Exploring the Effectiveness of CAR T-Cell Injections for CLL Patients

Researchers recently studied the influence genetics have on chronic lymphocytic leukemia (CLL) patients’ response to anti-CD19 chimeric antigen receptor (CAR)-T cell therapy.

Veronika Mancikova, PhD, Central European Institute of Technology (CEITEC), Masaryk University, Brno, Czech Republic, and colleagues, noted, “While achieving prolonged remissions in other B cell-derived malignancies, CAR-T cells still underperform when injected into patients with CLL.”

The study consisted of studying 32 primary CLL samples composed of 26 immunoglobulin heavy-chain gene variable (IGHV)-unmutated (9 ATM-mutated, 8 TP53-mutated, and 9 without mutations in ATM, TP53, NOTCH1 or SF3B1) and 6 IGHV-mutated samples without mutations in the above-mentioned genes.

The researchers then used 2S stimulation through interleukin-2 and nuclear factor kappa B in the primary cells to mimic a leukemic microenvironment.

“Finally, CRISPR/Cas9-generated ATM -knockout and TP53-knockout clones (four and seven, respectively) from CLL-derived cell lines MEC1 and HG3 were used,” explained Dr Mancikova and colleagues. “All these samples were exposed to CAR-T cells. In vivo survival study in NSG mice using HG3 wild-type (WT), ATM -knockout or TP53-knockout cells was also performed.”

Results of the study show that primary unstimulated CLL cells were eliminated after >24 hours of coculture with CAR-T cells, 2S stimulated cells saw increased survival when exposed to CAR-T cells—confirming the positive effect of this stimulation on CLL cells' in vitro fitness—and after 96 hours of coculture, there was no difference in survival among the genetic classes.

When CAR-T cells were activated in vitro in the presence of target knockout cell lines, there was no difference in knockout cells' survival. However, in vivo, CAR-T cells prolonged the survival of mice injected with WT, TP53-knockout, and ATM-knockout HG3 tumor cells as compared with CTRL T cells (p=0.0485, 0.0204 and <0.0001, respectively).

"While in vitro no differences in survival of CLL cells of various genetic backgrounds were observed, CAR-T cells showed a different effectiveness at eradicating tumor cells in vivo depending on the driver mutation," explained Dr Mancikova, and colleagues. “Early disease onset, high-tumor burden and inefficient T-cell engraftment, associated with TP53-knockout tumors in our experimental setting, ultimately led to inferior performance of CAR-T cells.”

—Edan Stanley

Reference:

Mancikova V, Peschelova H, Kozlova V, et al. Performance of anti-CD19 chimeric antigen receptor T cells in genetically defined classes of chronic lymphocytic leukemia. J Immunother Cancer. 2020;8(1):e000471. doi:10.1136/jitc-2019-000471