Antithrombotic potency of hirudin is increased in nonhuman primates by fibrin targeting.
BACKGROUND
Inhibition of thrombin by either the indirect thrombin inhibitor heparin or by more potent direct thrombin inhibitors such as hirudin reduces thrombus formation after arterial injury. The present study was designed to determine if a fibrin-specific thrombin inhibitor could, by local thrombin inhibition, prevent thrombosis more effectively.


RESULTS
We first studied antithrombotic potency in vitro, comparing fibrin-targeted hirudin (recombinant hirudin covalently linked to the Fab' fragment of the anti-fibrin monoclonal antibody 59D8) to recombinant hirudin in baboon plasma. Fibrin-targeted hirudin was nine times more effective than recombinant hirudin in inhibiting fibrin deposition on experimental clot surfaces in baboon plasma (P < .01). The potency of fibrin-targeted hirudin was then compared with that of recombinant hirudin in a baboon model of thrombus formation. 111In-labeled platelet deposition was measured in a synthetic graft segment of an extracorporeal arteriovenous shunt in control animals and in animals receiving either fibrin-targeted hirudin or hirudin. In these experiments, fibrin-targeted hirudin was 10-fold more potent than hirudin in inhibiting platelet deposition and thrombus formation (P < .05).


CONCLUSIONS
These data indicate that targeting a thrombin inhibitors such as hirudin to an epitope present in thrombi results in increased antithrombotic potency.
Bode
C
C
Medizinische Klinik III (Kardiologie), Heidelberg, Germany.
Hanson
S R
SR
Schmedtje
J F
JF
Haber
E
E
Mehwald
P
P
Kelly
A B
AB
Harker
L A
LA
Runge
M S
MS
D000818:Animals; D001166:Arteriovenous Shunt, Surgical; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology; D005263:Femoral Artery / Q000601:surgery; D005268:Femoral Vein / Q000601:surgery; D005337:Fibrin / Q000276:immunology*; D005340:Fibrinogen / Q000502:physiology; D005343:Fibrinolytic Agents / Q000494:pharmacology / Q000627:therapeutic use*; D024764:Hirudin Therapy; D006629:Hirudins / Q000494:pharmacology; D006801:Humans; D007140:Immunoglobulin Fab Fragments; D007700:Kinetics; D008297:Male; D010215:Papio; D011994:Recombinant Proteins / Q000494:pharmacology / Q000627:therapeutic use; D013917:Thrombin / Q000502:physiology; D013927:Thrombosis / Q000517:prevention & control*
D005343:Fibrinolytic Agents; D006629:Hirudins; D007140:Immunoglobulin Fab Fragments; D011994:Recombinant Proteins; D005337:Fibrin; D005340:Fibrinogen; D013917:Thrombin