Humanization, recombinant proteins

Ryffel, B. (1996). Safety of human recombinant proteins. Biomed. Environ. Sciences 10 65-71. 

FFeart disease, particularly clogged blood vessels, is also treated with recombinant products. Alteplase (Activase ), a human recombinant protein that breaks down fibrin, is used immediately after a stroke or heart attack to break down platelet-trapping clots in small blood vessels of the heart or brain and thus improve the patient s chances for recovery. Purified enzymes from bacteria are used for the same purposes. Abciximab (ReoPro ), a monoclonal antibody to... 

The availability of endogenous enzymes and their variants has allowed the use of enzymes as replacement therapy and as therapeutic agents. With continued refinement in recombinant protein technology, the cost of human recombinant proteins may become more affordable. As more novel human recombinant enzymes are developed, a wide variety of medical disorders will be amenable to enzyme therapies. Additional molecular engineering such as pegylation or creation and modification of... 

HEK-293 cells, derived from human embryo kidney, were transformed with human type 5 adenovirus (Graham et al., 1977). These cells exhibit epithelial morphology and can be adapted to suspension growth in serum-free media. In addition, this cell line is easily transfected and has been explored for viral vector production for gene therapy and for obtaining human recombinant proteins with normal glycosylation profiles. 

Anti-human recombinant protein antibody response may alter pharmacokinetics, neutralise biological effects, cause immune-complex lesions, or have no relevant consequence in animals. 

The analysis of effects on reproductive performance (including fertility) and development by human recombinant proteins is a complex issue. In general, non-human primates are often the most relevant species. The studies have generally been complicated by abortions however, there has been no evidence of a teratogenic effect (Trown et al, 1986 Terrel and Green, 1993). Particular consideration should be given to development of mechanistic-based studies to avoid the need for non-human primate studies for the next generation of IFN therapies. 

Farm animals produce recombinant proteins less expensively than bacteria or cells in culture because the farm animals produce large volumes of milk containing up to 5 g/L of recombinant protein. In addition, modifications to the proteins that can be performed only by mammalian cells are made by the cells of the mammary gland. Therefore, numerous pharmaceuticals that previously could only be made by cells in culture or extracted from human tissue or blood are being produced by lactating farm animals. 

Therapeutics. Therapeutic materials represent a class of polypeptides that are a low volume, high value product. The production system need not be very efficient but the quaHty of the recombinant protein has to be extremely pure (33,34). Thus high cost mammalian production systems can be tolerated. However, some of the therapeutic proteins such as insulin, human growth hormone, interleukins, interferon, and streptokinase are produced microbially. 

Another application shows the preparative purification and polishing of a therapeutic fusion protein with a humanized recombinant IgG protein. The fusion protein was expressed by the fermentation of baby hamster kidney cells. The filtered culture supernatant (155 liters) contained 2.2 g of IgG and 75.5 g of total protein. After the immunoglobulins were isolated by expanded bed adsorption and rebuffering, the IgG fraction was bound to Fractogel EMD SOj (M). This column achieved baseline separation of complete antibodies (fusion protein) from small amounts of antibodies lacking the fusion part. The resulting highly purified IgG fraction (110 ml) was diluted to 150 ml and... 

Previously, pharmacologists were constrained to the prewired sensitivity of isolated tissues for agonist study. As discussed in Chapter 2, different tissues possess different densities of receptor, different receptor co-proteins in the membranes, and different efficiencies of stimulus-response mechanisms. Judicious choice of tissue type could yield uniquely useful pharmacologic systems (i.e., sensitive screening tissues). However, before the availability of recombinant systems these choices were limited. With the ability to express different densities of human target proteins such as receptors has come a transformation in drug discovery. Recombinant cellular systems can now... 

Alefacept is a human recombinant integrin LFA3-IgG fusion protein that binds to the CD2 receptor thus blocking T-cell activation. 

Bernard GR, Vincent JL, Laterre PF, et al. Recombinant Human Protein C Worldwide Evaluation in Severe Sepsis (PROWESS) study group. Efficacy and safety of recombinant human activated protein C for severe sepsis. N Engl J Med 2001 344 699-709. 

---