title: Characterization of a low-level unknown isomeric degradation product using an integrated online-offline top-down tandem mass spectrometry platform.
abstract: An integrated online-offline platform was developed combining automated online LC-MS fraction collection, continuous accumulation of selected ions (CASI), and offline top-down electron capture dissociation (ECD) tandem mass spectrometry experiments to identify a low-level, unknown isomeric degradant in a formulated drug product during an accelerated stability study. By identifying the diagnostic ions of the isoaspartic acid (isoAsp), the top-down ECD experiment showed that the Asp9 in exenatide was converted to isoAsp9 to form the unknown isomeric degradant. The platform described here provides an accurate, straightforward, and low limit of detection method for the analysis of Asp isomerization as well as other potential low-level degradants in therapeutic polypeptides and proteins. It is especially useful for unstable and time-sensitive degradants and impurities.
authors.affiliation: Structure Elucidation Group, Global Process & Analytical Chemistry, Merck Research Laboratories , 556 Morris Ave., Summit, New Jersey 07901, United States.
authors.forename: Xiang
authors.initials: X
authors.lastname: Yu
authors.forename: Christopher
authors.initials: C
authors.lastname: Warme
authors.forename: Dinah
authors.initials: D
authors.lastname: Lee
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Wendy
authors.initials: W
authors.lastname: Zhong
mesh_terms: D026581:Isoaspartic Acid / Q000032:analysis*; D009862:Online Systems; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D026581:Isoaspartic Acid