In that emerging therapeutics that are designed to engage RNA interference (RNAi) pathways, implicated in many disease processes, have the potential to provide new, major ways ofdelivering targeted therapies to patients, Mark E. Davis, from California Institute of Technology (California, USA),and colleagues have designed nanoparticle-sized robots, each covered with transferring, a protein, that travel the bloodstream and seek out a specific receptor on tumors. After the nanoparticles find the cancer cell and invade it, they release small interfering RNAs (siRNAs) that block the gene responsible for the cancer growth protein known as ribonucleotide reductase. In a phase 1 clinical trial in patients with various types of tumors, the researchers gave doses of the targeted nanoparticles four times over 21 days in a 30-minute intravenous infusion.  Tumor samples subsequently taken from three people with melanoma showed the nanoparticles found their way inside tumor cells, and there was evidence that the therapy disabled ribonucleotide reductase as well.