Alternative method to determine Specific Activity of 177Lu by HPLC

Author(s): Wouter A. P. Breeman, Rory M. S. de Zanger, Ho Sze Chan, Erik de Blois.

Journal Name: Current Radiopharmaceuticals

Volume 8 , Issue 2 , 2015

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Abstract:

Peptide Receptor Radionuclide Therapy (PRRT) with 177Lu-DOTA-peptides requires 177Lu with high specific activity (SA) and values >740 GBq 177Lu per mg Lu to maximise the atom% of 177Lu over total Lu. Vendors provide SA values which are based on activity and mass of the target, whereas due to "burn-up" of target, these SA values are not accurate. For a radiochemist the SA of 177Lu is of interest prior to radiolabeling.

An alternative method to determine SA was developed by HPLC, which includes a metal titration of a known amount of DOTA-peptide with a known amount of activity (177Lu), and a unknown amount of metal (177+natLu). Based on an HPLC separation of radiometal-DOTA-peptide and DOTA-peptide, and the concordant ratio of these components the metal content (177+natLu) can be calculated, and eventually the SA of 177Lu can be accurately determined.

These experimentally determined SA values exceeded the estimated values provided by vendors by 27±16%, (range 6-73 %). The deviation of SA values for samples from the same Lu batch was <2% (n≥10).

In conclusion: the SA of 177Lu is apparently often higher as stated by vendors in comparison to the experimentally determined actual values. For this reason, the SA of 177Lu-DOTA-TATE and other Lu-DOTA-peptides could be increased accordingly.

Keywords: 177Lu-DOTA-TATE, DOTA-peptides, HPLC, Lutetium-177, specific activity, titration.

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Article Details

VOLUME: 8
ISSUE: 2
Year: 2015
Page: [119 - 122]
Pages: 4
DOI: 10.2174/1874471008666150312162340
Price: $58

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