Holvoet P, Laroche Y, Stassen J M, Lijnen H R, Van Hoef B, De Cock F, Van Houtven A, Gansemans Y, Matthyssens G, Collen D
Center for Thrombosis and Vascular Research, University of Leuven, Belgium.
Blood. 1993 Feb 1;81(3):696-703.
The pharmacokinetic and thrombolytic properties were determined of two recombinant single-chain chimeric plasminogen activators (PA) consisting of u-PA-33k, a low-molecular weight derivative of single-chain urokinase-type PA (scu-PA) comprising amino acids Ala132 through Leu411, and of either a single-chain variable region fragment (Fv) derived from the fibrin fragment D-dimer-specific monoclonal antibody MA-15C5 (K12G0S32) or of the deglycosylated single-chain Fv fragment obtained by substitution of Asn88 with Glu (K12G2S32). Following bolus injection in hamsters, clearances of recombinant scu-PA (rscu-PA) and of K12G0S32 were similar. In contrast, clearance of K12G2S32 was fourfold slower than that of rscu-PA. The thrombolytic potency (percent lysis per u-PA administered in milligrams per kilogram body weight) and specific thrombolytic activity (percent lysis per microgram per milliliter steady-state plasma u-PA antigen level) of these compounds were studied in hamsters with an experimental pulmonary embolus consisting of a human plasma clot injected via the jugular vein. The doses of K12G0S32 and K12G2S32 required to obtain maximal rate of clot lysis were sixfold and 11-fold lower than that of rscu-PA. The steady-state u-PA-related plasma antigen levels of K12G0S32 and K12G2S32 required to obtain maximal rate of clot lysis were 10-fold and fourfold lower than that of rscu-PA. Thus, targeting of K12G0S32 to the clot surface by means of its glycosylated Fv fragment results in a 10-fold increase of its specific thrombolytic activity and sixfold increase of its thrombolytic potency as compared with those of rscu-PA. Targeting of K12G2S32 to the clot surface by means of its deglycosylated Fv fragment results in only a twofold increase of its thrombolytic activity. However, its fourfold slower clearance, combined with its twofold higher specific thrombolytic activity, results in an 11-fold increase of its thrombolytic potency over that of rscu-PA. These findings indicate that the thrombolytic potency of chimeric antibody-targeted PA may be increased by increasing the specific thrombolytic activity, reducing the clearance, or both.
测定了两种重组单链嵌合纤溶酶原激活剂（PA）的药代动力学和溶栓特性。这两种激活剂分别由u-PA-33k（一种单链尿激酶型PA（scu-PA）的低分子量衍生物，包含氨基酸Ala132至Leu411）与源自纤维蛋白片段D-二聚体特异性单克隆抗体MA-15C5（K12G0S32）的单链可变区片段（Fv）或通过将Asn88替换为Glu获得的去糖基化单链Fv片段（K12G2S32）组成。在仓鼠中进行大剂量注射后，重组scu-PA（rscu-PA）和K12G0S32的清除率相似。相比之下，K12G2S32的清除率比rscu-PA慢四倍。在患有通过颈静脉注射人血浆凝块构成的实验性肺栓塞的仓鼠中，研究了这些化合物的溶栓效力（每千克体重每毫克u-PA给药的溶解百分比）和特异性溶栓活性（每微克每毫升稳态血浆u-PA抗原水平的溶解百分比）。获得最大凝块溶解速率所需的K12G0S32和K12G2S32剂量分别比rscu-PA低六倍和十一倍。获得最大凝块溶解速率所需的K12G0S32和K12G2S32的稳态u-PA相关血浆抗原水平分别比rscu-PA低十倍和四倍。因此，通过其糖基化Fv片段将K12G0S32靶向凝块表面，与rscu-PA相比，其特异性溶栓活性提高了十倍，溶栓效力提高了六倍。通过其去糖基化Fv片段将K12G2S32靶向凝块表面，仅使其溶栓活性提高了两倍。然而，其四倍慢的清除率，加上其两倍高的特异性溶栓活性，导致其溶栓效力比rscu-PA提高了十一倍。这些发现表明，嵌合抗体靶向的PA的溶栓效力可通过提高特异性溶栓活性、降低清除率或两者兼而有之来提高。
