SAN DIEGO, July 15 (UPI) -- Scientists have designed a nanoparticle activated by enzymes found only in cancer cells, potentially allowing doctors to target strong doses of drugs directly at tumors.
"We can start with a small molecule and build that into a nanoscale carrier that can seek out a tumor and deliver a payload of drug," said Cassandra Callmann, a graduate student in chemistry and biochemistry at the University of California San Diego, in a press release.
Researchers packed the cancer drug paclitaxel, used for lung, ovary and breast cancers, into tiny spheres coated by a peptide shell. The spheres also include a chemical handle that is essential to the drug being effective, allowing the inactivated drug to travel through the body without harming other cells or tissues.
The nanoparticles are actived by matrix metalloproteinases, or MMPs, which many cancers emit. MMPs chew through membranes to allow cancer cells to escape and often colonize other parts of the body. With nanoparticles, the MMPs tear up their peptide shell, releasing the drug to attack the cancer.
In tests with mice, researchers were able to safely use a dose of paclitaxel 16 times higher than the formulation used with cancer patients. Researchers also stopped the growth of tumors for about two weeks by delivering drug treatments using their nanoparticles. In mice treated with nanoparticles that did not include a peptide shell that can be cracked by MMPs, tumors grew to lethal sizes over two weeks.
Nathan Gianneschi, a professor of chemistry and biochemisty at the University of California San Diego, said the nanoparticle concept could be used for treatments other than the one they used in lab tests.
The goal, he said, is to find even better ways of delivering therapeutic payloads using the method while protecting the liver, spleen and kidneys from picking up the drugs and being damaged by them.
"We'll test this in other models - with other classes of drug and in mice with a cancer that mimics metastatic breast cancer, for example," Gianneschi said. "They'll also continue to modify the shell, to provide even greater protection and avoid uptake by organs such as liver, spleen and kidneys, he said. "We want to open up this therapeutic window."
The study is published in Advanced Materials.