WO2000071171A2

WO2000071171A2 - Sigma-1 ligands for determining carcinoma proliferative status

Info

Publication number: WO2000071171A2
Application number: PCT/US2000/013834
Authority: WO
Inventors: Robert H. Mach; Yunsheng Huang; Steven R. Childers; Kenneth T. Wheeler
Original assignee: Wake Forest University
Priority date: 1999-05-21
Filing date: 2000-05-19
Publication date: 2000-11-30
Also published as: WO2000071171A3; AU5032400A

Abstract

The invention provides a method for determining the proliferative status of cancer cells that express sigma-1 receptors, as well as detectably labeled compounds and pharmaceutically compositions that are useful for carrying out such methods.

Description

SIGMA-1 LIGANDS USEFUL FOR DETERMINING THE PROLIFERATIVE STATUS OF CANCER CELLS

Background of the Invention One of the major problems in the clinical management of cancer is the identification of an appropriate treatment strategy. For example, the choice of whether a patient is subjected to conventional versus fractionated radiation therapy is often dependent upon the proliferative status of a tumor. The primary measure of proliferative status is the determination of the S-phase fraction of a tumor. This is traditionally determined by flow cytometric measurements of tissue biopsy samples. Patients with tumors exhibiting a high S-phase fraction display a greater likelihood of tumor recurrence and have a higher death rate. These patients, who are predicted to have a poor response to conventional radiation therapy, are often chosen for an accelerated radiation fractionation schedule.

Although S-phase fraction is an objective method for measuring the proliferative status of tumors, there are a number of complications that limit the accuracy of the procedure. For example, in breast cancer, 30-40% of biopsy samples are unevaluable for flow cytometric analysis. Furthermore, tissue sampling by biopsy can be problematic since most tumors are heterogeneous, and consist of both proliferative and nonproliferative cells. Therefore, tissue samples obtained from a tumor biopsy may not be representative of the entire tumor cell population.

Imaging procedures that avoid many of the problems associated with traditional procedures include single photon emission computed tomography (SPECT) and positron emission tomography (PET). Unlike flow cytometry of biopsy samples, which sample only a fraction of the tumor, SPECT and PET can image and provide information about an entire tumor.

These imaging techniques have been used in conjunction with radiotracers that possess a high affinity for a protein having abnormal expression in tumor cells. The most prominent example of this approach is the use of radiolabeled monoclonal antibodies possessing a high affinity for tumor- radiolabeled monoclonal antibodies possessing a high affinity for tumor- associated antigens. Although some success has been obtained in this area, a number of complications, including heterogeneity of antigen-containing tumor cells, low tumor uptake, nonspecific radiotracer uptake in adjacent or other nontumor tissues, the presence of circulating antigens that compete with tumor cells for antibody, and the potential immunogenicity of the monoclonal antibody, have limited the general utility of this approach.

Another alternate approach for imaging tumors is the use of radiolabeled small molecules that possess a high affinity for receptors that are abnormally expressed in tumor cells. A number of studies have reported an overexpression of sigma receptors in a variety of human and murine tumors. For example, BJ. Nilner, et al. Cancer Research, 1995, 408-413, disclose that tumor cell lines of various tissue origins and species express sigma- 1 and sigma-2 receptors in high density. Although sigma- 1 sites were disclosed to be expressed in numerous cell lines, including T47D breast ductal carcinoma cells, MCF-7 breast adenocarcinoma cells showed little or no binding of [³H](+)-pentazocine, indicating the absence of sigma- 1 receptors in these cells. The authors concluded that sigma sites may be useful as markers in the non-invasive detection and visualization of a wide variety of tumors using single photon emission computed tomography and positron emission tomography technology. Additionally, C.S. John, et al., Cancer Research, 1995, 3022- 3027, disclose the synthesis of [^I25I]-Ν-(Ν-benzylpiperidin-4-yl)-4- iodobenzamide, which was found to bind to both sigma- 1 and sigma-2 receptor sub-types in brain and liver tissue. The compounds, [¹²³I]-N-(N-benzylpiperidin- 4-yl)-4-iodobenzamide and [¹³¹I]-N-(N-benzylpiperidin-4-yl)-4-iodobenzamide, were disclosed to be potentially useful for non-invasive (single photon emission computed tomography) imaging of breast cancer patients.

Although previous reports have demonstrated that sigma receptors may serve as a target for radiotracers that can be used to anatomically image solid tumors, they did not suggest a correlation between sigma receptor density and the proliferative status of tumor cells. PCT US97/04403, published 25 September 1997, discloses that sigma-2 receptor density correlates with the proliferative status of breast tumor cells, and discloses a non-invasive method to detect cancer cells or to assess the proliferative status of cancer cells which express sigma-2 receptors, using detectably labeled sigma-2 ligands.

Despite the reported use of detectably labeled sigma-2 ligands to determine the proliferative status of cancer cells, there is currently a need for additional methods for accurately assessing the proliferative status of cancer cells. An imaging procedure that could overcome some or all of the problems inherent to flow cytometry measurements of human tumors could have a significant impact on the clinical management of a variety of human cancers that express a high density of sigma receptors, such as ghoblastoma, melanoma, lung and prostate tumors.

Summary of the Invention The presnet invention provides a compound of formula I:

wherein:

R_] is hydrogen, (C,-C₆)alkyl, aryl, or aryl(C C₆)alkyl;

R₂ is aryl or heteroaryl;

A is NE^, -O-, CR_bR_c, or -S-;

B is NR_a, -O-, CR_bR_c, or -S-; C is two hydrogens, oxo (=O), or thioxo (=S); each R_a is independently hydrogen, or (C,-C₆)alkyl; each R_b is independently hydrogen, hydroxy, (C,-C₆)alkyl, or (C,- C₆)alkoxy; and each R_c is independently hydrogen, or (C C₆)alkyl; wherein any aryl or heteroaryl is optionally substituted with 1, 2,

3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, (C,-C₆)alkyl, (C C₆)alkoxy, (C,-C₆)alkanoyl, (C,-C₆)alkanoyloxy, (C C₆)alkoxycarbonyl, and methylenedioxy; or a pharmaceutically acceptable salt thereof; provided R_; is not benzyl, when A is NH, B is CH₂, C is oxo, and R₂ is phenyl, 1-naphthyl, 2-naphthyl, 2-thiophenyl, 3-thiophenyl, 2-pyridinyl, 3-, pyridinyl, 4-pyridinyl, 4-imidazolyl, 2-nitrophenyl, 3 nitrophenyl, 4-nitrophenyl, 4-(l-NO₂, 3-NO₂-Ph), 2-methoxyphenyl, 3-methoxyphenyl, 4-methoxyphenyl, 2,5-dimethoxyphenyl, 3,4-dimethoxyphenyl, 3,5-dimethoxyphenyl, 3,4,5- tromethoxyphenyl, 4-methylthiophenyl, 2-hydroxyphenyl, 3-hydroxyphenyl, 4- hydroxyphenyl, 3,4-dihydroxyphenyl, 3-chloro-4-hydroxyphenyl, 3,4- methylenedioxyphenyl, 4-fluorophenyl, 2,4-difluorophenyl, 2,5-difiuorophenyl, 2,6-difluorophenyl, 3,4-difluorophenyl, 3,5-difluorophenyl, 4-chlorophenyl, 2,4- dichlorophenyl, 2,6-dichlorophenyl, 3,4-dichlorophenyl, 2-bromophenyl, 3- bromophenyl, 4-bromophenyl, 2-trifluoromethylphenyl, 3- trifluoromethylphenyl, 4-trifluoromethylphenyl, 4-aminophenyl, 3-indolyl, 3-(5- methoxy-indolyl), 3-(2-methyl-5-methoxyindolyl), 3-(5-methoxy- 1 -indanone); and provided R₁ is not benzyl, when A is NH, B is NH, C is oxo, and R₂ is 1-naphthyl, 2,4-dimethoxyphenyl, or 4-methylthiophenyl; and provided R, is not benzyl, when A is NH, B is CH₂, C is two hydrogens, and R₂ is 2,3-dimethoxyphenyl; or a pharmaceutically acceptable salt thereof.

The present invention also provides for a compound of formula I:

wherein:

R_j is hydrogen, (C,-C₆)alkyl, aryl, or aryl(C_rC₆)alkyl; R₂ is aryl or heteroaryl; A is NR,, -O-, CR_bR_c, or -S-;

B is NR,, -O-, CR_bR_c, or -S-; C is two hydrogens, oxo (=O), or thioxo (=S); each R-_j is independently hydrogen, or (C_rC₆)alkyl; each R_b is independently hydrogen, hydroxy, (C_rC₆)alkyl, or (C_r C₆)alkoxy; and each R_c is independently hydrogen, or (C_rC₆)alkyl; wherein any aryl or heteroaryl is optionally substituted with 1, 2, 3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, (C C₆)alkyl, (C_r C₆)alkoxy, (C_rC₆)alkanoyl, (C,-C₆)alkanoyloxy, (C_rC₆)alkoxycarbonyl, and methylenedioxy; or a pharmaceutically acceptable salt thereof; provided R, is not phenyl, benzyl, or phenethyl.

The present invention also provides for a compound of formula I:

wherein:

R, is hydrogen, (C_rC₆)alkyl, aryl, or aryl(C_rC₆)alkyl;

R₂ is aryl or heteroaryl; A is NR_a, -O-, CR_bR_c, or -S-;

B is NR_a, -O-, CR_bR_c, or -S-;

C is two hydrogens, oxo (=O), or thioxo (=S); each R_a is independently hydrogen, or (C,-C₆)alkyl; each R_b is independently hydrogen, hydroxy, (C,-C₆)alkyl, or (C_r C₆)alkoxy; and each R_c is independently hydrogen, or (C,-C₆)alkyl; wherein any aryl of R_! is substituted with 1, 2, 3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, (C_]-C₆)alkoxy, (C,-C₆)alkanoyl, (C,- C₆)alkanoyloxy, (C^C^alkoxycarbonyl, and methylenedioxy; and wherein any aryl or heteroaryl of R₂ or heteroaryl of R, is optionally substituted with 1, 2, 3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, (C_rC₆)alkyl, (C,-C₆)alkoxy, (C,-C₆)alkanoyl, (C,- C₆)alkanoyloxy, (C,-C₆)alkoxycarbonyl, and methylenedioxy; or a pharmaceutically acceptable salt thereof.

