Design of a Mestranol 2-N-Piperazino-Substituted Derivative Showing Potent and Selective in vitro and in vivo Activities in MCF-7 Breast Cancer Models

Synthesis and biological activities of bicyclic pyridines integrated steroid hybrid

Reports on structural modification of heterosteroids through various reactions, and developed synthetic routes have considerably increased over the last decade. The present review encompasses the applicable approaches dealing with the utility of reactive moieties in various steroids for the synthesis of fused bicyclic pyridines, and binary bicyclic pyridines all over the years. The different sections include the synthesis of steroids-fused, and binary quinolines, pyridopyrimidines, imidazopyridines, spirocyclic imidazopyridines, pyrazolopyridines, thienopyridines, pyridinyl-thiazoles, and tetrazolopyridine hybrids, as well as, the diverse biological applications of these heterocyclic steroids. The researchers' interest was principally focused on investigating the flexibility of synthetic strategies for various derivatives of natural steroids and building proposals based on heterocyclic steroids for drug discovery, biological assessments, and synthetic applications.

Aminosteroid RM-581 Decreases Cell Proliferation of All Breast Cancer Molecular Subtypes, Alone and in Combination with Breast Cancer Treatments

Breast cancer (BC) is a heterogenous disease classified into four molecular subtypes (Luminal A, Luminal B, HER2 and triple-negative (TNBC)) depending on the expression of the estrogen receptor (ER), the progesterone receptor (PR) and the human epidermal receptor 2 (HER2). The development of effective treatments for BC, especially TNBC, remains a challenge. Aminosteroid derivative RM-581 has previously shown an antiproliferative effect in multiple cancers in vitro and in vivo. In this study, we evaluated its effect in BC cell lines representative of BC molecular subtypes, including metastatic TNBC. We found that RM-581 has an antiproliferative effect on all BC molecular subtypes, especially on Luminal A and TNBC, in 2D and 3D cultures. The combination of RM-581 and trastuzumab or trastuzumab-emtansine enhanced the anticancer effect of each drug for HER2-positive BC cell lines, and the combination of RM-581 and taxanes (docetaxel or paclitaxel) improved the antiproliferative effect of RM-581 in TNBC and metastatic TNBC cell lines. We also confirmed that RM-581 is an endoplasmic reticulum (EnR)-stress aggravator by inducing an increase in EnR-stress-induced apoptosis markers such as BIP/GRP78 and CHOP and disrupting lipid homeostasis. This study demonstrates that RM-581 could be effective for the treatment of BC, especially TNBC.

An Aminosteroid Derivative Shows Higher In Vitro and In Vivo Potencies than Gold Standard Drugs in Androgen-Dependent Prostate Cancer Models

The aminosteroid derivative RM-581 blocks with high potency the growth of androgen-dependent (AR⁺) prostate cancer VCaP, 22Rv1, and LAPC-4 cells. Notably, RM-581 demonstrated superior antiproliferative activity in LAPC-4 cells compared to enzalutamide and abiraterone, two drugs that exhibited a synergistic effect in combination with RM-581. These findings suggest that RM-581 may have an action that is not directly associated with the hormonal pathway of androgens. Furthermore, RM-581 completely blocks tumor growth in LAPC-4 xenografts when given orally at 3, 10, and 30 mg/kg in non-castrated (intact) nude mice. During this study, an accumulation of RM-581 was observed in tumors compared to plasma (3.3-10 folds). Additionally, the level of fatty acids (FA) increased in the tumors and livers of mice treated with RM-581 but not in plasma. The increase was greater in unsaturated FA (21-28%) than in saturated FA (7-11%). The most affected FA were saturated palmitic acid (+16%), monounsaturated oleic acid (+34%), and di-unsaturated linoleic acid (+56%), i.e., the 3 most abundant FA, with a total of 55% of the 56 FA measured. For cholesterol levels, there was no significant difference in the tumor, liver, or plasma of mice treated or not with RM-581. Another important result was the innocuity of RM-581 in mice during a 28-day xenograft experiment and a 7-week dose-escalation study, suggesting a favorable safety window for this new promising drug candidate when given orally.

