Danish researchers reported that a low-level CD19 exon 2 splice variant—detectable in pre-treatment RNA sequencing—correlates with relapse after anti-CD19 CAR-T therapy. The study links relapse risk to a measurable pre-existing molecular feature, suggesting a route for earlier identification of patients likely to fail on-target durability. The approach also fits a broader CAR-T theme in the literature: resistance can be present before infusion via transcript-level diversity rather than only emerging after therapy pressure. If validated prospectively, the splice-skipping signal could be incorporated into screening pipelines. For companies building CAR-T or improving manufacturing and selection, the work provides an actionable biomarker hypothesis that could inform patient stratification and trial design.