Technology evaluation: desmoteplase, PAION/Forest.

PAION GmbH, under license from Schering AG, is developing desmoteplase, a recombinant form of the anticlotting salivary plasminogen activator of the vampire bat Desmodus rotundus (DSPAalpha-1), for the potential treatment of acute ischemic stroke. The drug is currently undergoing phase II clinical trials.

The role of the low-density lipoprotein receptor-related protein (LRP) in the plasma clearance and liver uptake of recombinant single-chain urokinase-type plasminogen activator in rats.

Urokinase-type plasminogen activator (u-PA) is used as a thrombolytic agent in the treatment of acute myocardial infarction. In vitro, recombinant single-chain u-PA (rscu-PA) expressed in E.coli is recognized by the Low-Density Lipoprotein Receptor-related Protein (LRP) on rat parenchymal liver cells. In this study we investigated the role of LRP in the liver uptake and plasma clearance of rscu-PA in rats. A preinjection of the LRP inhibitor GST-RAP reduced the maximal liver uptake of 125I-rscu-PA at 5 min after injection from 50 to 30% of the injected dose and decreased the clearance of rscu-PA from 2.37 ml/min to 1.58 ml/min. Parenchymal, Kupffer and endothelial cells were responsible for 40, 50 and 10% of the liver uptake, respectively. The reduction in liver uptake of rscu-PA by the preinjection of GST-RAP was caused by a 91% and 62% reduction in the uptake by parenchymal and Kupffer cells, respectively. In order to investigate the part of rscu-PA that accounted for the interaction with LRP, experiments were performed with a mutant of rscu-PA lacking residues 11-135 (= delta 125-rscu-PA). Deletion of residues 11-135 resulted in a 80% reduction in liver uptake and a 2.4 times slower clearance (0.97 ml/min). The parenchymal, Kupffer and endothelial cells were responsible for respectively 60, 33 and 7% of the liver uptake of 125I-delta 125-rscu-PA. Preinjection of GST-RAP completely reduced the liver uptake of delta 125-rscu-PA and reduced its clearance to 0.79 ml/min. Treatment of isolated Kupffer cells with PI-PLC reduced the binding of rscu-PA by 40%, suggesting the involvement of the urokinase-type Plasminogen Activator Receptor (u-PAR) in the recognition of rscu-PA. Our results demonstrate that in vivo LRP is responsible for more than 90% of the parenchymal liver cell mediated uptake of rscu-PA and for 60% of the Kupffer cell interaction. It is also suggested that u-PAR is involved in the Kupffer cell recognition of rscu-PA.

Variaciones en la hemostasia y fibrinolisis durante el tratamiento del infarto agudo del miocardio (IAM) con activador tisular del plasminógeno (atPIG): estudio de 17 casos / Changes in coagulation and fibrinolytic systems during tissue-type plasminogen activator treatment of acute myocardial infarction

El propósito del trabajo fue investigar las variaciones que sufren las pruebas de coagulación y fibronolisis en los enfermos con infarto agudo del miocardio durante el tratamiento trombolítico con activador tisular del plasminógeno (at-PlG) y su relación con complicaciones hemorrágicas. Se estudiaron 17 enfermos a quienes se les administró at-PlG en infusión contínua durante 3 horas y se les practicaron tiempos de protrombina (TP), de tromboplastina y parcial (TTP), de trombina (TT), fibrinógeno (FG), productos de degradación del fibrinógeno (PDF), plasminógeno (PIG), alfa-2-antiplasmina (A-2AP) y antitrombina III (AT-III) durante y después de la aplicación del medicamento. En la mayoría de los casos se prolongaron los tiempos de coagulación, disminuyó tanto el FG como el PlG y se incrementaron los PDF. La a-2-AP y la AT-III no sugrieron modificaciones significativas. El PG se recuperó en las siguientes 3 horas y se presentó hiperfibrinogenemia después del segundo día. No se presentó hemorragia en ningún caso. Las alteraciones de laboratorio observadas no tuvieron expresión hemorrágica. El at-PiG produce menor hipofibrinogenemia que la reportada con otros trombolíticos

Effective thrombolysis without marked plasminemia after bolus intravenous administration of vampire bat salivary plasminogen activator in rabbits.

BACKGROUND: The use of recombinant tissue-type plasminogen activator (t-PA) in thrombolytic therapy is frequently associated with significant fibrinogenolysis. In contrast, recombinant vampire bat salivary plasminogen activator (Bat-PA) displays strict fibrin specificity, an attribute that could be desirable in a fibrinolytic agent. METHODS AND RESULTS: The efficacy and fibrin selectivity of Bat-PA was evaluated and compared with that of t-PA using a rabbit model of femoral arterial thrombosis. Administration of 8.1, 14, and 42 nmol Bat-PA/kg by bolus intravenous injection restored flow in 50%, 75%, and 80% of the rabbits, respectively. The incidence of reperfusion after bolus intravenous injection of 14 and 42 nmol t-PA/kg was 15% and 78%, respectively. The maximal femoral artery reperfusion flows were equivalent after treatment with 42 nmol Bat-PA/kg or 42 nmol t-PA/kg, but the time to reach maximal flow for Bat-PA was approximately one half that of t-PA. Furthermore, the rapid restoration of flow by 42 nmol Bat-PA/kg, in contrast to equimolar t-PA, was accomplished without fibrinogenolysis and with only small decreases in the plasminogen and alpha 2-antiplasmin levels. Equipotent doses of Bat-PA and t-PA both resulted in approximate 2.5-fold increases in the template bleeding times of aspirin-pretreated rabbits. The clearance of Bat-PA from rabbits exhibited biexponential elimination kinetics; approximately 80% was cleared by the relatively slow beta phase (half-life of 17.1 minutes). Overall, Bat-PA was cleared approximately fourfold slower than t-PA. CONCLUSIONS: Bolus intravenous administration of Bat-PA would facilitate prompt initiation of thrombolytic therapy, and the avoidance of plasminemia could result in fewer and less severe bleeding complications.