Mass Spectrometry Workflows in Cell and Gene Therapy

Cell and gene therapies present analytical challenges that conventional quality control methods were not designed to address. Advanced therapeutics require the highest resolution analytics available to ensure safety, and mass spectrometry has become the primary tool for characterizing viral vectors, confirming product identity, and detecting impurities at the molecular level. As regulatory scrutiny of these complex modalities intensifies, mass spectrometry (MS) workflows are increasingly embedded across the full manufacturing life cycle.

Viral vector characterization with high-resolution mass spectrometry

Viral vectors, particularly AAV serotypes and lentiviral vectors, require molecular characterization that extends well beyond simple titer measurements. LC-MS/MS-based peptide mapping workflows applied to tryptic digests of purified vector preparations confirm the amino acid sequence of capsid viral proteins, detect post-translational modifications including deamidation, oxidation, and phosphorylation, and localize modification sites that could influence in vivo tropism or immunogenicity.

Intact mass analysis using native MS extends this capability to the full assembled particle. Because AAV particles occupy the multi-megadalton range, conventional data-dependent acquisition is insufficient for direct intact mass measurement. Native electrospray ionization under non-denaturing conditions allows charge-state distributions from empty and genome-loaded capsids to be resolved, with empty particles producing distinct mass-to-charge clusters from full capsids. This approach provides orthogonal assessment of capsid content ratios without the extensive sample preparation required by analytical ultracentrifugation.

Online platforms coupling size-exclusion chromatography desalting to native MS have addressed one longstanding barrier to routine deployment: the need for highly pure, extensively desalted material prior to infusion. These integrated LC-native MS systems reduce analysis time and improve throughput, making capsid content ratio monitoring more compatible with manufacturing quality control timelines.

Host cell protein analysis by MS in gene therapy

Host cell proteins are process-related impurities co-purified from the production cell line alongside the viral vector. Enzyme-linked immunosorbent assay remains the regulatory standard for total host cell protein quantification, but it lacks the specificity to identify individual species or detect reagent coverage gaps. LC-MS/MS-based profiling addresses this limitation, enabling identification and relative quantification of hundreds of individual proteins within a single injection.

In gene therapy, host cell protein analysis is further complicated by the fact that certain proteins can be packaged inside viral capsids rather than remaining as external process impurities, requiring capsid lysis before extraction. Data-independent acquisition strategies improve the reproducibility and quantitative accuracy of these measurements compared with data-dependent approaches, particularly for low-abundance impurities detected against a high background of dominant capsid proteins. Establishing host cell protein clearance across downstream purification steps is a core deliverable for any gene therapy chemistry, manufacturing, and controls package.

MS in cell therapy and release testing

Cell therapy products, including chimeric antigen receptor T cell therapies, present a different analytical challenge: the product is a live, functionally complex cell population rather than a purified molecular entity. Bottom-up proteomics workflows applied to cell lysates generate comprehensive protein abundance profiles capturing receptor expression levels, co-stimulatory domain modification status, and activation state markers in a single multiplexed experiment. This molecular resolution directly supports potency and comparability assessments, particularly when manufacturing processes are transferred between facilities or scaled to commercial production.

FDA guidance published in early 2024 on chimeric antigen receptor T cell product development explicitly recommends orthogonal analytical methods for critical quality attribute assessment, positioning MS alongside flow cytometry and functional assays. For lot release and comparability testing across gene therapy products, LC-MS/MS-based HCP clearance tracking enables detection of abundance changes in individual impurities across downstream purification stages, providing quantitative data that supports process optimization and regulatory submission alongside functional and immunological assays.

Table 1. MS workflow applications across cell and gene therapy modalities.

MS as a foundation for CGT analytical strategy

MS workflows now span the full analytical life cycle of cell and gene therapy programs, from early process development through clinical manufacturing and post-approval lot release. Embedding MS data within the analytical characterization platforms that govern broader drug development programs creates consistency between the methods used to characterize the molecule and those used to release it.

For programs advancing through the clinic, alignment between manufacturing MS workflows and the industrial quality control frameworks that govern commercial-scale bioproduction reduces analytical gaps at technology transfer. The process analytical technology approaches shaping broader biopharma manufacturing increasingly frame MS as a complementary real-time or at-line characterization tool. MS does not replace established compendial methods but provides the molecular resolution needed to understand, control, and demonstrate comparability for products whose complexity exceeds the discriminating power of legacy assays.

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