A landscape of sequence variants in 51 commercial antibody therapeutics.

Background: Sequence variants (SVs), unintended amino acid substitutions, represent a quality attribute of antibody therapeutics with potential safety and efficacy implications. Although control strategies are evolving, a comprehensive landscape of SVs in commercial antibody products, including biosimilars, innovators, and those from different expression systems or geographical origins, remains largely unexplored. Methods: We systematically analyzed SVs in 51 commercial antibody therapeutics via optimized high-sensitivity LC-MS/MS peptide mapping. The panel encompassed originators and biosimilars from Chinese and multinational firms, eukaryotic (CHO, NS0) and prokaryotic ( Results: Across all products, 3006 SV occurrences were identified. The vast majority (92.5%) were ≤0.1% per site. Only 7.5% (226 SV occurrences) exceeded 0.1%, 2.4% (72 SV occurrences) exceeded 0.2%, and a minimal 0.4% (12 SV occurrences) exceeded 0.5%. SV levels of Chinese biosimilars and innovators were comparable to international counterparts. While prokaryotic-derived products showed more SVs above 0.2%, SV levels showed no significant correlation with antibody subclasses or formats. Batch-to-batch consistency was excellent across all products. Conclusions: This study provides the largest empirical SV dataset for marketed antibody therapeutics to date. It demonstrates manufacturing processes maintain SV levels below 0.2% per site and reveals no inherent SV disparity across product origin, subclass, or format. Empirically, this 0.2% threshold serves as a pragmatic benchmark for commercial antibody quality control. These findings provide a science-based reference for establishing cell line screening in-process limits, refining industrial SV control strategies, and guiding regulatory science.