Dr Hasan on the Preclinical Efficacy of ROR1-Specific CAR T-Cells in CLL

Md Kamrul Hasan, PhD, assistant project scientist, Department of Medicine, University of San Diego California, discusses the preclinical efficacy and safety of ROR1-specific CAR T-cells in a preclinical mouse model of chronic lymphocytic leukemia (CLL).

In this preclinical study, investigators developed a CAR T-cell construct using intracellular co-stimulatory domains (CD137 and CD3zeta), a CD28 transmembrane domain, and an IgG4 spacer region. This construct featured an anti-ROR1-scFv derived from the humanized scFv of zilovertamab. Zilovertamab (formerly UC-961/ cirmtuzumab) had previously demonstrated high affinity and a favorable safety profile in a phase 1 trial, Hasan details. The researchers employed this anti-ROR1 CAR construct to generate anti-ROR1 CAR T-cells from both healthy donors and patients with CLL. The cytotoxic activity of ROR1-CAR T-cells in both primary CLL cells and the CLL-derived mouse model was then assessed, Hasan explains.

Results showed that anti-ROR1 CAR T-cells was safe and exhibited potent cytotoxicity against autologous or allogenic primary CLL cells expressing high-risk adverse genetic features such as mutant TP53 or 17p deletions, or transfected cells expressing ROR1, Hasan reports. Notably, the cytotoxic activity of anti-ROR1 CAR T-cells was found to be specific for ROR1. This was previously demonstrated by the inhibition of killing capacity when CLL cells were pretreated with the anti-ROR1 monoclonal antibody zilovertamab.

Furthermore, researchers reported that anti-ROR1 CAR T-cells did not exhibit cytotoxic activity against normal B cells. This specificity was maintained even in co-culture with ROR1-expressing CLL cells, highlighting the potential of this approach to selectively target CLL cells without affecting normal CD19/CD20-expressing B cells.

In the immune-deficient murine model, anti-ROR1 CAR T-cells were active in eliminating ROR1-expressing cells, demonstrating their in-vivo efficacy. Investigators concluded that lentivirus encoding this anti-ROR1 CAR construct can successfully generate anti-ROR1 CAR T-cells from both healthy donors and CLL patients. These T-cells showed early efficacy when eliminating ROR1-expressing leukemia cells both in vitro and in vivo, providing a promising avenue for targeted CLL treatment with potential advantages in terms of selective killing and reduced impact on normal B cells. An evaluation of anti-ROR1 CAR T-cells in human patients is currently in development based on these results, Hasan concludes.