The present invention also provides for a compound of formula I:

wherein:

R_[ is hydrogen, (C,-C₆)alkyl, aryl, or aryl(C,-C₆)alkyl; R₂ is aryl or heteroaryl; A is-O-, CR_bR_c, or -S-; B is NR_a, -O-, CR_bR_c, or -S-; C is two hydrogens, oxo (=O), or thioxo (=S); each R_a is independently hydrogen, or ( -C^alkyl; each R_b is independently hydrogen, hydroxy, (C,-C₆)alkyl, or (C,- C₆)alkoxy; and each R_c is independently hydrogen, or (C,-C₆)alkyl; wherein any aryl or heteroaryl is optionally substituted with 1, 2,

3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, ( -C^alkyl, (C C₆)alkoxy, (C_rC₆)alkanoyl, ( -C^alkanoyloxy, (C,-C₆)alkoxycarbonyl, and methylenedioxy; or a pharmaceutically acceptable salt thereof.

The present invention also provides for a compound of formula I:

wherein:

R, is hydrogen, (C,-C₆)alkyl, aryl, or aryl(C_rC₆)alkyl; R₂ is aryl or heteroaryl; A is NR_a, -O-, CR^, or -S-; B is -O- or -S-;

C is two hydrogens, oxo (=O), or thioxo (=S); each R_a is independently hydrogen, or (C,-C₆)alkyl; each R_b is independently hydrogen, hydroxy, (C,-C₆)alkyl, or (C_r C₆)alkoxy; and each R_c is independently hydrogen, or (C_rC₆)alkyl; wherein any aryl or heteroaryl is optionally substituted with 1 , 2, 3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, (C,-C₆)alkyl, (C_r C₆)alkoxy, (C_rC₆)alkanoyl, (C_rC₆)alkanoyloxy, (C,-C₆)alkoxycarbonyl, and methylenedioxy; or a pharmaceutically acceptable salt thereof.

The present invention also provides for the compound N-(l- benzylpiperidin-4-yl)-2-fluorophenylacetamide, or a pharmaceutically acceptable salt thereof.

The present invention also provides for the compound ¹⁸F-N-(1- Benzylpiperidin-4-yl)-2-fluorophenylacetamide, or a pharmaceutically acceptable salt thereof.

The present invention also provides for a pharmaceutical composition comprising a detectably labeled compound of the present invention (e.g., sigma-1 ligand), and a pharmaceutically acceptable diluent or carrier.

The present invention also provides for a compound of the present invention that is useful in medical therapy.

The present invention also provides for a detectablt labeled compound of the present invention that is useful in medical imaging.

The present invention also provides for a detectablt labeled compound of the present invention that is useful to determine the proliferative status of a tumor (e.g., solid tumor) that comprises cells that express sigma-1 receptors. The proliferative status of a tumor is determined by: (a) contacting (e.g., in vivo or in vitro) the cells with the compound , and (b) determining the extent to which the compound binds to the cells, wherein the extent provides a measure of the proliferative status of the tumor. The compound can be contacting is. In addition,

The invention also provides a method for determining the proliferative status of cancer cells that express sigma-1 receptors, comprising:

(a) contacting the cells with a detectably labeled sigma-1 ligand, and

(b) determining the extent to which the ligand binds to the cells, wherein the extent provides a measure of the proliferative status of the cell.

The invention also provides novel compounds of formula (I), as described herein, both labeled and unlabeled.

The invention also provides a pharmaceutical composition comprising a detectably labeled sigma-1 ligand, and a pharmaceutically acceptable carrier.

The invention also provides a method for determining the proliferative status of cancer cells that express sigma-1 receptors and sigma-2 receptors, comprising:

(a) contacting the cells with a detectably labeled sigma-1 ligand and a detectably labeled sigma-2 ligand, and

(b) determining the extent to which the ligands bind to the cells, wherein the extent provides a measure of the proliferative status of the cell.

(a) contacting the cells with a detectably labeled ligand that binds to both sigma-1 receptors and to sigma-2 receptors, and

(b) determining the extent to which the ligand binds to sigma-1 receptors and to sigma-2 receptors, wherein the extent of binding to sigma-1 receptors and to sigma-2 receptors provides a measure of the proliferative status of the cells. The invention also provides a method for inhibiting the growth of cancer cells (e.g., breast cancer cells, prostate cancer cells, and/or bladder cancer cells) that express sigma-1 receptors comprising administering to a mammal in need of such treatment an effective inhibitory amount of a sigma-1 ligand labeled with a therapeutic radionuclide (e.g. Rhenium- 186 or Yttrium-90), or a pharmaceutically acceptable salt thereof.

The invention also provides the use of a detectably labeled sigma- 1 ligand (preferably a selective sigma-1 ligand or a compound of formula I) to prepare a medicament useful for determining the proliferative status of cancer (e.g., breast cancer, prostate cancer, and/or bladder cancer) cells.

The invention also provides the use of a combination of 1) a detectably labeled sigma-1 ligand (preferably a selective sigma-1 ligand or a compound of formula I), and 2) a sigma-2 ligand, to prepare a medicament useful for determining the proliferative status of cancer (e.g., breast cancer, prostate cancer, and/or bladder cancer) cells.

The invention also provides the use of a detectably labeled sigma- 1 and sigma-2 ligand to prepare a medicament useful for determining the proliferative status of cancer (e.g., breast cancer, prostate cancer, and/or bladder cancer) cells.

Brief Description of the Figures Figure 1 illustrates the results of a tissue culture sigma-1 receptor binding test. Figure 2 shows the relative density of sigma-1 and sigma-2 receptors from blocking studies in mouse brain and mouse mammary adenocarcinoma tumors in nude mice. Figure 3 shows F-l 8 labeled tumor uptake of a specific compound of the present invention

Figure 4 illustrates specific compounds of the present invention which are compounds of formula I labeled with a metal chelating group comprising a radionuclide M.

Detailed Description of the Tnvention

Applicant has discovered that sigma-1 receptor density is a biomarker of cancer cell proliferation, and herein discloses a method to assess the proliferative status of cancer cells using a detectably labeled sigma-1 ligand. Although previous studies suggest that sigma-1 receptors are not expressed by MCF-7 breast cancer cells, it has been determined that sigma-1 receptors on breast cancer cells are unstable under the isolation and storage conditions typically used for such cells. By labeling breast cancer cells with sigma-1 -selective ligands in vivo, or in freshly prepared tissue samples in vitro, it has been determined that sigma-1 receptors are expressed in high density by breast cancer cells. Thus, sigma-1 selective ligands are useful for assessing the proliferative status of breast cancer cells as well as other sigma-1 expressing cancer cells.

Sigma-1 ligands

As used herein, the term "sigma-1 ligand" comprises any compound that is capable of binding to sigma-1 receptors to a measurable degree. Suitable sigma-1 ligands are known in the art, for example, see Y. Huang et al., Poster Number MEDI 055, presented at the 213th American

Chemical Society Meeting, April 13-17, 1997, San Francisco, California; and Y. Huang, et al., J. Med. Chem., 1998, 41, 13, 2361-2370.

Preferably, the compound binds selectively to sigma-1 receptors over sigma-2 receptors. A compound's ability to bind to sigma-1 and sigma-2 receptors can be determined using binding assays that are known in the art (see for example, Y. Huang, et al., J. Med. Chem., 1998, 41, 13, 2361-2370) or can be determined using binding assays similar to those described hereinbelow. Preferred sigma-1 ligands bind at least 2, at least 3, at least 5, at least 10, or at least 25 times more readily to a sigma-1 receptor than to a sigma-2 receptor. A specific sigma-1 ligand that can be detectably labeled and used in the methods of the invention is a compound of formula I:

wherein:

R_j is hydrogen, (C,-C₆)alkyl, aryl, or ary^C_j-C^alkyl; R₂ is aryl or heteroaryl;

A is NR_a, -O-, CR_bR_c, or -S-;

B is NR_a, -O-, CR_bR_c, or -S-;

C is two hydrogens, oxo (=O), or thioxo (=S); each R_a is independently hydrogen, or (C,-C₆)alkyl; each R_b is independently hydrogen, hydroxy, (C₁-C₆)alkyl, or (C_r C₆)alkoxy; and each R_c is independently hydrogen, or (C_j-C₆)alkyl; wherein any aryl or heteroaryl is optionally substituted with 1, 2, 3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, (C,-C₆)alkyl, (C,- C₆)alkoxy, (C,-C₆)alkanoyl, ( -C^alkanoyloxy, (C,-C₆)alkoxycarbonyl, and methylenedioxy; or a pharmaceutically acceptable salt thereof. A preferred sigma-1 ligand that can be detectably labeled and used in the methods of the invention is l-benzyl-4-(2-fluorobenzyl- carbonylamino)-piperidine, or a pharmaceutically acceptable salt thereof.

Compounds of formula I can be labeled using any of a number of techniques which are well known in the art. For example, a radioisotope can be incorporated into said compound or appended to said compound of formula I using techniques well known in the art, for example, techniques analogous to those described in Arthur Murry III, D. Lloyd Williams; Organic Synthesis with Isotopes, vol. I and II, Interscience Publishers Inc., N.Y. (1958) and Melvin Calvin et al. Isotopic Carbon John Wiley and Sons Inc., N.Y. (1949). Any radioisotope capable of being detected in a diagnostic procedure can be employed as a label. For example, suitable radioisotopes include: carbon-11, fluorine-18, fluorine-19, iodine-123 and iodine-125. Preferably, a compound of formula I may be labeled by appending one or more radioisotopes of a halogen (e.g. iodine-123) to an aromatic ring. Additionally, a compound of formula I can be labeled with a metal chelating group optionally comprising a radionuclide, such as a metallic radioisotope. Such chelating groups are well known in the art and include polycarboxylic acids such as for example diethylenetriaminepentaacetic acid, ethylenediaminetetraacetic acid, and the like, or analogs or homologs thereof, as well as the chelating groups disclosed in S. Meegalla et al. J. Am. Chem. Soc. 117 11037-11038, 1995 and in S. Meegalla et al. Bioconjugate Chem. 7:421- 429, 1996. The chelating group or the radionuclide therein may be attached directly to a compound of formula I, or may be attached to a compound of formula I by means of a divalent or bifunctional organic linker group. Such bifunctional linker groups are well known in the art and are preferably less than about 50 angstroms in length. Examples of suitable linker groups include 2- aminoethyl, 2-mercaptoethyl, 2-aminopropyl, 2-mercaptopropyl, e-amino caproic acid, 1 ,4-diaminobutane, and the like. The linker group may be attached at any synthetically feasible position on the compound of formula I. Preferably, the linker group is attached to the piperidine nitrogen of a compound of formula I by replacement of the R, substituent. A compound of formula I bearing a linker group in place of R, can conveniently be prepared from a corresponding compound of formula I wherein R, is hydrogen by alkylation or acylation of the piperidine nitrogen. Suitable conditions for the acylation or alkylation of secondary amines are known in the art. Figure 4 shows four compounds of the invention (II, III, IV, and N) which are compounds of formula I labeled with a metal chelating group comprising a radionuclide M. Any metallic radioisotope capable of being detected in a diagnostic procedure can be employed as a radionuclide. For example, suitable radioisotopes include: Antimony-124, Antimony-125, Arsenic-74, Barium-103, Barium-140, Beryllium-7, Bismuth-206, Bismuth-207, Cadmium-109, Cadmium-115m, Calcium-45, Cerium-139, Cerium-141, Cerium-144, Cesium- 137, Chromium-51, Cobalt-56, Cobalt-57, Cobalt-58, Cobalt-60, Cobalt-64, Erbium-169, Europium-152, Gadolinium- 153, Gold-195, Gold-199, Hafnium- 175, Hafhium-175-181, Indium-I l l, Iridium-192, Iron-55, Iron-59, Krypton-85, Lead-210, Manganese-54, Mercury-197, Mercury-203, Molybdenum-99, Νeodymium-147, Neptunium-237, Nickel-63, Niobium-95, Osmium-185 + 191, Palladium- 103, Platinum- 195m, Praseodymium- 143, Promethium-147,

