Synthesis of 2,2-dimethyl-chroman-based stereochemically flexible and constrained anti-breast cancer agents.

Receptors are proteinous macromolecules which remain in the apo form under normal/unliganded conditions. As the ligand approaches, there are specific stereo-chemical changes in the apo form of the receptor as per the stereochemistry of a ligand. Accordingly, a series of substituted dimethyl-chroman-based stereochemically flexible and constrained Tamoxifen analogs were synthesized as anti-breast cancer agents. The synthesized compounds 19a-e, 20a-e, 21, and 22a-e, showed significant antiproliferative activity against estrogen receptor-positive (ER+, MCF-7) and negative (ER-, MDA MB-231) cells within IC50 value 8.5-25.0 µM. Amongst all, four potential molecules viz 19b, 19e, 22a, and 22c, were evaluated for their effect on the cell division cycle and apoptosis of ER+ and ER- cancer cells (MCF-7 & MDA MB-231cells), which showed that these compounds possessed antiproliferative activity through triggering apoptosis. In-silico docking experiments elucidated the possible affinity of compounds with estrogen receptors-α and -ß.

Replacing the Z-phenyl Ring in Tamoxifen® with a para-Connected NCN Pincer-Pt-Cl Grouping by Post-Modification †.

Post-modification of a series of NCN-pincer platinum(II) complexes [PtX(NCN-R-4)] (NCN = [C6H2(CH2NMe2)2-2,6]-, R = C(O)H, C(O)Me and C(O)Et), X = Cl- or Br-) at the para-position using the McMurry reaction was studied. The synthetic route towards two new [PtCl(NCN-R-4)] (R = C(O)Me and C(O)Et) complexes used above is likewise described. The utility and limitations of the McMurry reaction involving these pincer complexes was systematically evaluated. The predicted "homo-coupling" reaction of [PtBr(NCN-C(O)H-4)] led to the unexpected formation of 3,3',5,5'-tetra[(dimethylamino)methyl]-4,4'-bis(platinum halide)-benzophenone (halide = Br or Cl), referred to hereafter as the bispincer-benzophenone complex 13. This material was further characterized using X-ray crystal structure determination. The applicability of the pincer complexes in the McMurry reaction is shown to open a route towards the synthesis of tamoxifen-type derivatives of which one phenyl ring of Tamoxifen® itself is replaced by an NCN arylplatinum pincer fragment. The newly synthesized derivatives can be used as potential candidates in anti-cancer drug screening protocols. Two NCN-arylpincer platinum tamoxifen type derivatives, 5 and 6, were successfully synthesized and of 5 the separation of the diastereomeric E-/Z-forms was achieved. Compound 6, which is the pivaloyl protected NCN pincer platinum hydroxy-Tamoxifen® derivative, was obtained as a mixture of E-/Z-isomers. The new derivatives were further analyzed and characterized with 1H-, 13C{1H}- and 195Pt{1H}-NMR, IR, exact mass MS and elemental analysis.

Synthesis of novel flexible tamoxifen analogues to overcome CYP2D6 polymorphism and their biological evaluation on MCF-7 cell line.

Tamoxifen (TAM) is currently the endocrine treatment of choice for all stages of breast cancer; it has proven success in ER positive and ER negative patients. TAM is activated by endogenous CYP450 enzymes to the more biologically active metabolites 4-hydroxytamoxifen and endoxifen mainly via CYP2D6 and CYP3A4/5. CYP2D6 has been investigated for polymorphism; there is a large interindividual variation in the enzyme activity, this drastically effects clinical outcomes of tamoxifen treatment. Here in we report the design and synthesis of 10 novel compounds bearing a modified tamoxifen skeleton, ring C is substituted with different ester groups to bypass the CYP2D6 enzyme metabolism and employ esterase enzymes for activation. All compounds endorse flexibility on ring A. Compounds (II-X) showed MCF-7% growth inhibition >50% at a screening dose of 10 µM. These results were validated by yeast estrogen screen (YES) and E-Screen assay combined with XTT assay. Compound II (E/Z 4-[1-4-(3-Dimethylamino-propoxy)-phenyl)-3-(4-methoxy-phenyl)-2-methyl-propenyl]-phenol) showed nanomolar antiestrogenic activity (IC50 = 510 nM in YES assay) and was five times more potent in inhibiting the growth of MCF-7 BUS (IC50 = 96 nM) compared to TAM (IC50 = 503 nM). Esterified analogues VI, VII were three times more active than TAM on MCF-7 BUS (IC50 = 167 nM). Novel analogues are prodrugs that can ensure equal clinical outcomes to all breast cancer patients.

