Abstract Number: PB0524
Meeting: ISTH 2021 Congress
Theme: Hemophilia and Rare Bleeding Disorders » Hemophilia - Clinical
Background: Regular prophylactic replacement with factor IX (FIX) is the recommended treatment for patients with severe hemophilia B. rIX-FP, a fusion protein linking recombinant FIX with albumin, has been shown to be efficacious and well tolerated with prolonged dosing intervals of up to 21 days.
Aims: Assess the long-term clinical outcomes in previously-treated patients (PTPs) treated with rIX‑FP.
Methods: Data from PTPs participating across four studies in the PROLONG-9FP clinical program were included in an integrated analysis to evaluate the long-term efficacy and safety of rIX-FP. Dosing intervals were up to 14 days (50–75 IU/kg) if well-controlled, with no spontaneous bleeding in the previous 4 weeks, on the 7-day regimen (25–50 IU/kg); patients ≥18 years could switch to a 21-day regimen (100 IU/kg) if well-controlled on a 14-day regimen. Patients were included in analyses across multiple dose cohorts if they received ≥12 weeks’treatment.
Results: Ninety-nine PTPs participated across four PROLONG-9FP clinical studies. Patients receiving a 7- (n=92), 10- (n=24), 14- (n=51), or 21-day (n=11) dosing regimen received treatment for a mean (SD) of 726.0 (543.4), 765.5 (516.9), 821.5 (529.8) and 654.5 (333.78) days, respectively; bleeding rates are shown in Table 1. Median (Q1, Q3) annualized bleeding rates were 1.57 (0.00, 4.46), 1.37 (0.40, 4.97), 1.61 (0.30, 4.24) and 0.32 (0.00, 2.48) for patients treated with a 7-, 10-, 14-, or 21-day regimen, respectively. Mean (SD) age was 25.6 (17.11); 27.3% were pediatric patients (0–<12 years), 8.1% were adolescents (≥12–<18 years), and 64.6% were adults (≥18–65 years). No safety concerns were observed.
| Regimen | 7 day | 10 day | 14 day | 21 day |
| N | 92 | 24 | 51 | 11 |
| AsBR, median (Q1, Q3) | 0.00 (0.00, 1.36) | 0.13 (0.00, 1.46) | 0.29 (0.00, 1.88) | 0.00 (0.00, 0.45) |
| ABR, median (Q1, Q3) | 1.57 (0.00, 4.46) | 1.37 (0.40, 4.97) | 1.61 (0.30, 4.24) | 0.32 (0.00, 2.48) |
| Monthly infusions, mean (SD) | 4.3 (0.2) | 3.0 (0.2) | 2.2 (0.1) | 1.5 (0.0) |
| Dose per infusion, mean (SD) | 48.8 (11.5) | 70.8 (8.3) | 73.1 (7.5) | 100.6 (3.6) |
Bleeding rates across the PROLONG 9-FP clinical programABR, annualized bleeding rate; AsBR, annualized spontaneous bleeding rate
Conclusions: Treatment with rIX-FP was associated with low bleeding rates; no safety concerns were identified. Extended dosing regimens with rIX-FP may be suitable for selected patients provided they are well-controlled on a shorter rIX-FP dosing interval.
To cite this abstract in AMA style:
Pabinger I, Lissitchkov T, Nagao A, Lepatan LM, Li Y, Seifert W, Mancuso ME. Efficacy and Safety of rIX-FP: A Longitudinal Analysis of Patients Treated across the PROLONG-9FP Clinical Trials Program [abstract]. Res Pract Thromb Haemost. 2021; 5 (Suppl 2). https://abstracts.isth.org/abstract/efficacy-and-safety-of-rix-fp-a-longitudinal-analysis-of-patients-treated-across-the-prolong-9fp-clinical-trials-program/. Accessed November 29, 2023.« Back to ISTH 2021 Congress
ISTH Congress Abstracts - https://abstracts.isth.org/abstract/efficacy-and-safety-of-rix-fp-a-longitudinal-analysis-of-patients-treated-across-the-prolong-9fp-clinical-trials-program/