Jianquan Yang

Reduction of the ring size of radiolabeled lactam bridge-cyclized alpha-MSH peptide, resulting in enhanced melanoma uptake.

The purpose of this study was to examine the profound effect of the ring size of the radiolabeled lactam bridge–cyclized α-melanocyte–stimulating hormone (α-MSH) peptide on its melanoma-targeting properties. Methods: A novel cyclic α-MSH peptide, 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-Nle-c[Asp-His-d-Phe-Arg-Trp-Lys]-CONH2 (DOTA-Nle-CycMSHhex), was synthesized and radiolabeled with 111In. The melanocortin-1 receptor–binding affinity of DOTA-Nle-CycMSHhex was determined in B16/F1 melanoma cells. The internalization and efflux of 111In-DOTA-Nle-CycMSHhex were examined in B16/F1 cells. The melanoma-targeting properties and SPECT/CT characteristics of 111In-DOTA-Nle-CycMSHhex were determined in B16/F1 melanoma–bearing C57 mice. Results: DOTA-Nle-CycMSHhex displayed 1.77 nM receptor-binding affinity. 111In-DOTA-Nle-CycMSHhex exhibited rapid internalization and extended retention in B16/F1 cells. The tumor uptake of 111In-DOTA-Nle-CycMSHhex was 24.94% ± 4.58% and 10.53% ± 1.11% injected dose per gram at 0.5 and 24 h after injection, respectively. Greater than 82% of the injected radioactivity was cleared through the urinary system by 2 h after injection. The tumor-to-kidney uptake ratios reached 2.04 and 1.70 at 2 and 4 h after injection, respectively. Flank melanoma tumors were clearly visualized by SPECT/CT using 111In-DOTA-Nle-CycMSHhex as an imaging probe at 2 and 24 h after injection. The radioactivity accumulation in normal organs, except for the kidneys, was low at 2, 4, and 24 h after injection. Conclusion: The reduction of the peptide ring size dramatically increased the melanoma uptake and decreased the renal uptake of 111In-DOTA-Nle-CycMSHhex, providing a new insight into the design of a novel radiolabeled lactam bridge–cyclized α-MSH peptide for melanoma imaging and treatment.

Metastatic melanoma imaging with an 111In-labeled lactam bridge-cyclized α-melanocyte-stimulating hormone peptide

INTRODUCTION The purpose of this study was to examine whether a novel lactam bridge-cyclized (111)In-labeled 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-Gly-Glu-c[Lys-Nle-Glu-His-d-Phe-Arg-Trp-Gly-Arg-Pro-Val-Asp] {DOTA-GlyGlu-CycMSH} could be an effective imaging probe for metastatic melanoma detection. METHODS (111)In-DOTA-GlyGlu-CycMSH was prepared and purified by reverse-phase high-performance liquid chromatography (RP-HPLC). The internalization and efflux of (111)In-DOTA-GlyGlu-CycMSH were examined in B16/F10 melanoma cells. The biodistribution of (111)In-DOTA-GlyGlu-CycMSH was determined in B16/F10 pulmonary metastatic melanoma-bearing and normal C57 mice. Pulmonary metastatic melanoma imaging was performed by small-animal single-photon emission computed tomography (SPECT)/CT (Nano-SPECT/CT) using (111)In-DOTA-GlyGlu-CycMSH as an imaging probe and compared with 2-[(18)F]fluoro-2-deoxy-d-glucose ([(18)F]FDG) positron emission tomography (PET) imaging. RESULTS (111)In-DOTA-GlyGlu-CycMSH was readily prepared with greater than 95% radiolabeling yield. (111)In-DOTA-GlyGlu-CycMSH displayed rapid internalization and extended efflux in B16/F10 cells. (111)In-DOTA-GlyGlu-CycMSH exhibited significantly (P<.05) higher uptakes (2.00+/-0.74%ID/g at 2 h post-injection and 1.83+/-0.12%ID/g at 4 h post-injection) in metastatic melanoma-bearing lung than that in normal lung (0.08+/-0.08%ID/g and 0.05+/-0.05%ID/g at 2 and 4 h post-injection, respectively). The activity accumulation in normal organs was low (<0.5%ID/g) except for the kidneys 2 and 4 h post-injection. B16/F10 pulmonary melanoma metastases were clearly visualized with (111)In-DOTA-GlyGlu-CycMSH 2 h post-injection rather than with [(18)F]FDG 1 h post-injection. CONCLUSIONS (111)In-DOTA-GlyGlu-CycMSH exhibited favorable metastatic melanoma-targeting and -imaging properties, highlighting its potential as an effective imaging probe for metastatic melanoma detection.