Chemical Synthesis and Biological Evaluation of 3-Substituted Estrone/Estradiol Derivatives as 17β-Hydroxysteroid Dehydrogenase Type 1 Inhibitors Acting via a Reverse Orientation of the Natural Substrate Estrone

Estradiol (E2) plays an important role in the progression of diseases such as breast cancer and endometriosis. Inhibition of 17β-hydroxysteroid dehydrogenase type 1 (17β-HSD1), the enzyme that catalyzes the last step in the biosynthesis of the estrogenic hormone E2, therefore constitutes an interesting approach for the treatment of these two estrogen-dependent diseases. In order to obtain new inhibitors of 17β-HSD1, the impact of a m-carbamoylphenyloxy group at position three of an estrane nucleus was evaluated by preparing three derivatives of estrone (E1) and E2 using a microwave-assisted synthesis of diaryl ethers. Their inhibitory activity was addressed on two cell lines (T-47D and Z-12) representative of breast cancer and endometriosis, respectively, but unlike T-47D cells, Z-12 cells were not found suitable for testing potential 17β-HSD1 inhibitors. Thus, the addition of the m-carbamoylphenyl group at C3 of E1 (compound 5) did not increase the inhibition of E1 to E2 transformation by 17β-HSD1 present in T-47D cells (IC₅₀ = 0.31 and 0.21 μM for 5 and E1, respectively), and this negative effect was more obvious for E2 derivatives 6 and 10 (IC₅₀ = 1.2 and 1.3 μM, respectively). Molecular docking allowed us to identify key interactions with 17β-HSD1 and to highlight these new inhibitors' actions through an opposite orientation than natural enzyme substrate E1's classical one. Furthermore, molecular modeling experiments explain the better inhibitory activity of E1-ether derivative 5, as opposed to the E2-ether derivatives 6 and 10. Finally, when tested on T-47D and Z-12 cells, compounds 5, 6 and 10 did not stimulate the proliferation of these two estrogen-dependent cell lines. In fact, they reduced it.

Chemical synthesis, NMR characterization, and anticancer activity of androstene derivatives with a C17-side chain

Cancer remains one of the leading causes of death, worldwide. In addition, the lack of efficacy and selectivity of chemotherapeutic agents for cancer cells is a challenge that needs to be addressed through the development of new drugs. Since aminosteroids are of interest in fighting cancer, our group previously reported antiproliferative activity on several cancer cell lines of two representatives, RM-133 and RM-581. To extend the structure-activity relationship study of aminosteroids, of which RM-133 (androstane) and RM-581 (estrane) are the main candidates, we performed the chemical synthesis and biological evaluation on lung (SHP-77), breast (T-47D) and prostate (DU-145, PC-3 and LAPC-4) cancer cells of four analogues of RM-581. We moved the functionalized side chain from position 2 of the androstane and estrane derivatives to incorporate it into a new chain located at position 17. Chemical synthesis took place in 2 steps from steroidal side-chain carboxylic acids, allowing to obtain 4 steroid derivatives with acceptable yields, which were fully characterized by nuclear magnetic resonance spectroscopy (¹H and ¹³C NMR). After the evaluation of compounds 12-15, lower antiproliferative activities varying from 12 to 54%, 0-33% and 0-63% were observed for SHP-77, DU-145 and PC-3 cell lines, respectively, while higher activities varying from 33 to 62% and 45-84% were observed for T-47D and LAPC-4 cell lines, respectively, when tested at 10 µM. Overall, it was observed that these aminosteroids have a lower cytotoxic activity than that of RM-581 and, that moving the side chain from steroid position C2 to C17 is clearly detrimental for antiproliferative activity. However, this work has enabled us to expand our knowledge of the structural requirements to maintain the anticancer activity of aminosteroid derivatives.

