Effect of a Negatively Charged Amino Acid Linker on the Tumor-Targeting Properties of [ 177 Lu]Lu-Labeled 4- p -(Tolyl)butyric Acid-Conjugated Alpha-Melanocyte-Stimulating Hormone Peptides
Year: 2026
Type: article
Abstract: This study aimed to examine how negatively charged amino acid linkers influence the tumor-targeting and biodistribution properties of [ 177 Lu]Lu-labeled 4- p -(tolyl)butyric acid ( p -TBA)-conjugated alpha-melanocyte-stimulating hormone peptides. The p -TBA moiety functions as an albumin binder (ALB), either directly attached to the peptide or through a negatively charged aspartic acid (Asp) or glutamic acid (Glu) linker. DOTA-Lys( p -TBA)-GGNle-CycMSH hex {1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-Lys(4- p -(tolyl)butyric acid)-GlyGly-Nle-c[Asp-His-DPhe-Arg-Trp-Lys]-CONH 2 }, DOTA-Lys(Asp- p -TBA)-GGNle-CycMSH hex, and DOTA-Lys(Glu- p -TBA)-GGNle-CycMSH hex were synthesized using fluorenylmethoxycarbonyl (Fmoc) chemistry. Their melanocortin-1 receptor (MC1R) binding affinities were measured in B16/F10 melanoma cells, and the biodistribution of [ 177 Lu]Lu-labeled peptides was examined in B16/F10 melanoma-bearing mice at 0.5, 2, 4, and 24 h postinjection. Additionally, the melanoma imaging capability of [ 177 Lu]Lu-DOTA-Lys(Asp- p -TBA)-GGNle-CycMSH hex was examined in B16/F10 melanoma-bearing mice. The IC 50 values were 0.5 ± 0.09 ( p -TBA), 0.03 ± 0.03 (Asp- p -TBA), and 7.2 ± 0.07 nM (Glu- p -TBA). Among the three, [ 177 Lu]Lu-DOTA-Lys(Asp- p -TBA)-GGNle-CycMSH hex displayed the highest tumor/kidney and tumor/liver uptake ratios at 2 and 4 h postinjection. The B16/F10 melanoma uptake of [ 177 Lu]Lu-DOTA-Lys(Asp- p -TBA)-GGNle-CycMSH hex was 20.40 ± 1.91, 45.24 ± 1.72, 31.30 ± 2.85, and 11.16 ± 1.79%ID/g at 0.5, 2, 4, and 24 h postinjection, respectively. The B16/F10 melanoma lesions were clearly visualized by SPECT/CT using [ 177 Lu]Lu-DOTA-Lys(Asp- p -TBA)-GGNle-CycMSH hex as an imaging probe at 2 h postinjection. Overall, the presence and charge of the linker significantly affected MC1R binding and tumor uptake. The linker charge played a key role in the liver and kidney uptake of [ 177 Lu]Lu-DOTA-Lys(Asp- p -TBA)-GGNle-CycMSH hex and [ 177 Lu]Lu-DOTA-Lys(Glu- p -TBA)-GGNle-CycMSH hex . [ 177 Lu]Lu-DOTA-Lys(Asp- p -TBA)-GGNle-CycMSH hex exhibited the highest tumor/liver and tumor/kidney uptake ratios among the three [ 177 Lu]Lu-peptides, highlighting its potential for future melanoma therapy.
Language: English
Subfield: Radiology, Nuclear Medicine and Imaging
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W7131361708