Effect of DOTA Position on Melanoma Targeting and Pharmacokinetic Properties of 111In-labeled Lactam Bridge-Cyclized Alpha-Melanocyte Stimulating Hormone Peptide

UNLABELLED The purpose of this study was to examine the effect of DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) position on melanoma targeting and pharmacokinetics of radiolabeled lactam bridge-cyclized alpha-melanocyte stimulating hormone (alpha-MSH) peptide. METHOD A novel lactam bridge-cyclized alpha-MSH peptide, Ac-GluGlu-CycMSH[DOTA] {Ac-Glu-Glu-c[Lys-Nle-Glu-His-DPhe-Arg-Trp-Gly-Arg-Pro-Val-Lys(DOTA)]}, was synthesized using standard 9-fluorenylmethyloxycarbonyl (Fmoc) chemistry. DOTA was directly attached to the alpha-amino group of Lys in the cyclic ring, while the N-terminus of the peptide was acetylated to generate Ac-GluGlu-CycMSH[DOTA]. The MC1 receptor binding affinity of Ac-GluGlu-CycMSH[DOTA] was determined in B16/F1 melanoma cells. Melanoma targeting and pharmacokinetic properties of Ac-GluGlu-CycMSH[DOTA]-111In were determined in B16/F1 melanoma-bearing C57 mice and compared to that of 111In-DOTA-Gly-Glu-c[Lys-Nle-Glu-His-DPhe-Arg-Trp-Gly-Arg-Pro-Val-Asp] (111In-DOTA-GlyGlu-CycMSH; DOTA was coupled to the N-terminus of the peptide). RESULTS Ac-GluGlu-CycMSH[DOTA] displayed 0.6 nM MC1 receptor binding affinity in B16/F1 cells. Ac-GluGlu-CycMSH[DOTA]-111In was readily prepared with greater than 95% radiolabeling yield. Ac-GluGlu-CycMSH[DOTA]-111In exhibited high tumor uptake (11.42 +/- 2.20% ID/g 2 h postinjection) and prolonged tumor retention (9.42 +/- 2.41% ID/g 4 h postinjection) in B16/F1 melanoma-bearing C57 mice. The uptake values for nontarget organs were generally low (<1.3% ID/g) except for the kidneys 2, 4, and 24 h postinjection. CONCLUSIONS DOTA position exhibited profound effect on melanoma targeting and pharmacokinetic properties of Ac-GluGlu-CycMSH[DOTA]-111In, providing a new insight into the design of lactam bridge-cyclized peptide for melanoma imaging and therapy.

Evaluation of a novel Arg-Gly-Asp-conjugated α-melanocyte stimulating hormone hybrid peptide for potential melanoma therapy.

