The study, “Real‐world data demonstrate improved bleed control and extended dosing intervals for patients with haemophilia B after switching to recombinant factor IX Fc fusion protein (rFIXFc) for up to 5 years,” was published in the journal Haemophilia.
Sanofi Genzyme‘s Alprolix was the first approved extended half-life (EHL) factor IX (FIX) therapy, aimed at easing the need for replacement factor infusions. In clinical trials, EHL therapies such as Alprolix provided superior long-term protection (prophylaxis) against bleeding episodes.
While those results were encouraging, the relatively controlled settings of clinical trials do not fully capture a therapy’s effects among the broader patient populations in the real-world setting.
To address this gap, researchers across the U.S. conducted a Sanofi-funded review of the medical charts of hemophilia B patients who had received Alprolix either on-demand or prophylactically for at least six months.
The team, which included scientists at Sanofi, identified 64 patients with a median age of 22 (range, 2-to-78 years), the majority of whom (59%) had severe hemophilia. Among the rest, 27% of patients had moderate hemophilia and 14% had mild disease. The median follow-up time was 2.7 years.
Most patients began Alprolix after Phase 3 trials were completed. Seven participants had received the therapy before it had become commercially available, as they took part in the B-LONG (NCT01027364) and Kids B-LONG (NCT01440946) studies, as well as the B-YOND extension trial (NCT01425723).
All 34 patients who had taken preventative FIX therapy continued to use Alprolix in the same regimen. Of the 29 patients taking on-demand FIX replacement therapy, 19 switched to Alprolix prophylaxis and the other 10 switched to the therapy on-demand. Pre-Alprolix treatment data were missing for one patient.
Treatment with Alprolix was associated with fewer infusions, less factor consumption, better bleeding control, and stable if not better adherence to therapy.
Nearly 90% of those going from on-demand replacement therapy to prophylactic Alprolix maintained or lengthened their dosing intervals. Similarly, 81% of patients with specified pre-Alprolix dosing schedules lengthened their dosing interval after switching to the treatment. The remaining 19% maintained their schedule.
Once prophylactic Alprolix treatment began, most patients (74%) maintained a stable dosing schedule of once per week to once every two weeks. Approximately 17% lengthened their schedule from once weekly to every two weeks, while 9% shortened their schedule to a once-weekly regimen.
Weekly factor consumption after changing to Alprolix declined by approximately 50%, regardless of disease severity. Once using Alprolix, no further change in use was seen.
By the end of the review period, patients of all ages with severe disease used a median of 55 international units per kilogram (IU/kg) per week, and those with moderate condition used 58.5 IU/kg per week. This translated to declines of 44 IU/kg in people with severe hemophilia and 68.5 IU/kg in those with moderate disease.
Bleeding events declined with Alprolix use, including spontaneous and joint bleeds. By the review’s end, 32% of recurrent joint bleeds had resolved among patients on preventive Alprolix, while 47% of the on-demand patients who switched to preventive treatment reported no joint bleeds.
Compliance data showed that all but one patient adhered at least as well to Alprolix than to their prior replacement therapies.
Longer dosing intervals and improved or maintained compliance may help patients and physicians manage cases better, the researchers said.
The most common reason given for switching to Alprolix, cited by 44% of patients, was to reduce the burden of therapy. Other reasons included poor results with previous therapies, difficulties with injections, and adherence issues.
“These results support the findings of the pivotal trials and add to the pool of evidence supporting [Alprolix] for the treatment of haemophilia B,” the investigators concluded.
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