Synthesis, Characterization, and Drug Delivery Application of Self-assembling Amphiphilic Cyclodextrin.

The main aim of the research was to synthesize amphiphilic cyclodextrin (AMCD) by substituting C12 alkyl chain to a ß-cyclodextrin (ßCD) in a single step and to study its self-assembly in an aqueous medium. The drug delivery application of the AMCD was also evaluated by encapsulating tamoxifen citrate as a model hydrophobic drug. AMCD was able to self-assemble in aqueous media, forming nanovesicles of size < 200 nm, capable of encapsulating tamoxifen citrate (TMX). Molecular docking and MD simulation studies revealed the interaction between TMX and AMCD which formed a stable complex. TEM and AFM studies showed that nanovesicles were perfectly spherical having a smooth surface and a theoretical AMCD bilayer thickness of ~ 7.2 nm as observed from SANS studies. XRD and DSC studies revealed that TMX was amorphized and molecularly dispersed in AMCD bilayer which was released slowly following Fickian diffusion. AMCD has excellent hemocompatibility as opposed to ßCD and no genotoxicity. IC50 of TMX against MCF-7 cell lines was significantly reduced from 11.43 to 7.96 µg/ml after encapsulation in nanovesicle because of nanovesicles being endocytosed by the MCF-7 cells. AMCD was well tolerated by IV route at a dose of > 2000 mg/kg in rats. Pharmacokinetic profile of TMX after encapsulation was improved giving 3-fold higher AUC; extended mean residence time is improving chances of nanovesicle to extravasate in tumor via EPR effect.

An atom efficient synthesis of tamoxifen.

The direct carbolithiation of diphenylacetylenes and their cross-coupling procedure taking advantage of the intermediate alkenyllithium reagents are presented. By employing our recently discovered highly active palladium nanoparticle based catalyst, we were able to couple an alkenyllithium reagent with a high (Z/E) selectivity (10 : 1) and good yield to give the breast cancer drug tamoxifen in just 2 steps from commercially available starting materials and with excellent atom economy and reaction mass efficiency.

Selective estrogen receptor degraders with novel structural motifs induce regression in a tamoxifen-resistant breast cancer xenograft.

Potent estrogen receptor ligands typically contain a phenolic hydrogen-bond donor. The indazole of the selective estrogen receptor degrader (SERD) ARN-810 is believed to mimic this. Disclosed herein is the discovery of ARN-810 analogs which lack this hydrogen-bond donor. These SERDs induced tumor regression in a tamoxifen-resistant breast cancer xenograft, demonstrating that the indazole NH is not necessary for robust ER-modulation and anti-tumor activity.

Incorporation of histone deacetylase inhibitory activity into the core of tamoxifen - A new hybrid design paradigm.

Hybrid antiestrogen/histone deacetylase (HDAC) inhibitors were designed by appending zinc binding groups to the 4-hydroxystilbene core of 4-hydroxytamoxifen. The resulting hybrids were fully bifunctional, and displayed high nanomolar to low micromolar IC50 values against both the estrogen receptor α (ERα) and HDACs in vitro and in cell-based assays. The hybrids were antiproliferative against ER+ MCF-7 breast cancer cells, with hybrid 28b possessing an improved activity profile compared to either 4-hydroxytamoxifen or SAHA. Hybrid 28b displayed gene expression patterns that reflected both ERα and HDAC inhibition.

Anticancer properties of lipid and poly(ε-caprolactone) nanocapsules loaded with ferrocenyl-tamoxifen derivatives.

OBJECTIVE: We synthesized new tamoxifen derivatives as anticancer drug candidates and elaborated on convection-enhanced delivery (CED) as a strategy for delivery. METHODS: To overcome the issue of their poor solubility, these ferrocenyl-tamoxifen derivatives were esterified and encapsulated into different nanocarriers, that is lipid (LNC) and polymeric nanocapsules (PNL-NC). We describe the chemistry, the encapsulation and the physicochemical characterization of these formulations. KEY FINDINGS: Starting compounds [phthalimido-ferrocidiphenol and succinimido-ferrocidiphenol], esterified prodrugs and their nanocapsules formulations were characterized. These drug candidates displayed a strong in vitro activity against breast and glioblastoma cancer cells. The ester prodrugs were toxic for glioblastoma cells (IC50 = 9.2 × 10-2 µm and 6.7 × 10-2 µm, respectively). The IC50 values for breast cancer cells were higher for these compounds. The encapsulation of the esterified compounds in LNCs (≈50 nm) or PCL-NCs (≈300 nm) did not prevent their efficacy on glioblastoma cells. These anticancer effects were due to both blockade in the S-phase of the cell cycle and apoptosis. Moreover, the tamoxifen derivatives-loaded nanocapsules induced no toxicity for healthy astrocytes and showed no haemolytic properties. Loaded Lipid Nanocapsules (LNCs) presented interesting profiles for the optimal delivery of active compounds. CONCLUSIONS: Phthalimido- and Succinimido-esters represent an innovative approach to treat cancers with cerebral localizations such as glioblastoma or brain metastases from breast cancers.

