Recombinant Factor IX in Surgical Management of Hemostasis in Hemophilia B Patients: A Prospective Clinical Trial

Management of hemostasis with factor IX replacement during surgical procedures on patients with hemophilia B is vital to patient safety. A recombinant factor IX (rFIX, nonacog gamma, RIXUBIS, BAX 326) presents a treatment alternative for hemophilia B; nonacog gamma is manufactured with no materials of human or animal origin, and includes as two-step virus inactivation (solvent/detergent treatment and nanofiltration). This multi-national clinical trial was conducted to investigate the efficacy and safety of nonacog gamma for perioperative use in previously-treated patients with severe (FIX level < 1%) or moderately severe (FIX level 1-2%) hemophilia B. Interim results of 14 (11 major) surgeries showed that nonacog gamma is safe and effective in maintaining hemostasis in the surgical setting;¹ the results of all 38 surgeries are presented here.

Previously-treated hemophilia B immunocompetent patients aged 12 to 65 years with no evidence of a history of FIX inhibitors were eligible for participation if they were either: 1) participating in another trial with nonacog gamma and required an emergency or elective major or minor surgical, dental, or other invasive procedure; or 2) if not participating in any other nonacog gamma clinical study, they required elective major surgery and had been treated previously with plasma-derived and/or recombinant FIX concentrate(s) for a minimum of 150 exposure days. Pre-operative FIX levels were targeted at 80%-100% of normal for major, and 30%-60% of normal for minor surgeries, through an individualized nonacog gamma dosing approach. Hemostatic efficacy was evaluated intra- and post-operatively by determination of actual versus predicted blood loss and a semi-quantitative 4-point hemostatic efficacy rating scale (excellent, good, fair, none); safety was assessed in terms of the occurrence of adverse events.

Thirty patients participated in this study, 10 of whom underwent multiple surgeries and were re-enrolled for each surgery. Of a total of 38 surgeries performed, 21 were major (14 orthopedic) and 17 were minor.

Hemostatic efficacy for 37/38 surgeries (including 20/21 major surgeries) had a rating of 'excellent' and one was 'good' (a knee joint replacement). At drain removal (n=14), the ratings for all major surgeries were either 'excellent' (10/14) or 'good' (4/14). On postoperative day 3, 6 of 7 major surgeries where no drain was employed had a rating of 'excellent', and one had a rating of 'good'. At discharge from hospital, 12/21 were 'excellent', 7/21 were 'good' and 2 were 'fair' (both had ratings of 'excellent' intraoperatively and at drain removal).

For 16/21 major surgeries, the actual blood loss was below (n=8) or equal to (n=8) the average predicted blood loss and the mean post-operative blood loss was 552.4 mL (range: 11-1100 mL) in subjects who had a drain placed. For 12/17 minor surgeries, actual intraoperative blood loss was below the average predicted blood loss, for 4/17 minor surgeries, the actual intraoperative blood loss matched the average predicted blood loss, and for 1 minor surgery (intra-articular infiltration) actual blood loss was between the average predicted and maximum predicted blood loss.

Nonacog gamma was safe and well tolerated. One possibly related AE (hemorrhagic anemia) was reported. This event was resolved at the completion of the study. No thrombogenic events or severe allergic reactions, nor induction of inhibitory antibodies to FIX or total binding antibodies to FIX were observed.

Conclusion: Nonacog gamma provides a safe and effective treatment alternative for perioperative management of hemostasis in hemophilia B patients in a variety of surgical settings.

References

¹ Windyga J, Lissitchkov T, Stasyshyn O, et al. Efficacy and safety of a recombinant factor IX (Bax326) in previously treated patients with severe or moderately severe haemophilia B undergoing surgical or other invasive procedures: a prospective, open-label, uncontrolled, multicentre, phase III study. Haemophilia. 2014 Sep;20(5):651-8.