Prophylactic treatment of hemophilia B with extended half-life recombinant factor IX products is associated with improved clinical outcomes, but head-to-head comparative studies of available treatments are lacking. |
Matching-adjusted indirect comparisons (MAICs) are robust methods for conducting indirect treatment comparisons across trials. |
This study used MAICs to estimate the efficacy of recombinant factor IX albumin fusion protein (rIX-FP) in the PROLONG-9FP trial relative to recombinant factor IX Fc fusion protein (rFIXFc) in the B-LONG trial in subjects that were on weekly prophylaxis. |
The results demonstrated that rIX-FP may provide better clinical outcomes than rFIXFc relating to annualized bleeding rates and the proportions of patients without bleeding events of any nature. |
Introduction
Methods
Data Sources
B-LONG | PROLONG-9FP | |
---|---|---|
Trial design | Non-randomized, open-label phase 3 | Non-randomized, open-label phase 3 |
Population | Male subjects (≥ 12 years) with severe HB (endogenous FIX level of ≤ 2 IU/dL) | Male subjects (12–65 years) with severe HB (endogenous FIX level of ≤ 2 IU/dL) |
Treatment groups | Group 1: Subjects received weekly dose-adjusted prophylaxis (50 IU/kg) (n = 63); prior prophylactic or on-demand regimen | Group 1: Subjects received weekly prophylaxis (35–50 IU/kg) for 26 weeks and were eligible to switch to treatment every 10 or 14 days (75 IU/kg) if they had no spontaneous bleeds for ≥ 4 weeks (n = 40); prior prophylactic regimen |
Group 2: Subjects received interval adjusted prophylaxis starting with every 10 days (100 IU/kg) (n = 29); prior prophylactic or on-demand regimen | ||
Group 3: Subjects received on-demand treatment (20–100 IU/kg) (n = 27); prior on-demand regimen | Group 2: Subjects received on-demand treatment for 26 weeks (n = 23) followed by approximately 26 weeks of weekly prophylaxis (n = 19); prior on-demand regimen | |
Group 4: Subjects received treatment in the perioperative period (n = 12) |
Matching and Adjusting Baseline Characteristics of Subjects
Efficacy Outcomes
Estimating Relative Treatment Effects
Compliance with Ethics Guidelines
Results
Baseline Characteristics of Subjects Before and After Adjustment
Variables adjusted | rFIXFc | rIX-FP | |
---|---|---|---|
None | None | Four factorsa | |
n = 63 | n = 56 | ESSb = 43.1 | |
Annualized bleeding rate, annualized spontaneous bleeding rate, and annualized joint bleeding rate | |||
Disease severity, n (%) | |||
1–2 IU/dL | 13 (20.6) | 13 (23.2) | 10.3 (20.6) |
< 1 IU/dL | 50 (79.4) | 43 (76.8) | 39.4 (79.4) |
Age, years, mean (SD) | 32.3 (13.9) | 32.9 (14.1) | 32.3 (14.1) |
Prior FIX regimen, n (%) | |||
On-demand | 29 (46.8)c | 18 (32.1) | 23.2 (46.8) |
Prophylaxis | 33 (53.2)c | 38 (67.9) | 26.4 (53.2) |
n = 63 | n = 59 | ESSb = 49.8 | |
---|---|---|---|
Proportion of patients without bleeding events, spontaneous bleeds events, and joint bleeding events | |||
Disease severity, n (%) | |||
1–2 IU/dL | 13 (20.6) | 13 (22.0) | 10.8 (20.6) |
< 1 IU/dL | 50 (79.4) | 46 (78.0) | 41.6 (79.4) |
Age, years, mean (SD) | 32.3 (13.9) | 33.2 (14.2) | 32.3 (14.1) |
Prior FIX regimen, n (%) | |||
On-demand | 29 (46.8)c | 19 (32.2) | 24.5 (46.8) |
Prophylaxis | 33 (53.2)c | 40 (67.8) | 27.9 (53.2) |
BMI, kg/m2, mean (SD) | 24.8 (5.4) | 23.5 (4.3) | 24.8 (5.4) |
Efficacy Outcome Comparisons
Variables adjusted | rFIXFc | rIX-FP | |
---|---|---|---|
None | None | Four factorsa | |
n = 63 | n = 56 | ESSb = 43.1 | |
ABR | |||
RR (95% CI) | – | 0.56 (0.35, 0.91) | 0.75 (0.32, 1.75) |
Point estimate | 3.12 | 1.75 | 2.35 |
P value | – | P = 0.0199 | P = 0.5095 |
AsBR | |||
RR (95% CI) | – | 0.39 (0.22, 0.72) | 0.42 (0.22, 0.82) |
Point estimate | 1.65 | 0.65 | 0.69 |
P value | – | P = 0.0023 | P = 0.0107 |
AjBR | |||
RR (95% CI) | – | 0.61 (0.37, 1.01) | 0.82 (0.37, 1.82) |
Point estimate | 2.26 | 1.38 | 1.84 |
P value | – | P = 0.0564 | P = 0.6178 |
n = 63 | n = 59 | ESSb = 49.8 | |
---|---|---|---|
No bleeding events | |||
OR (95% CI) | – | 3.25 (1.50, 7.03) | 3.24 (1.41, 7.45) |
Point estimate | 0.230 | 0.492 | 0.491 |
P value | – | P = 0.0028 | P = 0.0057 |
No spontaneous bleeding events | |||
OR (95% CI) | – | 3.56 (1.71, 7.39) | 3.47 (1.56, 7.73) |
Point estimate | 0.410 | 0.712 | 0.707 |
P value | – | P = 0.0007 | P = 0.0023 |
No joint bleeding events | |||
OR (95% CI) | – | 2.59 (1.27, 5.30) | 2.41 (1.10, 5.26) |
Point estimate | 0.344 | 0.576 | 0.559 |
P value | – | P = 0.0092 | P = 0.0274 |