title: Active dimer of Epratuzumab provides insight into the complex nature of an antibody aggregate.
abstract: Understanding the intermolecular products of antibodies as a consequence of host-cell expression, aging, and heat-stress can be insightful especially when it involves the development of a stable biopharmaceutical product. The dimerized form of Epratuzumab (an IgG(1) antibody) with a molecular mass of approximately 300 kDa (twice the monomer antibody molecular weight of approximately 150 kDa) was examined to gain a better perspective of its properties pertaining to structure and activity. The nascent dimer was shown to partially dissociate upon incubation at 30 degrees C and 37 degrees C, exhibit no discernable alteration of structure (i.e., secondary or tertiary structure based on CD and 2nd derivative UV spectroscopy), have approximately 70% covalent forms (based upon CE-SDS results) and manifest twofold higher activity relative to the active monomer form (on a weight basis the dimer and monomer have equal activity). Interestingly, these properties were not attributed to a single dimer species, but rather to a more complex dimer assembly. The Epratuzumab dimer was digested with papain to reveal three uniquely dimerized aggregates. The relative molar distribution of Fab:Fab, Fc:Fc, and Fab:Fc was found to be 4:3:8, respectively. The data suggest that all three predominantly covalent dimer adducts are capable of full activity, shedding light on their complex nature and showing that their target specificity was unaltered. ESI-MS data indicated the presence of remnant levels of noncovalent dimers for all three dimerized forms. Material aged at 37 degrees C exhibited a similar papain digest molar distribution of the three dimerized forms, except with enhanced chemical heterogeneity and an increase in covalent forms to approximately 84%.
authors.affiliation: Amgen Inc., One Amgen Center Drive, Thousand Oaks, CA 91320-1799, USA. remmeler@amgen.com
authors.forename: Richard L
authors.initials: RL
authors.lastname: Remmele
authors.forename: William J
authors.initials: WJ
authors.lastname: Callahan
authors.forename: Sampathkumar
authors.initials: S
authors.lastname: Krishnan
authors.forename: Linda
authors.initials: L
authors.lastname: Zhou
authors.forename: Pavel V
authors.initials: PV
authors.lastname: Bondarenko
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Nichols
authors.forename: Gerd R
authors.initials: GR
authors.lastname: Kleemann
authors.forename: Gary D
authors.initials: GD
authors.lastname: Pipes
authors.forename: Sungae
authors.initials: S
authors.lastname: Park
authors.forename: Szilan
authors.initials: S
authors.lastname: Fodor
authors.forename: Eva
authors.initials: E
authors.lastname: Kras
authors.forename: David N
authors.initials: DN
authors.lastname: Brems
mesh_terms: D000911:Antibodies, Monoclonal / Q000737:chemistry*; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000737:chemistry; D019281:Dimerization; D010206:Papain / Q000737:chemistry; D013696:Temperature
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; C448700:epratuzumab; D010206:Papain