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FDA Approves Updated Altuviiio Label With Expanded Pediatric Data Confirming Highly Effective Bleed Protection in Children With Hemophilia

Paris, May 10, 2024 — The US Food and Drug Administration (FDA) has updated the label for Altuviiio® [Antihemophilic Factor (Recombinant), Fc-VWF-XTEN Fusion Protein-ehtl] to include full results from the phase 3 XTEND-Kids study showing that once-weekly dosing with Altuviiio delivers highly effective bleed protection in children with hemophilia A.

Altuviiio was first approved in February 2023 for adults and children with hemophilia A for routine prophylaxis and on-demand treatment to control bleeding episodes as well as for perioperative management (surgery). This label update builds on the interim XTEND-Kids data from 2023 to include full results, which highlight the growing body of clinical evidence for Altuviiio as a proven treatment option for all people with hemophilia A, a rare condition in which the ability of a person’s blood to clot properly is impaired.

Mindy Simpson, MD
Pediatric Hematologist/Oncologist and Assistant Professor of Pediatrics, Rush University Medical Center
“Hemophilia is a lifelong condition, so starting children on an early prophylactic regimen can help them stay ahead of bleeds and reduce other potential complications, such as joint damage and pain. Delivering significant bleed protection with a reduced treatment burden can allow families to spend more time on activities and less time focused on infusion schedules.”

Altuviiio provides effective bleed protection for children
Children with hemophilia typically clear administered factor concentrates in the blood at a higher rate than adults, so multiple injections of factor replacement products per week are often needed. Full results from the XTEND-Kids study reinforce that a once-weekly 50 IU/kg dose of Altuviiio provides highly effective bleed protection in children with hemophilia A.

Altuviiio met the primary endpoint of safety with no factor VIII inhibitor development detected (0% [95% confidence interval (CI): 0–4.9]). Key secondary endpoints were also met, including a mean annualized bleeding rate (ABR) of 0.6 (95% CI: 0.4-0.9) and a median ABR of 0.0 (interquartile range [IQR] 0.0-1.0) in the study of 72 patients evaluable for efficacy.

Altuviiio demonstrated a safety profile in XTEND-Kids similar to that shown in the XTEND-1 trial. No serious allergic reactions, anaphylaxis, or embolic or thrombotic events were reported. Although no inhibitors were detected in the XTEND-Kids study or reported in post-market surveillance to date, the formation of inhibitors and allergic reactions are possible when taking Altuviiio. The most common adverse drug reaction (>10%) was fever (pyrexia). No adverse events led to treatment discontinuation.

About Altuviiio®
Altuviiio [Antihemophilic Factor (Recombinant), Fc-VWF-XTEN Fusion Protein-ehtl] is a first-in-class high-sustained factor VIII therapy that is designed to extend protection from bleeds with once-weekly prophylactic dosing for adults and children with hemophilia A. In adults and adolescents, Altuviiio has a 3- to 4-fold longer half-life relative to standard and extended half-life factor VIII products. Once-weekly treatment with Altuviiio provides high-sustained factor activity levels within the normal to near-normal range for most of the week in adults and for approximately three days in children. Altuviiio is the first factor VIII therapy that has been shown to break through the von Willebrand factor ceiling, which imposes a half-life limitation on other factor VIII therapies. Altuviiio builds on the innovative Fc fusion technology by adding a region of von Willebrand factor and XTEN polypeptides to extend its time in circulation. To learn more, visit

Granted Breakthrough Therapy designation by the FDA in May 2022—the first factor VIII therapy to receive this designation —Altuviiio also received Fast Track designation in February 2021 and Orphan Drug designation in August 2017. The European Commission granted Orphan Drug designation in June 2019. The European Medicines Agency’s Committee for Medicinal Products for Human Use has adopted a positive opinion for efanesoctocog alfa in a similar indication for patients with hemophilia.

About the XTEND Clinical Programs
The XTEND clinical program is comprised of two phase 3 trials in hemophilia A: XTEND-1 in people 12 years or older and XTEND-Kids in children younger than 12 years. There is also an ongoing extension study (XTEND-ed).

The phase 3 XTEND-1 study (NCT04161495) was an open-label, nonrandomized interventional study assessing the safety, efficacy, and pharmacokinetics of once-weekly Altuviiio in people 12 years of age or older (n=159) with severe hemophilia A who were previously treated with factor VIII replacement therapy. The study consisted of two parallel treatment arms: the prophylaxis Arm A (n=133), in which patients who had received prior factor VIII prophylaxis were treated with once-weekly intravenous Altuviiio prophylaxis (50 IU/kg) for 52 weeks, and the on-demand Arm B (n=26), in which patients who had received prior on-demand factor VIII therapy began with 26 weeks of on-demand Altuviiio (50 IU/kg), then switched to once-weekly prophylaxis with Altuviiio (50 IU/kg) for an additional 26 weeks.

The primary efficacy endpoint of XTEND-1 was the mean annualized bleeding rate (ABR) in Arm A, and the key secondary endpoint was an intra-patient comparison of ABR during the Altuviiio weekly prophylaxis treatment period versus the prior factor VIII prophylaxis ABR for a subset of participants in Arm A who had participated in a previous observational study (Study 242HA201/OBS16221).

