Northwestern University scientists have achieved a breakthrough in cancer treatment by re-engineering a common chemotherapy drug into a nanostructured delivery system that demonstrates unprecedented effectiveness against acute myeloid leukemia (AML). The research, published in ACS Nano, shows the new approach kills cancer cells up to 20,000 times more effectively than traditional chemotherapy while eliminating detectable side effects.
Revolutionary Nanostructure Design
The research team, led by Chad A. Mirkin, designed the therapy as a spherical nucleic acid (SNA) — a nanostructure that weaves the chemotherapy drug 5-fluorouracil (5-Fu) directly into DNA strands coating tiny spheres. This structural redesign transforms a poorly soluble, weakly performing drug into a powerful, targeted cancer killer that leaves healthy cells unharmed.
"In animal models, we demonstrated that we can stop tumors in their tracks," said Mirkin, the George B. Rathmann Professor at Northwestern with appointments across multiple schools. "If this translates to human patients, it's a really exciting advance. It would mean more effective chemotherapy, better response rates and fewer side effects."
Dramatic Performance Improvements
In small animal models of AML, the SNA-based drug demonstrated remarkable improvements across multiple metrics compared to standard chemotherapy:
- Entered leukemia cells 12.5 times more efficiently
- Killed cancer cells up to 20,000 times more effectively
- Reduced cancer progression 59-fold
- Achieved these results without detectable side effects
The therapy eliminated leukemia cells to near completion in the blood and spleen while significantly extending survival in mouse experiments.
Addressing Fundamental Drug Delivery Challenges
The breakthrough addresses a critical limitation of 5-fluorouracil, which often fails to reach cancer cells efficiently due to poor solubility. According to Mirkin, less than 1% of 5-Fu dissolves in many biological fluids, causing the drug to clump or retain solid form that the body cannot absorb efficiently.
"We all know that chemotherapy is often horribly toxic," Mirkin explained. "But a lot of people don't realize it's also often poorly soluble, so we have to find ways to transform it into water soluble forms and deliver it effectively."
Targeted Cellular Recognition
The SNA design leverages the natural cellular recognition mechanisms of myeloid cells, which overexpress scavenger receptors on their surfaces. Unlike traditional chemotherapy that must force its way into cells, SNAs are naturally recognized and absorbed by these receptors.
"Most cells have scavenger receptors on their surfaces, but myeloid cells overexpress these receptors, so there are even more of them," Mirkin said. "If they recognize a molecule, then they will pull it into the cell."
Once inside the cancer cell, enzymes break down the DNA shell to release the drug molecules, which kill the cancer cell from within. This selective targeting mechanism explains why healthy tissues remained unharmed during treatment.
Broader Implications for Structural Nanomedicine
This work represents an advancement in structural nanomedicine, a field where scientists use precise structural and compositional control to fine-tune how nanomedicines interact with the human body. Currently, seven SNA-based therapies are in clinical trials, with potential applications extending beyond cancer to infectious diseases, neurodegenerative diseases, and autoimmune conditions.
"Today's chemotherapeutics kill everything they encounter," Mirkin noted. "So, they kill the cancer cells but also a lot of healthy cells. Our structural nanomedicine preferentially seeks out the myeloid cells. Instead of overwhelming the whole body with chemotherapy, it delivers a higher, more focused dose exactly where it's needed."
Clinical Translation Timeline
The research team plans to advance the therapy through a systematic progression of testing phases. Next steps include evaluation in larger cohorts of small animal models, followed by testing in larger animal models, and eventually human clinical trials once funding is secured.
Mirkin, who is also the founding director of the International Institute for Nanotechnology and a member of the Robert H. Lurie Comprehensive Cancer Center, invented and developed SNAs at Northwestern. His previous studies demonstrated that cells naturally recognize SNAs and invite them inside, forming the foundation for this therapeutic breakthrough.