Induction of Endoplasmic Reticulum Stress-Mediated Apoptosis by Aminosteroid RM-581 Efficiently Blocks the Growth of PC-3 Cancer Cells and Tumors Resistant or Not to Docetaxel

Aminosteroid derivative RM-581 was previously identified as an endoplasmic-reticulum (ER) stress inducer with potent in vitro and in vivo anticancer activities. We report its evaluation in androgen-independent prostate cancer (PC-3) cells. RM-581 efficiently blocks PC-3 cell proliferation with stronger activity than that of a selection of known antineoplastic agents. This later also showed a synergistic effect with docetaxel, able to block the proliferation of docetaxel-resistant PC-3 cells and, contrary to docetaxel, did not induce cell resistance. RM-581 induced an increase in the expression level of ER stress-related markers of apoptosis, potentially triggered by the presence of RM-581 in the ER of PC-3 cells. These in vitro results were then successfully translated in vivo in a PC-3 xenograft tumor model in nude mice, showing superior blockade than that of docetaxel. RM-581 was also able to stop the progression of PC-3 cells when they had become resistant to docetaxel treatment. Concomitantly, we observed a decrease in gene markers of mevalonate and fatty acid pathways, and intratumoral levels of cholesterol by 19% and fatty acids by 22%. Overall, this work demonstrates the potential of an ER stress inducer as an anticancer agent for the treatment of prostate cancers that are refractory to commonly used chemotherapy treatments.

16-Picolyl-androsterone derivative exhibits potent 17β-HSD3 inhibitory activity, improved metabolic stability and cytotoxic effect on various cancer cells: Synthesis, homology modeling and docking studies

A new androsterone derivative bearing a 16β-picolyl group (compound 5; FCO-586-119) was synthetized in four steps from the lead compound 1 (RM-532-105). We measured its inhibitory activity on 17β-HSD3 using microsomal fraction of rat testes as well as transfected LNCaP[17β-HSD3] cells. We then assessed its metabolic stability as well as its cytotoxic effect against a panel of cancer cell lines. The addition of a picolyl moiety at C-16 of RM-532-105 steroid core improves the 17β-HSD3 inhibitory activity in the microsomal fraction of rat testes, but not in whole LNCaP[17β-HSD3] cells. Interestingly, this structural modification enhances 3-fold the metabolic stability in conjunction with a significant cytotoxic effect against pancreatic, ovarian, breast, lung, and prostate cancer cells. Because the inhibitory activity data against 17β-HSD3 suggested that both steroid derivatives are non-competitive inhibitors, we performed docking and molecular dynamics simulations using a homology model of this membrane-associated enzyme. The results of these simulations revealed that both RM-532-105 (1) and FCO-586-119 (5) can compete for the cofactor-binding site displaying better binding energy than NADP+.

Turning a Quinoline-based Steroidal Anticancer Agent into Fluorescent Dye for its Tracking by Cell Imaging

RM-581 is an aminosteroid derivative comprised of a steroid core and a quinoline side chain showing potent cytotoxic activity on several types of cancer cells but for which the mechanism of action (MoA) remains to be fully elucidated. The opportunity to turn RM-581 into a fluorescent probe was explored because the addition of a N-dimethyl group was recently reported to induce fluorescence to quinoline derivatives. After the chemical synthesis of the N-dimethyl analogue of RM-581 (RM-581-Fluo), its fluorescent properties, as well as its cytotoxic activity in breast cancer MCF-7 cells, were confirmed. A cell imaging experiment in MCF-7 cells using confocal microscopy then revealed that RM-581-Fluo accumulated into the endoplasmic reticulum (ER) as highlighted by its colocalization with an ER-Tracker dye. This work provides a new tool for RM-581 MoA investigations as well as being a relevant example of a tailor-made quinolone-fluorescent version of a bioactive molecule.