Protactinium-233, Radium-226, Rhenium-186, Rubidium-86, Ruthenium- 103, Ruthenium- 106, Scandium-44, Scandium-46, Selenium-75, Silver-l lOm, Silver- I l l, Sodium-22, Strontium-85, Strontium-89, Strontium-90, Sulfur-35, Tantalum-182, Technetium-99m, Tellurium- 125, Tellurium- 132, Thallium-204, Thorium-228, Thorium-232, Thallium-170, Tin-113, Titanium-44, Tungsten- 185, Nanadium-48, Vanadium-49, Ytterbium- 169, Yttrium-88, Yttrium-90, Yttrium-91, Zinc-65, and Zirconium. Iodine-123 and technetium-99m may be particularly useful for SPECT imaging studies, and rhenium- 186 and Yttrium- 90 may be particularly useful for radiation therapy.

Any suitable imaging technique or diagnostic procedures that can be used to determine the extent to which a sigma-1 ligand binds to tumor cells can be used in conjunction with the methods of the invention. Suitable nuclear medicine imaging techniques include Single Photon Emission Computed Tomography (SPECT), Positron Emission Tomography (PET), Planar scintigraphy, and magnetic resonance imaging (see E. Bombardieri, et al. eur. J. Nuc. Med., 1997, 24, 809-824). Preferred imaging techniques include SPECT and PET, which can image and provide information about an entire tumor. The following definitions are used, unless otherwise described: halo is fluoro, chloro, bromo, or iodo. Alkyl, alkoxy, etc. denote both straight and branched groups; but reference to an individual radical such as "propyl" embraces only the straight chain radical, a branched chain isomer such as "isopropyl" being specifically referred to. Aryl denotes a phenyl radical or an ortho-fused bicyclic carbocyclic radical having about nine to ten ring atoms in which at least one ring is aromatic. Heteroaryl encompasses a radical attached via a ring carbon of a monocyclic aromatic ring containing five or six ring atoms consisting of carbon and one to four heteroatoms each selected from the group consisting of non-peroxide oxygen, sulfur, and Ν(X) wherein each X is absent or is H, O, ( -C^alkyl, phenyl or benzyl, as well as a radical of an ortho-fused bicyclic heterocycle of about eight to ten ring atoms derived therefrom, particularly a benz-derivative or one derived by fusing a propylene, trimethylene, or tetramethylene diradical thereto.

Specific and preferred values listed below for radicals, substituents, and ranges, are for illustration only and they do not exclude other defined values or other values within defined ranges for the radicals and substituents. Specifically, (C_rC₆)alkyl can be methyl, ethyl, propyl, isopropyl, butyl, iso-butyl, sec-butyl, pentyl, 3-pentyl, or hexyl; (C,-C₆)alkoxy can be methoxy, ethoxy, propoxy, isopropoxy, butoxy, iso-butoxy, sec-butoxy, pentoxy, 3-pentoxy, or hexyloxy; ( -C^alkanoyl can be acetyl, propanoyl or butanoyl; (C^C^alkoxycarbonyl can be methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, or hexyloxycarbonyl; (C₂-C₆)alkanoyloxy can be acetoxy, propanoyloxy, butanoyloxy, isobutanoyloxy, pentanoyloxy, or hexanoyloxy; aryl can be phenyl, indenyl, or naphthyl; and heteroaryl can be furyl, imidazolyl, triazolyl, triazinyl, oxazoyl, isoxazoyl, thiazolyl, isothiazoyl, pyrazolyl, pyrrolyl, pyrazinyl, tetrazolyl, pyridyl, (or its N-oxide), thienyl, pyrimidinyl (or its N-oxide), indolyl, isoquinolyl (or its N-oxide) or quinolyl (or its N-oxide).

The invention provides novel compounds of formula I as well as novel detectably labeled compounds of formula I. Unlabeled compounds of formula I are useful as intermediates for preparing labeled compounds of formula I. Certain compounds of formula I were disclosed as potential imaging agents by Y. Huang et al, Poster Number MEDI 055, presented at the 213th American Chemical Society Meeting, April 13-17, 1997, San Francisco, California. Accordingly, specific compounds of the invention exclude compounds of formula I wherein R_{ is benzyl, when A is NH, B is CH₂, C is oxo, and R₂ is phenyl, 1-naphthyl, 2-naphthyl, 2-thiophenyl, 3-thiophenyl, 2-pyridinyl, 3-, pyridinyl, 4-pyridinyl, 4-imidazolyl, 2-nitrophenyl, 3 nitrophenyl, 4-nitrophenyl, 4-(l-NO₂, 3-NO₂-Ph), 2-methoxyphenyl, 3- methoxyphenyl, 4-methoxyphenyl, 2,5-dimethoxyphenyl, 3,4-dimethoxyphenyl, 3,5-dimethoxyphenyl, 3,4,5-tromethoxyphenyl, 4-methylthiophenyl, 2- hydroxyphenyl, 3-hydroxyphenyl, 4-hydroxyphenyl, 3,4-dihydroxyphenyl, 3- chloro-4-hydroxyphenyl, 3,4-methylenedioxyphenyl, 4-fluorophenyl, 2,4- difluorophenyl, 2,5-difluorophenyl, 2,6-difluorophenyl, 3,4-difluorophenyl, 3,5- difluorophenyl, 4-chlorophenyl, 2,4-dichlorophenyl, 2,6-dichlorophenyl, 3,4- dichlorophenyl, 2-bromophenyl, 3-bromophenyl, 4-bromophenyl, 2- trifluoromethylphenyl, 3-trifluoromethylphenyl, 4-trifluoromethylphenyl, 4- aminophenyl, 3-indolyl, 3-(5-methoxy-indolyl), 3-(2-methyl-5-methoxyindolyl), 3-(5-methoxy-l-indanone); and exclude compounds of formula I wherein R_j is benzyl, when A is NH, B is NH, C is oxo, and R₂ is 1-naphthyl, 2,4-dimethoxyphenyl, or 4- methylthiophenyl; and exclude compounds of formula I wherein R, is benzyl, when A is NH, B is CH₂, C is two hydrogens, and R₂ is 2,3-dimethoxyphenyl; and pharmaceutically acceptable salts thereof.

Other compounds of formula I were disclosed by Y. Huang, et al., J. Med. Chem., 1998, 41, 13, 2361-2370. Accordingly, specific compounds of the invention exclude compounds of formula I wherein R_t is benzyl, when A is NH, B is CH₂, C is oxo, and R₂ is 2-chlorophenyl, 3-chlorophenyl, 4- chlorophenyl, 3,4-dichlorophenyl, 2,4-dichlorophenyl, 2,6-dichlorophenyl, 2- bromophenyl, 3-bromophenyl, 4-bromophenyl, 2-fluorophenyl, 3-fluorophenyl, 4-fluorophenyl, 2,4-difluorophenyl, 2,5-difluorophenyl, 2,6-difluorophenyl, 3,4- difluorophenyl, 3,5-difluorophenyl, 2-trifluoromethylphenyl, 3- trifluoromethylphenyl, 4-trifluoromethylphenyl, 2-nitrophenyl, 3 -nitrophenyl, 4- nitrophenyl, 2,4-dinitrophenyl, 2-hydroxyphenyl, 3-hydroxyphenyl, 4- hydroxyphenyl, 3,4-dihydroxyphenyl, 3-chloro-4-hydroxyphenyl, 2- methoxyphenyl, 3-methoxyphenyl, 4-methoxyphenyl, 2,5-dimethoxyphenyl, 3,4- dimethoxyphenyl, 3,5-dimethoxyphenyl, 3,4,5-trimethoxyphenyl, 3,4- methylenedioxyphenyl, 3,4-dimethoxyphenyl, 4-methylthiophenyl, or 4- aminophenyl; exclude the compound of formula I wherein R, is benzyl, when A is NH, B is -CH(OH)-, C is two hydrogens, and R₂ is 2,3-dimethoxyphenyl; and exclude the compound of formula I wherein Rj is benzyl, when A is NH, B is NH, C is oxo, and R₂ is 4-methylthiophenyl.

