Synthesis and in vitro receptor binding studies of fluorotamoxifen analogues

Synthesis and biological evaluation of novel tamoxifen-1,2,4-triazole conjugates

A new class of compounds, structurally related to the breast cancer drug tamoxifen, was designed and synthesized. The McMurry coupling reaction was used as the key synthetic step in the preparation of these analogs, and the structural assignments were made on the basis of [Formula: see text] NMR, [Formula: see text] NMR, and HRMS studies. The absolute stereochemistry of E and Z isomers was unambiguously confirmed by a single-crystal X-ray diffraction analysis. Water was found to be an inexpensive nontoxic and effective medium for the C-N bond formation. Utilizing this protocol, various tamoxifen derivatives were synthesized in good yields. Environmental acceptability, low cost, and high yields are the important features of this protocol. These compounds were evaluated for their antiproliferative activity on five human tumor cell lines. Compound 4p ([Formula: see text]) showed improved antiproliferative activity against breast cancer cell line (MDA-MB-231) compared to tamoxifen ([Formula: see text]), while the compound 4o ([Formula: see text]) exhibited similar activity against SiHa compared to the reference drug, tamoxifen ([Formula: see text]). In addition, these analogs were investigated for their antibacterial activity against six bacterial strains. Preliminary results indicate that some of the newly synthesized title compounds exhibited promising antibacterial activity compared with the standard drug, vancomycin. A new class of compounds were designed rationally by the replacement of a ethyl group in tamoxifen with a methylene (1H-1,2,4-triazole) group. The absolute stereochemistry of E and Z isomers were unambiguously confirmed by a single-crystal X-ray diffraction analysis. The title compounds were evaluated for their antiproliferative and antibacterial activities.

Design, synthesis and biological evaluation of novel triaryl (Z)-olefins as tamoxifen analogues

Tamoxifen (TAM) is used for the treatment and prevention of estrogen receptor positive breast cancer. However, the limited activity, toxicity and the development of resistance raised the current need for new potent nontoxic antiestrogen. Six novel TAM analogues 5a-f were synthesized using McMurry olefination reaction. Replacement of the dimethylamino group in TAM by piperidino, piperazino or N-methyl piperazino, substituting the phenyl ring with florine atom at p-position and changing the ethyl group by methyl, afforded compounds showing comparable activity to TAM (1). Compounds 5c and 5e showed significant increase in antiproliferative activity in two breast cancer cell lines (MCF-7 and MDA-MB-231) compared to tamoxifen, while other compounds showed similar activity. The increased anticancer activity of compounds 5c and 5e was attributed to their ability to induce ER-independent cell death.

Triaryl (Z)-olefins suitable for radiolabeling with iodine-124 or fluorine-18 radionuclides for positron emission tomography imaging of estrogen positive breast tumors

A group of (Z)-1,2-diphenyl-1-[4-[2-(4-methylpiperazin-1-yl)ethoxy]phenyl]but-1-enes were synthesized using methodologies that will allow incorporation of a [(124)I]iodine substituent at the para-position of either the C-1 phenyl ring or the C-2 phenyl ring, or a [(18)F]OCH(2)CH(2)F substituent at the para-position of the C-2 phenyl ring. These [(124)I] and [(18)F] radiotracers are designed as potential radiopharmaceuticals to image estrogen positive breast tumors using positron emission tomography (PET).

Influence of water on the solubility of two steroid drugs in hydrofluoroalkane (HFA) propellants

The objective of this research work was to investigate the influence of water level, temperature, and propellant composition on the solubility of two hydrophobic steroid drugs, triamcinolone acetonide (TAA) and beclomethasone diapropionate (BDP). pMDIs containing TAA or BDP, spiked water, and propellant blend with different ratios of HFA 134a and HFA 227 were prepared. The contents of the prepared pMDIs were filtered through a 0.22 mm Acrodisc, syringe filter into a receiving canister after the pMDIs were equilibrated at 15 degrees C, 25 degrees C, 30 degrees C, and 40 degrees C. The drug concentration in the receiving canisters was determined by HPLC and the drug solubility in the propellant blend was calculated. Also, the drug crystal collected on the filter from the donor pMDIs were characterized by x-ray diffraction. The solubility of TAA and BDP varied with propellant composition at all experimental temperatures investigated. The solubility of TAA and BDP increased as the temperature was increased at all propellant compositions and water levels studied, but decreased as the water level in the propellant system was increased at all compositions and temperatures. The x-ray diffraction results indicated that the water in the propellant system had no significant influence on the crystal characteristics of TAA in HFA propellant system, but had a significant impact on the crystal characteristics of BDP was higher than TAA at all propellant compositions, experimental temperatures and water levels investigated. The solubility of TAA and BDP was not only influenced by propellant composition and storage temperature, but also depended on the water level in the propellant system. As a consequence, the crystallinity of the drugs formulated in HFA propellant was influenced by the temperature, propellant composition and the water level in the propellant system. The impact of these factors on the crystallinity of formulated drugs.

