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Pediatric Study - Results

No Factor VIII inhibitors were detected during the XTEND-Kids study1*

Primary endpoint: Incidence of neutralizing antibodies to Factor VIII2


0.0% (95% Cl: 0.0-4.9)2

Formation of inhibitors to Factor VIII is possible following administration of ALTUVIIIO.1

* Defined as an inhibitor of ≥0.6 BU/mL and confirmed by a second test result from a separate sample drawn 2 to 4 weeks following the date of the original sample.2

Effective bleed protection with a once-weekly infusion1

In the XTEND-Kids trial:

ALTUVIIIO demonstrated proven bleed protection in children <12 years (n=72)*


0.0 Median ABR
(Q1, Q3: 0.0, 1.0)


0.6 Mean ABR
(95% Cl: 0.4-0.9)

* Based on treated bleeds.

Most patients experienced zero bleeds when treated with ALTUVIIIO prophylaxis1

In the XTEND-Kids trial*:


Zero bleeds

63.9% of patients (n=46/72) had zero bleeds


Zero spontaneous bleeds

87.5% of patients (n=63/72) had zero spontaneous bleeds


Zero joint bleeds

83.3% of patients (n=60/72) had zero joint bleeds

* Based on treated bleeds.

Effective on-demand bleed management with only 1 infusion1

Treatment of bleeding episodes in the XTEND-Kids trial1,2

To be filled

95.3% of bleeds* resolved with 1 infusion (n=41/43)

* Percentage based on the number of treated bleeding episodes in the sensitivity analysis set, which excluded two patients.1,2

Excellent perioperative response across both XTEND-1 and XTEND-Kids trials1

The hemostatic response of ALTUVIIIO was deemed “Excellent/Good*” by the investigator surgeon in:

To be filled.

100% of major surgeries†‡ (n=14/14)

14 major surgeries in 13 subjects (10 adults and 3 children)

* Hemostatic response during major surgery was assessed using the International Society on Thrombosis and Haemostasis (ISTH) 4-point response scale: excellent, good, moderate, or poor/none. Based on pooled data from XTEND-1 and XTEND-Kids.1
Defined as any surgical procedure, either elective or emergent, that usually involves general anesthesia and/or respiratory assistance, in which a major body cavity is penetrated and exposed, or a substantial impairment of physical or physiological functions is produced. Major surgeries include major orthopedic procedures such as arthroplasties; joint replacements of the knee, hip, and elbow; joint revisions; and ankle fusions. Other major surgeries include molar-tooth extractions, dental restoration and tooth extraction, circumcision, and rhinoplasty/mentoplasty.1,2
Median preoperative dose per surgery was 50 IU/kg (range: 12.7-61.9).1


Safety from the pediatric study

Find out more about the ALTUVIIIO safety profile in the XTEND-Kids clinical trial.


Learn the mechanism of ALTUVIIIO

Discover more about this high sustained factor therapy in pediatric patients.


ALTUVIIIO® [antihemophilic factor (recombinant), Fc-VWF-XTEN fusion protein-ehtl] is a von Willebrand Factor (VWF) independent recombinant DNA-derived, Factor VIII concentrate indicated for use in adults and children with hemophilia A (congenital factor VIII deficiency) for:

  • Routine prophylaxis to reduce the frequency of bleeding episodes
  • On-demand treatment & control of bleeding episodes
  • Perioperative management of bleeding
Limitation of Use

ALTUVIIIO is not indicated for the treatment of von Willebrand disease.

Important Safety Information

ALTUVIIIO is contraindicated in patients who have had severe hypersensitivity reactions, including anaphylaxis, to the product or its excipients.

Warnings and Precautions
  • Allergic-type hypersensitivity reactions, including anaphylaxis, may occur with ALTUVIIIO. Allergic-type hypersensitivity reactions were not reported in the clinical trials. Advise patients to discontinue use of ALTUVIIIO if hypersensitivity symptoms occur and contact a physician and/or seek immediate emergency care.
  • Formation of neutralizing antibodies (inhibitors) to Factor VIII are possible following administration of ALTUVIIIO. Neutralizing antibodies were not reported in the clinical trials. Monitor all patients for the development of Factor VIII inhibitors by appropriate clinical observations and laboratory tests.
  • If assessment of plasma Factor VIII activity is needed, it is recommended to use a validated one-stage clotting assay. The ALTUVIIIO Factor VIII activity level is overestimated by the chromogenic assay and a specific ellagic acid-based aPTT reagent in one-stage clotting assay by approximately 2.5-fold. If these assays are used, divide the result by 2.5 to approximate the patient's ALTUVIIIO Factor VIII activity level.
Adverse Reactions

The most common adverse reactions (>10% of subjects) reported in clinical trials were headache and arthralgia.

IndicationImportant Safety Information

ABR=annualized bleed rate; BU=Bethesda unit; CI=confidence interval; IU=international unit; Q1=25th percentile; Q3=75th percentile.

References: 1. ALTUVIIIO Prescribing Information. Bioverativ Therapeutics Inc. Waltham, MA. 2. Malec L, et al. Efanesoctocog Alfa Prophylaxis for Previously Treated Patients <12 Years of Age With Severe Hemophilia A. Oral presentation at: 2023 International Society on Thrombosis and Haemostasis (ISTH); June, 2023; Montreal, Canada.

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MAT-US-2403559-v1.0-05/2024 Last Updated: May 2024