The patient was administered with four doses of Calando's CALAA-01, a targeted siRNA nanoparticle, over a two week period. This development is another milestone for siRNA technology, which many people have high hopes for in the treatment of a diverse range of illnesses. Jeremy Heidel, Calando chief scientific officer for siRNA delivery, said: "The initiation of this Phase I clinical trial of CALAA-01 is a hallmark for Calando and for the field of RNAi therapeutics. "We look forward to the continued treatment of this patient and subsequent patients and the establishment of safety and efficacy profiles for CALAA-01 in humans." The siRNA was delivered using Calando's Rondel delivery technology, which the company describes as a "three-part RNAi /Oligonucleotide Nanoparticle Delivery technology". This entails a polymer binding along the length of the siRNA, with the resulting complex self-assembling into nanoparticles less than 100nm in diameter. This process serves to protect the siRNA from nuclease degradation. In addition, a molecule in the polymer called cyclodextrin facilitates the attachment of stabilizing agents and targeting ligands to the surface of the siRNA/polymer complex. These attachments prevent the delivery complexes from aggregating and also enable them to be delivered to specific tissues. The complexes are delivered intravenously and upon reaching the target cell the targeting ligands bind with receptors on the cell membrane. This allows the RNA-containing nanoparticle to enter the cell whereupon the siRNA is released from the complex. A week of firsts In addition to the Calando trial Santaris Pharma has started a Phase I human volunteer trial of the world's first microRNA medicine, Hepatitis C treatment SPC3649. The treatment targets microRNA-122, a small, liver-expressed RNA which facilitates human Hepatitis C virus replication in liver cells. Speaking on the launch of the trial Keith McCullagh, president and CEO of Santaris Pharma said: "The mechanism of action of this drug represents a potential breakthrough in medical science. "The ability to switch off the functions of particular microRNAs may enable clinicians to modulate entire networks of genes associated with disease or ill-health." Although there is still some way to go in the development of RNA interference technology these two breakthroughs bring it a little closer to reality.