Effect of Ibuprofen as an Albumin Binder on Melanoma-Targeting Properties of 177Lu-Labeled Ibuprofen-Conjugated Alpha-Melanocyte-Stimulating Hormone Peptides.

The purpose of this study was to examine how the introduction of ibuprofen (IBU) affected tumor-targeting and biodistribution properties of 177Lu-labeled IBU-conjugated alpha-melanocyte-stimulating hormone peptides. The IBU was used as an albumin binder and conjugated to the DOTA-Lys moiety without or with a linker to yield DOTA-Lys(IBU)-GG-Nle-CycMSHhex {1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-Lys(IBU)-Gly-Gly-Nle-c[Asp-His-DPhe-Arg-Trp-Lys]-CONH2}, DOTA-Lys(Asp-IBU)-GGNle-CycMSHhex, DOTA-Lys(Asn-IBU)-GGNle-CycMSHhex, and DOTA-Lys(Dab-IBU)-GGNle-CycMSHhex peptides. Their melanocortin-receptor 1 (MC1R) binding affinities were determined on B16/F10 melanoma cells first. Then the biodistribution of 177Lu-labeled peptides was determined on B16/F10 melanoma-bearing C57 mice at 2 h postinjection to choose the lead peptide for further examination. The full biodistribution and melanoma imaging properties of 177Lu-DOTA-Lys(Asp-IBU)-GGNle-CycMSHhex were further evaluated using B16/F10 melanoma-bearing C57 mice. DOTA-Lys(IBU)-GG-Nle-CycMSHhex, DOTA-Lys(Asp-IBU)-GGNle-CycMSHhex, DOTA-Lys(Asn-IBU)-GGNle-CycMSHhex, and DOTA-Lys(Dab-IBU)-GGNle-CycMSHhex displayed the IC50 values of 1.41 ± 0.37, 1.52 ± 0.08, 0.03 ± 0.01, and 0.58 ± 0.06 nM on B16/F10 melanoma cells, respectively. 177Lu-DOTA-Lys(Asp-IBU)-GGNle-CycMSHhex exhibited the lowest liver and kidney uptake among all four designed 177Lu peptides. Therefore, 177Lu-DOTA-Lys(Asp-IBU)-GGNle-CycMSHhex was further evaluated for its full biodistribution and melanoma imaging properties. The B16/F10 melanoma uptake of 177Lu-DOTA-Lys(Asp-IBU)-GGNle-CycMSHhex was 19.5 ± 3.12, 24.12 ± 3.35, 23.85 ± 2.08, and 10.80 ± 2.89% ID/g at 0.5, 2, 4, and 24 h postinjection, respectively. Moreover, 177Lu-DOTA-Lys(Asp-IBU)-GGNle-CycMSHhex could clearly visualize the B16/F10 melanoma lesions at 2 h postinjection. The conjugation of IBU with or without a linker to GGNle-CycMSHhex affected the MC1R binding affinities of the designed peptides. The charge of the linker played a key role in the liver and kidney uptake of 177Lu-Asp-IBU, 177Lu-Asn-IBU, and 177Lu-Dab-IBU. 177Lu-Asp-IBU exhibited higher tumor/liver and tumor/kidney uptake ratios than those of 177Lu-Asn-IBU and 177Lu-Dab-IBU, underscoring its potential evaluation for melanoma therapy in the future.

The Effect of Albumin-Binding Moiety on Tumor Targeting and Biodistribution Properties of 67Ga-Labeled Albumin Binder-Conjugated Alpha-Melanocyte-Stimulating Hormone Peptides.

