Trends in Prescribing Practices for Management of Hemophilia

Introduction: Over the past 21 years, treatment options for hemophilia have evolved significantly. The objective of this study is to describe the trends observed in clinician prescribing practices for management of hemophilia A (HA) and B (HB) in the United States (US) via three surveys from 1999-2021.

Methods: We administered surveys to members of the Hemostasis & Thrombosis Research Society (HTRS) via an in-person paper survey at its annual symposia in 1999 and 2015, and an online survey in 2021. The survey participants included physicians, physician assistants, and nurse practitioners who manage the care of hemophilia patients at hemophilia treatment centers in the US. The surveys collected information regarding: 1) characteristics of clinician practice, 2) prescribed clotting factor products and dosages used for routine bleeds or major life-threatening bleeding, total joint replacement, and port placement, 3) reasons for changing doses, 4) frequency of recommendation for prophylaxis and inhibitor treatment for associated factor and non-factor products, and 5) gene therapy.

Results: Forty-one clinicians completed the survey in 1999 and 2021, 53 in 2015. The mean number of patients seen by respondents increased from 142 (range: 0-314) for children and 101 (0-480) for adults in 1999 to 202 (0-900) for children and 154 (0-500) for adults in 2021. The proportion of clinicians prescribing >40 units/kg of Standard Half Life (SHL) Factor IX concentrates for routine bleeding events in HB patients increased from 22.5% in 1999 to 50.9% in 2015, and 87.8% in 2021. The proportion of clinicians reported SHL Factor VIII usage for routine bleeding at a dose of >40 units/kg in HA patients increased from none in 1999 to 11.3% in 2015 and 29.3 % in 2021. The reported rates of prescribing an average >60 units/kg factor to treat major life-threatening bleeds increased from 67.5% in 1999 to 90.3% in 2021 for HB; rates were 2.5% in 1999, 17.3% in 2015 and 7.3% in 2021 for treating HA. For children <4 years old, 22.2% of clinicians prescribed primary prophylaxis all of the time in 1999. This rose to 68.2% in 2015, and 86.5% in 2021. For adults, 12.5% of clinicians prescribed secondary prophylaxis all of the time in 1999, 27.3% in 2015 and 42.5% in 2021. For treatment of patients with HA or HB inhibitors, the proportions of clinicians who reported prescribing immune tolerance induction (ITI) therapy all of the time for pediatric patients were 50%, 75.0% and 63.2% in three surveys, but <25% for adult patients. In the 2021 survey, >91% of clinicians reported prescribing emicizumab to treat HA inhibitors in patients of all ages, while >87% reported prescribing it to treat HA without inhibitor. Clinicians were more likely to always prescribe emicizumab to treat HA patients with inhibitors (63.2% for children and 57.1% for adults), as compared to always prescribing it for those without inhibitors (13.2% for children and 5.7% for adults). The most frequent reported method to treat a patient with a history of inhibitors on emicizumab who had break through bleeds was rFVIIa: 85.4% for children, and 75.6% for adults. The most frequently reported reasons for switching from FVIII to emicizumab were fewer injections/visits (87.8%), and improved patient quality of life (82.9%). Thirty-nine percent of clinicians reported caring for patients currently in gene therapy trials, 27.5% had patients who had completed gene therapy. When asked about potential future prescribing practices, 14.6% reported that they would prescribe gene therapy "all the time", 4.9% would prescribe it "about 3/4 of the time", 29.3% "about 1/2 the time", 29.3% "about 1/4 the time", and 22.0% "rarely or never".

Conclusion: These data indicate changes in prescribing practices among hemophilia specialists in the US over the past 21 years. Prescribing of high doses of factor (>40 units/kg) increased, while ITI prescribing practices remained similar over time. To treat patients with major life-threatening bleeds, a larger proportion of clinicians prescribed high doses of factor (>60 units/kg) for patients with HB as compared to HA. Most clinicians frequently prescribed emicizumab for patients with HA inhibitors, but less frequently for those without inhibitors. At this time, there is wide diversity among clinicians in the expected uptake of gene therapy.