title: Resolving self-association of a therapeutic antibody by formulation optimization and molecular approaches.
abstract: A common challenge encountered during development of high concentration monoclonal antibody formulations is preventing self-association. Depending on the antibody and its formulation, self-association can be seen as aggregation, precipitation, opalescence or phase separation. Here we report on an unusual manifestation of self-association, formation of a semi-solid gel or "gelation." Therapeutic monoclonal antibody C4 was isolated from human B cells based on its strong potency in neutralizing bacterial toxin in animal models. The purified antibody possessed the unusual property of forming a firm, opaque white gel when it was formulated at concentrations >30 mg/mL and the temperature was <6°C. Gel formation was reversible with temperature. Gelation was affected by salt concentration or pH, suggesting an electrostatic interaction between IgG monomers. A comparison of the C4 amino acid sequences to consensus germline sequences revealed differences in framework regions. A C4 variant in which the framework sequence was restored to the consensus germline sequence did not gel at 100 mg/mL at temperatures as low as 1°C. Additional genetic analysis was used to predict the key residue(s) involved in the gelation. Strikingly, a single substitution in the native antibody, replacing heavy chain glutamate 23 with lysine (E23K), was sufficient to prevent gelation. These results indicate that the framework region is involved in intermolecular interactions. The temperature dependence of gelation may be related to conformational changes near glutamate 23 or the regions it interacts with. Molecular engineering of the framework can be an effective approach to resolve the solubility issues of therapeutic antibodies.
authors.affiliation: a MassBiologics of the University of Massachusetts Medical School ; Boston , MA USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Casaz
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Boucher
authors.forename: Rachel
authors.initials: R
authors.lastname: Wollacott
authors.forename: Brian G
authors.initials: BG
authors.lastname: Pierce
authors.forename: Rachel
authors.initials: R
authors.lastname: Rivera
authors.forename: Maja
authors.initials: M
authors.lastname: Sedic
authors.forename: Sadettin
authors.initials: S
authors.lastname: Ozturk
authors.forename: William D
authors.initials: WD
authors.lastname: Thomas
authors.forename: Yang
authors.initials: Y
authors.lastname: Wang
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics*; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry* / Q000235:genetics* / Q000627:therapeutic use; D057134:Antibodies, Neutralizing / Q000737:chemistry / Q000235:genetics / Q000627:therapeutic use; D004167:Diphtheria Toxin / Q000037:antagonists & inhibitors; D005782:Gels / Q000737:chemistry; D018698:Glutamic Acid / Q000235:genetics; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007143:Immunoglobulin Heavy Chains / Q000737:chemistry / Q000235:genetics; D008239:Lysine / Q000235:genetics; D008958:Models, Molecular; D011485:Protein Binding / Q000235:genetics; D015202:Protein Engineering / Q000379:methods*; D017434:Protein Structure, Tertiary; D055672:Static Electricity; D013696:Temperature
chemical_list: D000911:Antibodies, Monoclonal; D057134:Antibodies, Neutralizing; D004167:Diphtheria Toxin; D005782:Gels; D007143:Immunoglobulin Heavy Chains; D018698:Glutamic Acid; D008239:Lysine
keywords: CDR, complementarity-determining regions; PDB, Protein Data Bank; antibody; formulation; framework; gelation; monoclonal