PROBLEM TO BE SOLVED : To provide modified serpin molecules with altered specificity, in particular serpin molecules modified to have increased specificity for anticoagulant proteases, such as activated Protein C (APC). SOLUTION : The invention provides a modified serpin having mutations at one or both of residues P1' and P2 and optionally at residues P1 and/or P4 in the reactive center loop (RCL) thereof. A pharmaceutical composition for the treatment or prevention of bleeding or the promotion of hemostasis in an individual comprises a modified serpin and a pharmaceutically acceptable excipient. SELECTED DRAWING : Figure 1 COPYRIGHT : (C)2019, JPO&INPIT