Switchable CAR-T Cells Offer New Hope for Cancer Treatment

Engineered immune cells, known as chimeric antigen-receptor (CAR) T cells, have revolutionized the treatment of blood cancers, but limitations remain. Researchers are now developing CAR-T cells that can be switched on and off on demand, potentially expanding their use to solid tumors and reducing dangerous side effects.

The Promise and Challenges of CAR-T Cell Therapy

CAR T-cell therapy involves genetically engineering a patient’s own T cells to attack cancer cells. Although highly effective against certain blood cancers like acute lymphoblastic leukemia, non-Hodgkin lymphoma, and multiple myeloma , CAR-T cell therapy faces challenges. These include limited efficacy against solid tumors and the risk of killing healthy cells or triggering a severe immune overreaction .

A New Approach: Remote-Controlled CAR-T Cells

Researchers at the Ludwig Institute for Cancer Research and the École Polytechnique Fédérale de Lausanne (EPFL) have engineered a CAR-T cell with a switch that can be activated or deactivated as needed . This new system utilizes a cancer drug already in clinical use, venetoclax, to control CAR-T cell activation.

How the DROP-CAR System Works

The newly designed CAR-T cell, dubbed “drug-regulated off-switch PPI CAR” (DROP-CAR), features a unique mechanism for controlling its activity. The internal signaling component of the CAR is linked to a protein strip on the cell’s exterior, which binds to a protein named BCL-2. The cancer-sensing part of the CAR similarly carries a fragment of BCL-2. This spontaneous protein-protein interaction keeps the CAR functional until venetoclax disrupts the connection, effectively switching off the CAR-T cell.

When venetoclax is withdrawn, the CAR reassembles, and the T cells resume killing cancer cells. Unlike previous controllable CAR designs, this system uses only human protein components and a clinically approved drug to directly disrupt tumor cell binding, enhancing safety and preserving the CAR-T cells for continued treatment.

Mitigating T Cell Exhaustion

Controlling CAR-T cell activity could also address T cell “exhaustion,” a phenomenon where continuous stimulation leads to T cells becoming functionally sluggish and unable to kill cancer cells. By allowing periods of rest between active targeting, DROP-CAR-T cells may assist reverse the genomic alterations that drive exhaustion and improve their effectiveness.

Clinical Potential

Because venetoclax is already approved for cancer therapy, the researchers believe their CAR-T system is well-positioned for clinical evaluation. This new approach offers a promising pathway to overcome current limitations and expand the benefits of CAR-T cell therapy to a wider range of patients and cancer types.