A specific compound of formula I is a compound wherein _x is hydrogen, (C,-C₆)alkyl, aryl, or aryl(C_rC₆)alkyl; R₂ is aryl or heteroaryl; A is NR_a, -O-, CR_bR_c, or -S-; B is NR,, -O-, CR_bR_c, or -S-; C is two hydrogens, oxo (=O), or thioxo (=S); each R_a is independently hydrogen, or (C,-C₆)alkyl; each R_b is independently hydrogen, hydroxy, (C_j-C₆)alkyl, or (C,-C₆)alkoxy; and each R_c is independently hydrogen, or (C C₆)alkyl; wherein any aryl or heteroaryl is optionally substituted with 1, 2, 3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, (C,-C₆)alkyl, (C,-C₆)alkoxy, (C_rC₆)alkanoyl, (C C₆)alkanoyloxy, (C_]-C₆)alkoxycarbonyl, and methylenedioxy; or a pharmaceutically acceptable salt thereof; provided R_{ is not phenyl, benzyl, or phenethyl. Another specific compound of formula I is a compound wherein:

R, is hydrogen, (C,-C₆)alkyl, aryl, or aryl(C,-C₆)alkyl; R₂ is aryl or heteroaryl; A is NR_a, -O-, CR_bR_c, or -S-; B is NR,, -O-, CR^, or -S-; C is two hydrogens, oxo (=O), or thioxo (^S); each R^ is independently hydrogen, or (C C₆)alkyl; each R_b is independently hydrogen, hydroxy, (C₁-C₆)alkyl, or ( -C^alkoxy; and each R_c is independently hydrogen, or (C,-C₆)alkyl; wherein any aryl of R, is substituted with 1, 2, 3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, (C_r C₆)alkoxy, (C_rC₆)alkanoyl, (C,-C₆)alkanoyloxy, (C,-C₆)alkoxycarbonyl, and methylenedioxy; and wherein any aryl or heteroaryl of R₂ or heteroaryl of R is optionally substituted with 1, 2, 3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, (C,-C₆)alkyl, (C,-C₆)alkoxy, (C,-C₆)alkanoyl, (C C₆)alkanoyloxy, (C_rC₆)alkoxycarbonyl, and methylenedioxy; or a pharmaceutically acceptable salt thereof. Another specific compound of formula I is a compound wherein:

R₎ is benzyl, which is substituted with 1, 2, 3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, (C,-C₆)alkyl, (C,-C₆)alkoxy, (C₁-C₆)alkanoyl, (C,-C₆)alkanoyloxy, (C_j-C^alkoxycarbonyl, and methylenedioxy; or a pharmaceutically acceptable salt thereof.

Another specific compound of formula I is a compound wherein: R, is benzyl, which is substituted with 2, 3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, (C_rC₆)alkyl, ( -C^alkoxy, (C,-C₆)alkanoyl, (C_rC₆)alkanoyloxy, (C,-C₆)alkoxycarbonyl, and methylenedioxy.

Another specific compound of formula I is a compound wherein: R, is hydrogen, (C,-C₆)alkyl, aryl, or aryl(C_rC₆)alkyl; R₂ is aryl or heteroaryl; A is-O-, CR_bR_c, or -S-; B is NR_a, -O-, CR_bR_c, or -S-; C is two hydrogens, oxo (=O), or thioxo (=S); each R_a is independently hydrogen, or (C_j-C₆)alkyl; each R_b is independently hydrogen, hydroxy, (C_rC₆)alkyl, or (C C₆)alkoxy; and each R_c is independently hydrogen, or (C,-C₆)alkyl; wherein any aryl or heteroaryl is optionally substituted with 1, 2, 3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, (C_rC₆)alkyl, (C_rC₆)alkoxy, (C_rC₆)alkanoyl, (C_r C₆)alkanoyloxy, (C_rC₆)alkoxycarbonyl, and methylenedioxy; or a pharmaceutically acceptable salt thereof.

Another specific compound of formula I is a compound wherein: R, is hydrogen, (C C₆)alkyl, aryl, or aryl(C_rC₆)alkyl; R₂ is aryl or heteroaryl; A is NR_a, -O-, CR_bR_c, or -S-; B is -O- or -S-; C is two hydrogens, oxo (=O), or thioxo (=S); each R-, is independently hydrogen, or (C,-C₆)alkyl; each R_b is independently hydrogen, hydroxy, (C,-C₆)alkyl, or (C,-C₆)alkoxy; and each R_c is independently hydrogen, or (C,-C₆)alkyl; wherein any aryl or heteroaryl is optionally substituted with 1, 2, 3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, (C,-C₆)alkyl, (C_rC₆)alkoxy, (C_rC₆)alkanoyl, (C_r C₆)alkanoyloxy, (C,-C₆)alkoxycarbonyl, and methylenedioxy; or a pharmaceutically acceptable salt thereof. A specific value for R, is benzyl.

Another specific value for R, is benzyl, which is substituted with 1, 2, 3, or 4 independent halo substituents.

Another specific value for R, is phenethyl.

Another specific value for R, is phenethyl, which is substituted with 1, 2, 3, or 4 independent halo substituents.

Another specific value for R_x is phenethyl, which is substituted with 1, 2, 3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, (C,-C₆)alkyl, (C_rC₆)alkoxy, (C,-C₆)alkanoyl, (C,-C₆)alkanoyloxy, (C,-C₆)alkoxycarbonyl, and methylenedioxy.

A specific value for R₂ is phenyl or naphthyl, optionally substituted with 1, 2, or 3, substituents independently selected from the group consisting of halo, cyano, hydroxy, trifluoromethyl, trifluoromethoxy, (C_]- C₆)alkyl, (C,-C₆)alkoxy, (C_rC₆)alkanoyl, (C_rC₆)alkanoyloxy, and (C,- C₆)alkoxycarbonyl .

A specific value for R₂ is pyridinyl, imidazolyl, indolyl or pyrimidinyl, optionally substituted with 1, 2, or 3, substituents independently selected from the group consisting of halo, cyano, hydroxy, trifluoromethyl, trifluoromethoxy, (C,-C₆)alkyl, (C_rC₆)alkoxy, (C,-C₆)alkanoyl, (C,- C₆)alkanoyloxy, and (C,-C₆)alkoxycarbonyl.

A specific value for R₂ is thiophenyl, optionally substituted with 1 or 2 substituents independently selected from the group consisting of halo, cyano, hydroxy, trifluoromethyl, trifluoromethoxy, (C,-C₆)alkyl, (C_rC₆)alkoxy, (C_rC₆)alkanoyl, (C_rC₆)alkanoyloxy, and (C,-C₆)alkoxycarbonyl.

A specific value for A is NH.

A specific value for B is NH, CH_2ι or CH(OH).

Compounds of formula I can be prepared using procedures similar to those described by Y. Huang, et al., J. Med. Chem., 1998, 41, 13, 2361-2370.

Pharmaceutically acceptable salts of a detectably labeled sigma-1 ligand may be obtained using standard procedures well known in the art, for example by reacting a sufficiently basic compound such as an amine with a suitable acid affording a physiologically acceptable anion. Alkali metal (for example, sodium, potassium or lithium) or alkaline earth metal (for example calcium) salts of carboxylic acids can also be made.

The compounds can be formulated as pharmaceutical compositions and administered to a mammalian host, such as a human patient in a variety of forms adapted to the chosen route of administration, i.e., orally or parenterally, by intravenous, intramuscular, topical or subcutaneous routes.

Thus, the detectably labeled sigma-1 ligands may be systemically administered, e.g., orally, in combination with a pharmaceutically acceptable vehicle such as an inert diluent or an assimilable edible carrier. They may be enclosed in hard or soft shell gelatin capsules, may be compressed into tablets, or may be incorporated directly with the food of the patient's diet. For oral therapeutic administration, the compound may be combined with one or more excipients and used in the form of ingestible tablets, buccal tablets, troches, capsules, elixirs, suspensions, syrups, wafers, and the like. Such compositions and preparations should contain at least 0.1% of the compound. The percentage of the compositions and preparations may, of course, be varied and may conveniently be between about 2 to about 60% of the weight of a given unit dosage form. The amount of compound in such therapeutically useful compositions is such that an effective dosage level will be obtained.

The tablets, troches, pills, capsules, and the like may also contain the following: binders such as gum tragacanth, acacia, corn starch or gelatin; excipients such as dicalcium phosphate; a disintegrating agent such as corn starch, potato starch, alginic acid and the like; a lubricant such as magnesium stearate; and a sweetening agent such as sucrose, fructose, lactose or aspartame or a flavoring agent such as peppermint, oil of wintergreen, or cherry flavoring may be added. When the unit dosage form is a capsule, it may contain, in addition to materials of the above type, a liquid carrier, such as a vegetable oil or a polyethylene glycol. Various other materials may be present as coatings or to otherwise modify the physical form of the solid unit dosage form. For instance, tablets, pills, or capsules may be coated with gelatin, wax, shellac or sugar and the like. A syrup or elixir may contain the compound, sucrose or fructose as a sweetening agent, methyl and propylparabens as preservatives, a dye and flavoring such as cherry or orange flavor. Of course, any material used in preparing any unit dosage form should be pharmaceutically acceptable and substantially non-toxic in the amounts employed. In addition, the compound may be incorporated into sustained-release preparations and devices.

The detectably labeled sigma-1 ligands may also be administered intravenously or intraperitoneally by infusion or injection. Solutions of a compound or its salts can be prepared in water, optionally mixed with a nontoxic surfactant. Dispersions can also be prepared in glycerol, liquid polyethylene glycols, triacetin, and mixtures thereof and in oils. Under ordinary conditions of storage and use, these preparations contain a preservative to prevent the growth of microorganisms.

The pharmaceutical dosage forms suitable for injection or infusion can include sterile aqueous solutions or dispersions or sterile powders adapted for the extemporaneous preparation of sterile injectable or infusible solutions or dispersions. The ultimate dosage form should be sterile, fluid and stable under the conditions of manufacture and storage. The liquid carrier or vehicle can be a solvent or liquid dispersion medium comprising, for example, water, ethanol, a polyol (for example, glycerol, propylene glycol, liquid polyethylene glycols, and the like), vegetable oils, nontoxic glyceryl esters, and suitable mixtures thereof. The proper fluidity can be maintained, for example, by the formation of liposomes, by the maintenance of the required particle size in the case of dispersions or by the use of surfactants. The prevention of the action of microorganisms can be brought about by various antibacterial and antifungal agents, for example, parabens, chlorobutanol, phenol, sorbic acid, thimerosal, and the like. In many cases, it will be preferable to include isotonic agents, for example, sugars, buffers or sodium chloride. Prolonged absorption of the injectable compositions can be brought about by the use in the compositions of agents delaying absorption, for example, aluminum monostearate and gelatin. Sterile injectable solutions are prepared by incorporating a compound in the required amount in the appropriate solvent with various of the other ingredients enumerated above, as required, followed by filter sterilization. In the case of sterile powders for the preparation of sterile injectable solutions, the preferred methods of preparation are vacuum drying and the freeze drying techniques, which yield a powder.

For topical administration, the detectably labeled sigma-1 ligands may be applied in pure form, i.e., when they are liquids. However, it will generally be desirable to administer them to the skin as compositions or formulations, in combination with a dermatologically acceptable carrier, which may be a solid or a liquid.

