Yttrium-90 and Rhenium-188 Radiopharmaceuticals for Radionuclide Therapy

13.3. CONCLUSION
In conclusion, this chapter describes a simple and convenient method to
purify the rhenium tricarbonyl precursor 4 that will facilitate the labelling of
other small molecules and biomolecules such as His-tagged peptides/proteins
with 188 Re in high radiochemical yields and purities [13.24]. Also described here
is the synthesis of 5 as a new radiopharmaceutical for the radionuclide therapy
of bone metastases, and its technetium analogue 6. Complex 5 can be easily
synthesized with high specific activity in two steps using a kit based methodology
and, in contrast with the clinically approved 186/188 Re HEDP, it forms an inert,
single species that has been well characterized. The strategy of using a designed
chelating agent for rhenium rather than relying on the chelating properties of
the bisphosphonate group is vindicated in that 5 displays superior stability, bone
targeting and retention properties. Complex 5 is therefore an attractive candidate
for further clinical studies.
Similarly, the new 99m Tc tracer 9 shows prolonged retention in bone and
higher stability and binding to HA in serum compared to 99m Tc MDP. Because of
the selection of a stable, well characterized metal core in which the technetium
and rhenium complexes are known to behave analogously and retain structural
integrity, the 188 Re complex is expected to behave similarly and deserves
investigation as a potential therapeutic radiopharmaceutical.
ACKNOWLEDGEMENTS
This work was supported by Cancer Research UK (grant C789/A7649)
and conducted within the King’s College London–UCL Comprehensive Cancer
Imaging Centre supported by Cancer Research UK and the Engineering and
Physical Sciences Research Council, in association with the Medical Research
Council and the Department of Health (UK). This collaborative study was
performed within the framework of the European Cooperation in Science and
Technology action BM0607 on targeted radionuclide therapy. The nanoSPECT
scanner was funded by an equipment grant from the Wellcome Trust. We thank
K. Sunassee and S. Clarke for assistance with nanoSPECT imaging.
REFERENCES TO CHAPTER 13
[13.1] FLEISH, H., Bisphosphonates in Bone Disease: From the Laboratory to the Patient,
Parthenon Publishing Group, London (1995).
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