Researchers at Université Claude Bernard Lyon’s Institut des Sciences Analytiques reported scout-triggered MRM (st-MRM), a targeted proteomics workflow designed to improve host-cell protein (HCP) monitoring across shifting matrices in biomanufacturing. Using assays spanning 97 CHO-derived HCPs through 240 peptides, the team showed that conventional retention-time-scheduled MRM can miss peptides and lose transferability when retention time shifts by minutes across drug substances and intermediates. st-MRM uses scout peptides to dynamically trigger transitions during runs, enabling detection across multiple matrices from a single injection and reporting quantification down to 2.9 ppm in purified drug substance—an approach aimed at more robust impurity control under regulator expectations.