Differential fibrinolytic properties of the recombinant plasminogen activator BM 06.022 in human plasma and blood clot systems in vitro.

The effects of the unglycosylated recombinant plasminogen activator BM 06.022, consisting of the kringle 2 and protease domains of tissue-type plasminogen activator (t-PA), on clot lysis were evaluated in an in vitro system. Fresh and aged 125I-labelled human platelet-poor (PPP) and platelet-rich plasma (PRP) and whole blood clots were immersed in human plasma. Clot lysis was quantitated by measurement of released 125I. Fresh PPP clots were time- and concentration-dependently lysed by BM 06.022, alteplase, melanoma t-PA (mt-PA), and urokinase. Fifty per cent clot lysis at 4 h required 3.2-, 6.4- and 15.2-fold higher nM concentrations of mt-PA, BM 06.022, and urokinase respectively compared with alteplase. Maximal lysis (Emax) at 4 h was similar (84.1-87.6%) for BM 06.022, alteplase, and mt-PA, but lower (65.3 +/- 0.6%) for urokinase. Emax for BM 06.022 was lower (P < 0.05) than for alteplase for fresh and aged PRP and whole blood clot lysis. These data suggest that in vitro BM 06.022 achieved, compared with alteplase, the same maximal efficacy in fresh PPP-clot lysis despite a lower potency, but was less effective in lysing aged and fresh PRP and whole blood clots.