Clinical studies using autologous CAR T cells have achieved
spectacular remissions in refractory CD19+ B cell leukaemia,
however some of the patient treatments with CAR T cells
failed. Beside the heterogeneity of leukaemia, the distribution and senescence of the autologous cells from heavily
pretreated patients might be further reasons for this. We performed six consecutive large-scale manufacturing processes
for CD20 CAR T cells from healthy donor leukapheresis using
the automated CliniMACS Prodigy® platform. Starting with
a CD4/CD8-positive selection, a high purity of a median
of 97% T cells with a median 65-fold cell expansion was
achieved. Interestingly, the transduction rate was significantly higher for CD4+ compared to CD8+ T cells and reached
in a median of 23%. CD20 CAR T cells showed a good specific IFN-γ secretion after cocultivation with CD20+ target
cells which correlated with good cytotoxic activity. Most importantly, 3 out of 5 CAR T cell products showed an increase
in telomere length during the manufacturing process, while
telomere length remained consistent in one and decreased
in another process. In conclusion, this shows for the first time
that beside heterogeneity among healthy donors, CAR T cell
products also differ regarding cell senescence, even for cells
manufactured in a standardised automated process
