Recombinant Porcine Factor VIII, Obi-1, Successfully Controlled Gastrointestinal Bleeding in a Patient with Acquired Hemophilia A

Introduction: Acquired hemophilia A (AHA) is a rare, life-threatening bleeding diathesis categorized by low levels of Factor VIII (FVIII) due to an acquired auto-antibody against FVIII. Treatment for AHA requires both control of the bleeding and eradication of the inhibitor. Recombinant activated factor VII (rFVIIa) maybe used to control the bleeding, but with only mixed results in controlling gastrointestinal bleeding (GIB). rFVIIa is associated with thrombosis risk and lack of ability to monitor. The recombinant porcine FVIII (rpFVIII), OBI-1, recently obtained regulatory approval based on the results of Phase 2/3 trial, but the patients in this cohort did not have GIBs. Here we present a patient with AHA admitted with a GIB and successfully treated with OBI-1.

Case: A 69 year old African American female with T1N0M0 infiltrative ductal carcinoma of the left breast and Stage IVA Squamous cell carcinoma of the cervix, treated in 1997 and 2007 respectively, presented to the emergency department with two days of painless bright red blood per rectum. She was orthostatic (supine: HR 79, BP 112/77 and standing: HR 111, BP 100/72) with hemoglobin (Hb) of 5.7gms/dl. An EGD demonstrated a bleeding vessel and multiple arteriovenous malformations (AVM) in the gastric body that were secured with clipping. Over the next 5 days EGD was repeated twice and multiple endoclips were placed in an attempt to achieve hemostasis. She subsequently underwent angiography to identify a target vessel for embolization, but one could not be found. On hospital day 11, hematology was consulted for a prolonged aPTT (113.8 seconds) and inadequate correction with mixing studies (63.7 seconds). FVIII level was <1% with factor VIII inhibitor titer of 245 Bethesda Units/ml (BU). Prior to starting OBI-1, she received 9 units of packed red blood cells and 2 units of fresh frozen plasma. OBI-1 was started at 200u/kg q4h for first 2 days and then decreased to q8h, with cessation of bleeding within 24 hours. Upon completion of the bolus of OBI-1, her FVIII level was 14%, then 38% at 8 hours, 48% at 16 hours and 62% at 24 hours. Rituximab (375mg/m2 weekly) and corticosteroids (prednisone 1mg/kg daily x7 days) were given in an attempt to eliminate the inhibitor. She remained stable for 6 days but subsequently developed abdominal pain. A CT of the abdomen revealed free air prompting emergent surgical intervention. She had internal hernia in the pelvis, ischemic small bowel and perforated jejunum requiring extensive resection. During this time she remained on rpFVIII (200u/kg q8h) with FVIII pre-infusion levels ranging from 2% - 14% and post-infusion levels from 80% to 217% and had only 25ml estimated blood loss during surgery. Unfortunately, 1 day after surgery she developed multi-organ failure and expired on hospital day 19.

Discussion: OBI-1 is a glycosylated, B-domain deleted recombinant porcine factor VIII that retains the ability to interact with Factor IXa and activate Factor X, but it is less inhibited by auto-antibodies to human FVIII. For FVIII inhibitor titers >5 BU, an inhibitor bypassing agent is usually necessary because human FVIII products are not able to overcome the inhibitor. Given the high FVIII inhibitor titers in this patient, administration of rFVIIa or OBI-1 was necessary. Our own institutional experience of treating GIBs in patients with AHA had poor outcomes. The efficacy of rFVIIa in treating GIB is inconclusive, with response rate ranging from 53% to 71%. However, rFVIIa is associated with a risk of thrombosis approaching 9.4%, especially in older patients and those with vasculopathy, a common demographic in AHA. Unlike rFVIIa, OBI-1 allows close monitoring of FVIII and in the aforementioned Phase 2/3 trial, there were no thrombotic complications or serious adverse events. We were successful in controlling the bleeding within 24 hours with OBI-1 and were able to achieve therapeutic levels of FVIII despite high Bethesda titers. Unfortunately, our patient died from an ischemic bowel and perforated jejunum that was likely related to hernia or repeated instrumentation in an attempt to stop the bleeding prior to the diagnosis of AHA.

Conclusion: OBI-1 appears to effectively and rapidly overcome a high titer FVIII inhibitor and control bleeding in a patient with AHA and GIB. While this is a promising therapy, additional study is necessary to determine safety, efficacy, and cost-effectiveness.