Background: The purpose of this study was to examine the effect of 4-p-(tolyl)butyric acid as an albumin-binding (ALB) moiety on tumor targeting and biodistribution properties of 67Ga-labeled albumin binder-conjugated alpha-melanocyte-stimulating hormone peptides. Materials and Methods: DOTA-Lys(ALB)-G/GG/GGG-Nle-CycMSHhex {1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-Lys(ALB)-Gly/GlyGly/GlyGlyGly-Nle-c[Asp-His-DPhe-Arg-Trp-Lys]-CONH2} were synthesized with 4-p-(tolyl)butyric acid serving as an ALB moiety. The melanocortin-1 receptor (MC1R)-binding affinities of the peptides were determined on B16/F10 melanoma cells. The biodistribution of 67Ga-DOTA-Lys(ALB)-G/GG/GGG-Nle-CycMSHhex was examined on B16/F10 melanoma-bearing C57 mice at 2 h postinjection to select a lead peptide for further evaluation. The melanoma targeting and imaging properties of 67Ga-DOTA-Lys(ALB)-GGNle-CycMSHhex {67Ga-ALB-G2} were determined on B16/F10 melanoma-bearing C57 mice. Results: The IC50 value of DOTA-Lys(ALB)-G/GG/GGG-Nle-CycMSHhex {ALB-G1, ALB-G2, ALB-G3} was 0.67 ± 0.07, 0.5 ± 0.09 and 0.51 ± 0.03 nM on B16/F10 cells, respectively. 67Ga-ALB-G2 was further evaluated as a lead peptide because of its higher tumor uptake (30.25 ± 3.24%ID/g) and lower kidney uptake (7.09 ± 2.22%ID/g) than 67Ga-ALB-G1 and 67Ga-ALB-G3 at 2 h postinjection. The B16/F10 melanoma uptake of 67Ga-ALB-G2 was 15.64 ± 4.55, 30.25 ± 3.24, 26.76 ± 3.23, and 10.71 ± 1.21%ID/g at 0.5, 2, 4, and 24 h postinjection, respectively. The B16/F10 melanoma lesions were clearly visualized by SPECT/CT using 67Ga-ALB-G2 as an imaging probe at 2 h postinjection. Conclusions: The introduction of 4-p-(tolyl)butyric acid as an ALB moiety increased the blood retention, and resulted in higher tumor/kidney ratio of 67Ga-ALB-G2 as compared with its counterpart without an albumin binder. However, the resulting high uptake of 67Ga-ALB-G2 in blood and liver need to be further reduced to facilitate its therapeutic application when replacing 67Ga with therapeutic radionuclides.

Facile preparation of a novel Ga-67-labeled NODAGA-conjugated lactam-cyclized alpha-MSH peptide at room temperature for melanoma targeting.

In this study, the melanoma targeting property of 67Ga-NODAGA-GGNle-CycMSHhex {1,4,7-triazacyclononane,1-gluteric acid-4,7-acetic acid-GlyGlyNle-c[Asp-His-D-Phe-Arg-Trp-Lys]-CONH2} was determined on B16/F10 melanoma-bearing C57 mice to demonstrate the feasibility of NODAGA as a radiometal chelator for facile room temperature radiolabeling of NODAGA-GGNle-CycMSHhex. The IC50 value of NODAGA-GGNle-CycMSHhex was 0.87 ± 0.12 nM on B16/F10 melanoma cells. 67Ga-NODAGA-GGNle-CycMSHhex was readily prepared at room temperature with greater than 98% radiolabeling yield and displayed MC1R-specific binding on B16/F10 melanoma cells. The B16/F10 melanoma uptake of 67Ga-NODAGA-GGNle-CycMSHhex was 10.31 ± 0.78, 14.96 ± 1.34, 13.7 ± 3.33 and 10.4 ± 2.2% ID/g at 0.5, 2, 4 and 24 h post-injection, respectively. Approximately 85% of the injected dose was cleared out the body via urinary system at 2 h post-injection. 67Ga-NODAGA-GGNle-CycMSHhex showed high tumor/blood, tumor/muscle and tumor/skin uptake ratios after 2 h post-injection. Overall, 67Ga-NODAGA-GGNle-CycMSHhex could be easily prepared at room temperature and exhibited favorable melanoma targeting property, suggesting the potential use of NODAGA as a radiometal chelator for facile room temperature radiolabeling of α-MSH peptides.

Novel [99mTc]-Tricarbonyl-NOTA-Conjugated Lactam-Cyclized Alpha-MSH Peptide with Enhanced Melanoma Uptake and Reduced Renal Uptake.

