Once‐weekly prophylactic treatment vs. on‐demand treatment with nonacog alfa in patients with moderately severe to severe haemophilia B

<jats:sec><jats:title>Introduction</jats:title><jats:p>Limited data are available on optimal prophylaxis regimens of factor <jats:styled-content style="fixed-case">IX</jats:styled-content> (<jats:styled-content style="fixed-case">FIX</jats:styled-content>) replacements for patients with haemophilia B.</jats:p></jats:sec><jats:sec><jats:title>Aim</jats:title><jats:p>This multicentre, open‐label study evaluated the efficacy and safety of once‐weekly prophylaxis with nonacog alfa compared with on‐demand treatment in adolescent and adult patients.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>Males aged 12–65 years with moderately severe to severe haemophilia B (<jats:styled-content style="fixed-case">FIX</jats:styled-content>:C ≤ 2%) were eligible for enrolment. Patients received on‐demand treatment for 26 weeks, followed by once‐weekly prophylaxis of 100 IU kg<jats:sup>−1</jats:sup> for 52 weeks. The primary efficacy end point was the annualized bleeding rate (<jats:styled-content style="fixed-case">ABR</jats:styled-content>). Secondary end points included response to on‐demand treatment, the number of infusions used to treat bleeding events, and the incidence of less‐than‐expected therapeutic effect (<jats:styled-content style="fixed-case">LETE</jats:styled-content>). <jats:styled-content style="fixed-case">FIX</jats:styled-content>:C was measured on day 1 and at weeks 26 and 78.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Mean (±<jats:styled-content style="fixed-case">SD</jats:styled-content>) <jats:styled-content style="fixed-case">ABR</jats:styled-content> was lower during prophylaxis vs. on‐demand treatment [3.6 (±4.6) vs. 32.9 (±17.4) events, respectively; <jats:italic>P </jats:italic><<jats:italic> </jats:italic>0.0001]. The majority (88.4%) of bleeding events had excellent or good responses upon the first infusion; 82.1% of events responded to the first infusion. No incident of <jats:styled-content style="fixed-case">LETE</jats:styled-content> occurred. No thrombotic events or <jats:styled-content style="fixed-case">FIX</jats:styled-content> inhibitors were reported. Eight of 17 <jats:styled-content style="fixed-case">FIX</jats:styled-content>:C approximately 1 week after dosing were >2 IU dL<jats:sup>−1</jats:sup> (min–max of 2.13–10.39 IU dL<jats:sup>−1</jats:sup>).</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>Once‐weekly prophylaxis of 100 IU kg<jats:sup>−1</jats:sup> was associated with lower <jats:styled-content style="fixed-case">ABR</jats:styled-content> compared with on‐demand treatment in adolescents and adults with moderately severe to severe haemophilia B. Once‐weekly prophylaxis was well tolerated, with a similar safety profile as that reported during the on‐demand treatment period. Residual <jats:styled-content style="fixed-case">FIX</jats:styled-content>:C may be supportive of effectiveness.</jats:p></jats:sec>