UNLABELLED The purpose of this study was to determine whether Arg-Gly-Asp (RGD)-conjugated α-melanocyte stimulating hormone (α-MSH) hybrid peptide could be employed to target melanocortin-1 (MC1) receptor for potential melanoma therapy. METHODS The RGD motif {cyclic(Arg-Gly-Asp-DTyr-Asp)} was coupled to [Cys(3,4,10), DPhe(7), Arg(11)]α-MSH(3-13) {(Arg(11))CCMSH} to generate RGD-Lys-(Arg(11))CCMSH hybrid peptide. The MC1 receptor binding affinity of RGD-Lys-(Arg(11))CCMSH was determined in B16/F1 melanoma cells. The internalization and efflux, melanoma targeting and pharmacokinetic properties and single photon emission computed tomography/CT (SPECT/CT) imaging of (99m)Tc-RGD-Lys-(Arg(11))CCMSH were determined in B16/F1 melanoma cells and melanoma-bearing C57 mice. Clonogenic cytotoxic effect of RGD-Lys-(Arg(11))CCMSH was examined in B16/F1 melanoma cells. RESULTS RGD-Lys-(Arg(11))CCMSH displayed 2.1 nM MC1 receptor binding affinity. (99m)Tc-RGD-Lys-(Arg(11))CCMSH showed rapid internalization and extended retention in B16/F1 cells. The cellular uptake of (99m)Tc-RGD-Lys-(Arg(11))CCMSH was MC1 receptor-mediated. (99m)Tc-RGD-Lys-(Arg(11))CCMSH exhibited high tumor uptake (14.83 ± 2.94% ID/g 2 h postinjection) and prolonged tumor retention (7.59 ± 2.04% ID/g 24 h postinjection) in B16/F1 melanoma-bearing mice. Nontarget organ uptakes were generally low except for the kidneys. Whole-body clearance of (99m)Tc-RGD-Lys-(Arg(11))CCMSH was rapid, with approximately 62% of the injected radioactivity cleared through the urinary system by 2 h postinjection. Flank melanoma tumors were clearly imaged by small animal SPECT/CT using (99m)Tc-RGD-Lys-(Arg(11))CCMSH as an imaging probe 2 h postinjection. Single treatment (3 h incubation) with 100 nM of RGD-Lys-(Arg(11))CCMSH significantly (p < 0.05) decreased the clonogenic survival of B16/F1 cells by 65% compared to the untreated control cells. CONCLUSION Favorable melanoma targeting property of (99m)Tc-RGD-Lys-(Arg(11))CCMSH and remarkable cytotoxic effect of RGD-Lys-(Arg(11))CCMSH in B16/F1 cells warranted the further evaluation of (188)Re-labeled α-MSH hybrid peptides as novel therapeutic peptides for melanoma treatment once the strategies of amino acid coinjection or structural modification of peptide sequence substantially reduce the renal uptake.

Effects of the amino acid linkers on the melanoma-targeting and pharmacokinetic properties of 111In-labeled lactam bridge-cyclized alpha-MSH peptides.

The purpose of this study was to examine the profound effects of the amino acid linkers on the melanoma-targeting and pharmacokinetic properties of 111In-labeled lactam bridge–cyclized DOTA-[X]-CycMSHhex {1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-[X]-c[Asp-His-dPhe-Arg-Trp-Lys]-CONH2; X = GGNle, GENle, or NleGE; GG = -Gly-Gly- and GE = -Gly-Glu-} peptides. Methods: Three novel peptides (DOTA-GGNle-CycMSHhex, DOTA-GENle-CycMSHhex, and DOTA-NleGE-CycMSHhex) were designed and synthesized. The melanocortin-1 (MC1) receptor–binding affinities of the peptides were determined in B16/F1 melanoma cells. The melanoma-targeting and pharmacokinetic properties of 111In-DOTA-GGNle-CycMSHhex and 111In-DOTA-GENle-CycMSHhex were determined in B16/F1 melanoma–bearing C57 mice. Results: DOTA-GGNle-CycMSHhex and DOTA-GENle-CycMSHhex displayed 2.1 and 11.5 nM MC1 receptor–binding affinities, whereas DOTA-NleGE-CycMSHhex showed 873.4 nM MC1 receptor–binding affinity. The introduction of the -GG- linker maintained high melanoma uptake while decreasing kidney and liver uptake of 111In-DOTA-GGNle-CycMSHhex. The tumor uptake of 111In-DOTA-GGNle-CycMSHhex was 19.05 ± 5.04 and 18.6 ± 3.56 percentage injected dose per gram at 2 and 4 h after injection, respectively. 111In-DOTA-GGNle-CycMSHhex exhibited 28%, 32%, and 42% less kidney uptake than 111In-DOTA-Nle-CycMSHhex we reported previously, and 61%, 65%, and 68% less liver uptake than 111In-DOTA-Nle-CycMSHhex at 2, 4, and 24 h after injection, respectively. Conclusion: The amino acid linkers exhibited profound effects on the melanoma-targeting and pharmacokinetic properties of the 111In-labeled lactam bridge–cyclized α-melanocyte–stimulating hormone peptides. Introduction of the -GG- linker maintained high melanoma uptake while reducing kidney and liver uptake of 111In-DOTA-GGNle-CycMSHhex, highlighting its potential as an effective imaging probe for melanoma detection, as well as a therapeutic peptide for melanoma treatment when labeled with a therapeutic radionuclide.

