Researchers develop TIM-3 decoy to enhance CAR-T therapy effectiveness for B-ALL tumors

B-cell Acute Lymphoblastic Leukemia (B-ALL) is a life-threatening and highly aggressive form of blood cancer. It is the most common childhood cancer, making up 35% of pediatric cancer cases, but it can affect people of any age. CAR-T cell therapy has significantly improved outcomes for B-ALL patients, but relapse still occurs in over 50% of cases, leaving many with limited treatment options. Ongoing research aims to address this challenge and improve CAR-T therapy effectiveness.

One of the major challenges in treating B-cell Acute Lymphoblastic Leukemia (B-ALL) with CAR-T cell therapy is relapse. A key issue that researchers are investigating is why CAR-T cells, which are a living medicine, sometimes fail to respond to cancer cells, even in their presence. A promising lead has emerged from examining the interaction between the tumor and immune cells, including CAR-T cells.

It turns out that B-ALL tumors may take advantage of the body’s natural defense mechanisms, specifically the immune checkpoint pathways. These pathways usually act as “off switches,” telling immune cells to stop attacking once the infection or threat has been cleared. However, tumors can hijack this system to avoid being attacked by the immune system.

CAR-T cells ‘turned off’ by the tumor

In CAR-T therapy, T-lymphocytes are extracted from the patient’s blood to be treated and modified in the laboratory, so that they can specifically recognize and target cancer cells. Once modified, T-lymphocytes are reintroduced into the patient’s body.

In the case of B-ALL, researchers discovered that relapsed leukemia cells have unusually high levels of galectin-9, a ligand that is part of the immune checkpoint system. On the other hand, CAR-T cells express high levels of TIM-3, a receptor that normally interacts with galectin-9 to suppress immune activity. The tumor seems to use this interaction to “turn off” the CAR-T cells, allowing the cancer to persist.

To address this problem, researchers created a TIM-3 decoy, a soluble version of the TIM-3 protein, that could block the ligand-receptor interaction. The idea was that this decoy would prevent the tumor from turning off the CAR-T cells, without directly signaling them to stop their immune activity.

In laboratory tests using genetically modified mice with human B-ALL cells, the results were promising. CAR-T cells engineered to secrete the TIM-3 decoy showed improved anti-leukemia effectiveness and long-term persistence.

Although still in the preclinical stage, this research marks an important first step toward improving treatments for B-ALL patients. The goal is to enhance the effectiveness of CAR-T therapy and reduce relapses, two major challenges faced by patients undergoing current CAR-T treatments. This approach could also pave the way for developing “armored CAR-T cells” and expanding the potential of CAR-T therapy to treat solid tumors in the future.

This international study has been led by researchers from the Josep Carreras Leukaemia Research Institute and the Hospital Universitario 12 de Octubre – Spanish National Cancer Research Centre (CNIO), in collaboration with Salamanca University, Hospital Clinic, and other Spanish and European research institutions. The research team was led by Aïda Falgàs, Rodrigo Lázaro-Gorines and Samanta Romina Zanetti, under the supervision of Pablo Menéndez, Clara Bueno, and Luis Álvarez-Vallina.