Spanish researchers have performed a multi-omics analysis of individual cells in an infusion product of therapeutic chimeric antigen receptor T cells and found that the composition and properties of the cells in it, as well as their dynamics after administration, significantly affect the effectiveness of the treatment. A report on the work is published in the journal Cell Reports Medicine.
T-lymphocytes with chimeric antigen receptors (CAR-T-lymphocytes) allow achieving radical success in the treatment of oncological diseases, up to a complete cure (you can read more about this technology in the article “Chimera against cancer”). Currently, drugs for the treatment of B-cell oncohematological neoplasms and one of the types of synovial sarcoma have reached clinical use. At the same time, they effectively help about half of the patients for whom other types of therapy have failed, and the other half have an insufficient or absent response. The likelihood of success depends on many factors, the study of which is currently ongoing.
Pablo Menéndez (Josep Carreras Leukemia Research Institute) and colleagues performed an integrated analysis of the clonal kinetics and transcriptomic heterogeneity of CD19-CAR T-cell infusion products (varnimcabtagene autoleucel, varni-cel) manufactured ex vivo for five patients with refractory or relapsed B-cell acute lymphoblastic leukemia. To do this, they performed sequencing of the αβ T-cell receptor and RNA in individual cells isolated by flow cytometry based on CAR expression. The cellular dynamics analysis included both CAR-transduced (CAR-positive) and non-transduced (CAR-negative) T cells in the product.
The CAR transduction rate in the infusion products ranged from 23 to 38 percent. The levels of CAR T cell expansion in patients varied, peaking between the first and fourth weeks after infusion. Two patients had early relapses in the second and third months, one had a late relapse in the sixth month, and two had a durable complete response to therapy. A total of 37.1 thousand single high-quality T cells were analyzed across all samples at different stages. They clearly distinguished clusters of naive CD4+ cells; effector, memory and cytotoxic CD8+ cells; and cytotoxic γδ T cells.
Comparison of CAR-positive and CAR-negative cell subtypes in the infusion product showed that the former proliferate significantly more actively, while the non-proliferating fraction of the latter contains a significantly higher proportion of effector CD8+ cells. As it turned out, in patients with a complete response to therapy, there were at least three times more CAR-positive CD4+ cells in the infusion product than CD8+. The impact of this ratio on efficacy was confirmed (p = 0.03) in a separate cohort of 47 patients with B-cell acute lymphoblastic leukemia. At the same time, the expression of markers of T-lymphocyte depletion preceding transduction negatively correlated with the success of therapy.
At the peak of proliferation in patients, the proportion of proliferating CAR-positive and CAR-negative T lymphocytes decreased, being replaced by CD8+ cells, which predominated over CD4+ among non-proliferating CAR-positive ones. At the same time, the population of both positive and negative γδ T lymphocytes increased significantly at the peak, and its growth directly correlated with the effectiveness of therapy. The clinical significance of these cells was confirmed in retrospective cohorts of 18 patients with acute B-cell lymphoblastic leukemia who received varnicel and 58 patients with diffuse large B-cell lymphoma who received axicel or tisacel.
The obtained results indicate the complex nature of the T-cell response in CD19-CAR-T therapy, which is not limited to CAR-positive αβ T lymphocytes. In particular, the CD4+/CD8+ ratio in the infusion product, prior cell depletion and the expansion of γδ T lymphocytes after infusion are of great importance. Influencing these factors may potentially improve the success of treatment, the authors conclude.
Previously, American researchers were able to increase the effectiveness of CAR-T therapy many times over in preclinical trials on mice using experimental modified human interleukin-7, which stimulates the growth of lymphocytes.
