Idelvion Helps Hemophilia B Patients Adhere to Prophylactic Treatment, Studies Show

Treatment with Idelvion (rIX-FP) helps children and adults with hemophilia B stick to prophylactic dosing schedules by reducing treatment burden, according to a study using clinical trial and real-world data.

The study, “High adherence to prophylaxis regimens in haemophilia B patients receiving rIX‐FP: Evidence from clinical trials and real‐world practice,” was published in the journal Haemophilia.

Prophylaxis, or preventive treatment, is standard for hemophilia patients and is associated with significantly improved medical outcomes compared to on-demand therapy. Adherence to treatment schedules is essential to achieve these outcomes and prevent bleeding episodes.

Clinical studies have shown that prophylaxis with recombinant FIX therapies can reduce bleeding rates by up to 91%, compared to on-demand treatment. However, prophylaxis can be more challenging than on-demand treatment. Patients who fail to adhere to prophylactic regimens often cite time commitment and inconvenience as their greatest challenges.

Idelvion (marketed by CSL Behring) is a long-acting fusion protein linking recombinant factor IX (rFIX) and albumin, the most abundant protein in blood plasma. FIX is the blood clotting protein missing or defective in people with hemophilia.

As an extended half-life product, Idelvion is thought to improve adherence to prophylactic therapy by maintaining higher therapeutic levels of FIX over a longer period of time and reducing the frequency of infusions.

To better understand such benefits, an international team of researchers evaluated treatment adherence across two CSL Behring-sponsored Phase 3 clinical trials (NCT01496274 and NCT01662531) and patient-reported real-world data.

The team analyzed adherence to 7-, 10-, and 14-day dosing regimens with Idelvion being given at 75 international units (IU)/kg, after the first six months with weekly doses within 35–50 IU/kg. Prophylaxis adherence was defined as receiving a minimum of 80% of the expected number of injections, and dose adherence as receiving within 10% of the prescribed dose at least 80% of the time. Prophylactic rates were compared to a separate group of patients receiving on-demand therapy for the initial six months.

Among patients 12 and older in clinical studies, treatment adherence was higher on the seven-day schedule (at 95%) than on the 10-day (85.7%) or the 14-day regimen (81%).

In particular, adherence was highest when infusions could be scheduled on the same day of the week, resulting in 97.5% adherence on the seven-day schedule and 100% adherence on the 14-day schedule. A comparatively lower proportion of patients — 85.7% — maintained proper adherence while on the 10-day regimen, although this reflects the fact that one of the seven patients in this group did not meet the definition of adherence, the team said.

The proportion of adherent patients in on-demand treatment for six months was relatively low, at 52.2% (12 of 23 patients). Nineteen of these patients later switched to a seven-day prophylactic schedule, which boosted their adherence to 84.2%.

All 27 of the children under 12 generally adhered to a seven-day regimen, with a mean adherence rate of 97.9%.

Outside of clinical trials, the team analyzed data from 36 patients at three treatment centers. The group included seven patients treated at the Rush Hemophilia and Thrombophilia Center, in the U.S., 14 treated at the Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, in Italy, and 15 patients at the Hemophilia Center University Clinic Bonn, in Germany.

Real-world data from medical practices provide an important comparison to data from clinical studies, as patients deemed unable to adhere to such schedules may be excluded from these studies, the researchers said. Also, the regular monitoring of patients in a trial may help increase adherence, thereby not reflecting what may happen in clinical practice.

Adherence rates to treatment regimens was 57.1% at Rush and 100% at the two other centers. The relatively low rate at the U.S. center occurred because one patient lost their insurance, one had insurance with a company that did not cover the therapy, while the parents of another patient lacked time and communication to motivate their child to adhere to treatment.

Despite the low numbers of patients surveyed, results suggest that the patient-reported adherence seen in clinical studies is possible to achieve in real-world settings, the investigators said.

In all cases, adherence to treatment regimens resulted in low bleeding rates.

“In clinical studies, patients with haemophilia B had high adherence rates to rIX‐FP [Idelvion] prophylaxis regimens with a variety of dosing intervals, enabling them to achieve very low bleeding rates,” the scientists wrote. “Initial data from haemophilia treatment centres confirm high adherence to rIX‐FP prophylaxis regimens in real‐world practice.”