Tissue plasminogen activator process

The first large-scale process to circumvent these limitations was one developed by Genentech, Inc. (South San Francisco, CA) for production of recombinant tissue plasminogen activator (tPA). This protein dissolves blood clots and can be used to treat heart attacks and strokes. This process was developed in the mid-1980s, resulting in final product licensure in 1987. The process required both regulatory and technical breakthroughs. 

Datar, R.V. Cartwright, T., and Rosen, C.G. 1993. Process economics of animal cell and bacterial fermentations a case study analysis of tissue plasminogen activator. Bio/Technology 11, 340-357. 

Van Reis et al. [92] reported the scale-up of a HF system for the recovery of human tissue plasminogen activator (t-PA) produced by recombinant CHO cells from the 2.5-m to the 180-m scale. A robust and reproducible process was achieved by combining hnear scale-up principles, control of fluid dynamic parameters and experimentally defined limits of product retention, which meant maintaining channel length, wall shear rate and flux constant. 

Mechanism of Action A tissue plasminogen activator that acts as a CV-thrombolytic by binding to the fibrin in a thrombus and converting entrapped plasminogen to plas-min. This process initiates fibrinolysis. Therapeutic Effect Degrades fibrin clots, fibrinogen, and other plasma proteins. 

Fibrinolysis refers to the process of fibrin digestion by the fibrin-specific protease, plasmin. The fibrinolytic system is similar to the coagulation system in that the precursor form of the serine protease plasmin circulates in an inactive form as plasminogen. In response to injury, endothelial cells synthesize and release tissue plasminogen activator (t-PA), which converts plasminogen to plasmin (Figure 34-3). Plasmin remodels the thrombus and limits its extension by proteolytic digestion of fibrin. 

For hypothermia, one major possible difficulty involves the effect of low temperature on metabolism and enzyme activity. Many pharmaceutical agents have reduced biological activity at lower temperature compared with higher temperature. The thrombolytic activity of recombinant tissue plasminogen activator (rt-PA), for example, is clearly temperature dependent, with decreased activity at lower temperature (1). Thus, the assumption that hypothermia will not have an adverse effect on other treatment agents cannot be presumed. Hypothermia is also known to reduce the activity of inflammatory and antiinfectious biological processes. This could potentially result in increased susceptibility to infection. This possibility is of particular concern because infections are a major cause of morbidity in stroke patients (2). Therefore, combination therapy with hypothermia and antiinflammatory agents could potentially worsen outcome. 

Other enzymes in clinical use, manufactured using similar processes, include tissue plasminogen activator, other thrombolytic agents and aglu-cerase (Ceredase, Genzyme Corp.) for Type 1 Gaucher disease. These illustrate the diverse clinical applications that enzymes may find. 

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