Researchers at the University of California, San Francisco (UCSF) have engineered CAR T-cells with a novel "zip code" system to enhance their precision in targeting brain tumors while minimizing damage to healthy tissue. This innovative approach, published in Science, incorporates a two-factor authentication-like mechanism, showing promise for treating glioblastoma and other central nervous system (CNS) disorders.
Engineering Precision with a “Zip Code” Approach
The brain presents unique therapeutic challenges due to the blood-brain barrier and the need to avoid off-target effects on normal tissues. The UCSF team addressed this by programming T-cells to recognize specific molecular markers within the brain’s extracellular matrix. Traditional therapies often target a single molecular marker, potentially leading to off-target effects. Wendell Lim, co-senior author, explained, "It’s better to mail a letter with a zip code and a street address. With a living cell, this is what they typically do. They have instructions about where to go in the body, and then they look for molecular targets."
The team utilized brevican, a protein abundant in the brain’s extracellular matrix. "We engineered synNotch receptors that can recognize [brevican] and then turn on transcription," Lim stated. Upon detecting brevican, the T-cells activate a secondary program that expresses a "killing receptor" to target and destroy tumor cells.
Two-Factor Authentication for Targeted Therapy
This multi-step process acts as a two-factor authentication, requiring the presence of brevican (indicating the T-cells are in the brain) and the identification of tumor-specific antigens to activate their killing function. This dual requirement prevents the T-cells from attacking healthy tissue outside the brain. "It’s like writing a program that says, ‘If in the brain, now kill this tumor,’" Lim explained. "We found that this worked really well…we could even implant the same tumor outside the brain, and the cells would leave that alone but clear the tumor in the mouse brain."
Expanding Application Beyond Glioblastoma
The team demonstrated that this technique could target breast cancer metastases in the brain and potentially treat neuroinflammation and autoimmune diseases like multiple sclerosis. The engineered T-cells exhibited remarkable specificity and durability in preclinical trials. Lim highlighted, "We re-challenged the mice. We took mice that were treated, cleared of their tumors, then re-injected a brain tumor…and they were able to clear it immediately." This suggests the therapy could provide long-term immune memory.
Clinical Trials and Future Directions
The team plans to initiate a clinical trial in 2025, focusing on glioblastoma and pediatric brain tumors. The modular nature of the "zip code" system allows for applications in other organs and diseases. "We’re excited to think about whether we could design similar systems that recognize other organs in the body," Lim said, envisioning organ-specific targeting as a cornerstone of cellular therapy.
