Kite Pharma (a Gilead company) described a new approach to characterize individual lentiviral vector particles using flow virometry, targeting deeper batch consistency assessment for next-generation in vivo CAR T therapies. The technique aims to overcome limitations of ensemble-averaged assays by mapping attributes such as vector size and surface proteins at the single-particle level—potentially allowing more robust comparability across lots and stages of development. Kite said the approach is relevant to a broader set of gene and cell therapy products that use enveloped viruses, and it could improve understanding of what constitutes the “virus is the product” for translational manufacturing. In an expanding in vivo vector category, improved analytics may become a gating factor for process development, release criteria, and clinical translation of vector engineering decisions.