Minor chemical modifications of the aminosteroid derivative RM-581 lead to major impact on its anticancer activity, metabolic stability and aqueous solubility

The aminosteroid (AM) RM-581 is built around a mestranol backbone and has recently emerged as this family's lead candidate, showing in vitro and in vivo potency over different types of cancer, including high fatality pancreatic cancer. To extend the structure-activity relationships (SAR) to other estrane analogs, we synthesized a focused series of RM-581 derivatives at position C3 or C2 of its steroidal core. These new AM derivatives were first tested on a large selection of prostate, breast, pancreatic and ovarian cancer cell lines. The impact of these modifications on metabolic stability (human liver microsomes) was also measured. A SAR study revealed a fine regulation of anticancer activity related to the nature of the substituent. Indeed, the addition of potential prodrug groups like acetate, sulfamate or phosphate (compounds 8, 9 and 10) at C3 of the phenolic counterpart provided better antiproliferative activities than RM-581 in breast and pancreatic cancer cell types while maintaining activity in other cancer cell lines. Also, the phosphate group was highly beneficial on water solubility. However, the bulkier carbamate prodrugs 6 (N,N-dimethyl) and 7 (N,N-diethyl) were less active. Otherwise, carbon homologation (CH₂) at C2 (compound 33) was beneficial to metabolic stability and, in the meantime, this AM conserved the same anticancer activity as RM-581. However, the replacement of the hydroxy or methoxy at C3 by a hydrogen or an acetyl (compound 17 or 21b) was detrimental for anticancer activity, pointing to a crucial molecular interaction of the aromatic oxygen atom at this position. Overall, this work provided a better knowledge of the structural requirements to maintain RM-581's anticancer activity, and also identified minor structural modifications to increase both metabolic stability and water solubility, three important parameters of pharmacological development.

Design, Synthesis and Anticancer Evaluation of Novel Series of Indibulin Analogues

Background:

Cancer is an important cause of human death worldwide. During the last decades, many anticancer agents with anti-tubulin mechanism have been synthesized or extracted from nature and some of them also entered clinical use. Indibulin is one of the most potent tubulin polymerization inhibitors with minimal peripheral neuropathy, which is a big problem by some of the antimitotic agents such as taxanes and vinka alkaloids. With respect to this giant benefit, herein we decided to design and synthesize novel indibulin related compounds and investigate their anticancer activity against HT-29, Caco-2 and T47-D cancerous cell lines as well as NIH-T3T as normal cell line.

Objective:

The aim of this study was to synthesize new anti-cancer agents and evaluates their cytotoxic activity on diverse cancerous and normal cell lines.

Method:

Target compounds were synthesized in multistep reaction and cytotoxic activity was investigated by MTT cell viability assay.

Results:

Herein, nine novel target compounds were synthesized in moderate to good yield. Some of the compounds exerted good cytotoxic activity against cancerous cell lines. Annexin V/PI staining showed that compound 4g could induce apoptosis and necrosis in HT-29 cell line.

Conclusion:

It is valuable to do further investigation on compound 4g which showed the highest activity against HT-29 and Caco-2 (IC50 values are 6.9 and 7 &µM respectively). Also, synthesis of new derivatives of current synthesized compounds is suggested.

Design, synthesis and cytotoxicity evaluation of indibulin analogs

Indibulin is one of the most potent tubulin polymerization inhibitors with minimal peripheral neuropathy. The design and synthesis of new indibulin analogs were carried out in order to investigate their anti-cancer activity. The target compounds 4a–i were synthesized in multistep reactions starting with the related indole derivatives. Compound 4f shows the highest cytotoxic activity on HT-29 and Caco-2 cell lines with the respective half maximal inhibitory concentration (IC50) values of 5.1 μm and 7.3 μm. In the case of the T47-D cell line, compound 4c exerts the best cytotoxic activity with an IC50 value of 11.5 μm. In the cell cycle analysis on HT-29 cells, compound 4f at 5.1 μm showed an increase in the percentage of cells in the sub-G1 phase. Altogether, nine target compounds were synthesized and characterized by infrared spectroscopy (IR), proton nuclear magnetic resonance (1H NMR), carbon-13 nuclear magnetic resonance (13C NMR), mass spectrometry (MS) and elemental analysis. Some of the compounds show good cytotoxic activity against cancerous cell lines.

