Fulltext

Preclinical evaluation of novel organometallic 99mTc-folate and 99mTc-pteroate radiotracers for folate receptor-positive tumour targeting

Müller, Cristina ; Hohn, Alexander ; Schubiger, P. ; Schibli, Roger

In: European Journal of Nuclear Medicine and Molecular Imaging, 2006, vol. 33, no. 9, p. 1007-1016

Ajouter à la liste personnelle
    Titre
    • Preclinical evaluation of novel organometallic 99mTc-folate and 99mTc-pteroate radiotracers for folate receptor-positive tumour targeting
    Auteur
    • Müller, Cristina. Center for Radiopharmaceutical Science ETH-PSI-USZ, Paul Scherrer Institute, 5232, Villigen-PSI, Switzerland
    • Hohn, Alexander. Center for Radiopharmaceutical Science ETH-PSI-USZ, Paul Scherrer Institute, 5232, Villigen-PSI, Switzerland
    • Schubiger, P.. Center for Radiopharmaceutical Science ETH-PSI-USZ, Paul Scherrer Institute, 5232, Villigen-PSI, Switzerland
    • Schibli, Roger. Center for Radiopharmaceutical Science ETH-PSI-USZ, Paul Scherrer Institute, 5232, Villigen-PSI, Switzerland
    Type de document
    • Postprint
    Langue
    • Anglais
    Publié dans
    • European Journal of Nuclear Medicine and Molecular Imaging, 2006, vol. 33, no. 9, p. 1007-1016. Springer-Verlag
    Autre version électronique
    Identifiant OAI-PMH
    • oai:doc.rero.ch:316861
    Summary
    Purpose: The folate receptor (FR) is a valuable tumour marker, since it is frequently overexpressed on various cancer types. The purpose of the present study was to pre-clinically evaluate novel site-specifically modified 99mTc(CO)3 folate (γ-derivative 4, α-derivative 5) and pteroate (6) conjugates for FR targeting. Methods: The 99mTc(CO)3 radiotracers 4-6 were prepared by a kit-like procedure. In vitro characterisation (K D and B max) of the radiotracers was performed with FR-positive KB cells. Tissue distribution was studied in tumour-bearing mice. SPECT/CT experiments were performed with a dedicated small animal SPECT/CT scanner. Results: The complexes 4-6 were formed in high yields (>92%). Binding constants of the radiotracers (K D in nM: 4: 2.09; 5: 2.51; 6: 14.52) were similar to those of 3H-folic acid (K D in nM: 7.22). In vivo the folate derivatives showed significantly better tumour uptake (4: 2.3±0.4% ID/g and 5: 1.2±0.2% ID/g, 4h p.i.) than the pteroate derivative (6: 0.4±0.2% ID/g, 4h p.i.). Clearance of all radiotracers from the blood pool and from non-targeted tissues was efficient (tumour to blood ratio approx. 200-350, 24h p.i.). FR-positive tissue and organs were successfully visualised via small animal SPECT/CT. Conclusion: Radiotracers 4-6 are the first 99mTc(CO)3 tracers prepared via a kit formulation which exhibit full biological activity in vitro and in vivo. Folate derivatives 4 and 5 revealed significantly better pharmacokinetic properties than the pteroate derivative 6. Promising pre-clinical SPECT results warrant further assessment of 99mTc(CO)3 radiofolates for detection of FR-positive tumours