Useful dosages of the detectably labeled sigma-1 ligands can be determined by comparing their in vitro activity, and in vivo activity in animal models. Methods for the extrapolation of effective dosages in mice, and other animals, to humans are known to the art; for example, see U.S. Pat. No. 4,938,949. Generally, the concentration of the compound(s) in a liquid composition, such as a lotion, will be from about 0.1-25 wt-%, preferably from about 0.5-10 wt-%. The concentration in a semi-solid or solid composition such as a gel or a powder will be about 0.1-5 wt-%, preferably about 0.5-2.5 wt-%. Single dosages for injection, infusion or ingestion will generally vary between 50-1500 mg, and may be administered, i.e., 1-3 times daily, to yield levels of about 0.5 - 50 mg/kg, for adults.

The invention will be further described by reference to the following nonlimiting examples.

Example 1 Stability of sigma-1 receptors on 67P cells.

Because an initial series of sigma-1 receptor binding studies in 67P cells produced inconsistent results: in some experiments there appeared to be a high density of sigma-1 receptors in 67 membrane homogenates, while in others there was no detectable binding of a sigma-1 radiotracer, a series of in vitro binding studies were conducted in 67P cells in which cell membranes were assayed for sigma-1 receptors immediately following membrane preparation and after one or more days of storage at -80 ° C.

Results of this study indicated that there was a high level of sigma-1 receptors in 67 P and 67Q cell membranes when assayed either immediately after the membrane preparation or after storing at -80 °C overnight. However, there was no detectable binding of [³H](+)-pentazocine after the same membrane preparation was stored at -80 °C for only 3 days (Figure 1). These data suggest that sigma-1 receptors in certain tumor cells, are unstable under standard storage conditions. This finding may explain why Vilner et al. (above) did not find evidence of sigma-1 receptors in MCF-7 tumor cells.

Example 2

In vitro binding of sigma-1 receptors on proliferative and quiescent mouse mammary adenocarcinoma cells.

The mouse mammary adenocarcinoma line 66 is known to be an appropriate in vitro model system for studying biomarkers of cell proliferation. Thus, the expression of sigma-1 receptors on proliferative (P) and quiescent (Q) 66 cells was examined. Scatchard analyses of sigma-1 receptors were performed on 66P and 66Q cell membranes stored overnight at -80°C (Table 1). See Y.C. Cheng, et al, Biochem. Pharmacol, 1973, 22, 3099-4022. Table 1. Sigma-1 receptor binding studies in 3-day 66P cells and either 7- day, 10-day, or 12 day 66 Q cells

⁰max Receptors/cell

(fmol/mg protein)

3 -day P cells 2531 ± 941 45,874 ± 17,055 7-day Q cells 1420 ± 300 5976 ± 1262

P:Q ratio 1.8 7.7

3-day P cells 3870 ± 479 98,201 ± 12,154 10-day Q cells 1620 ± 298 9652 ± 1775

P:Q ratio 2.4 10.1

3-day P cells 3870 ± 479 98,201 ±.12,154 12-day Q cells 1647 ± 261 8578 ± 1359

P:Q ratio 2.4 11.4

The density of sigma-1 receptors in 66P and 66Q cells was slightly lower than that which was observed for sigma-2 receptors in the same cell line, however, the P:Q ratio of sigma-1 receptors was somewhat higher (10- 11 for sigma-1 receptors versus 8-10 for sigma-2 receptors). These results demonstrate that sigma-1 receptors are expressed in high density in mouse mammary adenocarcinoma cells. Since the density of sigma-1 receptors was substantially higher in 66P cells than in 66Q cells (P:Q ratio ~11), sigma-1 receptors can be used as a biomarker for tumor cell proliferation, and may be used for noninvasively assessing the proliferative status of tumors (e.g., breast tumors, prostate tumors, and/or bladder tumors). Additionally, because sigma-1 receptors were found to have a higher P:Q ratio than sigma-2 receptors, the methods of the instant invention may possess an advantage over previous methods that use sigma-2 ligands to determine the proliferative status of cancer cells. Example 3 In vivo labeling of sigma-1 receptors in vivo with an ¹⁸F-Iabeled mixed sigma-l/sigma-2 receptor imaging agent.

In order to confirm that sigma-1 receptors are present in mouse mammary tumors, a series of studies were conducted in tumor-bearing mice using the ¹⁸F-labeled radiotracer corresponding to compound 143. This ligand was chosen because of its high affinity for both receptors. Using compound 143 and differential blocking with the selective sigma-1 compound ¹⁸F-N-(1- benzylpiperidin-4-yl)-2-fluorophenylacetamide, it was possible to determine the relative density of sigma-1 and sigma-2 receptors in these mouse tumors.

Female nude mice were injected subcutaneously in the inguinal region with 1.5 x 10⁶ 66 mouse breast tumor cells. Tumors were allowed to grow to >250 mg. To measure the biodistribution of both sigma-1 and sigma-2 receptors, mice were given a tail vein injection of ¹⁸F 143. To measure the relative density of sigma-1 and sigma-2 receptors, mice were injected with either sigma- 1 -selective ' ⁸F-N-( 1 -benzylpiperidin-4-yl)-2-fluorophenylacetamide (IC, sigma-1 = 3.6 nM, IC, sigma-2 = 670 nM) or the carrier compound 143 (2 mg/kg, i.v.).

Mice were sacrificed at 2 hours post-i.v. injection. The tumor and other organs of interest were removed, weighed and counted. Sigma-1 and sigma-2 biodistribution was calculated by measuring %I.D./c.c. tissue sample, as well as by tissue:blood ratio. Results are shown in Table 2.

Table 2. In vivo biodistribution of sigma-1 and sigma-2 receptors in nude mice with mammary adenocarcinoma tumors.

Results indicate that it is possible to label both sigma-1 and sigma-2 receptors in vivo. There was a high tissue uptake and a high tissue:blood ratio in all organs known to have a high density of sigma- receptors. The tumor uptake of compound 143 was also high, resulting in a tumoπblood ratio of 25 at 2 hours post-injection of the radiotracer.

The relative density of sigma-1 and sigma-2 receptors was analyzed by comparing the uptake of the radiotracer alone and when co-injected with the blocking agents (Figures 2). The sigma-1 blocking study reduced both the % I.D./c.c. and tumor:blood ratio of compound 143, suggesting that there is a high density of sigma-1 receptors in these mouse tumors.

The results show that the uptake of radioactivity in both the mouse brain and the tumors, as measured by either the %ID/cc tissue or the tissue:blood ratio, is due to the labeling of sigma receptors, since it is possible to differentially block these sites with sigma ligands. Although data from only brain and tumor are shown, similar results were also observed in all of the tissues (except blood) shown in Table 2. The ability to image sigma-1 tumors in solid tumor xenographs was also demonstrated with a fluorine- 18 labeled sigma-1 selective radiotracer (compound 137). The results of this study (Figure 3) demonstrate that a sigma-1 selective radiotracer provides a high tumor uptake and suitable tumor background ratio for imaging purposes. These data, in concert with in vitro binding data from 66P and

66Q cells, demonstrates that sigma-1 receptors are a biomarker of cell proliferation in breast cancer cells, prostate cancer cells, and/or bladder cancer cells. More specifically, these data, in concert with in vitro binding data from 66P and 66Q cells, demonstrates that sigma-1 receptors are a biomarker of cell proliferation in breast cancer cells.

Example 4 5 Sigma receptor binding affinity of representative compounds of formula I.

Representative compounds of formula I were prepared and their affinity for sigma- 1 and sigma-2 receptors was determined using synthetic procedures and biological assays similar to those described by Y. Huang, et al., 10 J. Med. Chem., 1998, 41, 13, 2361-2370. The data is shown m Table 3.

Table 3. Sigma- Receptor Binding For Compounds of Formula I

^! guinea pig brain [ H](+)-pentazocιne * rat hver [Η]DTG + (+)-pentazocιne

Representative compounds of formula I were also prepared as descπbed in Examples 5-20. Labeled compounds of formula I can convemently be prepared using procedures similar to those described below by substituting a labeled starting material (e.g. a starting material that includes a radionuclide) for the corresponding starting material described below.

Example 5 N-(l-(2-fluorobenzyl)piperidin-4-yl)phenylacetamide (105).

A mixture of 4-phenylacetamidopiperidine (0.22 g, 1 mmol), 2-fluorobenzyl bromide (0.19 g, 1 mmol), and triethylamine (0.5 mL) in dichloromethane (50 mL) was stirred at room temperature overnight. The solvent was removed in vacuo and the residue was dissolved in ethyl acetate (50 mL), washed with 0.5 N NaOH, water, and dried over Na_jSO^ Solvent was removed and the residue was purified by silica gel column with CHCl₃-EtOH (9.5:0.5) as the eluent. The resulting material was recrystallized from EtOAc-hexane to give N-(l-(2-fluorobenzyl)piperidin-4-yl)phenylacetamide (0.27 g, 83%); mp 108-109 °C.

The intermediate 4-phenylacetamidopiperidine was prepared as follows.

a. N-(l-benzylpiperidin-4-yl)phenylacetamide. To an ice-cold solution of phenylacetic acid (3.4 g, 25 mmol) in dry THF (100 mL) was added DCC (5.2 g, 25 mmol). After stirring for 15 minutes, 4-amino-l-benzylpiperidine (4.8 g, 25 mmol) was added. The reaction was continued at room temperature overnight. The solid was removed by filtration, the solvent was removed, and the resulting residue was extracted with CH₂C1₂ (3 x 30 mL). The combined organic layers were washed with IN NaOH, saturated aqueous NaCI, dried over Na-.SO₄, and concentrated in vacuo. The residue was purified by chromatography on a silica gel column using CHC1₃, then CHCl₃-EtOH (9.5:0.5) as the eluents. The product was recrystallized from ethyl acetate/hexane to give N-(l-benzylpiperidin-4-yl)phenylacetamide (6.3 g, 81%); mp 136-137 °C.

b. 4-Phenylacetamidopiperidine. N-(l-berιzylpiperidin-4-yl)phenylacetamide (4.0 g, 13 mmol) was dissolved in methanol (100 mL) containing palladium hydroxide on carbon (20 mg) and hydrogenated under 50 psi for 12 hours. The catalyst was filtered and the solution was evaporated under reduced pressure to give a residue which was recrystallized from ethyl acetate-hexane to give 4-phenylacetamidopiperidine (2.57 g, 90%); mp 127-129 °C.

Example 6 N-(l-(3-fluorobenzyl)piperidin-4-yl)phenylacetamide (106).

Using a procedure similar to that described in Example 5, except replacing the 2-fluorobenzyl bromide with 3-fluorobenzyl bromide, the title compound was prepared; yield 58%; mp 117-118 °C.

Example 7 N-(l-(4-fluorobenzyI)piperidin-4-yl)phenylacetamide (107).