Gallium-67-Labeled Lactam Bridge-Cyclized Alpha-Melanocyte Stimulating Hormone Peptide for Primary and Metastatic Melanoma Imaging

The purpose of this study was to examine the melanoma imaging properties of a novel 67Ga-labeled lactam bridge-cyclized alpha-melanocyte stimulating hormone (alpha-MSH) peptide. A lactam bridge-cyclized alpha-MSH peptide, DOTA-GlyGlu-CycMSH {DOTA-Gly-Glu-c[Lys-Nle-Glu-His-DPhe-Arg-Trp-Gly-Arg-Pro-Val-Asp]}, was synthesized and radiolabeled with 67Ga. The melanoma targeting and pharmacokinetic properties of 67Ga-DOTA-GlyGlu-CycMSH were determined in B16/F1 flank primary melanoma-bearing and B16/F10 pulmonary metastatic melanoma-bearing C57 mice. Flank primary melanoma and pulmonary metastatic melanoma imaging were performed by small animal single photon emission computed tomography (SPECT)/CT using 67Ga-DOTA-GlyGlu-CycMSH as an imaging probe. 67Ga-DOTA-GlyGlu-CycMSH was readily prepared with greater than 95% radiolabeling yield. 67Ga-DOTA-GlyGlu-CycMSH exhibited substantial tumor uptake (12.93 +/- 1.63%ID/g at 2 h postinjection) and prolonged tumor retention (5.02 +/- 1.35%ID/g at 24 h postinjection) in B16/F1 melanoma-bearing C57 mice. The uptake values for nontarget organs were generally low (<0.30%ID/g) except for the kidneys at 2, 4, and 24 h postinjection. 67Ga-DOTA-GlyGlu-CycMSH exhibited significantly (p < 0.05) higher uptakes (1.44 +/- 0.75%ID/g at 2 h postinjection and 1.49 +/- 0.69%ID/g at 4 h postinjection) in metastatic melanoma-bearing lung than those in normal lung (0.15 +/- 0.10%ID/g and 0.17 +/- 0.11%ID/g at 2 and 4 h postinjection, respectively). Both flank primary B16/F1 melanoma and B16/F10 pulmonary melanoma metastases were clearly visualized by SPECT/CT using 67Ga-DOTA-GlyGlu-CycMSH as an imaging probe 2 h postinjection. 67Ga-DOTA-GlyGlu-CycMSH exhibited favorable melanoma targeting and imaging properties, highlighting its potential as an effective imaging probe for early detection of primary and metastatic melanoma.

Technetium-99m-labeled Arg-Gly-Asp-conjugated alpha-melanocyte stimulating hormone hybrid peptides for human melanoma imaging

INTRODUCTION The purpose of this study was to examine whether (99m)Tc-labeled Arg-Gly-Asp (RGD)-conjugated alpha-melanocyte stimulating hormone (α-MSH) hybrid peptide targeting both melanocortin-1 (MC1) and α(v)β(3) integrin receptors was superior in melanoma targeting to (99m)Tc-labeled α-MSH or RGD peptide targeting only the MC1 or α(v)β(3) integrin receptor. METHODS RGD-Lys-(Arg(11))CCMSH, RAD-Lys-(Arg(11))CCMSH and RGD-Lys-(Arg(11))CCMSHscramble were designed to target both MC1 and α(v)β(3) integrin receptors, MC1 receptor only and α(v)β(3) integrin receptor only, respectively. The MC1 or α(v)β(3) integrin receptor binding affinities of three peptides were determined in M21 human melanoma cells. The melanoma targeting properties of (99m)Tc-labeled RGD-Lys-(Arg(11))CCMSH, RAD-Lys-(Arg(11))CCMSH and RGD-Lys-(Arg(11))CCMSHscramble were determined in M21 human melanoma-xenografted nude mice. Meanwhile, the melanoma uptake of (99m)Tc-RGD-Lys-(Arg(11))CCMSH was blocked with various non-radiolabeled peptides in M21 melanoma xenografts. RESULTS RGD-Lys-(Arg(11))CCMSH displayed 2.0 and 403 nM binding affinities to both MC1 and α(v)β(3) integrin receptors, whereas RAD-Lys-(Arg(11))CCMSH or RGD-Lys-(Arg(11))CCMSHscramble lost their α(v)β(3) integrin receptor binding affinity by greater than 248-fold or MC1 receptor binding affinity by more than 100-fold, respectively. The melanoma uptake of (99m)Tc-RGD-Lys-(Arg(11))CCMSH was 2.49 and 2.24 times (P < .05) the melanoma uptakes of (99m)Tc-RAD-Lys-(Arg(11))CCMSH and (99m)Tc-RGD-Lys-(Arg(11))CCMSHscramble at 2 h post-injection, respectively. Either RGD or (Arg(11))CCMSH peptide co-injection could block 42% and 57% of the tumor uptake of (99m)Tc-RGD-Lys-(Arg(11))CCMSH, whereas the coinjection of RGD+(Arg(11))CCMSH peptide mixture could block 66% of the tumor uptake of (99m)Tc-RGD-Lys-(Arg(11))CCMSH. CONCLUSIONS Targeting both MC1 and α(v)β(3) integrin receptors enhanced the melanoma uptake of (99m)Tc-RGD-Lys-(Arg(11))CCMSH in M21 human melanoma xenografts. Flank M21 human melanoma tumors were clearly visualized by single photon emission computed tomography/computed tomographic imaging using (99m)Tc-RGD-Lys-(Arg(11))CCMSH as an imaging probe, highlighting its potential use as a dual-receptor-targeting imaging probe for human melanoma detection.

