title: Mass spectrometric characterization of transglutaminase based site-specific antibody-drug conjugates.
abstract: Antibody drug conjugates (ADCs) are becoming an important new class of therapeutic agents for the treatment of cancer. ADCs are produced through the linkage of a cytotoxic small molecule (drug) to monoclonal antibodies that target tumor cells. Traditionally, most ADCs rely on chemical conjugation methods that yield heterogeneous mixtures of varying number of drugs attached at different positions. The potential benefits of site-specific drug conjugation in terms of stability, manufacturing, and improved therapeutic index has recently led to the development of several new site-specific conjugation technologies. However, detailed characterization of the degree of site specificity is currently lacking. In this study we utilize mass spectrometry to characterize the extent of site-specificity of an enzyme-based site-specific antibody-drug conjugation technology that we recently developed. We found that, in addition to conjugation of the engineered site, a small amount of aglycosylated antibody present in starting material led to conjugation at position Q295, resulting in approximately 1.3% of off-target conjugation. Based on our detection limits, we show that Q295N mutant eliminates the off-target conjugation yielding highly homogeneous conjugates that are better than 99.8% site-specific. Our study demonstrates the importance of detailed characterization of ADCs and describes methods that can be utilized to characterize not only our enzyme based conjugates, but also ADCs generated by other conjugation technologies.
authors.affiliation: Rinat-Pfizer Inc. , 230 East Grand Avenue, South San Francisco, California 94080, United States.
authors.forename: Santiago E
authors.initials: SE
authors.lastname: Farias
authors.forename: Pavel
authors.initials: P
authors.lastname: Strop
authors.forename: Kathy
authors.initials: K
authors.lastname: Delaria
authors.forename: Meritxell
authors.initials: M
authors.lastname: Galindo Casas
authors.forename: Magdalena
authors.initials: M
authors.lastname: Dorywalska
authors.forename: David L
authors.initials: DL
authors.lastname: Shelton
authors.forename: Jaume
authors.initials: J
authors.lastname: Pons
authors.forename: Arvind
authors.initials: A
authors.lastname: Rajpal
mesh_terms: D000906:Antibodies / Q000737:chemistry*; D002853:Chromatography, Liquid; D004364:Pharmaceutical Preparations / Q000737:chemistry*; D053719:Tandem Mass Spectrometry / Q000379:methods*; D011503:Transglutaminases / Q000737:chemistry*
chemical_list: D000906:Antibodies; D004364:Pharmaceutical Preparations; D011503:Transglutaminases