Uptake, Internalization and Degradation of the Novel Plasminogen Activator Reteplase (BM 06.022) in the Rat

Abstract

SummaryThe catabolism of the novel plasminogen activator reteplase (BM 06.022) was described. For this purpose BM 06.022 was radiolabelled with l25I or with the accumulating label l25I-tyramine cellobiose (l25I-TC).BM 06.022 was injected at a pharmacological dose of 380 μg/kg b.w. and it was cleared from the plasma in a biphasic manner with a half-life of about 1 min in the α-phase and t1/2of 20-28 min in the β-phase. 28% and 72% of the injected dose was cleared in the α-phase and β-phase, respectively. Initially liver, kidneys, skin, bones, lungs, spleen, and muscles contributed mainly to the plasma clearance. Only liver and the kidneys, however, were responsible for the uptake and subsequent degradation of BM 06.022 and contributed for 75% to the catabolism of BM 06.022. BM 06.022 was degraded in the lysosomal compartment of both organs. Parenchymal liver cells were responsible for 70% of the liver uptake of BM 06.022. BM 06.022 associated rapidly to isolated rat parenchymal liver cells and was subsequently degraded in the lysosomal compartment of these cells. BM 06.022 bound with low-affinity to the parenchymal liver cells (550 nM) and the binding of BM 06.022 could be displaced by t-PA (IC50 5.6 nM), indicating that the low-density lipoprotein receptor-related protein (LRP) could be involved in the binding of BM 06.022. GST-RAP, which is an inhibitor of LRP, could in vivo significantly inhibit the uptake of BM 06.022 in the liver.It is concluded that BM 06.022 is metabolized primarily in the liver and the kidneys. These organs take up and degrade BM 06.022 in the lysosomes. The uptake mechanism of BM 06.022 in the kidneys is unknown, while LRP is responsible for a low-affinity binding and uptake of BM 06.022 in parenchymal liver cells.

Albumin Therapy Augments the Effect of Thrombolysis on Local Vascular Dynamics in a Rat Model of Arteriolar Thrombosis

“…14,15 It is cleared from the plasma in a biphasic manner, with a half-life of about 1 minute in the ␣-phase (28% cleared) and 20 to 28 minutes in the ␤-phase (72% cleared). 16 The findings of the present study show that the addition of albumin to subthrombolytic doses of reteplase results in a robust improvement of microvascular hemodynamics distal to an arteriolar thrombosis.…”

Generation and characterization of tissue-type plasminogen activator transgenic rats

“…is approved for the treatment of ischemic stroke within 4.5 h of symptom onset [ 2 ], demonstrating fibrinolysis enhancement is one of the promising approaches for the treatment of thrombotic disorders [ 3 ]. In fact, other classes of fibrinolytic enhancers such as tPA derivatives [ 4 , 5 ], plasmin derivatives [ 6 ], Stachybotrys microspora triprenyl phenols (SMTPs) [ 7 ], and activated form of thrombin-activatable fibrinolysis inhibitor (TAFIa) inhibitors [ 8 – 11 ] have been reported, and several clinical trials are ongoing. However, there have been few successful clinical trials in human patients, at least regarding stroke [ 12 , 13 ].…”

Carbohydrate analysis throughout the development of a protein therapeutic

“…Some of the increase in half-life seen with Tenecteplase can be attributed to the removal of the oligomannose structures (because of clearance by mannose receptors) but not all, since a mutant with only the oligomannose site removed does not have a half-life as long as tenecteplase [ 74 ]. A nonglycosylated version of t-PA (produced in E. coli ) in which a large part of the molecule has been deleted (reteplase) has a similar half-life to tenectaplase [ 75 ].…”