An estrogen receptor targeted ruthenium complex as a two-photon photodynamic therapy agent for breast cancer cells.

In this study, we reported a tamoxifen modified Ru(ii) polypyridyl complex (Ru-tmxf) as an estrogen receptor (ER) targeted photosensitizer. Ru-tmxf displays enhanced cellular uptake and PDT efficiency toward breast cancer cells with high ER expression due to the specific targeting of tamoxifen to ER and finally localizes in lysosomes. Moreover, Ru-tmxf can be activated by two-photon excitation, generating 1O2 to damage lysosomes and result in cell death.

A multi-gram-scale stereoselective synthesis of Z-endoxifen.

Z-Endoxifen is widely regarded as the most active metabolite of tamoxifen, and has recently demonstrated a 26.3% clinical benefit in a phase I clinical trial to treat metastatic breast cancer after the failure of standard endocrine therapy. Future pharmacological and pre-clinical studies of Z-endoxifen would benefit from reliable and efficient synthetic access to the drug. Here, we describe a short and efficient, stereoselective synthesis of Z-endoxifen capable of delivering multi-gram (37 g) quantities of the drug in >97% purity with a Z/E ratio >99% after trituration.

Synthesis and biological evaluation of novel cyclopropyl derivatives as subtype-selective ligands for estrogen receptor.

OBJECTIVES: Tamoxifen is the most commonly used selective estrogen receptor modulators (SERMs); however, patients often develop the acquired drug resistance on tamoxifen therapy. The aim of this study was to develop new SERMs. METHODS: Several novel cyclopropyl derivatives were designed and synthesized. The binding affinities of these compounds as well as the selectivity on subtype of estrogen receptor (ER) were assessed by fluorescence polarization. The antagonistic activity was also evaluated by dual-luciferase reporter assay. KEY FINDINGS: Our data identified five compounds (9a, 9b, 9d, 9e and 9f) with a higher selectivity on ERα than ERß subtype, warranting further development as a subtype-selective ER modulator. The study of antiestrogen activity also demonstrated that compounds 9a, 9c-f acted as full functional antagonists for ERα. These compounds had no or very low cytotoxicity. CONCLUSIONS: Although these cyclopropyl derivatives showed lower binding affinities on ERs compared to 17ß-estradiol, five of these compounds exhibited binding to ERα only and therefore might serve as a promising lead compound for further development of novel subtype-selective SERMs.

Photoredox-Catalyzed C-H Arylation of Internal Alkenes to Tetrasubstituted Alkenes: Synthesis of Tamoxifen.

Visible-light-induced direct C-H arylation of S,S-functionalized internal alkenes, that is, α-oxo ketene dithioacetals and analogues, has been efficiently realized with aryldiazonium salts (ArN2BF4) as coupling partners and Ru(bpy)3Cl2·6H2O as photosensitizer at ambient temperature. The strategy to activate the internal olefinic C-H bond by both the alkylthio and electron-withdrawing functional groups was investigated. The synthetic protocol was successfully applied to the synthesis of all-carbon tetrasubstituted alkenes including tamoxifen.

Novel Selective Estrogen Receptor Ligand Conjugates Incorporating Endoxifen-Combretastatin and Cyclofenil-Combretastatin Hybrid Scaffolds: Synthesis and Biochemical Evaluation.

Nuclear receptors such as the estrogen receptors (ERα and ERß) modulate the effects of the estrogen hormones and are important targets for design of innovative chemotherapeutic agents for diseases such as breast cancer and osteoporosis. Conjugate and bifunctional compounds which incorporate an ER ligand offer a useful method of delivering cytotoxic drugs to tissue sites such as breast cancers which express ERs. A series of novel conjugate molecules incorporating both the ER ligands endoxifen and cyclofenil-endoxifen hybrids covalently linked to the antimitotic and tubulin targeting agent combretastatin A-4 were synthesised and evaluated as ER ligands. A number of these compounds demonstrated pro-apoptotic effects, with potent antiproliferative activity in ER-positive MCF-7 breast cancer cell lines and low cytotoxicity. These conjugates displayed binding affinity towards ERα and ERß isoforms at nanomolar concentrations e.g., the cyclofenil-amide compound 13e is a promising lead compound of a clinically relevant ER conjugate with IC50 in MCF-7 cells of 187 nM, and binding affinity to ERα (IC50 = 19 nM) and ERß (IC50 = 229 nM) while the endoxifen conjugate 16b demonstrates antiproliferative activity in MCF-7 cells (IC50 = 5.7 nM) and binding affinity to ERα (IC50 = 15 nM) and ERß (IC50 = 115 nM). The ER binding effects are rationalised in a molecular modelling study in which the disruption of the ER helix-12 in the presence of compounds 11e, 13e and 16b is presented These conjugate compounds have potential application for further development as antineoplastic agents in the treatment of ER positive breast cancers.

