Real-world experience of rIX-FP prophylaxis at dosing intervals of up to 14 days in a pediatric patient with hemophilia B during the COVID-19 pandemic

ABSTRACT

Background: rIX-FP, a recombinant factor IX (rFIX) linked with recombinant human albumin, has demonstrated efficacy in prophylactic regimens up to every 21 days in patients with hemophilia B. Aims: To describe real world experience for a rural pediatric patient during the COVID-19 pandemic. Methods: Demographic, clinical (HEAD-US and Hemophilia Joint Health Score) and pharmacokinetic (PK) data were collected for up to one year following a switch from rFIX to rIX-FP. Results: In May 2018, a 3-year-old patient (moderate hemophilia B, FIX 2.7 IU/dL) experienced hemarthrosis in the left knee and initiated prophylaxis with rFIX (40 IU/kg 2×/week). In March 2020, the patient switched to weekly rIX-FP prophylaxis (40 IU/kg), due to difficulties with venous access and accessing the clinic during the pandemic. Trough levels of 7.7% two weeks post-infusion and 5.1% 20 days post-infusion were maintained. Functional and joint assessment on day 90 of rIX-FP treatment showed no change, and no FIX inhibitors developed. On day 95 of treatment, a post-traumatic otorrhagia subsided after a single 40 IU/kg dose of rIX-FP. On day 120, the treatment interval was extended to 10 days without complications. After 160 days, the patient was diagnosed with an asymptomatic SARS-CoV-2 infection and self-isolated at home for 14 days with no changes to prophylactic treatment. On day 200, after a new PK study (trough levels of 6.9% at 14 days post-infusion), the prophylaxis interval was prolonged to 70 IU/kg every 14 days without incident. With 14-day dose intervals, monthly consumption reduced by 56.2% and the number of infusions by 75% compared with the initial rFIX treatment, without affecting efficacy or adherence. Conclusions: Switching to rIX-FP in this pediatric patient reduced the number of administrations and clinic visits without affecting efficacy or adherence, a fact that is relevant in the current context of the pandemic.