Residual host cell protein analysis of NISTmAb: From simplified sample preparation to reliable results

Význam tématu

Accurate detection of residual host cell proteins (HCPs) in monoclonal antibody (mAb) products is critical for ensuring safety and efficacy of biotherapeutics. Low-level impurities may compromise drug stability, immunogenicity or patient safety. Regulatory guidelines recommend minimizing total HCP content to under 100 ppm and individual species to under 10 ppm, yet universal thresholds remain undefined. Traditional immunoassays such as ELISA offer sensitivity but are limited by reagent specificity and lack of individual protein identification.

Cíle a přehled studie

This application note presents an optimized workflow combining non-denaturing tryptic digestion, high-efficiency UHPLC separation, high-resolution accurate-mass (HRAM) mass spectrometry and advanced data processing to enhance identification of low-abundance HCPs in the NISTmAb reference material. The objectives are to reduce sample dynamic range, improve HCP coverage down to sub-1 ppm levels and demonstrate reproducibility.

Použitá metodika

Non-denaturing digestion was carried out at 37 °C using a SMART Digest kit with immobilized trypsin to selectively limit mAb proteolysis while preserving HCP peptides. Following a 3-hour digestion, undigested mAb was precipitated by heating to 95 °C and removed by centrifugation. Peptide separations employed a 2.1 × 250 mm Acclaim VANQUISH C18 column over a 90-minute gradient of 0.1% formic acid in water (mobile phase A) and 0.1% formic acid in acetonitrile (mobile phase B). Data acquisition on an Orbitrap Exploris 480 was performed in data-dependent Top15 mode with a 4 m/z isolation window, MS1 resolution at 120 000 and MS2 resolution at 30 000. Automated sample handling utilized a KingFisher Duo Prime system. Data processing in Proteome Discoverer 2.4 included Feature Mapper, Precursor Detector, Sequest HT and Percolator for confident protein identifications and label-free quantification.

Použitá instrumentace

• Thermo Scientific Vanquish Horizon UHPLC system
• Thermo Scientific Acclaim VANQUISH C18 column (2.1 × 250 mm, 2.2 µm)
• Thermo Scientific Orbitrap Exploris 480 mass spectrometer
• SMART Digest Trypsin Kit with magnetic beads
• KingFisher Duo Prime purification system
• Proteome Discoverer 2.4 software

Hlavní výsledky a diskuse

Non-denaturing digestion reduced mAb sequence coverage and MS peak count by over 80% compared to denaturing conditions, effectively lowering sample complexity and dynamic range. Across triplicate analyses, more than 80 HCPs were identified with three or more unique peptides and over 120 HCPs with at least two peptides. Identified HCPs spanned abundances from 222 ppm down to below 0.5 ppm. The Orbitrap Exploris 480 provided high mass accuracy (<2 ppm) and spectral quality that supported confident identifications. Consistent peptide profiles and HCP counts across replicates demonstrated the workflow’s reproducibility.

Přínosy a praktické využití metody

• Detailed profiling of residual HCPs for quality control and process optimization
• Simplified and automatable non-denaturing digestion reduces hands-on time
• Wide isolation window and chimeric spectra analysis enhance sensitivity for low-level impurities
• Label-free HRAM quantification enables monitoring of HCP levels throughout purification

Budoucí trendy a možnosti využití

Integration of ion mobility separation could further reduce spectral complexity and improve resolution of isobaric peptides. Data-independent acquisition and machine learning–based deconvolution may advance quantitation of co-eluting species. Development of targeted assays and expanded spectral libraries for critical HCPs will support more robust impurity monitoring in biotherapeutic development and release.

Závěr

The optimized workflow combining non-denaturing SMART digestion, high-performance UHPLC, HRAM MS detection and advanced informatics delivers robust identification of low-abundance HCPs in mAb preparations. This approach addresses dynamic range challenges, offers high reproducibility and complements traditional immunoassays for comprehensive impurity profiling.

Reference

1. United States Pharmacopeia. Residual Host Cell Protein Measurement in Biopharmaceuticals. USP General Chapter 1132.
2. Fengqiang W et al. Host-Cell Protein Measurement and Control. BioPharm International. 2015;28(6):32–38.
3. Huang L et al. A novel sample preparation for shotgun proteomics characterization of HCPs in antibodies. Anal Chem. 2017;89(10):5436–5444.
4. Doneanu CE et al. Enhanced detection of low-abundance HCP impurities in high-purity mAbs using ion mobility MS. Anal Chem. 2015;87:10283–10291.