The XTEND-Kids study (NCT04759131) was an open-label, nonrandomized interventional study of the safety, efficacy, and pharmacokinetics of once-weekly Altuviiio in previously treated patients younger than 12 years with severe hemophilia A. Patients (n=74) received once-weekly Altuviiio prophylaxis (50 IU/kg) for 52 weeks. The primary endpoint was the occurrence of inhibitor development.


Altuviiio® [antihemophilic factor (recombinant), Fc-VWF-XTEN fusion protein-ehtl] is an injectable medicine that is used to control and reduce the number of bleeding episodes in people with hemophilia A (congenital Factor VIII deficiency).

Your healthcare provider may give you Altuviiio when you have surgery.


What is the most important information I need to know about Altuviiio?
Do not attempt to give yourself an injection unless you have been taught how by your healthcare provider or hemophilia center. You must carefully follow your healthcare providers instructions regarding the dose and schedule for injecting Altuviiio so that your treatment will work best for you.

Who should not use Altuviiio?
You should not use Altuviiio if you have had an allergic reaction to it in the past.

What should I tell my healthcare provider before using Altuviiio?
Tell your healthcare provider if you have had any medical problems, take any medications, including prescription and non-prescription medicines, supplements, or herbal medicines, are breastfeeding, or are pregnant or planning to become pregnant.

What are the possible side effects of Altuviiio?
You can have an allergic reaction to Altuviiio. Call your healthcare provider or emergency department right away if you have any of the following symptoms: difficulty breathing, chest tightness, swelling of the face, rash, or hives.

Your body can also make antibodies called “inhibitors” against Altuviiio. This can stop Altuviiio from working properly. Your healthcare provider may give you blood tests to check for inhibitors.

The common side effects of Altuviiio are headache and joint pain.

These are not the only possible side effects of Altuviiio. Tell your healthcare provider about any side effect that bothers you or does not go away.

Please see full Prescribing Information.

About Hemophilia A
Hemophilia A is a rare condition in which the ability of a person’s blood to clot properly is impaired, leading to excessive and spontaneous bleeds into joints that can result in joint damage and chronic pain, and potentially impact quality of life. Disease severity is determined by the level of clotting factor activity in a person’s blood, meaning there is a negative correlation between bleeding risk and factor activity levels.

About the Sanofi and Sobi collaboration
Sobi and Sanofi collaborate on the development and commercialization of Alprolix® and Elocta®/Eloctate®. The companies also collaborate on the development and commercialization of efanesoctocog alfa, or Altuviiio in the US Sobi has final development and commercialization rights in the Sobi territory (essentially Europe, North Africa, Russia and most Middle Eastern markets). Sanofi has final development and commercialization rights in North America and all other regions in the world excluding the Sobi territory.

About Sobi®
Sobi is a specialised international biopharmaceutical company transforming the lives of people with rare and debilitating diseases. Providing reliable access to innovative medicines in the areas of haematology, immunology and specialty care, Sobi has approximately 1,800 employees across Europe, North America, the Middle East, Asia and Australia. In 2023, revenue amounted to SEK 22.1 billion. Sobi’s share (STO:SOBI) is listed on Nasdaq Stockholm. More about Sobi at, LinkedIn and YouTube.

About Sanofi
We are an innovative global healthcare company, driven by one purpose: we chase the miracles of science to improve people’s lives. Our team, across some 100 countries, is dedicated to transforming the practice of medicine by working to turn the impossible into the possible. We provide potentially life-changing treatment options and life-saving vaccine protection to millions of people globally, while putting sustainability and social responsibility at the center of our ambitions.

Sanofi Forward-Looking Statements
This press release contains forward-looking statements as defined in the Private Securities Litigation Reform Act of 1995, as amended. Forward-looking statements are statements that are not historical facts. These statements include projections and estimates regarding the marketing and other potential of the product, or regarding potential future revenues from the product. Forward-looking statements are generally identified by the words “expects”, “anticipates”, “believes”, “intends”, “estimates”, “plans” and similar expressions. Although Sanofi’s management believes that the expectations reflected in such forward-looking statements are reasonable, investors are cautioned that forward-looking information and statements are subject to various risks and uncertainties, many of which are difficult to predict and generally beyond the control of Sanofi, that could cause actual results and developments to differ materially from those expressed in, or implied or projected by, the forward-looking information and statements. These risks and uncertainties include among other things, unexpected regulatory actions or delays, or government regulation generally, that could affect the availability or commercial potential of the product, the fact that product may not be commercially successful, the uncertainties inherent in research and development, including future clinical data and analysis of existing clinical data relating to the product, including post marketing, unexpected safety, quality or manufacturing issues, competition in general, risks associated with intellectual property and any related future litigation and the ultimate outcome of such litigation, and volatile economic and market conditions, and the impact that pandemics or other global crises may have on us, our customers, suppliers, vendors, and other business partners, and the financial condition of any one of them, as well as on our employees and on the global economy as a whole. The risks and uncertainties also include the uncertainties discussed or identified in the public filings with the SEC and the AMF made by Sanofi, including those listed under “Risk Factors” and “Cautionary Statement Regarding Forward-Looking Statements” in Sanofi’s annual report on Form 20-F for the year ended December 31, 2023. Other than as required by applicable law, Sanofi does not undertake any obligation to update or revise any forward-looking information or statements.

Source: Sanofi

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