Using a procedure similar to that described in Example 5, except replacing the 2-fluorobenzyl bromide with 4-fluorobenzyl bromide, the title compound was prepared; yield 90%; mp 120-121 °C.

Example 8 N-(l-(3,4-difluorobenzyl)piperidin-4-yl)phenylacetamide (110).

Using a procedure similar to that described in Example 5, except replacing the 2-fluorobenzyl bromide with 3,4-difluorobenzyl bromide, the title compound was prepared; yield 55%; mp 110-111 °C.

Example 9 N-(l-(3-iodobenzyl)piperidin-4-yl)phenylacetamide (104).

Using a procedure similar to that described in Example 5, except replacing the 2-fluorobenzyl bromide with 3-iodobenzyl bromide, the title compound was prepared; yield 67%; mp 134-135 °C.

Example 10 N-(l-(4-iodobenzyl)piperidin-4-yl)phenylacetamide (100). Using a procedure similar to that described in Example 5, except replacing the 2-fluorobenzyl bromide with 4-iodobenzyl bromide, the title compound was prepared; yield 41%; mp 136-138 °C.

Example 11 N-(l-benzyl)piperidinτ4-yI)-4-iodophenylacetamide (136).

4-Iodophenylacetic acid was condensed with the requisite amine to give the title compound 87%; mp 145-147 °C.

Example 12 N-(l-(4-fluorobenzyl)piperidin-4-yl)-2-fluorophenylacetamide (137).

4-(2-Fluorophenyl)acetamidopiperidine (0.118 g, 0.5 mmol) in dichloromethane (40 mL) was combined with 4-fluorobenzyl bromide (0.095 g, 0.5 mmol) and triethylamine (0.5 mL). After stirring at room temperature overnight, the solvent was removed in vacuo. The residue was dissolved in ethyl acetate (50 mL), washed with 0.5 N NaOH and water, and dried over Na^O^ The solvent was removed in vacuo and the product was purified on a silica gel column, with CHCl₃-EtOH (9.5:0.5) as the eluent. Recrystallization from EtOAc-hexane gave N-(l-(4-fluorobenzyl)piperidin-4-yl)-2-fluorophenylacetamide (0.10 g, 59%); mp 129- 131 °C.

The intermediate 4-(2-fluorophenyl)acetamidopiperidine was prepared as follows. a. l-Benzyl-4-trifluoroacetamidopiperidine. To a solution of 4-amino-l- benzylpiperidine (9.5 g, 50 mmol) in dry dichloromethane (200 mL) was added trifluoroacetic anhydride (12.6 g, 60 mmol) and triethylamine (5 mL) under ice and stirring. After stirring at room temperature for 12 hours, the solvent was removed under vacuo, the residue was dissolved in ethyl acetate and washed with aqueous NaHCO₃, water and dried over Na-SO^ The solvent was removed and the product was recrystallized from ethyl acetate to give l-benzyl-4-trifluoroacetamidopiperidine (13.5 g, 94%). b. 4-Amino-l-(tert-butoxycarbonyl)piperidine. The product from sub-part a was dissolved in methanol (150 mL) containing palladium hydroxide on carbon (50 mg) and hydrogenated at 50 psi for 12 hours. The catalyst was removed by filtration and the solution was concentrated in vacuo to give an oil which was reacted with di-tert-butyl-di-carbonate (11.0 g, 50 mmol) in dicholoromethane (200 mL) for 6 hours. The reaction mixture was transfeπed into a separatory funnel and washed with aqueous NaHCO₃, water and dried over Na^O^ After removal of the solvent, the residue was dissolved in methanol (100 mL) and of 30% ammonium hydroxide (50 mL) and refluxed for 6 hours. The solvent was removed and the residue was dissolved in dichloromethane (100 mL), washed with 1 N NaOH, water and dried over Na^O,,. The solvent was removed and the product was recrystallized from ethyl acetate-hexane to give 4-amino-l-(tert-butoxycarbonyl)piperidine (5.75 g, 58%).

c. 4-(2-Fluorophenyl)acetamidopiperidine. A mixture of 2-fluorophenylacetic acid (1.54 g, 10 mmol) and DCC (2.06 g, 10 mmol) in dichloromethane (50 mL) was stirred for 5 minutes, 4-amino-l-(tert-butoxycarbonyl)piperidine (2.0 g, 10 mmol) was added and the solution was stirred at room temperature overnight. The solid was removed by filtration and the solution was concentrated in vacuo to afford a residue which was then reacted with CF₃COOH to remove the tert-butoxycarbonyl group to afford 4-(2- fluorophenyl)acetamidopiperidine (0.80 g, 34%); mp 126-128 °C.

Examples 13-19

Using a procedure similar to that described in Example 12, except using the specified piperidine and the requisite substituted benzyl bromide, the following compounds were prepared.

Example 13. N-(l-(4-iodobenzyl)piperidin-4-yl)-2-fluorophenylacetamide (138): yield 57% from 4-(2-fluorophenyl)acetamidopiperidine; mp 126-128 °C.

Example 14 N-(l-(4-fluorobenzyl)piperidin-4-yl)-3-fluorophenylacetamide (139): yield 58% from 4-(3-fluorophenyl)acetamidopiperidine; mp 115-117 °C; Anal. (C₂₀H₂₂N₂OF₂) C, H,

N. Example 15 N-(l-(4-iodobenzyl)piperidin-4-yl)-3-fluorophenylacetamide (140): yield 57% from 4-(3-fluorophenyl)acetamidopiperidine; mp 109-111 °C.

Example 16 N-(l-(4-fluorobenzyl)piperidin-4-yl)-3-chlorophenylacetamide (141): yield 67% from 4-(3-chlorophenyl)acetamidopiperidine; mp 101-102 °C.

Example 17 N-(l-(4-iodobenzyl)piperidin-4-yl)-3-chlorophenylacetamide (142): yield 60% from 4-(3-chlorophenyl)acetamidopiperidine; mp 102-103 °C.

Example 18 N-(l-(4-fluoroben--yI)piperidin-4-yl)-3-bromophenylacetamide (143): yield 69% from 4-(3-bromophenyl)acetamidopiperidine; mp 109-110 °C.

Example 19 N-(l-(4-iodobenzyl)piperidin-4-yI)-3-bromophenylacetamide (144): yield 66%o from 4-(3-bromophenyl)acetamidopiperidine; mp 103-104 °C.

Example 20 N-(l-Benzylpiperidin-4-yl)-2-fluorophenylacetamide (145).

Using a procedure similar to that described in Example 12, sub-part c, except replacing the 4-amino-l-(tert-butoxycarbonyl)piperidine used therein with 4-amino-l- benzylpiperidine, the title compound was prepared; mp 131-132 °C (free amine).

The sigma-1 and sigma-2 binding affinities for the compounds of Examples 5- 20 are shown in Table 4.

Table 4. Sigma- Receptor Binding For Compounds of Formula I

All publications, patents, and patent documents are incorporated by reference herein, as though individually incorporated by reference. The invention has been described with reference to various specific and prefeπed embodiments and techniques. However, it should be understood that many variations and modifications may be made while remaining within the spirit and scope of the invention.

Claims

ClaimsWhat is Claimed is:

1. A compound of formula I:

wherein:

R, is hydrogen, (C_rC₆)alkyl, aryl, or aryl(C_rC₆)alkyl;

R₂ is aryl or heteroaryl; A is NR_a, -O-, CR_bR_c, or -S-;

B is NR_a, -O-, CR_bR_c, or -S-;

C is two hydrogens, oxo (=O), or thioxo (=S); each R_a is independently hydrogen, or (C,-C₆)alkyl; each R_b is independently hydrogen, hydroxy, (C,-C₆)alkyl, or (C,- C₆)alkoxy; and each R_c is independently hydrogen, or (C₁-C₆)alkyl; wherein any aryl or heteroaryl is optionally substituted with 1, 2, 3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, (C,-C₆)alkyl, (C,- C₆)alkoxy, (C C₆)alkanoyl, (C_rC₆)alkanoyloxy, (C,-C₆)alkoxycarbonyl, and methylenedioxy; or a pharmaceutically acceptable salt thereof; provided R, is not benzyl, when A is NH, B is CH₂, C is oxo, and R₂ is phenyl, 1-naphthyl, 2-naphthyl, 2-thiophenyl, 3-thiophenyl, 2-pyridinyl, 3-, pyridinyl, 4-pyridinyl, 4-imidazolyl, 2-nitrophenyl, 3 nitrophenyl, 4-nitrophenyl, 4-(l-NO₂, 3-NO₂-Ph), 2-methoxyphenyl, 3-methoxyphenyl, 4-methoxyphenyl, 2,5-dimethoxyphenyl, 3,4-dimethoxyphenyl, 3,5-dimethoxyphenyl, 3,4,5- tromethoxyphenyl, 4-methylthiophenyl, 2-hydroxyphenyl, 3-hydroxyphenyl, 4- hydroxyphenyl, 3,4-dihydroxyphenyl, 3-chloro-4-hydroxyphenyl, 3,4- methylenedioxyphenyl, 4-fluorophenyl, 2,4-difluorophenyl, 2,5-difluorophenyl, 2,6-difluorophenyl, 3,4-difluorophenyl, 3,5-difluorophenyl, 4-chlorophenyl, 2,4- dichlorophenyl, 2,6-dichlorophenyl, 3,4-dichlorophenyl, 2-bromophenyl, 3- bromophenyl, 4-bromophenyl, 2-trifluoromethylphenyl, 3- trifluoromethylphenyl, 4-trifluoromethylphenyl, 4-aminophenyl, 3-indolyl, 3-(5- methoxy-indolyl), 3-(2-methyl-5-methoxyindolyl), 3-(5-methoxy- 1 -indanone); and provided R_j is not benzyl, when A is NH, B is NH, C is oxo, and R₂ is 1-naphthyl,

2,4-dimethoxyphenyl, or 4-methylthiophenyl; and provided R, is not benzyl, when A is NH, B is CH₂, C is two hydrogens, and R₂ is 2,3-dimethoxyphenyl; or a pharmaceutically acceptable salt thereof.

The compound of claim 1 wherein R, is benzyl.

3. The compound of claim 1 wherein R₂ is phenyl or naphthyl, optionally substituted with 1, 2, or 3, substituents independently selected from the group consisting of halo, cyano, hydroxy, trifluoromethyl, trifluoromethoxy, (C,-C₆)alkyl, (C,-C₆)alkoxy, (C,-C₆)alkanoyl, (C_rC₆)alkanoyloxy, and (C,- C₆)alkoxycarbonyl.

