Thrombin generation to predict breakthrough bleeding in patients with acquired hemophilia A under emicizumab prophylaxis.

Acquired hemophilia A (AHA) is a serious bleeding disorder due to neutralizing autoantibodies against factor VIII (FVIII). Emicizumab mimics the activity of FVIIIa restoring thrombin generation. It was shown to protect patients with AHA from bleeding, but some patients experience clinically relevant breakthrough bleeding. Therefore, monitoring the efficacy of emicizumab might be useful, potentially through thrombin generation assay (TGA). The aims of this study were to assess (i) how TGA is related to emicizumab levels, residual FVIII activity, and antigen concentration of other coagulation factors, and (ii) whether it can predict breakthrough bleeding during emicizumab prophylaxis. We used samples from patients enrolled into the GTH-AHAEMI study that prospectively assessed the risk of bleeding in AHA patients receiving emicizumab for 12 weeks. Calibrated automated thrombogram assay was used with minute amounts of tissue factor (TF-TGA) or factor XIa (FXIa-TGA) to initiate coagulation. We observed that FXIa-TGA peak thrombin generation increased with emicizumab levels and FVIII activity. Higher peak thrombin values were associated with lower rates of bleeding as indicated by incident rate ratios below 1 (IRR 0.40 [0.17-0.84], p.

PMID: 41230703