Thrombolysis by chemically modified coagulation factor Xa

Abstract

SummaryBackground-Enzymatic thrombolysis carries the risk of hemorrhage and re-occlusion must be evaded by co-administration with an anticoagulant. Toward further improving these shortcomings, we report a novel dual-functioning molecule, Xai-K, which is both a non-enzymatic thrombolytic agent and an anticoagulant. Xai-K is based on clotting factor Xa, whose sequential plasminmediated fragments, FXaβ and Xa33/13, accelerate the principal thrombolytic agent, tissue plasminogen activator (tPA), but only when localized to anionic phospholipid.

Rivaroxaban and apixaban induce clotting factor Xa fibrinolytic activity

“…We have reported that irreversible modification of the active site with chloromethyl ketones (CMKs) prevents Xa33/13 production (Fig. C), allowing the persistence of t‐PA cofactor function in plasma . The current study addresses the hypothesis that, like CMK‐modified FXa , direct oral anticoagulants (DOACs) specific for the FXa active site (rivaroxaban and apixaban) enhance fibrinolysis by stabilizing FXaβ.…”

“…Positioned at the convergence of the intrinsic and extrinsic branches of coagulation, the activated form of factor X, FXa, is an important target for drug development . FXa is localized to the site of vascular damage by calcium‐dependent association with the cofactors activated FV and anionic phospholipid‐containing membrane (PL), where it converts prothrombin to thrombin.…”

“…However, a role for other cofactors that may participate in the initial production of plasmin has been underinvestigated. Recently, the use of lower t‐PA concentrations within the physiological range revealed that FXa and other clotting factors act as auxiliary t‐PA cofactors . These are cleaved by plasmin more effectively than fibrin, providing early C‐terminal lysine‐mediated t‐PA enhancement in the context of clotting.…”

“…Regardless of whether FX aβ is produced when bound to PL , clotting function is maintained, but Xa40 and Xa33/13 have negligible clotting activity in plasma (data not shown). Gla, γ‐carboxyglutamic acid‐containing domain ( PL ‐binding site); I, active site inhibitor; ▲, plasmin cleavage site determined by N‐terminal amino acid sequencing; ▵, plasmin cleavage site inferred by N‐terminal amino acid sequencing and lack of Pg binding ; ◊, inferred from electrophoretic mobility and Pg binding ).…”

“…When evaluated by the use of purified proteins, Xa33/13 enhances t‐PA activity more effectively than the precursor FXaβ . However, as compared with FXaβ, the t‐PA cofactor function of Xa33/13 is rapidly degraded in plasma . We have reported that irreversible modification of the active site with chloromethyl ketones (CMKs) prevents Xa33/13 production (Fig.…”