Objective:
To analyse real-world FIX dosing and treatment interval patterns. A secondary objective was to compare the observed dosing patterns with the dosing regimens for FIX products evaluated in clinical studies.
Methods:
A retrospective analysis was conducted using aggregate Specialty Pharmacy Provider (SPP) records from 2012 through Q12014. SPP data included 63 different attributes for each prescription, including trade name, NDC, quantity shipped, prescribed infusion dose, days supplied, and dose frequency. Patients were considered eligible for the analysis if they received a shipment of any FIX product. Patients were excluded from the analysis if they were being treated episodically, for immune tolerance induction, or their pharmacy records did not specify a prescribed infusion dose. Patients with missing or extremely abnormal weights were also excluded. The patient’s weekly consumption was calculated for each shipment record by multiplying the prescribed infusion dose by the dose frequency and dividing the product by the patient’s weight, resulting in the patient’s average weekly prescribed dose (IU/kg/week). Patients were also categorized according to dosing interval.
Summary:
The analysis included 118 hemophilia B patients with a median age of 20 (range: 2-63) and median weight of 55.4 kg (range: 9.5-129 kg). Pharmacy dispensing records represented 78 distinct prescribers across 29 states. FIX therapies evaluated included Benefix®, Alphanine®, Mononine®, and Rixubis®. The average weekly consumption across all therapies was 139.0 IU/kg/week (95% CI, 128.7-150.3). Dosing frequency ranged from every other day to once weekly. Twice weekly was the most common dosing interval, representing 56.8% of patient records. According to clinical trial data and FDA labelled dosing for FIX therapies, lower weekly consumption may be expected. For BeneFIX the mean weekly consumption was 80.6 IU/kg, 40.3 IU/kg administered twice-weekly. For Rixubis the mean weekly consumption was 88.9 IU/kg, 49.4 IU/kg administered 1.8 times/week and a US dosing recommendation of 40-60 IU/kg dosed twice-weekly. Two prophylactic regimens have been evaluated for AlprolixTM. In the last 3 months of B-LONG, in the weekly prophylaxis arm, the overall median dose on study was 40.5 IU/kg. The individualized interval prophylaxis arm had a median weekly dose of 50.0 IU/kg, 100 IU/kg administered every 14 days. No real world dosing is available for Alprolix due to its recent approval.
Conclusions:
Dosing regimens evaluated in the real world for conventional FIX products indicate greater consumption than reported in clinical trials. This may result in unpredictability for payers who are responsible for healthcare budgets.