Abstract
Background and aims
Alteplase is produced as a single chain enzyme but is converted into a more active two-chain form by plasmin. Tenecteplase is structurally similar to alteplase and shows higher resistance to PAI-1. Factors influencing two-chain conversion of tenecteplase are poorly understood. Several formulations of TNK are now available. We compared two-chain conversion of alteplase and four tenecteplase formulations and downstream consequences on plasminogen activation, fibrinogenolysis, and PAI-1 resistance.
Methods
Alteplase and four tenecteplase formulations: Metalyse (Boehringer Ingelheim), Tenectase (Gennova, India), Mingfule (CSPC, China), GenetPA (BioApower, China) were compared. Two-chain conversion was achieved with plasmin and by western blotting. Proteolytic activity and the effect of PAI-1 was evaluated using amidolytic or fibrinolysis assays.
Results
Plasmin caused a dose-dependent conversion of alteplase and all tenecteplase formulations into their two-chain forms resulting in a ~2.5-fold increase in proteolytic activity. Two-chain conversion of alteplase, but not tenecteplase, occurred in plasma coinciding with off-target fibrinogen depletion. Metalyse contained ~3-fold more two-chain tenecteplase compared to other formulations, resulting in higher proteolytic activity in the absence of fibrin. However, all tenecteplase formulations showed similar activity in their two-chain form. Two-chain conversion of all tenecteplase formulations increased PAI-1 binding and a significant decrease in PAI-1 resistance.
Conclusions
Generation of two-chain tPA promotes fibrinogenolysis. Metalyse contains 3-fold more two-chain species and is more active in the absence of fibrin than other tenecteplase formulations. However, all tenecteplase formulations have similar proteolytic activity in their two-chain form but lose some resistance to PAI-1.
Conflict of interest
Liu: Nothing to disclose; Tippett: Nothing to disclose; McCutcheon: Nothing to disclose; Keragala: Nothing to disclose; Lin: Nothing to disclose; Xiong: Nothing to disclose; Wang: Nothing to disclose; Campbell: Nothing to disclose; Parsons: Nothing to disclose; Medcalf: Nothing to disclose