Replacement of the Lys linker with an Arg linker resulting in improved melanoma uptake and reduced renal uptake of Tc-99m-labeled Arg-Gly-Asp-conjugated alpha-melanocyte stimulating hormone hybrid peptide.

The purpose of this study was to reduce the non-specific renal uptake of Arg-Gly-Asp (RGD)-conjugated alpha-melanocyte stimulating hormone (alpha-MSH) hybrid peptide through structural modification or L-lysine co-injection. The RGD motif {cyclic(Arg-Gly-Asp-DTyr-Asp)} was coupled to [Cys(3,4,10), D-Phe7, Arg11] alpha-MSH3-13 {(Arg11)CCMSH} through the Arg linker (substituting the Lys linker) to generate a novel RGD-Arg-(Arg11)CCMSH hybrid peptide. The melanoma targeting and pharmacokinetic properties of 99mTc-RGD-Arg-(Arg11)CCMSH were determined in B16/F1 melanoma-bearing C57 mice. The effect of L-lysine co-injection on the renal uptake was determined through the co-injection of L-lysine with 99mTc-RGD-Arg-(Arg11)CCMSH or 99mTc-RGD-Lys-(Arg11)CCMSH. Replacement of the Lys linker with an Arg linker exhibited a profound effect in reducing the non-specific renal uptake of 99mTc-RGD-Arg-(Arg11)CCMSH, as well as increasing the tumor uptake of 99mTc-RGD-Arg-(Arg11)CCMSH compared to 99mTc-RGD-Lys-(Arg11)CCMSH. 99mTc-RGD-Arg-(Arg11)CCMSH exhibited high tumor uptake (21.41+/-3.74% ID/g at 2 h post-injection) and prolonged tumor retention (6.81+/-3.71% ID/g at 24 h post-injection) in B16/F1 melanoma-bearing mice. The renal uptake values of 99mTc-RGD-Arg-(Arg11)CCMSH were 40.14-64.08% of those of 99mTc-RGD-Lys-(Arg11)CCMSH (p<0.05) at 0.5, 2, 4 and 24 h post-injection. Co-injection of L-lysine was effective in decreasing the renal uptakes of 99mTc-RGD-Arg-(Arg11)CCMSH by 27.7% and 99mTc-RGD-Lys-(Arg11)CCMSH by 52.1% at 2 h post-injection. Substitution of the Lys linker with an Arg linker dramatically improved the melanoma uptake and reduced the renal uptake of 99mTc-RGD-Arg-(Arg11)CCMSH, warranting the further evaluation of 188Re-labeled RGD-Arg-(Arg11)CCMSH as a novel MC1 receptor-targeting therapeutic peptide for melanoma treatment in the future.

