Preparation and biological evaluation of cyclopentadienyl-based 99mTc-complexes [(Cp-R)99mTc(CO)3] mimicking benzamides for malignant melanoma targeting.

The biological evaluation of half-sandwich (99m)Tc-complexes that surrogate iodobenzamide with a high affinity for melanin tumor tissue is described. We have synthesized via retro Diels-Alder reaction two models of (99m)Tc complexes which possess the piano stool [Cp(99m)Tc(CO)(3)] motif instead of a phenyl ring as in the original iodobenzamide (123)I-N-(N-benzylpiperidin-4-yl)-2-iodobenzamide (2-IBP) and N-(2-diethylaminoethyl)-4-iodobenzamide (BZA). Diels-Alder products 2a-b (HCp-CONHR)(2) (2a, R=2-diethylaminoethyl; 2b, R=benzylpiperidin-4-yl) were prepared and reacted with fac-[(99m)Tc(H(2)O)(3)(CO)(3))](+) 1 in water to produce the corresponding (99m)Tc complexes [(2a)(99m)Tc(CO)(3))] 4a and [(2b)(99m)Tc(CO)(3))] 4b. The structures of the (99m)Tc complexes on the no-carrier-added level have been confirmed by chromatographic comparison with the corresponding rhenium complexes 3a and 3b, macroscopically characterized by IR, NMR, ESI-MS and X-ray crystallography for 3a [triclinic, P-1, a=7.3518(1) A, b=8.0309(2) A, c=17.5536(3) A, alpha=99.1260(5) degrees, beta=90.4215(14) degree , gamma=117.0187(11) degrees]. The radioconjugate 4b showed good in vitro stability. In murine melanoma B16F1 cells, significant cellular uptake (43.9% of the total applied activity) was attained after 4 h at 37 degrees C with about 50% of the cell-associated radioactivity being internalized in the cells (22% of the applied activity). Furthermore, in melanoma-bearing C57BL6 mice, tumor uptake values of 3.39+/-0.50 %ID g(-1) and 3.21+/-0.26 %ID g(-1) at 1 and 4 h postinjection, respectively, were observed indicating a good retention of 4b in the tumor.

[1]  B. Spingler,et al.  Aqueous synthesis of derivatized cyclopentadienyl complexes of technetium and rhenium directed toward radiopharmaceutical application. , 2003, Inorganic chemistry.

[2]  A. Veyre,et al.  123I-N-(2-diethylaminoethyl)-2-iodobenzamide: a potential imaging agent for cutaneous melanoma staging , 2002, European Journal of Nuclear Medicine and Molecular Imaging.

[3]  W. Bowen,et al.  Synthesis and characterization of [125I]-N-(N-benzylpiperidin-4-yl)-4- iodobenzamide, a new sigma receptor radiopharmaceutical: high-affinity binding to MCF-7 breast tumor cells. , 1994, Journal of medicinal chemistry.

[4]  R. Alberto,et al.  Aqueous One-Pot Synthesis of Derivatized Cyclopentadienyl-Tricarbonyl Complexes of (99m) Tc with an In Situ CO Source: Application to a Serotonergic Receptor Ligand. , 2001, Angewandte Chemie.

[5]  J. Zubieta,et al.  Single Amino Acid Chelates (SAAC): A Strategy for the Design of Technetium and Rhenium Radiopharmaceuticals , 2009 .

[6]  J. Boire,et al.  Synthesis and evaluation of new iodine-125 radiopharmaceuticals as potential tracers for malignant melanoma. , 1991, Journal of nuclear medicine : official publication, Society of Nuclear Medicine.

[7]  D. Hughes,et al.  Rhenium Carbonyl Complexes of .beta.-Estradiol Derivatives with High Affinity for the Estradiol Receptor: An Approach to Selective Organometallic Radiopharmaceuticals , 1995 .

[8]  B. Redman,et al.  Phase I/II trial of tremelimumab in patients with metastatic melanoma. , 2009, Journal of clinical oncology : official journal of the American Society of Clinical Oncology.

[9]  K. Merz,et al.  Synthesis, characterization, X-ray crystallography, and cytotoxicity of a cymantrene keto carboxylic acid for IR labelling of bioactive peptides on a solid support. , 2008, Journal of inorganic biochemistry.

[10]  A. Veyre,et al.  Uptake in melanoma cells of N-(2-diethylaminoethyl)-2-iodobenzamide (BZA2), an imaging agent for melanoma staging: relation to pigmentation. , 2005, Nuclear medicine and biology.

[11]  A. Veyre,et al.  Phase II scintigraphic clinical trial of malignant melanoma and metastases with iodine-123-N-(2-diethylaminoethyl 4-iodobenzamide). , 1993, Journal of nuclear medicine : official publication, Society of Nuclear Medicine.

[12]  T. Quinn,et al.  99mTc- and 111In-labeled alpha-melanocyte-stimulating hormone peptides as imaging probes for primary and pulmonary metastatic melanoma detection. , 2007, Journal of nuclear medicine : official publication, Society of Nuclear Medicine.

[13]  G. Sheldrick.  A short history of SHELX. , 2008, Acta crystallographica. Section A, Foundations of crystallography.

[14]  S. Jurisson,et al.  Melanoma-targeting properties of (99m)technetium-labeled cyclic alpha-melanocyte-stimulating hormone peptide analogues. , 2000, Cancer research.

[15]  M. Friebe,et al.  [99mTc]oxotechnetium(V) complexes amine-amide-dithiol chelates with dialkylaminoalkyl substituents as potential diagnostic probes for malignant melanoma. , 2001, Journal of medicinal chemistry.

