Understanding the Propensity of Sequence Variants During Cell Line and Culture Process Development
18th March 2019 | 10.00 am EST | Dr. Lisa Marzilli, Associate Research Fellow and group leader at Pfizer, USA |BOOK FREE SEAT
Sequence variants (SVs) are protein isoforms that contain one or more unintended amino acid substitutions. They can arise at a single amino acid site due to a genetic (RNA/DNA) mutation or at multiple amino acid locations, potentially due to translational errors, also referred to as misincorporations. The ability to detect SVs in protein biotherapeutics is critical due to their potential impact on structural/functional characteristics, safety and efficacy. Trypsin peptide mapping with liquid chromatography-ultrahigh resolution tandem mass spectrometry (LC-MS/MS) provides the ideal workflow for the detection, identification, and relative quantitation of both genetic and translational SVs. LC-MS/MS complements next-generation sequencing (NGS) of product cDNA and amino acid analysis (AAA) of cell culture medium during clone selection and process optimization in providing sensitive, comprehensive screening to strategically prevent/minimize SVs and ensure high product quality.
The occurrence of genetic SVs was evaluated using Sanger sequencing and LC/MS. In this work, mAbs with known high and low-level genetic SVs were studied at various cell culture conditions including scale, process and cell age. While scale and process had no significant impact on genetic SV levels, low-level SVs were found to decrease with cell age whereas high level SVs remained constant.
Multiple cell culture process options and the final process conditions are analyzed via LC-MS/MS prior to lock-down of the manufacturing process. Additionally, the cell culture medium (days in culture) for all small scale, pilot and clinical batches are analyzed by AAA to ascertain amino acid nutrient levels, which provides indirect monitoring of possible misincorporation situations. For mAbs with confirmed misincorporations, AAA and LC-MS/MS-peptide mapping results primarily correlated with amino acid nutrient depletion. If misincorporations are detected above a particular alert limit, then the daily feed rate and/or amino acid concentrations are increased to prevent amino acid depletion.
Presented by Dr. Lisa Marzilli, Associate Research Fellow and Group Leader – Mass Spectrometry at Pfizer, USA
Currently an Associate Research Fellow, Lisa is a group leader in the Mass Spectrometry and Biophysical Characterization group at Pfizer in Andover, MA. Lisa received a Bachelor of Science degree in biology from Union College in Schenectady NY and a Masters in Teaching from Boston University. She taught high school chemistry before returning to graduate school for a Ph.D. degree in Analytical Chemistry from Northeastern University, Boston, MA. Before joining Wyeth, Lisa was a postdoctoral fellow at Johns Hopkins Medical School, Baltimore, MD. She joined the mass spectrometry group of Genetics Institute (Wyeth) in Andover, MA, in 2000 and has continuously worked on the structural characterization of protein therapeutics using mass spectrometry-based techniques.