Efficacy, safety and pharmacokinetics of emicizumab (ACE910) prophylaxis in persons with hemophilia A with inhibitors: randomized, multicenter, open-label, phase 3 study (HAVEN 1)
Objectives:
Emicizumab, a bispecific humanized monoclonal antibody in development to address unmet medical needs in persons with hemophilia A with inhibitors (PwHAwI), bridges FIXa and FX to replace the function of missing FVIIIa, needed for effective hemostasis. This study assessed efficacy, safety and PK of emicizumab prophylaxis in PwHAwI.
Methods:
Study NCT02622321 was conducted at 43 centers/sites, and enrolled PwHAwI ≥12 y.o. Participants (pts) receiving prior episodic bypassing agents (BPAs) were randomized (2:1) to emicizumab prophylaxis vs no prophylaxis (Arm A vs B). Primary endpoint compared treated bleed rates in Arm A vs B. PwHAwI receiving prior prophylactic BPA received emicizumab prophylaxis in Arm C. Emicizumab was injected subcutaneously at 3 mg/kg/wk for 4 wks, and 1.5 mg/kg/wk thereafter.
Summary:
109 male PwHAwI were enrolled; median age 28 (range 12–75) yrs. Median (range) emicizumab treatment exposure was 24.0 (3.0–47.9) wk overall and 29.5 (3.3–47.9) wk in Arm A. Statistically significant, clinically meaningful reductions (87%) in treated bleed rates were observed between emicizumab prophylaxis vs no prophylaxis (Arm A vs B) (annualized bleeding rate [95% confidence interval] 2.9 [1.69 to 5.02] versus 23.3 [12.33 to 43.89], P<0.0001), and in all secondary bleed-related endpoints (spontaneous, joint, target joint, and all bleeds). Of note, a 79% reduction in treated bleed rate was seen with emicizumab prophylaxis (Arm C) vs BPA prophylaxis prior to study entry in a non-interventional study (NCT02476942; intra-individual comparison, P=0.0003). Overall, 67.3% of PwHAwI on emicizumab prophylaxis had zero treated bleeds. Statistically significant, clinically meaningful improvements in health-related quality of life (HRQoL) and health status were seen for Arm A vs B. Emicizumab was well tolerated. Total of 198 adverse events (AEs) were reported in 103 pts; most common AEs were injection-site reactions (15%), and 12 serious AEs were reported in 9 (8.7%) pts. Thrombotic microangiopathy and thrombosis (2 pts each in primary analysis) were reported and associated with high cumulative aPCC doses averaging >100 U/kg daily for >24 hr prior to event onset. No events occurred with emicizumab prophylaxis alone. Both TMA events resolved once aPCC treatment was stopped, and the thrombotic events did not require anticoagulation; 2 pts resumed emicizumab without sequelae (1 with TMA, 1 with thrombosis). No antidrug antibodies were detected. Mean trough emicizumab concentrations >50 μg/mL were achieved after 4 loading doses (3 mg/kg/wk) and sustained with maintenance doses of 1.5 mg/kg/wk.
Conclusion:
Emicizumab prophylaxis prevented or substantially reduced bleeds in PwHAwI and meaningfully improved HRQoL. Emicizumab had acceptable safety without excess thrombotic risk in the absence of concomitant aPCC. PK levels were sustained with once- weekly maintenance doses. These promising data could support a paradigm shift in the management and lives of PwHAwI.
