Relative molecular weight selection of PEG
The choice of molecular weight must take into account both biological activity and pharmacokinetics. Previous studies have shown that the action time of modified protein drugs in vivo is directly proportional to the number and relative molecular weight of coupled PEG, and the biological activity in vitro is inversely proportional to the number and relative molecular weight of coupled PEG. The choice of specific PEG molecular weight for modification is determined experimentally. Generally, PEG with a molecular weight in the range of 40,000 to 60,000 is selected as a modifier.
Selection of modification sites
When PEG modification is performed on a protein, the surface residues of the protein that are not bound to the receptor should be selected as the modification site according to the analysis of the structure-activity relationship of the protein. In this way, the modified protein can retain high biological activity. The modification site of organic small molecule drugs has nothing to do with biological activity. The ideal PEG modification technology is to select the appropriate PEG according to the site to be modified, so as to obtain a uniform product.
Related: The Classification of Polymer PEG Derivatives
Other chemical factors
(1) pH value of modification reaction; (2) molar ratio of drug to PEG; (3) drug concentration; (4) reaction time; (5) reaction temperature. The PEG modification reaction requires high specificity and mild reaction conditions, and one or several influencing factors can be controlled to obtain the target modified drug with high yield.
Related: PEGylation Reagents Selection Guide
Common Structures and Applications of PEGs