CD19 car circRNA-LNP, a lipid nanoparticle containing CD19 car circRNA, is designed for applications in RNA delivery, translation efficiency, and cell viability assessment. This compound is utilized in chimeric antigen receptor T cell immunotherapy (CAR-CD19), leveraging CD19 car, a chimeric antigen receptor that targets CD19. CD19, a CD molecule found on B cells (i.e., leukocyte differentiation antigen), plays a crucial role in B cell proliferation, differentiation, activation, and antibody production by facilitating BCR signal transduction [1] [2].