Background
RCT (Joint Outcome Study), N=65, boys <30 months with severe hemophilia A (FVIII <2 U/dL), ≤2 hemorrhages per index joint, normal baseline joint imaging, no FVIII inhibitor, normal platelets and joint motion. Randomized to prophylactic vs episodic recombinant FVIII.
Interventions and follow up
Arm A: prophylaxis rFVIII 25 IU/kg every other day (40 IU/kg ×1 for hemarthrosis)
Arm B: episodic rFVIII at joint hemorrhage, ≥3 doses totaling ≥80 IU/kg (40 + 20 + 20 at time of bleed, 24 h, 72 h), then 20 IU/kg every other day until joint mobility improved (up to 4 wks)
Primary endpoint: incidence of bone/cartilage damage in index joints by X-ray or MRI at age 6
Arm B: episodic rFVIII at joint hemorrhage, ≥3 doses totaling ≥80 IU/kg (40 + 20 + 20 at time of bleed, 24 h, 72 h), then 20 IU/kg every other day until joint mobility improved (up to 4 wks)
Primary endpoint: incidence of bone/cartilage damage in index joints by X-ray or MRI at age 6
Results
Median annual joint bleeds (prophylaxis vs on-demand): 0.2 vs 4.65/yr, P<.001
Median total hemorrhages: 1.15 vs 17.13, P<.003
MRI joint damage: 7% vs 45%, P=.002
X-ray joint damage: 4% vs 19%, P=.01
Total FVIII infusions: 20,829 vs 6,176, P<.001
FVIII units used: ~11.3 million vs ~3.7 million, P<.001
Median total hemorrhages: 1.15 vs 17.13, P<.003
MRI joint damage: 7% vs 45%, P=.002
X-ray joint damage: 4% vs 19%, P=.01
Total FVIII infusions: 20,829 vs 6,176, P<.001
FVIII units used: ~11.3 million vs ~3.7 million, P<.001
Adverse events
Inhibitor development: infrequent, similar between groups
Catheter-related infections: occurred in both arms
Deaths/unexpected safety signals: none reported
Catheter-related infections: occurred in both arms
Deaths/unexpected safety signals: none reported
Conclusions
In boys with severe hemophilia A, prophylactic FVIII started before joint damage prevented joint destruction and reduced joint and other hemorrhages vs episodic treatment, at the cost of substantially greater factor use.
Key Limitations
Small N; open-label by nature of regimens; high FVIII consumption and cost; index-joint imaging endpoint may not capture all joint disease; venous access/infection burden in young children.
Clinical Context
Landmark trial establishing primary prophylaxis as standard of care for severe hemophilia A in young children to prevent arthropathy; underpins current WFH and hematology-society recommendations favoring early prophylaxis.