural process to delay this breakdown through three steps: binding, redirecting, and recirculating the clotting factor.

Alprolix in clinical trials

Several Phase 3 clinical trials studied Alprolix. One trial (NCT01027364), called B-LONG, studied the effects of injected Alprolix in 123 males aged 12 and older for prophylaxis, treatment of current bleeding episodes, or treatment prior to surgery. The results of the study, published in the New England Journal of Medicine, showed that 90% of bleeding episodes stopped with one treatment of Alprolix. The study also found that patients tolerated the treatment well, with none of them developing inhibitors against it. Adverse event levels were consistent with other hemophilia treatments.

Another open-label Phase 3 trial (NCT01440946), Kids B-LONG, studied 30 boys aged 16 and younger with hemophilia B. Investigators gave the boys weekly infusions of Alprolix for roughly 50 weeks. The results of the trial showed that 10 out of the 30 participants reported no bleeding during the trial period, and 19 had no joint bleeding.

A Phase 3 extension trial (NCT01425723) called B-YOND investigated the long-term effects of Alprolix in 116 patients who took part in the B-LONG and the Kids B-LONG trials. Patients used Alprolix either as a prophylactic or on-demand treatment. The results showed that Alprolix was well tolerated and effective as a long-term prophylactic. No patients generated inhibitors against the treatment. For on-demand treatment, one to two doses were sufficient to control 97% of bleeding episodes in adults and adolescents and 95% of bleeding episodes in children.

The three studies all involved patients who had received some form of factor IX product before enrolling. A Phase 3 study (NCT02234310) called PUPs B-LONG investigated Alprolix in previously untreated participants (PUPs) up to age 17 with hemophilia B. The patients received weekly doses of Alprolix until they reached 50 exposure days. The study concluded in August 2019, but results are not yet available.

A non-interventional study (NCT03655340) called B-SURE enrolled 91 participants in France. The aim is to observe how patients use Alprolix for prophylaxis and on-demand treatment for 24 months. The study will measure the annualized bleeding rate (ABR), injection frequency, and amount of factor used in the prophylaxis group. It will also look at the amount of factor and number of injections needed to treat a bleed in the on-demand group. The study has finished recruiting participants, and will be completed in September 2021.

Another observational study (NCT03901755), B-MORE, is currently recruiting patients in Norway and Sweden to evaluate the real-world effectiveness and usage of Alprolix in patients with hemophilia B. Similar to B-SURE, this study will observe patients for 24 months. Investigators will measure the ABR, injection frequency, and amount of factor consumed during the study period. The trial also has sites in Greece, Ireland, Italy, Saudi Arabia, United Arab Emirates, and the U.K. that will start enrolling participants soon. The expected completion date is March 2023.

Other details

The recommended starting treatment dosage for Alprolix is 50 IU per kg once weekly, or 100 IU per kg every 10 days. Doctors can adjust this based on the response of each patient.

Children under age 12 may have higher body weight-adjusted clearance, shorter half-life, and lower recovery of factor IX. Consequently, they may need more frequent administration or a higher dose of the treatment.

Common side effects of Alprolix include anxiety, blurred vision, dizziness, confusion, headache, numbness, itching, chest pain, difficulty breathing, shortness of breath, coughing, difficulty swallowing, nausea, vomiting, pain, tiredness, and weakness.


Last updated: March 5, 2020


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