Protect from light: Photodegradation and protein biologics

The exposure of proteins to light and the ensuing chemical and physical degradation has been studied extensively for many ears. The residues in proteins that undergo primary photooxidation include tryptophan, tyrosine, phenylalanine, and cysteine/cystine. While photooxidation has been recognized as a major contributor to protein degradation, the effects of photoinduced damage have not been widely studied for biopharmaceuticals. This is particularly important since photodegradation can lead to changes in primary, secondary, and tertiary structures of protein and these changes, while not definitively established, could lead to differences in long-term stability, bioactivity, or immunogenicity. In this review we briefly describe the major pathways of photodegradation for proteins followed by a description of the limited data on photodegradation of biopharmaceuticals and methods that have been used to reduce or prevent damage. It is our intent to spur additional research in this area for increasing the safety and effectiveness of biopharmaceutical products. (C) 2007 Wiley-Liss, Inc.