Kite Pharma, a Gilead company, described a new cytometry technique intended to characterize individual lentiviral vector particles for in vivo CAR T therapy development. The approach uses flow virometry to assess particle-level attributes such as size and surface proteins, aiming to improve consistency and batch characterization versus population-averaging methods. Kite said traditional techniques like Western blotting can obscure heterogeneity by averaging high- and low-protein-expressing particles together. The new particle-level assay is intended to map protein distribution across individual particles rather than rely solely on bulk measurements. The company plans to incorporate the method throughout development and into final-stage consistency checks, aligning with the still-evolving analytical requirements for in vivo viral vector manufacturing and release testing.