JOIN-us, a low-interventional study aiming to prospectively describe the overall joint health in patients with hemophilia prophylactically treated with recombinant factor VIII Fc fusion protein (rFVIIIFc) or recombinant factor IX Fc fusion protein (rFIXFc), is estimated to begin on June 2023.

JOIN-us will enroll approximately 250 participants aged 6 years or older with a confirmed diagnosis of hemophilia A or B.

Participants will receive efmoroctocog alfa or eftrenonacog alfa according to usual clinical practice. At baseline and at the end of study visits, participants will be assessed using the Haemophilia Joint Health Score and patient questionnaires.

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In addition, the study comprises 6 monthly visits over a period of 18 months where participants will undergo a Haemophilia Early Arthropathy Detection with Ultrasound (HEAD-US) protocol.

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The primary outcome measure of JOIN-us is the change from baseline in total HEAD-US score up to month 18 (end of study).

Secondary objectives include the change from baseline in HEAD-US score for hypertrophic synovium, cartilage, and bone; the change from baseline in total Haemophilia Joint Health Score; the number and location of target joints; total, joint, target joint, and traumatic/spontaneous annualized bleeding rates; Patient-Reported Outcomes Measurement Information System measures; and International Physical Activity Questionnaire-Short Form.

Participants must have at least 6 months documented prestudy treatment data regarding treatment prescriptions and bleeding episodes prior to the baseline visit and previous treatment for hemophilia with any marketed recombinant and/or plasma-derived FVIII or FIX concentrate. Moreover, they must have initiated prophylactic treatment with rFVIIIFc or rFIXFc prior to study enrollment or latest at the baseline visit.

Exclusion criteria for JOIN-us include any medical condition that in the opinion of the investigator makes the subject patient unsuitable for inclusion, prophylactic treatment with nonfactor therapy during the 6 months prior to enrollment, and presence of factor VIII or FIX inhibitors at the latest available inhibitor test.

The study is sponsored by Swedish Orphan Biovitrum, in collaboration with Syneos Health. The estimated study completion date is December 2025.


An 18-month low-interventional study to assess joint health in haemophilia A and B patients on prophylaxis with efmoroctocog alfa or eftrenonacog alfa (JOIN-us). May 12, 2023. Accessed May 22, 2023.