Kite Pharma, a Gilead company, developed a technique for analyzing individual lentiviral vector particles using flow virometry—an approach intended to support more detailed characterization of in vivo CAR T therapy products. Traditional methods like Western blotting can average signals across particles, potentially masking differences in particle-to-particle protein content. By staining and quantifying surface proteins at the single-particle level, Kite aims to improve consistency assessment during development, including late-stage batch-to-batch comparability. The company positions the approach as relevant to the growing lentiviral delivery space, where product definition increasingly requires resolution beyond ensemble averages. The initiative reflects a broader trend in gene therapy quality systems: analytical methods are being upgraded to measure heterogeneity that could affect efficacy and safety profiles.