UCSF Scientists Develop Groundbreaking CRISPR Method to Reprogram Cancer-Fighting Immune Cells Directly Inside the Body

UCSF researchers use CRISPR to reprogram immune cells inside the body, successfully treating leukemia and solid tumors without external manufacturing.

By: AXL Media

Published: Mar 19, 2026, 4:34 AM EDT

Source: Information for this report was sourced from University of California - San Francisco

The Evolution of Precision Immunotherapy

The landscape of oncology has been transformed by Chimeric Antigen Receptor (CAR) T cell therapy, a process that traditionally involves a complex "vein-to-vein" cycle. In the standard model, a patient’s immune cells are extracted, shipped to specialized laboratories for genetic modification, and then returned weeks later for infusion. While life-saving, this logistical hurdle costs hundreds of thousands of dollars and often leaves critically ill patients waiting while their disease progresses. Scientists at UCSF have now pioneered a method to bypass this entire infrastructure, using molecular tools to provide the necessary genetic instructions to T cells while they are still circulating in the patient’s bloodstream.

A Dual-Particle Delivery System

To achieve precise reprogramming without removing cells from the body, the research team designed a sophisticated "delivery vehicle" consisting of two distinct particles. The first particle is coated with specific antibodies that act as a homing device, ensuring the CRISPR-Cas9 gene-editing machinery only enters T cells and ignores other biological tissues. The second particle carries the large DNA sequence required to build the cancer-fighting receptor, along with a "molecular on-switch" that only activates once the gene is integrated into the correct location of the T cell genome. This targeted approach prevents the risks associated with random DNA integration, a common drawback of traditional virus-based methods.

Rapid Clearance of Aggressive Cancers

The efficacy of this in-body manufacturing was tested in "humanized" mice suffering from highly aggressive forms of leukemia. According to the study's lead authors, a single injection of the dual-particle system was sufficient to clear all detectable cancer in nearly every subject within just two weeks. The newly engineered CAR-T cells quickly multiplied to make up as much as 40% of the immune cells in key organs, effectively hunting down and eliminating tumor cells in both the bone marrow and the spleen. This rapid response time suggests that in vivo therapy could provide a critical advantage for patients with fast-moving malignancies who cannot afford a month-long manufacturing delay.