Induction of endoplasmic reticulum stress by aminosteroid derivative RM-581 leads to tumor regression in PANC-1 xenograft model

The high fatality and morbidity of pancreatic cancer have remained almost unchanged over the last decades and new clinical therapeutic tools are urgently needed. We determined the cytotoxic activity of aminosteroid derivatives RM-133 (androstane) and RM-581 (estrane) in three human pancreatic cancer cell lines (BxPC3, Hs766T and PANC-1). In PANC-1, a similar level of antiproliferative activity was observed for RM-581 and RM-133 (IC₅₀ = 3.9 and 4.3 μM, respectively), but RM-581 provided a higher selectivity index (SI = 12.8) for cancer cells over normal pancreatic cells than RM-133 (SI = 2.8). We also confirmed that RM-581 induces the same ER stress-apoptosis markers (BIP, CHOP and HERP) than RM-133 in PANC-1 cells, pointing out to a similar mechanism of action. Finally, these relevant in vitro results have been successfully translated in vivo by testing RM-581 using different doses (10-60 mg/kg/day) and modes of administration in PANC-1 xenograft models, which have led to tumor regression without any sign of toxicity in mice (animal weight, behavior and histology). Interestingly, RM-581 fully reduced the pancreatic tumor growth when administered orally in mice.

The first Pd-catalyzed Buchwald-Hartwig aminations at C-2 or C-4 in the estrone series

A facile Pd-catalyzed C(sp²)–N coupling to provide a range of 2- or 4-[(subst.)phenyl]amino-13α-estrone derivatives has been achieved under microwave irradiation. The reactions were mediated with the use of Pd(OAc)₂ as a catalyst and KOt-Bu as a base in the presence of X-Phos as a ligand. The desired products have been obtained in good to excellent yields. The nature and the position of the aniline substituent at the aromatic ring influenced the outcome of the couplings. 2-Amino-13α-estrone was also synthesized in a two-step protocol including an amination of 2-bromo-13α-estrone 3-benzyl ether with benzophenone imine and subsequent hydrogenolysis.

Implication of STARD5 and cholesterol homeostasis disturbance in the endoplasmic reticulum stress-related response induced by pro-apoptotic aminosteroid RM-133

The aminosteroid derivative RM-133 is an effective anticancer molecule for which proof of concept has been achieved in several mouse xenograph models (HL-60, MCF-7, PANC-1 and OVCAR-3). To promote this new family of molecules toward a clinical phase 1 trial, the mechanism of action governing the anticancer properties of the representative candidate RM-133 needs to be characterized. In vitro experiments were first used to determine that RM-133 causes apoptosis in cancer cells. Then, using proteomic and transcriptomic experiments, RM-133 cytotoxicity was proven to be achieved via the endoplasmic reticulum (ER)-related apoptosis, which characterizes RM-133 as an endoplasmic reticulum stress aggravator (ERSA) anticancer drug. Furthermore, an shRNA-genome-wide screening has permitted to identify the steroidogenic acute regulator-related lipid transfer protein 5 (STARD5) as a major player in the RM-133 ER-related apoptosis mechanism, which was validated by an in vitro binding experiment. Altogether, the results presented herein suggest that RM-133 provokes a disturbance of cholesterol homeostasis via the implication of STARD5, which delivers an ERSA molecule to the ER. These results will be a springboard for RM-133 in its path toward clinical use.