PO18 - Successful long-term tolerance in patients with hemophilia A and inhibitors receiving emicizumab prophylaxis: A single Saudi center experience

Background: The most severe side effect of FVIII replacement therapy in hemophilia A patient is the development of inhibitors against FVIII, which affects approximately one-third of patients. Eradication of inhibitors with immune tolerance induction (ITI) in hemophilia A patients receiving emicizumab prophylaxis is challenging. Regional data on the use of ITI in hemophilia A patients with inhibitors who are receiving prophylactic emicizumab are lacking.

Aims: The study aims to report the outcome of ITI and the risk of inhibitor relapse in a single-center experience.

Methods: Methods and Results
Patient 1 is a 5-year boy known to have severe hemophilia A who received aggressive therapy with standard half-life recombinant factor VIII (SHL-rVIII) to treat intracranial hemorrhage and subsequently developed high titer inhibitors. Patient 2 is a 3-year boy with severe hemophilia A who developed high titer inhibitors after frequent treatment of the right knee target joint with SHL-rVIII. Both patients were started on subcutaneous emicizumab prophylaxis then first-time ITI (Atlanta protocol) was added in Table 1.
Patients responded well to ITI and tolerated therapy apart from the occasional unavailability of testing inhibitor titers while on emicizumab. There was one mild bleeding event and no thrombotic event. After ITI, Bethesda titers turned and remained negative, and recovery of factor VIII was more than 66% in both patients Table 2.

Results: Same as above

Conclusion(s): Eradication of inhibitors in hemophilia A patients receiving emicizumab is feasible with a low risk of inhibitor relapse and extends the therapeutic options in case of surgery or breakthrough bleeding.