Evaluation of New Tc-99m-Labeled Arg-X-Asp-Conjugated α-Melanocyte Stimulating Hormone Peptides for Melanoma Imaging

The purpose of this study was to examine the melanoma targeting and imaging properties of two new (99m)Tc-labeled Arg-X-Asp-conjugated α-melanocyte stimulating hormone (α-MSH) peptides. RTD-Lys-(Arg(11))CCMSH {c[Asp-Arg-Thr-Asp-DTyr]-Lys-Cys-Cys-Glu-His-DPhe-Arg-Trp-Cys-Arg-Pro-Val-NH2} and RVD-Lys-(Arg(11))CCMSH peptides were synthesized, and their melanocortin-1 (MC1) receptor binding affinities were determined in B16/F1 melanoma cells. The biodistribution and melanoma imaging properties of (99m)Tc-RTD-Lys-(Arg(11))CCMSH and (99m)Tc-RVD-Lys-(Arg(11))CCMSH were determined in B16/F1 melanoma-bearing C57 mice. The IC50 values of RTD-Lys-(Arg(11))CCMSH and RVD-Lys-(Arg(11))CCMSH were 0.7 ± 0.07 and 1.0 ± 0.3 nM in B16/F1 melanoma cells. Both (99m)Tc-RTD-Lys-(Arg(11))CCMSH and (99m)Tc-RVD-Lys-(Arg(11))CCMSH displayed high melanoma uptake. (99m)Tc-RTD-Lys-(Arg(11))CCMSH exhibited the highest tumor uptake of 18.77 ± 5.13% ID/g at 2 h postinjection, whereas (99m)Tc-RVD-Lys-(Arg(11))CCMSH reached the highest tumor uptake of 19.63 ± 4.68% ID/g at 4 h postinjection. Both (99m)Tc-RTD-Lys-(Arg(11))CCMSH and (99m)Tc-RVD-Lys-(Arg(11))CCMSH showed low accumulation in normal organs (<1.7% ID/g) except for the kidneys at 2 h postinjection. The renal uptake of (99m)Tc-RTD-Lys-(Arg(11))CCMSH and (99m)Tc-RVD-Lys-(Arg(11))CCMSH was 135.14 ± 23.62 and 94.01 ± 18.31% ID/g at 2 h postinjection, respectively. The melanoma lesions were clearly visualized by single-photon emission computed tomography (SPECT)/CT using either (99m)Tc-RTD-Lys-(Arg(11))CCMSH or (99m)Tc-RVD-Lys-(Arg(11))CCMSH as an imaging probe at 2 h postinjection. Overall, the introduction of Thr or Val residue retained high melanoma uptake of (99m)Tc-RTD-Lys-(Arg(11))CCMSH and (99m)Tc-RVD-Lys-(Arg(11))CCMSH. However, high renal uptake of (99m)Tc-RTD-Lys-(Arg(11))CCMSH and (99m)Tc-RVD-Lys-(Arg(11))CCMSH need to be reduced to facilitate their future applications.

Substitution of Gly with Ala enhanced the melanoma uptake of technetium-99m-labeled Arg-Ala-Asp-conjugated alpha-melanocyte stimulating hormone peptide

The purpose of this study was to determine the melanoma targeting property of (99m)Tc-RAD-Lys-(Arg(11))CCMSH in B16/F1 melanoma-bearing C57 mice and compare with (99m)Tc-RGD-Lys-(Arg(11))CCMSH we previously reported. (99m)Tc-RAD-Lys-(Arg(11))CCMSH exhibited rapid and high tumor uptake (19.91±4.02% ID/g at 2h post-injection) in B16/F1 melanoma-bearing C57 mice. The tumor uptake of (99m)Tc-RAD-Lys-(Arg(11))CCMSH was 1.51, 1.34 and 1.43 times the tumor uptake of (99m)Tc-RGD-Lys-(Arg(11))CCMSH at 0.5, 2 and 4h post-injection, respectively. Flank B16/F1 melanoma lesions were clearly imaged at 2h post-injection using (99m)Tc-RAD-Lys-(Arg(11))CCMSH as an imaging probe. The substitution of Gly with Ala significantly enhanced the melanoma uptake of (99m)Tc-RAD-Lys-(Arg(11))CCMSH compared to (99m)Tc-RGD-Lys-(Arg(11))CCMSH in B16/F1 melanoma-bearing C57 mice, providing a new insight into the design of α-MSH peptides for melanoma targeting.