Real world impact of emicizumab & immunosuppression on Acquired Hemophilia A: A Multicenter US Cohort.

ABSTRACT

Acquired Hemophilia A (AHA) is an autoimmune bleeding disorder from anti-factor VIII (FVIII) antibodies with high morbidity and mortality due to bleeding and complications from immunosuppression (IST). To address the real-world implications of the FVIII mimetic antibody, emicizumab, and the role of IST, we retrospectively collected deidentified data on 62 AHA patients treated with off label emicizumab for a median of 10 weeks at 12 US hemophilia treatment centers. Most patients (95.2%) had acute bleeding at diagnosis with 62.9% having partial or no control of bleeds despite use of hemostatic agents at the time emicizumab was started. The main reason for initiating emicizumab was outpatient bleeding prophylaxis. After initiation of emicizumab, 87.1% had no additional bleeds. There were 6 breakthrough bleeds (2 spontaneous) in 5 patients and no fatal bleeding events on maintenance emicizumab. The mean breakthrough bleed rate per patient-week was 0.02 (95% CI 0.0 - 0.03) during the first 12 weeks of emicizumab for the 55 patients with at least 12 weeks of follow up. Of these patients, 92.7% received IST with 74.5% given rituximab-based regimens. Complete resolution of inhibitor and normalization of FVIII levels occurred in 56% overall and 63% of the patients treated with rituximab. Overall, the median time to discontinue emicizumab and IST was 18 weeks. Two patients had thrombotic events on emicizumab, but no adverse events were attributed to emicizumab and there were no infections due to IST. Emicizumab provides effective outpatient bleeding prophylaxis for AHA, and concurrent IST may further mitigate bleeding.