RNA, or ribonucleic acid, is an important chemical that scientists believe is a key player in the disease process. Several biotechnology and pharmaceutical companies seek ways to manipulate RNA so that it blocks genes that manufacture disease-causing proteins involved in cancer, AIDS and other diseases.
Those firms include Alnylam, Merck, Pfizer, Novartis and Roche.
Until now, targeting that treatment to specific areas of the body has been difficult. But researchers at the California Institute of Technology created tiny molecules made of two polymers and a protein called transferrin that can find the intended target and turn off cancer-causing genes.
The researchers created the particles from two polymers plus a protein that binds to receptors on the surface of cancer cells and pieces of RNA called small-interfering RNA, or siRNA, designed to stop the RRM2 gene from being translated into protein. The siRNA works by sticking to the messenger RNA (mRNA) that carries the gene's code to the cell's protein-making machinery and ensuring that enzymes cut the mRNA at a specific spot.
The particles are about 70 nanometers in diameter and assemble when mixed together with water.
Researchers can then administer the nanoparticles into a patient's bloodstream. The molecules circulate until they encounter blood vessels that supply tumors with blood, passing through the vessels to the tumor, where they bind to the cell.
Once the molecules are absorbed, they disassemble, releasing the siRNA. Leftover components are small enough to pass out of the body in urine.
In a clinical trial, patients with various types of tumors were given doses of targeted nanoparticles four times over 21 days in a 30-minute intravenous infusion.
Tumor samples taken from three people with melanoma showed the nanoparticles found their way inside tumor cells, and evidence was found that the therapy had disabled ribonucleotide reductase, the protein in question.
While more data from clinical trials is needed to ensure that such therapies are safe to use in humans, the development gives hope for a cancer treatment with a higher quality of life than chemotherapy.
Nanoparticles aren't the only vehicle to treat cancer. Pfizer last week announced a deal with Canadian biotech Tekmira Pharmaceuticals to use fats or lipids as a delivery vehicle for its RNAi drugs.
Roche and Alnylam also have similar therapies in development.