Alternative method to determine Specific Activity of ¹⁷⁷Lu by HPLC

Title:Alternative method to determine Specific Activity of ¹⁷⁷Lu by HPLC

Volume: 8 Issue: 2

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

Affiliation:

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

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.

Cite this article as:

Breeman A. P. Wouter, de Zanger M. S. Rory, Chan Sze Ho and Blois de Erik, Alternative method to determine Specific Activity of ¹⁷⁷Lu by HPLC, Current Radiopharmaceuticals 2015; 8 (2) . https://dx.doi.org/10.2174/1874471008666150312162340