[16]  J. Correia,et al.  A 99mTc(CO)3-labeled pyrazolyl–α-melanocyte-stimulating hormone analog conjugate for melanoma targeting , 2008 .

[17]  L. Holmqvist,et al.  Accumulation of 125I-labelled thiouracil and propylthiouracil in murine melanotic melanomas. , 1982, British Journal of Cancer.

[18]  W. Bowen,et al.  A malignant melanoma imaging agent: synthesis, characterization, in vitro binding and biodistribution of iodine-125-(2-piperidinylaminoethyl)4-iodobenzamide. , 1993, Journal of nuclear medicine : official publication, Society of Nuclear Medicine.

[19]  E. Hindié,et al.  Secondary Ion Mass Spectrometry as a Tool for Investigating Radiopharmaceutical Distribution at the Cellular Level: The Example of I-BZA and 14C-I-BZA , 2005 .

[20]  G. Mariani,et al.  Imaging with 131I-labeled monoclonal antibodies to a high-molecular-weight melanoma-associated antigen in patients with melanoma: efficacy of whole immunoglobulin and its F(ab')2 fragments. , 1985, Cancer research.

[21]  G. Jaouen,et al.  Labeling of proteins by organometallic complexes of rhenium. (I). Synthesis and biological activity of the conjugates. , 1993, Bioconjugate chemistry.

[22]  C. Orvig,et al.  99m‐Technetium Carbohydrate Conjugates as Potential Agents in Molecular Imaging , 2009 .

[23]  J. Katzenellenbogen,et al.  Preparation of Cyclopentadienyltricarbonylrhenium Complexes Using a Double Ligand-Transfer Reaction , 1998 .

[24]  R. Schibli,et al.  Synthesis and properties of boranocarbonate: a convenient in situ CO source for the aqueous preparation of [(99m)Tc(OH(2))3(CO)3]+. , 2001, Journal of the American Chemical Society.

[25]  M. E. Gulden,et al.  Synthesis and Pharmacological Characterization of 4-[125I]-N-(N-Benzylpiperidin-4-yl)-4-iodobenzamide: A High Affinity σ Receptor Ligand for Potential Imaging of Breast Cancer , 1995 .

[26]  M. E. Gulden,et al.  Synthesis, in vitro binding, and tissue distribution of radioiodinated 2-[125I]N-(N-benzylpiperidin-4-yl)-2-iodo benzamide, 2-[125I]BP: a potential sigma receptor marker for human prostate tumors. , 1998, Nuclear medicine and biology.

[27]  E. Pauwels,et al.  Potential radiopharmaceuticals for the detection of ocular melanoma. Part I. 5-iodo-2-thiouracil derivatives , 1983, European Journal of Nuclear Medicine.

[28]  Yu Liu,et al.  Aqueous syntheses of [(Cp-R)M(CO)3] type complexes (Cp = cyclopentadienyl, M = Mn, 99mTc, Re) with bioactive functionalities , 2009 .

[29]  Anthony L. Spek,et al.  Journal of , 1993 .

[30]  I. Greguric,et al.  Synthesis and evaluation of novel radioiodinated benzamides for malignant melanoma. , 2007, Journal of medicinal chemistry.

[31]  Yu Liu,et al.  Metal-mediated retro Diels-Alder of dicyclopentadiene derivatives: a convenient synthesis of [(Cp-R)M(CO)3] (M = 99mTc, Re) complexes. , 2008, Journal of the American Chemical Society.

[32]  G. Jaouen,et al.  Synthesis of cyclopentadienyltricarbonylrhenium(I) carboxylic acid from perrhenate , 1999 .

[33]  J. Papon,et al.  Ultra-structural cell distribution of the melanoma marker iodobenzamide: improved potentiality of SIMS imaging in life sciences , 2004, Biomedical engineering online.

[34]  Klaus Schwochau,et al.  Technetium Radiopharmaceuticals: Fundamentals, Synthesis, Structure, and Development , 1995 .

[35]  R. Pasqualini,et al.  A potential melanoma tracer: synthesis, radiolabeling, and biodistribution in mice of a new nitridotechnetium bis(aminothiol) derivative pharmacomodulated by a N-(diethylaminoethyl)benzamide. , 2000, Journal of medicinal chemistry.

[36]  Alun G. Jones,et al.  Melanoma uptake of (99m)Tc complexes containing the N-(2-diethylaminoethyl)benzamide structural element. , 2002, Journal of medicinal chemistry.

[37]  G. Kloss,et al.  Accumulation of radioiodinated tyrosine derivatives in the adrenal medulla and in melanomas , 1979, European Journal of Nuclear Medicine.

[38]  G. Jaouen,et al.  Direct Synthesis of Tricarbonyl(cyclopentadienyl)rhenium and Tricarbonyl(cyclopentadienyl)technetium Units from Ferrocenyl Moieties − Preparation of 17α‐Ethynylestradiol Derivatives Bearing a Tricarbonyl(cyclopentadienyl)technetium Group , 2004 .

[39]  M. D’incan,et al.  Nouveaux traceurs TEMP : exemple des traceurs des protéoglycanes et de la mélanine , 2009 .

[40]  A. Veyre,et al.  Melanin affinity of N-(2-diethylaminoethyl)-4-iodobenzamide, an effective melanoma imaging agent , 2002, Melanoma research.

[41]  Maria Cristina Burla,et al.  SIR97: a new tool for crystal structure determination and refinement , 1999 .

[42]  M. Eisenhut,et al.  Melanoma affine radiopharmaceuticals I. A comparative study of 131I-labeled quinoline and tyrosine derivatives. , 1981, European journal of nuclear medicine.