GEN-MKT-18-7897-A
Jan 10, 2017 | Biopharma, Blogs | 0 comments
Protein-based biotherapeutics, including monoclonal antibodies (mAbs) and antibody-drug conjugates (ADCs) are a growing component of pharmaceutical companies’ drug pipelines. The growth of ADCs in particular is due to their ability to selectivity target and deliver a potent molecule to a cancer cell based on a specific tumor marker. In order to support this growing class of new drug molecules, robust and reliable bioanalytical methods are required. While ligand binding assays (LBAs) like ELISA have been the most popular platform for biotherapeutic quantitation, bioanalytical scientists have been increasingly adopting hybrid LBA/LC-MS methods in this area.
The strengths of hybrid LC-MS assays for this application include:
For a bioanalytical scientist inexperienced in hybrid LBA/LC-MS signature peptide quantitation, the various workflows can appear complex and difficult. BioBA sample preparation kits are designed to make this complex process simple by enabling a magnetic bead-based approach to immunoaffinity sample preparation and providing all the reagents necessary (buffers, reagents, enzyme and bead) to complete the workflow.
Most ADCs are heterogeneous mixtures of species and an example is ado-trastuzumab emtansine, a lysine-linked ADC that is an approved treatment for patients with Her2+ breast cancer. The nature of the chemistry involved in lysine conjugation makes the drug product a heterogeneous mixture of species with a drug to antibody (DAR) of 0 to 8. The heterogeneous character of ADCs like adotrastuzumab emtansine require several bioanalytical assays during the drug development process. Some of these include:
Hybrid LBA/LC-MS assays can be used to address conjugated and total antibody assays by choosing an appropriate immunocapture reagent. An anti-payload antibody can be used to immunopurify and assay conjugated ADC species. To assay the total antibody, a generic anti-human Fc antibody can be employed for immunocapture, or a target-specific immunocapture strategy can be employed with recombinant target protein or an anti-idiotype antibody.
Download the tech note to see a full demonstration of a total antibody assay of ado-trastuzumab emtansine using hybrid LBA/LC-MS approach employing the BioBA sample preparation kit and a generic immunocapture strategy.
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As an analytical strategy, middle-down mass spectrometry (MS) workflows characterize biotherapeutic proteins by analyzing large, digested protein fragments or defined subunits, rather than fully intact proteins (top-down) or digested peptides (bottom-up). A middle-down strategy combines the strengths of top-down and bottom-up approaches by delivering high sequence coverage and structural specificity while maintaining relatively simple sample preparation. In practice, middle-down analysis enables accurate mass measurement, rapid sequence confirmation, and localization of key post-translational modifications (PTMs) on protein subunits that are directly relevant to product quality.
In biopharmaceutical development, sequence variants (SV) are considered an inherent risk of producing complex proteins in living systems. Sequence variants are unintended changes to the amino acid sequence of a biotherapeutic and can be caused by errors in transcription or translation in the host cell, or cell culture and process conditions. Detailed analysis of SVs is important in process and product development to ensure the drug’s safety and efficacy. Even low‑level sequence variants can have significant implications for product quality, safety, and efficacy, making their accurate detection and characterization a critical requirement across development, process optimization, and regulatory submission.
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