Polyethylene glycol-derivatized cysteine-substitution variants of recombinant staphylokinase for single-bolus treatment of acute myocardial infarction

Background-Thrombolytic therapy of acute myocardial infarction (AMI) is evo lving toward bolus administration. Derivatization of proteins with polyethy lene glycol (PEG) may reduce their clearance. Methods and Results-A staphylokinase (SakSTAR) variant with 12 amino acid s ubstitutions to reduce its antigenicity, SakSTAR (K35A, E65Q, K74R, E80A, D 82A, T90A, E99D, T101S, E108A, K109A, R130T, K135R), and with Ser in positi on 3 mutated into Cys (code SY161), was derivatized with maleimide-PEG with M-r of 5000 (P5), 10 000 (P10), or 20 000 (P20). The PEGylated variants re cognized only one third of the antibodies elicited with wild-type SakSTAR i n AMI patients. In experimental animals, plasma clearances were reduced 2.5 - to 5-fold with P5, 5- to 20-fold with P10, and 20-fold with P20, and bolu s injection induced pulmonary plasma clot lysis at doses inversely related to their clearance. Intravenous bolus injection of 5 mg of the P5, P10, or P20 variants in AMI patients was associated with plasma half-lives (t(1/2 a lpha)) of 13, 30, and 120 minutes and clearances of 75, 43, and 8 mL/min, r espectively, compared with 3 minutes and 360 mL/min for SakSTAR. Injection of 5 mg P5 variant restored TIMI-3 flow within 60 minutes in 14 of Is AMI p atients (78%, 95% CI 55% to 91%) and of 2.5 mg in 7 of 11 patients (63%, 95 % CT 35% to 85%), both in the absence of fibrinogen degradation. The immuno genicity of the variants was significantly (P<0.002) reduced. Conclusions-The staphylokinase variant SY161-P5, derivatized with one linea r polyethylene glycol molecule of M-r 5000, is a promising fibrin-selective agent for single-bolus coronary thrombolysis.