4. The compound of claim 1 wherein R₂ is pyridinyl, imidazolyl, indolyl or pyrimidinyl, optionally substituted with 1, 2, or 3, substituents independently selected from the group consisting of halo, cyano, hydroxy, trifluoromethyl, trifluoromethoxy, (C,-C₆)alkyl, (C_rC₆)alkoxy, (C,-C₆)alkanoyl, (C,-C₆)alkanoyloxy, and (C,-C₆)alkoxycarbonyl.

5. The compound of claim 1 wherein R₂ is thiophenyl, optionally substituted with 1 or 2 substituents independently selected from the group consisting of halo, cyano, hydroxy, trifluoromethyl, trifluoromethoxy, (C,- C₆)alkyl, (C_rC₆)alkoxy, (C_rC₆)alkanoyl, (C_rC₆)alkanoyloxy, and (C,- C₆)alkoxycarbonyl.

6. The compound of claim 1 wherein A is NH.

7. The compound of claim 1 wherein B is NH, CH₂ or CH(OH).

8. A compound of formula I:

wherein:

R, is hydrogen, (C,-C₆)alkyl, aryl, or aryl(C,-C₆)alkyl;

R₂ is aryl or heteroaryl;

A is NR_a, -O-, CR_bR_c, or -S-; B is NR_a, -O-, CR_bR_c, or -S-;

C is two hydrogens, oxo (=O), or thioxo (=S); each R., is independently hydrogen, or (C,-C₆)alkyl; each R_b is independently hydrogen, hydroxy, (C_j-C^alkyl, or (C,- C₆)alkoxy; and each R_c is independently hydrogen, or (C,-C₆)alkyl; wherein any aryl or heteroaryl is optionally substituted with 1, 2, 3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, ( -C^alkyl, (C C₆)alkoxy, (C,-C₆)alkanoyl, (C,-C₆)alkanoyloxy, (C_rC₆)alkoxycarbonyl, and methylenedioxy; or a pharmaceutically acceptable salt thereof; provided R, is not phenyl, benzyl, or phenethyl.

9. A compound of formula I :

wherein:

R, is hydrogen, (C_rC₆)alkyl, aryl, or aryl(C,-C₆)alkyl;

R₂ is aryl or heteroaryl; A is NR_a, -O-, CR_bR_c, or -S-;

B is NR,, -O-, CR_bR_c, or -S-;

C is two hydrogens, oxo (=O), or thioxo (=S); each R_a is independently hydrogen, or (C,-C₆)alkyl; each R_b is independently hydrogen, hydroxy, (C,-C₆)alkyl, or (C,- C₆)alkoxy; and each R_c is independently hydrogen, or (C,-C₆)alkyl; wherein any aryl of R is substituted with 1, 2, 3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, (C,-C₆)alkoxy, (C,-C₆)alkanoyl, (C,- C₆)alkanoyloxy, (C,-C₆)alkoxycarbonyl, and methylenedioxy; and wherein any aryl or heteroaryl of R₂ or heteroaryl of R, is optionally substituted with 1, 2, 3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, (C_rC₆)alkyl, (C,-C₆)alkoxy, (C,-C₆)alkanoyl, ( - C₆)alkanoyloxy, (C_rC₆)alkoxycarbonyl, and methylenedioxy; or a pharmaceutically acceptable salt thereof.

10. The compound of claim 9 wherein R, is benzyl, which is substituted with 1, 2, 3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, (C,- C₆)alkyl, (C,-C₆)alkoxy, (C,-C₆)alkanoyl, (C_rC₆)alkanoyloxy, (C,- C₆)alkoxycarbonyl, and methylenedioxy.

11. The compound of claim 9 wherein R_j is benzyl, which is substituted with 2, 3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, (C₍- C₆)alkyl, (C,-C₆)alkoxy, (C,-C₆)alkanoyl, (C,-C₆)alkanoyloxy, (C_r C₆)alkoxycarbonyl, and methylenedioxy.

12. A compound of formula I

wherein:

R, is hydrogen, (C,-C₆)alkyl, aryl, or aryl(C,-C₆)alkyl; R₂ is aryl or heteroaryl;

A is-O-, CR_bR_c, or -S-;

B is NR_a, -O-, CR_bR_c, or -S-;

C is two hydrogens, oxo (=O), or thioxo (=S); each R_a is independently hydrogen, or (C,-C₆)alkyl; each R_b is independently hydrogen, hydroxy, (C,-C₆)alkyl, or (C,-

C₆)alkoxy; and each R_c is independently hydrogen, or (C,-C₆)alkyl; wherein any aryl or heteroaryl is optionally substituted with 1, 2, 3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, (C,-C₆)alkyl, (C C₆)alkoxy, (C₁-C₆)alkanoyl, (C,-C₆)alkanoyloxy, (C_rC₆)alkoxycarbonyl, and methylenedioxy; or a pharmaceutically acceptable salt thereof;

13. A compound of formula I:

wherein:

Ri is hydrogen, (C,-C₆)alkyl, aryl, or aryl(C,-C₆)alkyl;

R₂ is aryl or heteroaryl;

A is NR_a, -O-, CR_bR_c, or -S-; B is -O- or -S-;

C is two hydrogens, oxo (=O), or thioxo (=S); each R_a is independently hydrogen, or (C,-C₆)alkyl; each R_b is independently hydrogen, hydroxy, (C,-C₆)alkyl, or (C,- C₆)alkoxy; and each R_c is independently hydrogen, or (C₁-C₆)alkyl; wherein any aryl or heteroaryl is optionally substituted with 1, 2, 3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, (C,-C₆)alkyl, (C_r C₆)alkoxy, (C_rC₆)alkanoyl, (C,-C₆)alkanoyloxy, (C,-C₆)alkoxycarbonyl, and methylenedioxy; or a pharmaceutically acceptable salt thereof.

14. N-(l-benzylpiperidin-4-yl)-2-fluorophenylacetamide, or a pharmaceutically acceptable salt thereof.

15. The compound of any one of claims 1 to 14 that is detectably labeled.

16. The compound of claim 15 that is labeled with at least one atom selected from the group consisting of carbon-11, fluorine-18, fluorine-19, iodine- 123 and iodine- 125.

17. The compound of claim 16 that is labeled with iodine-123.

18. The compound of claim 15 wherein the label comprises a radionuclide.

19. The compound of claim 18 wherein the radionuclide is a metallic radioisotope.

20. The compound of claim 19 wherein the metallic radioisotope is selected from the group consisting of Antimony- 124, Antimony- 125, Arsenic-

74, Barium-103, Barium-140, Beryllium-7, Bismuth-206, Bismuth-207, Cadmium-109, Cadmium-115m, Calcium-45, Cerium-139, Cerium-141, Cerium-144, Cesium-137, Chromium-51, Cobalt-56, Cobalt-57, Cobalt-58, Cobalt-60, Cobalt-64, Erbium-169, Europium-152, Gadolinium-153, Gold-195, Gold-199, Hafhium-175, Hafhium-175-181, Indium-I l l, Iridium-192, Iron-55, Iron-59, Krypton-85, Lead-210, Manganese-54, Mercury-197, Mercury-203, Molybdenum-99, Neodymium-147, Neptunium-237, Nickel-63, Niobium-95, Osmium- 185 + 191, Palladium- 103, Platinum- 195m, Praseodymium- 143, Promethium-147, Protactinium-233, Radium-226, Rhenium-186, Rubidium-86, Ruthenium- 103, Ruthenium- 106, Scandium-44, Scandium-46, Selenium-75,

Silver-l lOm, Silver-I l l, Sodium-22, Strontium-85, Strontium-89, Strontium-90, Sulfur-35, Tantalum-182, Technetium-99m, Tellurium- 125, Tellurium- 132, Thallium-204, Thorium-228, Thorium-232, Thallium- 170, Tin- 113, Titanium- 44, Tungsten-185, Vanadium-48, Vanadium-49, Ytterbium- 169, Yttrium-88, Yttrium-90, Yttrium-91, Zinc-65, and Zirconium.

21. The compound of claim 19 wherein the metallic radioisotope is technetium-99m.

22. ¹⁸F-N-(l-Benzylpiperidin-4-yl)-2-fluorophenylacetamide, or a pharmaceutically acceptable salt thereof.

23. A pharmaceutical composition comprising a detectably labeled sigma-1 ligand, and a pharmaceutically acceptable diluent or carrier.

24. A pharmaceutical composition comprising a detectably labeled sigma-1 ligand of claim 15, and a pharmaceutically acceptable diluent or carrier.

25. A method for determining the proliferative status of a tumor that comprises cells that express sigma-1 receptors, comprising:

(a) contacting the cells in vitro with a compound of claim 22 , and

(b) determining the extent to which the compound binds to the cells, wherein the extent provides a measure of the proliferative status of the tumor.

26. A method for determining the proliferative status of a tumor that comprises cells that express sigma-1 receptors and sigma-2 receptors, comprising: (a) contacting the cells in vitro with a detectably labeled sigma-1 ligand and a detectably labeled sigma-2 ligand, and

(b) determining the extent to which the ligands bind to the cells, wherein the extent provides a measure of the proliferative status of the tumor.

27. A method for determining the proliferative status of a tumor that comprises cells that express sigma-1 receptors and sigma-2 receptors, comprising:

(a) contacting the cells in vitro with a detectably labeled ligand that binds to both sigma-1 receptors and to sigma-2 receptors, and (b) determining the extent to which the ligand binds to sigma-1 receptors and to sigma-2 receptors, wherein the extent of binding to sigma-1 receptors and to sigma-2 receptors provides a measure of the proliferative status of the tumor.

28. A method for determining the proliferative status of a tumor that comprises cells that express sigma-1 receptors, comprising:

(a) contacting the cells in vitro with a detectably labeled sigma-1 ligand, and

(b) determining the extent to which the ligand binds to the cells, wherein the extent provides a measure of the proliferative status of the tumor.

29. The method of claim 28 wherein the tumor is a solid tumor.

30. The method of claim 28 wherein the tumor is a breast cancer tumor, a bladder tumor, or a prostate tumor.

31. The method of claim 28 wherein the extent to which the compound binds to the cells is determined using PET or SPECT imaging.

