Figure 1.

Expected FIX activity levels after doses of rFIXFc or rFIX (50 IU/kg body weight) were administered intravenously in multiple patients at time 0 hours.

Notes: FIX activity was followed for the specified intervals. The immediate post-dose recovery giving a FIX activity level of 50% is as expected for both the short-acting rFIX (black triangles) and the extended half-life rFIXFc (gray circles). The red line indicates the hours when the FIX activity level is <2% in this individual after taking the short-acting rFIX, and thus when the individual is at risk of bleeding. The vertical lines represent the standard deviation of FIX activity levels for 23 patients with hemophilia B. From N Engl J Med, Powell JS, Pasi KJ, Ragni MV, et al, Phase 3 study of recombinant factor IX Fc fusion protein in hemophilia B, 369:2313–2323. Copyright © 2013 Massachusetts Medical Society. Modified with permission. Available from http://www.nejm.org/doi/full/10.1056/NEJMoa1305074.²⁹

Abbreviations: FIX, factor IX; rFIXFc, recombinant factor IX fused with the fragment, crystallizable domain of IgG; Ig, immunoglobulin; rFIX, recombinant fix.