| Autor: |
Lan W; Drug Product Development, Bristol Myers Squibb, New Brunswick, United States., Valente JJ; Drug Product Development, Bristol Myers Squibb, New Brunswick, United States., Ilott A; Drug Product Development, Bristol Myers Squibb, New Brunswick, United States., Chennamsetty N; Biophysics Center of Excellence, Global Product Development and Supply, Bristol Myers Squibb, New Brunswick, United States., Liu Z; Drug Product Development, Bristol Myers Squibb, New Brunswick, United States., Rizzo JM; Discovery Biotherapeutics, Bristol Myers Squibb, Pennington, United States., Yamniuk AP; Discovery Biotherapeutics, Bristol Myers Squibb, Pennington, United States., Qiu D; Chemical Process Department, Bristol Myers Squibb, New Brunswick, United States., Shackman HM; Chemical Process Department, Bristol Myers Squibb, New Brunswick, United States., Bolgar MS; Drug Product Development, Bristol Myers Squibb, New Brunswick, United States. |
| Abstrakt: |
During the development of a therapeutic monoclonal antibody (mAb-1), the charge variant profile obtained by pH-gradient cation exchange chromatography (CEX) contained two main peaks, each of which exhibited a unique intrinsic fluorescence profile and demonstrated inter-convertibility upon reinjection of isolated peak fractions. Domain analysis of mAb-1 by CEX and liquid chromatography-mass spectrometry indicated that the antigen-binding fragment chromatographed as two separate peaks that had identical mass. Surface plasmon resonance binding analysis to antigen demonstrated comparable kinetics/affinity between these fractionated peaks and unfractionated starting material. Subsequent molecular modeling studies revealed that the relatively long and flexible complementarity-determining region 3 (CDR3) loop on the heavy chain could adopt two discrete pH-dependent conformations: an "open" conformation at neutral pH where the HC-CDR3 is largely solvent exposed, and a "closed" conformation at lower pH where the solvent exposure of a neighboring tryptophan in the light chain is reduced and two aspartic acid residues near the ends of the HC-CDR3 loop have atypical pKa values. The pH-dependent equilibrium between "open" and "closed" conformations of the HC-CDR3, and its proposed role in the anomalous charge variant profile of mAb-1, were supported by further CEX and hydrophobic interaction chromatography studies. This work is an example of how pH-dependent conformational changes and conformation-dependent changes to net charge can unexpectedly contribute to perceived instability and require thorough analytical, biophysical, and functional characterization during biopharmaceutical drug product development. |
