PK

Plasma ACE910 concentrations were determined by a validated sandwich enzyme-linked immunosorbent assay. In brief, ACE910 was captured by a rabbitized anti-idiotype monoclonal antibody against FX-binding antigen-binding fragment¹⁷ and detected by a mouse anti-idiotype monoclonal antibody against FIXa-binding antigen-binding fragment,¹⁷ followed by a horseradish peroxidase–conjugated goat anti-mouse immunoglobulin G (Southern Biotechnology Associates Inc., Birmingham, AL). The lower limit of quantification was 0.05 μg/mL. Plasma concentrations of ACE910 target antigens (FIX and FX, including activated forms) were determined using commercially available sandwich enzyme-linked immunosorbent assay kits (Assaypro LLC, St. Charles, MO).