A California Institute of Technology (Caltech)-led team of researchers and clinicians has published the first proof that a targeted nanoparticle—used as an experimental therapeutic and injected directly into a patient's bloodstream—can traffic into tumors, deliver double-stranded small interfering RNAs (siRNAs), and turn off an important cancer gene using a mechanism known as RNA interference (RNAi). Moreover, the team provided the first demonstration that this new type of therapy, infused into the bloodstream, can make its way to human tumors in a dose-dependent fashion—i.e., a higher number of nanoparticles sent into the body leads to a higher number of nanoparticles in the tumor cells. These results demonstrate the feasibility of using both nanoparticles and RNAi-based therapeutics in patients, and open the door for future "game-changing" therapeutics that attack cancer and other diseases at the genetic level, said lead author Dr. Mark Davis, the Warren and Katharine Schlinger Professor of Chemical Engineering at Caltech. The scientific results are from an ongoing phase 1 clinical trial of these nanoparticles (image, Caltech/Derek Bartlett) that began treating patients in May 2008. Phase 1 trials are, by definition, safety trials; the idea is to see if and at what level the drug or other therapy turns harmful or toxic. These trials can also provide an in-human scientific proof of concept—which is exactly what is being reported in the current article. The current results were published online on March 21, 2010 in Nature. [Press release] [Nature abstract]
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