R-Hirudin

Neuhaus KL, von Essen R, Tebbe U, etal. Safety observations from the pilot phase of the randomized r-hirudin for improvement of thrombolysis (HIT-111) study. Circulation 1994 90 1638-1642. 

Bostrom SL, Hansson GF Sarich TC, et al. The inhibitory effect of melagatran, the active form of the oral direct thrombin inhibitor ximelagatran, compared with enoxaparin and r-hirudin on ex vivo thrombin generation in human plasma. Thromb Res 2004 I 13 85-91. 

Sarich TC, Wolzt M, Eriksson UG, et al. Effects of ximelagatran, an oral direct thrombin inhibitor, r-hirudin and enoxaparin on thrombin generation and platelet activation in healthy male subjects, J Am Coll Cardiol 2003 41 557-564,... 

LahannJ, Klee D, Pluester W, Hoecker H, Bioactive immobilization of r-hirudin on CVD-coated metallic implant devices. Biomaterials 2001 22(8) 817-826. 

Stockmans F, Stassen JM, Vermylen J et al. (1997) A technique to investigate mural thrombus formation in arteries and veins II. Effects of aspirin, heparin, r-hirudin and G-4120. Ann Plastic Surg 38(1) 63—68... 

Van Wyk V, Neethling WML, Badenhorst PN, Kotze HF (1998) r-Hirudin inhibits platelet-dependent thrombosis during cardiopulmonary bypass in baboons. J Cardiovasc Surg 39 633-639... 

Functional bioavailability is variable and dependent on the structure of r-hirudin. 

Huhle G, Geberth M, Hoffmann U, Heene DL, Harenberg J. Management of heparin-associated thrombocytopenia in pregnancy with subcutaneous r-hirudin. Gynecol Obstet Invest 2000 49(l) 67-9. 

Using an arteriovenous shunt model of thrombosis in the rat, compounds 4 and 7 were evaluated for their ability to maintain patency of the extracorporeal circuit which serves as a thrombogenic surface [76]. Table 2 shows that on a gravimetric basis r-hirudin and inhibitor 4, were equipotent [r-hirudin EDis = 1.4 mg/kg 4 EDi5= 1.2 mg/kg i.v. bolus]. The thrombin inhibitor 7 was less effective in this assay having an EDi5= 6.3 mg/kg. 

The in vivo efficacy of the bifunctional thrombin inhibitors 4 and 7 was also assessed in a chemically-induced thrombosis model where deep arterial injury to the rat carotid artery is mediated by FeCb [79]. Stenosis of the blood vessel resulting from FeCb-mediated injury results in decreased blood flow and an abrupt temperature drop across the stenosed area due to arterial occlusion. Both bifunctional thrombin inhibitors 4 and 7 doubled the mean occlusion time (MOT) at an i.v. bolus dose of 1 mg/kg. At a dose of 2 mg/kg i.v. of compound 7, the vessel remained patent for over 60 minutes compared to saline treated control rats (MOT = 19 1 minute), r-hirudin was slightly more potent, doubling the mean occlusion time at an i.v. dose of 0.5 mg/kg. 

In addition to its intrinsic reduced affinity for thrombin, the higher doses required for inhibitor 7 may be correlated to its pharmacokinetics and metabolic susceptibility. The t /2p of r-hirudin and inhibitor 7 were approximately the same in the rat (25-30 minutes) while for the low molecular weight inhibitor 7 it is less than 3 minutes. It is well known that the kidney serves as the primary site of elimination of many polypeptide based drugs [77]. Indeed hirudin is excreted intact in the urine of several species [78]. We found that differences in the rate of elimination between inhibitors 4 and 7 may be explained in part by differences in the metabolic susceptibility toward rat kidney membrane proteases. The principal result from these studies is that the truncated inhibitor 7 is much more proteolytically labile compared to 4 in vitro. In 7, the proteolytic products arise rmidly (< 5 min) firom the cleavage of the Phe -Glu bond followed by cleavage of Asp -Phe, both of which are sufficient to inactivate the peptide. In inhibitor 4, three principal proteolytic sites were identified, two of which are within the spacer residues 1) Leu -Gln 2) Asn -Asp and 3) Gln -Ser . However, intact compound could still be detected after 30 minutes. 

Antithrombotic effect of r-hirudin, heparin and experimental compounds in various models of thrombosis in the rat... 

Revasc (r hirudin) S. cerevisiae Ciba Novartis/Europharm Prevention of venous thrombosis... 

A typical MALDl spectrum is shown in Pig. 4.9. It is the spectrum of r-hirudin, a protein consisting of 64 amino acids. As little or no fragmentation occurs, only oriQ major peak, [M- -H]+, and two minor peaks, [M- -2H] + and the agglomerate [2M- -H]+ are observed. This peak-pattern is very typical of MALDI-TOF spectra. Depending on the salt concentrations in the buffers used for sample preparation, peaks like [M -f Na]+ and [M -f K]+ are also observed. 

Fig. 4.9. Positive ion mass spectrum of the protein r-hirudin with MW 6963.5 Da. The matrix used was sinapinic acid (courtesy of Olaf Bdrnsen, Novartis).

These amino groups can be used for the immobilization of thrombin inhibitors such as R-hirudin. The functionalization is useful for devices that are in contact with native blood. A potential field of applications is stents with reduced restenosis, i.e., a reduced tendency of blocking the blood flow. ... 

A poly(amino-p-xylylene) coated functional surface was used to immobilize a polymeric drug release system consisting of poly(A-isopropylacryl-amide)-co-poly(acrylic acid). Into the drug release system, the thrombin inhibitor R-hirudin was incorporated. ... 

An LDPE model surface was coated with polyaminoxylene via chemical vapour deposition polymerisation. The functional surface was used to immobilise a polymeric drug release system consisting of isopropyl acrylamide-acrylic acid copolymer. The coupled drug release system was used to incorporate the thrombin inhibitor r-hirudin. 16 refs. 

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