T cells bearing a chimeric antigen receptor (CAR) T-cell consisting of the fusion of the NKG2D NK receptor with the intracellular domain of CD3zeta (CYAD-01) can recognize eight stress ligands expressed in a large variety of cancers. However, activated T cells undergo stress and transiently express NKG2D ligands (NKG2DL). Consequently, CYAD-01 T cells kill sister cells preventing the large-scale manufacturing of CYAD-01 for clinical application.
Inclusion of the PI-3K inhibitor LY294002 into the manufacturing process was the first strategy used as an initial effort focused upon blunting the activity of the CAR T cells. We subsequently developed a process that included a NKG2D blocking antibody during the expansion phase of cell culture.
LY294002 was shown to reversibly reduce NKG2D expression at the cell surface. Consequently, this inhibitor partially controlled fratricide during manufacturing and enhanced viability post-thawing which enabled the initiation of the THINK (NCT03018405) clinical trial. As the trial moved through the dose-escalation phase towards the upper dose level (production of more than 1010 cells), there was an increase in the level of manufacturing failures. This was largely linked to the effect of LY294002 upon T cell proliferation and the challenge faced manufacturing CAR T cells from patients with advanced cancer. Therefore, we subsequently developed a process that included a NKG2D blocking antibody during the expansion phase of cell culture. This strategy enabled the expansion of CYAD-01 T cells to the levels required for the THINK clinical trial. After fine tuning the process, the CYAD-01 CAR T cells generated showed high comparability to the CYAD-01 CAR T cells produced in the first part of the trial. This process has been in place for the THINK trial since January 2018.
Together, these results indicate that when fratricide is an issue preventing clinical development, CAR T cells can be efficiently manufactured through PI-3K inhibition and antibody mediated receptor blockade.
Clinical trial identification
Legal entity responsible for the study
Has not received any funding.
B. Demoulin B. Eytan, D. Gilham: Employee of Celyad SA.