A rapid and prolonged accumulation in the kidneys of the radioactivity from radiolabeled peptides is a well-recognized issue [26] and [33]. We recorded relatively high kidney retention, which may result in nephropathy at therapeutic dose. This problem should be addressed in planning further animal studies. The optimization of kidney uptake was not a goal of this article; however, it has been shown in the literature that coinfusion of positively charged V5 Tag counteracts the reabsorption of 90Y-DOTA-TOC and 177Lu-DOTA-TATE peptides, the approach which might be useful also in this case [33] and [34].
5. Conclusion
We have demonstrated that DOTA-BN[2–14]NH2, a novel BN analog, can be labeled with high SAs and radiochemical yields with 90Y (NCA) and 177Lu (CA). Presented comparison between 90Y-DOTA-BN[2–14]NH2 and 177Lu-DOTA-BN[2–14]NH2 revealed significant differences in the in vitro assays, which were confirmed by the biodistribution experiments. Good agreement between the in vitro and in vivo results indicates that the receptor affinity of these two analogs is metal mediated with preference to the 177Lu-labeled derivative. However, further comparative investigation in tumor-bearing animals is planned.