Protein pharmaceuticals degradation pathway

T. J. Ahern and M. J. Manning, Stability of Protein Pharmaceuticals, Part A, Chemical and Physical Pathways of Protein Degradation, Plenum Press, New York, 1992. 

M. A. Hanson and S. K. E. Rouan, Introduction to formulation of protein pharmaceuticals, in Stability of Protein Pharmaceuticals, Part B In Vivo Pathways of Degradation and Strategies for Protein Stabilization (T. J. Ahem and M. C. Manning, eds.), Plenum Press, New York, 1992, pp. 209-233. 

Goolcharran C, Khossravi M, Borchardt RT. Chemical pathways of peptide and protein Degradation. In Frokjaer S, Hovgaard L, eds. Pharmaceutical Formulation Development of Peptides and Proteins. (Pharmaceutical Science.) U.K. Taylor and Francis, 1999. 

The complexity of biological macromolecules when compared with small molecule therapeutics, differences in manufacturing, and the broad variety of potential degradation pathways lead to special requirements in quality assurance and analytical testing of pharmaceutical proteins. The product-related impurities are molecular variants formed during manufacture, storage, or use, and their properties are different from the desired product with respect to activity, efficacy, and safety. 

Kinetic analysis has even been attempted for the degradation of peptide and protein pharmaceuticals for which the mechanism and pathways are unknown. Apparent inactivation of a-chymotrypsin and bromelain in aqueous solutions was described by monoexponential... 

Clarke S, Stephenson R C, Lowenson J D (1992). Lability of asparagine and aspartic acid residues in proteins and peptides Spontaneous deamidation and isomerization reactions. In T J Ahern, M C Manning, (eds.). Stability of Protein Pharmaceuticals Part A Chemical and Physical Pathways of Protein Degradation, Plenum Press, New York, pp. 1-29. 

Oxidation. Oxidation is an important chemical degradation pathway for several proteins and can occur during all steps of its pharmaceutical development. The amino acids that are labile to oxidation are Met, His, Cys, Trp, Phe, Tyr, and Pro. Met has been identified as one of the most easily oxidized amino acids in proteins... 

Purity determination is an essential component of the assessment of the quality of any drug. However, the purity determination of biopharmaceuticals is not as straightforward as that of small-molecule pharmaceuticals, since biopharmaceuticals are structurally complex and have a wide range of potential impurities. Approaches usually involve the judicious choice of a combination of methods that enable the detection and quantitation of impurities from which an overall purity assessment can be derived. As mentioned previously, proteins undergo degradation or modification through a number of pathways. Most of the more common variants encountered in protein preparations... 

Many potential degradation products are not observed in protein pharmaceuticals, primarily because much care is taken in the choice of formulations, lyophilization, and storage conditions in order to maintain protein stability. Thus, degradation is minimized and usable shelf lives are on the order of years. In order to study the degradation pathways of a biopharmaceutical protein, and to evaluate the stability-indicating ability of the analytical methods, it is sometimes necessary to perform forced degradation studies, where the biopharmaceutical protein is subjected to a variety of stress conditions, such as varying pH, elevated temperature, or the addition of oxidants. 

A comprehensive survey of the degradation products of 73 protein pharmaceuticals indicates that the primary chemical pathway of degradation is succinimide formation at Asn and Asp residues to yield Asp and isoAsp at both residues. Deamidation at Gin in Gln-Gly sequences, hydrolysis at Asp-Pro bonds and Met oxidation were also observed at a lesser extent. These reactions are briefly discussed below. 

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