The evolving role of specific estrogen receptor modulators (SERMs)

Estrogens are the most effective therapy for women with postmenopausal problems. However, relatively few women use estrogen and then often for a limited time because of the fear of its carcinogenic effects on the uterus and breast; in addition, estrogen is not advised for women who have had breast cancer. Selective estrogen receptor modulators (SERMs) are agents with antagonist action on the uterus and breast and agonist action on the bones, cardiovascular system, and brain. Unlike estrogens, however, existing SERMs do not help alleviate the vasomotor and urogenital problems associated with menopause. A comprehensive review of the literature published from January 1995 to June 1999 was conducted. Reports were identified using Medline and Cancer Lit. The effect of menopausal problems on the health of women and the socioeconomic effects of menopause are discussed. All currently available and investigational SERMs are reviewed and discussed, including their mechanism of action, metabolism, dose scheduling, antitumor activity, and potential role in maintaining the health of menopausal women and in preventing breast cancer.

Diagnostic and therapeutic potential of poly(benzyl L-glutamate)

Poly(benzyl L-glutamate) (PBLG) microcapsules, prepared by a solvent evaporation technique for intravenous injection, are evaluated for their potential use in diagnostic computed tomographic enhancement of liver images. The smaller microcapsules, < 3 microns, loaded with a radiopaque contrast material, ethyl iopanoate (IOPAE), produced prolonged opacification of the liver when delivered intravenously. In vivo tissue distribution studies of PBLG-131I-IOPAE (5 microCi/rat, iv) showed that liver had the highest uptake (percent of injected dose/g of tissue) among other organs 24 h postinjection. An in vitro estrogen receptor assay in pig uteri indicated that PBLG conjugated with estrone did not interfere with estrogen receptor affinity, suggesting the estrogen therapy potential of PBLG-estrone.

Imaging, biodistribution and therapy potential of halogenated tamoxifen analogues

Tamoxifen binds to estrogen receptors (ERs) and prevents breast cancer cell proliferation. This study is aimed at developing a ligand for imaging ER (+) breast tumors by positron emission tomography (PET) or single photon emission computed tomography (SPECT). [18F]-Labeled tamoxifen analogue ([18F]FTX) was prepared in 30-40% yield and [131I]-labeled tamoxifen analogue ([131I]ITX) was prepared in 20-25% yield. In mammary tumor-bearing rats, the biodistribution of [18F]FTX at 2 h showed a tumor uptake value (% injected dose/gram tissue) of 0.41 +/- 0.07; when rats were pretreated with diethylstilbestrol (DES), the value changed to 0.24 +/- 0.017. [131I]ITX at 6 h showed a tumor uptake value of 0.26 +/- 0.166; when rats were pretreated with DES, the value changed to 0.22 +/- 0.044. Priming tumor-bearing rats with estradiol, a tumor uptake value for [131I]ITX was increased to 0.48 +/- 0.107 at 6 h. In the [3H]estradiol receptor assay, tumors had a mean estrogen receptor density of 7.5 fmol/mg of protein. In gamma scintigraphic imaging studies with [131I]ITX, the rabbit uterus uptake can be blocked by pretreatment with DES. Both iodo-tamoxifen and tamoxifen reduced ER(+) breast tumor growth at the dose of 50 micrograms in tumor-bearing mice. The findings indicate that tamoxifen analogue uptake in tumors occurs via an ER-mediated process. Both analogues should have potential for diagnosing functioning ER(+) breast cancer.

Synthesis of [18F]fluoroalanine and [18F]fluorotamoxifen for imaging breast tumors

To develop ligands for imaging breast tumors, [18F]fluoro analogue of tamoxifen and [18F]fluoroalanine were radiosynthesized. In vivo biodistribution studies were performed in mammary tumor-bearing rats. In studies on the biodistribution of an [18F]fluoro analogue of tamoxifen, tumor uptake decreased when rats were pretreated with diethylstilbestrol (DES), suggesting that tracer uptake in tumors was receptor-mediated. An estrogen receptor assay indicated that tumors have a receptor density of 7.5 fmol/mg protein. Studies of the distribution of [18F]fluoroalanine in tissue showed that the tumor-to-tissue ratio increases as a function of time. Positron emission tomography (PET) images of tumor-bearing rats demonstrated that tumors can be visualized 1 h after rats are injected with an [18F]fluoro analogue of tamoxifen. PET imaging of pigs after injection of 10 mCi of [18F]fluoro analogue of tamoxifen showed uterine uptake that could be blocked by DES (50 mg). The findings suggest that both radiotracers are useful for imaging breast tumors.