Research ArticleNanomedicine

Clinical translation of an ultrasmall inorganic optical-PET imaging nanoparticle probe

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Science Translational Medicine  29 Oct 2014:
Vol. 6, Issue 260, pp. 260ra149
DOI: 10.1126/scitranslmed.3009524

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First-in-Human Nanoparticles for Molecular Cancer Imaging

Molecular targeting and nanotechnology together have a promising future in cancer imaging. Tiny particles can be coated with antibodies or peptides to target a molecule specific to cancer, improving diagnostic accuracy and patient stratification. Yet, these decorated nanoparticles have been slow in making it to clinical trials. Now, Phillips and colleagues describe the translation of ultrasmall (<10 nm) inorganic nanoparticles, called “C dots,” from animals to patients. The C dots comprised a silica shell encapsulating the fluorescent Cy5 dye, coated with a polymer called poly(ethylene glycol) (PEG), and then decorated with the integrin-targeting, radiolabeled peptide 124I-cRGDY. With the Cy5 and 124I, the particle could be imaged by optical methods (fluorescence) and by positron emission tomography (PET). The goal of this first-in-human study was to evaluate pharmacokinetics and biodistribution of the 124I-cRGDY–PEG–C dots when injected systemically, with molecular targeting and cancer imaging as a secondary effort. The authors found that the nanoparticles were not toxic in a small group of five patients with metastatic melanoma and that the particles were excreted intact via the kidneys and bladder (by contrast, larger or uncoated particles often get lodged in the liver). In some patients, the C dots were visible in the tumor region by PET imaging. Many more patients will need to be studied to confirm lack of toxicity and to optimize tumor targeting, but this first demonstration in people suggests that such ultrasmall nanoparticles can be tested in people, heralding in a new era of molecular cancer imaging.