32. The method of claim 28 wherein the sigma-1 ligand is a detectably labeled compound of formula I:

wherein:

R_] is hydrogen, (C_rC₆)alkyl, aryl, or aryl(C,-C₆)alkyl; R₂ is aryl or heteroaryl; A is NR,, -O-, CR_bR_c, or -S-; B is NR,, -O-, CR_bR_c, or -S-; C is two hydrogens, oxo (=O), or thioxo (=S); and each R_a is independently hydrogen, or (C,-C₆)alkyl; each R_b is independently hydrogen, hydroxy, (C,-C₆)alkyl, or (C C₆)alkoxy; and each R_c is independently hydrogen, or ( -C^alkyl; wherein any aryl or heteroaryl is optionally substituted with 1, 2,

3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, (C,-C₆)alkyl, (C_r C₆)alkoxy, (C_rC₆)alkanoyl, (C,-C₆)alkanoyloxy, (C,-C₆)alkoxycarbonyl, and methylenedioxy; or a pharmaceutically acceptable salt thereof.

33. The method of claim 32 wherein R, is benzyl.

34. The method of claim 32 wherein R₂ is phenyl or naphthyl, optionally substituted with 1, 2, or 3, substituents independently selected from the group consisting of halo, cyano, hydroxy, trifluoromethyl, trifluoromethoxy, (C_rC₆)alkyl, (C_rC₆)alkoxy, (C,-C₆)alkanoyl, (C,-C₆)alkanoyloxy, and (C_r C₆)alkoxycarbonyl.

35. The method of claim 32 wherein R₂ is pyridinyl, imidazolyl, indolyl or pyrimidinyl, optionally substituted with 1, 2, or 3, substituents independently selected from the group consisting of halo, cyano, hydroxy, trifluoromethyl, trifluoromethoxy, (C_rC₆)alkyl, (C_rC₆)alkoxy, ( -C^alkanoyl, (C,-C₆)alkanoyloxy, and (C,-C₆)alkoxycarbonyl.

36. The method of claim 32 wherein R₂ is thiophenyl, optionally substituted with 1 or 2 substituents independently selected from the group consisting of halo, cyano, hydroxy, trifluoromethyl, trifluoromethoxy, (C,- C₆)alkyl, (C_rC₆)alkoxy, (C,-C₆)alkanoyl, (C_rC₆)alkanoyloxy, and (C,- C₆)alkoxycarbonyl.

37. The method of claim 32 wherein A is NH.

38. The method of claim 32 wherein B is NH, CH₂ or CH(OH).

39. The method of claim 32 wherein the compound of formula I is labeled with at least one atom selected from the group consisting of carbon-11, fluorine- 18, fluorine-19, iodine-123 and iodine- 125.

40. The method of claim 32 wherein the compound of formula I is labeled with iodine-123.

41. The method of claim 32 wherein the detectable label comprises a radionuclide.

42. The method of claim 41 wherein the radionuclide is a metallic radioisotope.

43. The method of claim 42 wherein the metallic radioisotope is selected from the group consisting of Antimony- 124, Antimony-125, Arsenic- 74, Barium-103, Barium-140, Beryllium-7, Bismuth-206, Bismuth-207, Cadmium-109, Cadmium-115m, Calcium-45, Cerium-139, Cerium-141, Cerium-144, Cesium-137, Chromium-51, Cobalt-56, Cobalt-57, Cobalt-58, Cobalt-60, Cobalt-64, Erbium-169, Europium-152, Gadolinium- 153, Gold-195, Gold-199, Hafhium-175, Hafhium-175-181, Indium-111, Iridium-192, Iron-55, Iron-59, Krypton-85, Lead-210, Manganese-54, Mercury-197, Mercury-203, Molybdenum-99, Neodymium-147, Neptunium-237, Nickel-63, Niobium-95, Osmium-185 + 191, Palladium- 103, Platinum- 195m, Praseodymium- 143, Promethium-147, Protactinium-233, Radium-226, Rhenium-186, Rubidium-86, Ruthenium- 103, Ruthenium- 106, Scandium-44, Scandium-46, Selenium-75,

Silver- 110m, Silver-I l l, Sodium-22, Strontium-85, Strontium-89, Strontium-90, Sulfur-35, Tantalum-182, Technetium-99m, Tellurium- 125, Tellurium- 132, Thallium-204, Thorium-228, Thorium-232, Thallium-170, Tin-113, Titanium-

44. Tungsten-185, Vanadium-48, Vanadium-49, Ytterbium- 169, Yttrium-88, Yttrium-90, Yttrium-91, Zinc-65, and Zirconium.

44. The method of claim 42 wherein the metallic radioisotope is technetium-99m.

45. The method of any one of claims 25 to 44 wherein the sigma-1 ligand binds selectively to sigma-1 receptors over sigma-2 receptors.

46. A compound of any one of claims 1-14 that is useful in medical therapy.

47. A compound of any one of claims 15-22 that is useful in medical imaging.

48. A compound of any one of claims 1-22 that is useful to prepare a medicament for determining the proliferative status of a tumor that comprises cells that express sigma-1 receptors.

49. The compound of claim 48 wherein the proliferative status of a tumor is determined by:

(a) contacting the cells with the compound , and

50. The compound of claim 49 wherein the contacting is in vivo.

51. The compound of claim 49 wherein the contacting is in vitro.

52. The compound of formula 48 wherein the tumor is a solid tumor.

53. The compound of claim 48 wherein the tumor is a breast cancer tumor, a bladder cancer tumor, or a prostate cancer tumor.

54. The compound of claim 48 wherein the proliferative status of a tumor is determined using PET or SPECT imaging.

55. The compound of claim 48 wherein thecompound is a detectably labeled compound of formula I:

wherein:

R_j is hydrogen, (C_rC₆)alkyl, aryl, or aryl(C_rC₆)alkyl; R₂ is aryl or heteroaryl; A is NR_a, -O-, CR_bR_c, or -S-;

B is NR_a, -O-, CR_bR_c, or -S-;

C is two hydrogens, oxo (=O), or thioxo (=S); and each R_a is independently hydrogen, or (C,-C₆)alkyl; each R_b is independently hydrogen, hydroxy, (C,-C₆)alkyl, or (C_r

C₆)alkoxy; and each R_c is independently hydrogen, or (C,-C₆)alkyl; wherein any aryl or heteroaryl is optionally substituted with 1, 2, 3, or 4 substituents independently selected from the group consisting of halo, cyano, hydroxy, nitro, trifluoromethyl, trifluoromethoxy, (C_rC₆)alkyl, (C C₆)alkoxy, (C,-C₆)alkanoyl, (C,-C₆)alkanoyloxy, (Cι-C₆)alkoxycarbonyl, and methylenedioxy; or a pharmaceutically acceptable salt thereof.

56. The compound of claim 55 wherein R, is benzyl.

57. The compound of claim 55 wherein R₂ is phenyl or naphthyl, optionally substituted with 1, 2, or 3, substituents independently selected from the group consisting of halo, cyano, hydroxy, trifluoromethyl, trifluoromethoxy, (C,-C₆)alkyl, (C_rC₆)alkoxy, (C_rC₆)alkanoyl, (C,-C₆)alkanoyloxy, and (C_r C₆)alkoxycarbonyl.

58. The compound of claim 55 wherein R₂ is pyridinyl, imidazolyl, indolyl or pyrimidinyl, optionally substituted with 1, 2, or 3, substituents independently selected from the group consisting of halo, cyano, hydroxy, trifluoromethyl, trifluoromethoxy, (C,-C₆)alkyl, (C C₆)alkoxy, (C,-C₆)alkanoyl, (C,-C₆)alkanoyloxy, and (C_rC₆)alkoxycarbonyl.

59. The compound of claim 55 wherein R₂ is thiophenyl, optionally substituted with 1 or 2 substituents independently selected from the group consisting of halo, cyano, hydroxy, trifluoromethyl, trifluoromethoxy, (C_r C₆)alkyl, (C,-C₆)alkoxy, (C_rC₆)alkanoyl, (C,-C₆)alkanoyloxy, and (C,- C₆)alkoxycarbonyl.

60. The compound of claim 55 wherein A is NH.

61. The compound of claim 55 wherein B is NH, CH₂ or CH(OH).

62. The compound of claim 55 wherein the compound of formula I is labeled with at least one atom selected from the group consisting of carbon-11, fluorine-18, fluorine-19, iodine-123 and iodine-125.

63. The compound of claim 55 wherein the compound of formula I is labeled with iodine- 123.

64. The compound of claim 55 wherein the detectable label comprises a radionuclide.

65. The compound of claim 64 wherein the radionuclide is a metallic radioisotope.

66. The compound of claim 65 wherein the metallic radioisotope is selected from the group consisting of Antimony- 124, Antimony-125, Arsenic- 74, Barium- 103, Barium- 140, Beryllium-7, Bismuth-206, Bismuth-207, Cadmium-109, Cadmium-115m, Calcium-45, Cerium-139, Cerium-141, Cerium-144, Cesium-137, Chromium-51, Cobalt-56, Cobalt-57, Cobalt-58, Cobalt-60, Cobalt-64, Erbium-169, Europium-152, Gadolinium- 153, Gold-195, Gold-199, Hafhium-175, Hafhium-175-181, Indium-I l l, Iridium-192, Iron-55, Iron-59, Krypton-85, Lead-210, Manganese-54, Mercury-197, Mercury-203, Molybdenum-99, Neodymium-147, Neptunium-237, Nickel-63, Niobium-95, Osmium- 185 + 191, Palladium- 103, Platinum- 195m, Praseodymium- 143, Promethium-147, Protactinium-233, Radium-226, Rhenium-186, Rubidium-86, Ruthenium- 103, Ruthenium- 106, Scandium-44, Scandium-46, Selenium-75, Silver-110m, Silver-111, Sodium-22, Strontium-85, Strontium-89, Strontium-90, Sulfur-35, Tantalum-182, Technetium-99m, Tellurium- 125, Tellurium- 132, Thallium-204, Thorium-228, Thorium-232, Thallium-170, Tin-113, Titanium- 44, Tungsten-185, Vanadium-48, Vanadium-49, Ytterbium- 169, Yttrium-88, Yttrium-90, Yttrium-91, Zinc-65, and Zirconium.

67. The compound of claim 65 wherein the metallic radioisotope is technetium-99m.

68. The compound of any one of claims 48 to 67 wherein the compound selectively binds to sigma-1 receptors over sigma-2 receptors.

69. A compound of any one of claims 18-21 that is useful for preparing a medicament for inhibiting the growth of cancer cells that express sigma-1 receptors.

70. The compound of claim 69 wherein the cancer cells are breast cancer cells, bladder cancer cells, or prostate cancer cells.

71. The compound of claim 69 wherein the therapeutic radionuclide is Rhenium- 186 or Yttrium-90.