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Optimizing Human Therapeutic Proteins

As valuable therapeutic protein candidates are identified, their properties will most likely need to be optimized to meet clinical expectations. Many promising protein drug leads fail clinically due to efficacy, immunogenicity, stability, pharmacokinetic properties, or manufacturing costs. Many of these issues can be circumvented by the application of protein engineering technologies. There are many examples where protein engineering have significantly advanced a product to market, or enhanced the protein's competitive advantage over existing products. Eli Lily's Centocor's ReoPro® (GP IIb/IIIa inhibitor), Amgen's Immunex's Enbrel® (TNF- αinhibitor), and Genentech's Herceptin® (anti-Her2/Neu) have attained blockbuster drug status only through the intervention of protein engineering. The need for superior protein based drugs with unique physical, catalytic or structural properties continues to grow at an unprecedented rate. There are a number of companies involved in protein engineering, but their technology is mainly limited to random approaches using error prone PCR, DNA shuffling or phage display each combined with high throughput selection. APT's protein engineering technologies is mainly based on rational design. It takes full advantage of the increasing amount of three-dimensional protein structural information and combines it with an extensive knowledge of enzyme catalysis. In addition, rational protein redesign does not have a limited or biased mutational spectrum since precise changes are preconceived based on a detailed knowledge of protein structure, function and mechanism. APT's technology also makes the engineering of a protein secondary structure possible. This is a significant advantage of APT's approach since changes in protein secondary structure may be needed to drastically alter the protein's function to the desired commercial application.

Selected Publications

1. Chen R. (2001). Redesigning binding and catalytic specificities of enzymes. In Enzyme Technologies for Pharmaceutical and Biotechnological Application. Kirst HA, Yeh WK and Zmijewski MJ eds. Academic Press (in press).
2. Chen, R. (2001). Enzyme engineering: Rational design vs directed evolution. Trends Biotech 19: 13-14.
3. Miller S., Chen R., Karschnia E.J., Romfo C., Dean A. and LaPorte D.C. (2000) Locations of the regulatory sites for isocitrate dehydrogenase kinase/phosphatase. J. Biol. Chem. 275: 833-839.
4. Chen R. (1999). A general strategy for enzyme engineering. Trends in Biotechnology 17, 344-345.
5. Chen R., Greer A. and Dean, A. D. (1997). Structural Constrains in Protein Engineering: The Coenzyme Specificity of Escherichia coli Isocitrate Dehydroganase. Eur. J. Biochem. 250: 578-582.
6. Chen R., Greer A., Dean A.D. and Hurley L.H. (1997). Engineering secondary structure to invert coenzyme specificity in isopropylmalate dehydrogenase. In Techniques in Protein Chemistry VIII. pp 809-816. Marshak ed. Academic Press.
7. Chen R., Grobler J., Hurley J. H. and Dean A. D. (1996). Second-site supression of regulatory phosphorylation in Escherichia coli isocitrate dehydrogenase. Protein Science. 5: 287-295.
8. Hurley J.H., Chen R. and Dean A. D. (1996). Determinants of cofactor specificity in isocitrate dehydrogenase: structure of an engineered NADP>NAD specificity-reversal mutant. Biochemistry. 35: 5670-5678.
9. Chen R., Greer A. and Dean A. D. (1996). Redesigning secondary structure to invert coenzyme specificity in isopropylmalate dehydrogenase. Proc. Natl. Acad. Sci. USA. 93: 12171-12176.
10. Chen R., Greer A. and Dean A. D. (1995). A highly active decarboxylating dehydrogenase with rationally inverted coenzyme specificity. Proc. Natl. Acad. Sci. USA. 92: 11666-11670.