A Molecular Combination of Zinc(II) Phthalocyanine and Tamoxifen Derivative for Dual Targeting Photodynamic Therapy and Hormone Therapy.

The combination of photodynamic therapy and other cancer treatment modalities is a promising strategy to enhance therapeutic efficacy and reduce side effects. In this study, a tamoxifen-zinc(II) phthalocyanine conjugate linked by a triethylene glycol chain has been synthesized and characterized. Having tamoxifen as the targeting moiety, the conjugate shows high specific affinity to MCF-7 breast cancer cells overexpressed estrogen receptors (ERs) and tumor tissues, therefore leading to a cytotoxic effect in the dark due to the cytostatic tamoxifen moiety, and a high photocytotoxicity due to the photosensitizing phthalocyanine unit against the MCF-7 cancer cells. The high photodynamic activity of the conjugate can be attributed to its high cellular uptake and efficiency in generating intracellular reactive oxygen species. Upon addition of exogenous 17ß-estradiol as an ER inhibitor, the cellular uptake and photocytotoxicity of the conjugate are reduced significantly. As shown by confocal microscopy, the conjugate is preferentially localized in the lysosomes of the MCF-7 cells.

Preparation, characterization and in-vivo evaluation of microemulsions containing tamoxifen citrate anti-cancer drug.

The aim of this study was to prepare and characterize a new nanocarrier for oral delivery of tamoxifen citrate (TMC) as a lipophilic oral administrated drug. This drug has low oral bioavailability due to its low aqueous solubility. To enhance the solubility of this drug, the microemulsion system was applied in form of oil-in-water. Sesame oil and Tween 80 were used as drug solvent oil and surfactant, respectively. Two different formulations were prepared for this purpose. The first formulation contained edible glycerin as co-surfactant and the second formulation contained Span 80 as a mixed surfactant. The results of characterization showed that the mean droplet size of drug-free samples was in the range of 16.64-64.62nm with a PDI value of <0.5. In a period of 6months after the preparation of samples, no phase sedimentation was observed, which confirmed the high stability of samples. TMC with a mass ratio of 1% was loaded in the selected samples. No significant size enlargement and drug precipitation were observed 6months after drug loading. In addition, the drug release profile at experimental environments in buffers with pH=7.4 and 5.5 showed that in the first 24h, 85.79 and 100% of the drug were released through the first formulation and 76.63 and 66.42% through the second formulation, respectively. The in-vivo results in BALB/c female mice showed that taking microemulsion form of drug caused a significant reduction in the growth rate of cancerous tumor and weight loss of the mice compared to the consumption of commercial drug tablets. The results confirmed that the new formulation of TMC could be useful for breast cancer treatment.

Tamoxifen and Fulvestrant Hybrids Showed Potency as Selective Estrogen Receptor Down-Regulators.

BACKGROUND: Estrogen receptors (ERs) are an important target for the management of breast cancers. Selective estrogen receptor down-regulators (SERDs) block ER activity, as well as reduce ERα protein levels in cells, and therefore are promising therapeutic agents for the treatment of breast cancers. OBJECTIVE: In order to develop potent SERDs, we prepared tamoxifen and fulvestrant hybrids and evaluated their binding activity and down-regulation of ERα. METHODS: We designed and synthesized tamoxifen derivatives, which had a 4,4,5,5,5- pentafluoropentyl group on the terminal alkyl chain. The oxidation state of the sulfur atom and alkyl length between the sulfur and nitrogen atoms were varied. Western blotting was performed to determine the ability to down-regulate ERα. Binding affinities of synthesized compounds were evaluated by a fluorescence polarization-based competitive binding assay. RESULTS: We successfully prepared nine compounds. Treatment with 11, 14, and 17 effectively reduced ERα protein levels in MCF-7 cells in a concentration-dependent manner. This reduction was inhibited by a proteasome inhibitor. The ability of 14 to down-regulate the ERα protein level was equal to fulvestrant. All compounds showed a largely equal affinity for ERα. CONCLUSION: As indicated by Western blots, the ERα degradation activity was observed only in the series of butyl linker derivatives, namely, 11, 14, and 17. These findings suggest that the specific length of the alkyl chain is an important factor in controlling the down-regulation of ER. These results provide useful information for designing promising SERD candidates.

