Patients with hemophilia who require routine prophylaxis may be more adherent to emicizumab than to previous factor or bypass agents, according to a study presented at the American Society of Hematology Annual Meeting and Exposition.

The study aimed to assess adherence rates and examine potential predictors of nonadherence associated with emicizumab treatment outside of clinical trials. Emicizumab is a subcutaneously administered, humanized bispecific monoclonal antibody that was recently approved for hemostatic prophylaxis in patients with hemophilia A with or without factor VIII inhibitors.

For the study, the researchers included 48 patients with moderate-to-severe hereditary hemophilia (FVIII <5%), clinical recommendation for routine prophylaxis, receipt of clinical care and medication from a hemophilia treatment center (HTC), at least 12 months of prior exposure to factor or bypass products, and at least 3 months of emicizumab treatment. For patients previously enrolled in clinical trials, adherence data were collected from the time of first commercial product administration.

At the time of the study, patients had a median duration on emicizumab of 7 months. Seventy-seven percent of patients were dosed with weekly administration. Of the patients who had severe hemophilia, 42% had a history of inhibitor and 25% were previously enrolled in an emicizumab interventional trial. Prior to emicizumab initiation, 46% of patients had 5 or more self-reported annualized bleeds. The most common reasons for emicizumab initiation were patient preference, followed by breakthrough bleeding, difficult venipuncture, and shortened factor half-life.

According to the data, adherence to emicizumab was 89% among the 12 patients who previously received only on demand treatment. Among the 36 patients who previously received routine prophylaxis, their adherence was significantly higher on emicizumab (98%) than factor/bypass products (89%) (p=0.002). The study showed that 38% of these patients had factor/bypass adherence less than 75% (or refused prophylaxis) and 4% of patients had emicizumab adherence less than 75%.

The researchers also assessed factors related to increased emicizumab nonadherence. Overall, age group demonstrated the strongest association, with young and older adult patients exhibiting greater non-adherence than children and adolescents. Additionally, active inhibitor and prior factor/bypass non-adherence were also significantly associated with increased emicizumab nonadherence.

Overall, the study found that patients with hemophilia were more likely to be adherent to emicizumab than previous factor or bypass agents.

“Given the long half-life of the drug, the significance of non-perfect adherence on bleeding outcomes needs to be studied prospectively with longer clinical follow-up,” the researchers concluded.

Reference

Li A, Goodfriend C, Sokol J, et al. Patterns and predictors of emicizumab adherence in people with hemophilia [abstract]. Presented at: ASH Annual Meeting & Exposition. December 7, 2019. Orlando, Florida.