Assessing factor consumption and bleeding outcomes of prophylaxis with 3 commonly prescribed factor IX products for hemophilia B: A retrospective patient medical record analysis in the United States.

BACKGROUND

In the United States, rIX-FP, rFIXFc, and rFIX are approved as treatment options for people with hemophilia B (PwHB). Although clinical trials have demonstrated the efficacy and safety of each product, real-world data can help to understand their use and treatment outcomes in the absence of direct head-to-head trials.

OBJECTIVE

To assess real-world factor IX (FIX) consumption and bleeding outcomes for PwHB receiving rIX-FP, rFIXFc, or rFIX prophylaxis.

METHODS

Retrospective, deidentified medical record information for PwHB with moderate or severe hemophilia B (FIX activity ≤5%) treated with rIX-FP, rFIXFc, or rFIX prophylaxis for at least 12 months was obtained from Hemophilia Treatment Centers in the United States between 2020 and 2023. FIX consumption was calculated using the most recently prescribed dosing frequency and dosage. Annualized bleeding rate (ABR), annualized spontaneous bleeding rate, and annualized joint bleeding rate were calculated based on the number of bleeding events over the observation period. Generalized linear models adjusting for covariates were used to test the statistical significance of the differences of consumption and ABR among the products.

RESULTS

Overall, 213 PwHB (53% with severe disease) aged 12 years and older were included for main analysis, with a mean age (range) of 32.7 (12-84) years. PwHB treated with rIX-FP prophylaxis had significantly lower mean FIX consumption compared with those receiving rFIXFc (45.8 vs 65.4 IU/kg/week; P = 0.0003) and rFIX (95.7 IU/kg/week; P < 0.0001). The mean dosing interval was 10.2, 7.3, and 5.2 days for rIX-FP, rFIXFc, and rFIX, respectively. Mean ABR was significantly lower in PwHB receiving rIX-FP compared with the other 2 products (rIX-FP vs rFIXFc: 1.2 vs 2.1; P = 0.0119; rIX-FP vs rFIX: 1.2 vs 2.3; P = 0.004). Mean annualized spontaneous bleeding rate was 0.4, 1.0, and 0.7 for rIX-FP, rFIXFc, and rFIX, respectively. Mean annualized joint bleeding rate was 0.7, 1.1, and 1.2 for rIX-FP, rFIXFc, and rFIX, respectively. The pattern of results for PwHB of all ages (including those aged <12 years, N = 50) were similar to those reported for PwHB aged 12 years and older. In a subgroup of 16 PwHB who switched to rIX-FP from a previous FIX product, mean FIX consumption was significantly reduced after switching to rIX-FP (49.0 vs 94.2 IU/kg/week; P = 0.0004). Mean ABR was also significantly reduced after switching to rIX-FP (3.2 vs 1.7; P = 0.0009).

CONCLUSIONS

In this retrospective study, rIX-FP prophylaxis was associated with lower FIX consumption and potentially improved protection against bleeds compared with prophylactic treatment with rFIXFc and rFIX.