Insights of a Lead Optimization Study and Biological Evaluation of Novel 4-Hydroxytamoxifen Analogs as Estrogen-Related Receptor γ (ERRγ) Inverse Agonists.

We evaluated the in vitro pharmacology as well as the absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties of chemical entities that not only were shown to be highly selective agonists for ERRγ but also exhibited enhanced pharmacokinetic profile compared with 3 (GSK5182). 6g and 10b had comparable potency to 3 and were far more selective for ERRγ over the ERRα, -ß, and ERα. The in vivo pharmacokinetic profiles of 6g and 10b were further evaluated, as they possessed superior in vitro ADMET profiles compared to the other compounds. Additionally, we observed a significant increase of fully glycosylated NIS protein, key protein for radioiodine therapy in anaplastic thyroid cancer (ATC), in 6g- or 10b-treated CAL62 cells, which indicated that these compounds could be promising enhancers for restoring NIS protein function in ATC cells. Thus, 6g and 10b possess advantageous druglike properties and can be used to potentially treat various ERRγ-related disorders.

Synthesis and biological evaluation of novel 4-hydroxytamoxifen analogs as estrogen-related receptor gamma inverse agonists.

Estrogen-related receptor gamma (ERRγ) has recently been recognized as an attractive target for treating inflammation, cancer, and metabolic disorders. Herein, we discovered and demonstrated the in vitro pharmacology as well as the absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties of chemical entities that could act as highly selective inverse agonists for ERRγ. The results were comparable to those for GSK5182 (4), a leading ERRγ inverse agonist ligand. Briefly, the half-maximal inhibitory concentration (IC50) range of the synthesized compounds for ERRγ was 0.1-10 µM. Impressively, compound 24e exhibited potency comparable to 4 but was more selective for ERRγ over three other subtypes: ERRα, ERRß, and estrogen receptor α. Furthermore, compound 24e exhibited a superior in vitro ADMET profile compared to the other compounds. Thus, the newly synthesized class of ERRγ inverse agonists could be lead candidates for developing clinical therapies for ERRγ-related disorders.

Design and synthesis of novel flexible ester-containing analogs of tamoxifen and their evaluation as anticancer agents.

BACKGROUND: Tamoxifen (TAM) is metabolized to the more active 4-hydroxytamoxifen by CYP2D6 enzyme. Due to the genetic polymorphisms in CYP2D6, clinical outcomes of TAM treatment vary. Novel flexible TAM analogs with altered activation pathway were synthesized and were tested for their antiproliferative action on MCF-7 cell lines and their binding affinity for ERα and ERß. RESULTS: All compounds showed better antiproliferative activity than TAM. Compound 3 showed 80-times more ERα binding than TAM, 900-times more selectivity toward ERα. Compound 3 was tested on the entire National Cancer Institute cancerous cell lines; results indicated a broad spectrum anticancer activity. CONCLUSION: The novel analogs were more potent than TAM with higher selectivity toward ERα and with potential metabolic stability toward CYP2D6.

Synthesis and evaluation of tamoxifen derivatives with a long alkyl side chain as selective estrogen receptor down-regulators.

Estrogen receptors (ERs) play a major role in the growth of human breast cancer cells. An antagonist that acts as not only an inhibitor of ligand binding but also an inducer of the down-regulation of ER would be useful for the treatment for ER-positive breast cancer. We previously reported the design and synthesis of a selective estrogen receptor down-regulator (SERD), (E/Z)-4-(1-{4-[2-(dodecylamino)ethoxy]phenyl}-2-phenylbut-1-en-1-yl)phenol (C12), which is a tamoxifen derivative having a long alkyl chain on the amine moiety. This compound induced degradation of ERα via a proteasome-dependent pathway and showed an antagonistic effect in MCF-7 cells. With the aim of increasing the potency of SERDs, we designed and synthesized various tamoxifen derivatives that have various lengths and terminal groups of the long alkyl side chain. During the course of our investigation, C10F having a 10-fluorodecyl group on the amine moiety of 4-OHT was shown to be the most potent compound among the tamoxifen derivatives. Moreover, computational docking analysis suggested that the long alkyl chain interacted with the hydrophobic region on the surface of the ER, which is a binding site of helix 12 and coactivator. These results provide useful information to develop promising candidates as SERDs.