Investigation of a vitamin B12 conjugate as a PET imaging probe

ChemMedChem. 2014 Jun;9(6):1244-51. doi: 10.1002/cmdc.201400048. Epub 2014 Apr 17.


Nutrient demand is a fundamental characteristic of rapidly proliferating cells. Vitamin B12 is vital for cell proliferation; thus neoplastic cells have an increased demand for this essential nutrient. In this study we exploited the vitamin B12 uptake pathway to probe the nutritional demand of proliferating cells with a radiolabeled B12 derivative in various preclinical tumor models. We describe the synthesis and biological evaluations of copper-64-labeled B12 -ethylenediamine-benzyl-1,4,7-triazacyclononane-N,N',N''-triacetic acid (B12 -en-Bn-NOTA-(64) Cu), the first example of a B12 derivative for positron emission tomography (PET) imaging. Small-animal imaging and pharmacological evaluation show high tumor uptake ranging from 2.20 to 4.84% ID g(-1) at 6 h post-administration. Competition studies with excess native B12 resulted in a 95% decrease in tumor accumulation, indicating the specificity of this radiopharmaceutical for B12 endocytotic transport proteins. These results show that a vitamin B12 PET radiopharmaceutical has potential utility for non-invasive imaging of enhanced nutrient demand in proliferating cells.

Keywords: CD320; cobalamin; positron emission tomography; radiochemistry; vitamins.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line, Tumor
  • Coordination Complexes / chemistry*
  • Coordination Complexes / pharmacokinetics
  • Copper Radioisotopes / chemistry
  • HCT116 Cells
  • Heterocyclic Compounds / chemistry
  • Heterocyclic Compounds, 1-Ring
  • Humans
  • Melanoma, Experimental / diagnosis
  • Melanoma, Experimental / diagnostic imaging
  • Mice
  • Mice, Nude
  • Positron-Emission Tomography
  • Radiopharmaceuticals / chemistry*
  • Radiopharmaceuticals / pharmacokinetics
  • Tissue Distribution
  • Tomography, X-Ray Computed
  • Transplantation, Heterologous
  • Transplantation, Homologous
  • Vitamin B 12 / chemistry*


  • Coordination Complexes
  • Copper Radioisotopes
  • Heterocyclic Compounds
  • Heterocyclic Compounds, 1-Ring
  • Radiopharmaceuticals
  • 1,4,7-triazacyclononane-N,N',N''-triacetic acid
  • Vitamin B 12