The purpose of this study was to examine the melanoma targeting and imaging properties of 99mTc(CO)3-NOTA-GGNle-CycMSHhex {1,4,7-triazacyclononane-1,4,7-triyl-triacetic acid-GlyGlyNle-c[Asp-His-DPhe-Arg-Trp-Lys]-CONH2} and 99mTc(CO)3-NODAGA-GGNle-CycMSHhex {1,4,7-triazacyclononane,1-gluteric acid-4,7-acetic acid-GlyGlyNle-c[Asp-His-DPhe-Arg-Trp-Lys]-CONH2} on B16/F10 melanoma-bearing C57 mice to demonstrate the feasibility of NOTA/NODAGA as metal chelators for 99mTc(CO)3+ radiolabeling. NOTA/NODAGA-GGNle-CycMSHhex were synthesized using fluorenylmethoxycarbonyl (Fmoc) chemistry. The melanocortin-1 (MC1) receptor binding affinities of the peptides were determined on B16/F10 melanoma cells. The biodistribution of 99mTc(CO)3-NOTA-GGNle-CycMSHhex and 99mTc(CO)3-NODAGA-GGNle-CycMSHhex were determined on B16/F10 melanoma-bearing C57 mice at 2 h postinjection to select a lead peptide for further evaluation. The melanoma targeting and imaging properties of 99mTc(CO)3-NOTA-GGNle-CycMSHhex and 99mTc(CO)3-NODAGA-GGNle-CycMSHhex were determined on B16/F10 melanoma-bearing C57 mice. The IC50 values of NOTA/NODAGA-GGNle-CycMSHhex were 0.8 ± 0.1 and 0.9 ± 0.1 nM on B16/F10 cells. 99mTc(CO)3-NOTA-GGNle-CycMSHhex and 99mTc(CO)3-NODAGA-GGNle-CycMSHhex were readily prepared via the [99mTc(CO)3(OH2)3]+ intermediate and displayed MC1R-specific binding on B16/F10 cells. 99mTc(CO)3-NOTA-GGNle-CycMSHhex was further evaluated as a lead peptide because of its higher tumor uptake (19.76 ± 3.62% ID/g) and lower kidney uptake (1.59 ± 0.52% ID/g) at 2 h postinjection than 99mTc(CO)3-NODAGA-GGNle-CycMSHhex. The B16/F10 melanoma uptake of 99mTc(CO)3-NOTA-GGNle-CycMSHhex was 16.07 ± 4.47, 19.76 ± 3.62, 11.30 ± 2.81, and 3.16 ± 2.28% ID/g at 0.5, 2, 4, and 24 h postinjection, respectively. 99mTc(CO)3-NOTA-GGNle-CycMSHhex showed high tumor to normal organ uptake ratios after 2 h postinjection. The B16/F10 melanoma lesions were clearly visualized by SPECT/CT using 99mTc(CO)3-NOTA-GGNle-CycMSHhex as an imaging probe at 2 h postinjection. High tumor uptake, low kidney uptake, and fast urinary clearance of 99mTc(CO)3-NOTA-GGNle-CycMSHhex highlighted its potential for melanoma imaging and facilitated the evaluation of 188Re(CO)3-NOTA-GGNle-CycMSHhex for melanoma therapy.

Imaging human melanoma using a novel Tc-99m-labeled lactam bridge-cyclized alpha-MSH peptide.

In this study, the human melanoma targeting property of (99m)Tc(EDDA)-HYNIC-AocNle-CycMSHhex {hydrazinonicotinamide-8-aminooctanoic acid-Nle-c[Asp-His-DPhe-Arg-Trp-Lys]-CONH2} was determined in M21 human melanoma-xenografts to demonstrate its potential for human melanoma imaging. The IC50 value of HYNIC-AocNle-CycMSHhex was 0.48±0.01nM in M21 human melanoma cells (1281receptors/cell). The M21 human melanoma uptake of (99m)Tc(EDDA)-HYNIC-AocNle-CycMSHhex was 4.03±1.25, 3.26±1.23 and 3.36±1.48%ID/g at 0.5, 2 and 4h post-injection, respectively. Approximately 92% of injected dose cleared out the body via urinary system at 2h post-injection. (99m)Tc(EDDA)-HYNIC-AocNle-CycMSHhex showed high tumor/blood, tumor/muscle and tumor/skin uptake ratios after 2h post-injection. The M21 human melanoma-xenografted tumor lesions were clearly visualized by SPECT/CT using (99m)Tc(EDDA)-HYNIC-AocNle-CycMSHhex as an imaging probe at 2h post-injection. Overall, (99m)Tc(EDDA)-HYNIC-AocNle-CycMSHhex exhibited favorable human melanoma imaging property, highlighting its potential as an imaging probe for human metastatic melanoma detection.