“Conventional cancer treatments are effective, but often cause significant side effects. As they are not targeted, they can damage healthy areas of the body, notes Patrick Couvreur, director of the Physico-chemistry, pharmacotechnics and biopharmacy Unit (University Paris XI / CNRS). With nanovectors, it’s different: they will be targeted on the tumor. “
Nanoparticles enter cells
The principle is clever: graft the active molecule into nanoparticles which protect and convey it. “While a classic drug is a single molecule, a nanomedicine is a molecular structure made up of a nanoparticle, a guidance system and the therapeutic molecule”, explains Patrick Curmi, research doctor at the University of Evry (Génopole / Inserm).
Researchers can shape nanoparticles because their size (on the order of a millionth of a millimeter) gives them unique properties. This allows them to enter cells to deliver the drug. There are different families of nanoparticles, and different scaffolds are built depending on the therapeutic application.
Nanomedicines: reducing the toxicity of chemo
The first generation nanomedicines are targeted at the liver and tested in cases of hepatic cancers resistant to conventional chemotherapy.
Those of the second generation are said to be stealthy: “Covered with polymers (polyethylene glycol), they are not recognized by the liver cells and circulate in the blood”, explains Patrick Couvreur. They already reduce the toxicity of chemotherapy.
For example, in France, Abraxane® (nanoparticles of albumin and paclitaxel) is recommended in the treatment of metastatic resistant breast cancer. It avoids taking corticosteroids necessary during certain chemotherapy (taxol). Other combinations (liposomal doxorubicin) are used in the treatment of sarcomas to reduce cardiac toxicity from conventional chemotherapy.
A third generation of nanomedicines under study
Finally, the most anticipated, third generation nanovectors, are being studied. “Equipped with a ‘homing head’, which can be an antibody, a peptide or a sugar, they will be able to precisely reach their target”, continues the specialist. If the researchers are enthusiastic about these new drugs, their safety remains to be proven and the results remain to be confirmed. Therefore, caution is in order.