Chemical synthesis, NMR analysis and evaluation on a cancer xenograft model (HL-60) of the aminosteroid derivative RM-133

Synthesis and characterization of targeted 17β-hydroxysteroid dehydrogenase type 7 inhibitors

Sex steroid hormones such as estrogen estradiol (E2) and androgen dihydrotestosterone (DHT) are involved in the development of hormone-dependent cancers. Blockade of 17β-hydroxysteroid dehydrogenase type 7 (17β-HSD7), a member of the short chain dehydrogenase/reductase superfamily, is thought to decrease E2 levels while increasing those of DHT. Therefore, its unique double action makes this enzyme as an interesting drug target for treatment of breast cancer. The chemical synthesis, molecular characterization, and preliminary biological evaluation as 17β-HSD7 inhibitors of novel carbamate derivatives 3 and 4 are described. Like previous 17β-HSD7 inhibitors 1 and 2, compounds 3 and 4 bear a hydrophobic nonyl side chain at the C-17β position of a 4-aza-5α-androstane nucleus, but compound 3 has an oxygen atom replacing the CH2 in the steroid A-ring C-2 position, while compound 4 has a C17-spiranic E-ring containing a carbamate function. They both inhibited the in vitro transformation of estrone (E1) into E2 by 17β-HSD7, but the introduction of a (17 R)-spirocarbamate is preferable to replacing C-2 methylene with an oxygen atom since compound 4 (IC50 = 63 nM) is an inhibitor 14 times more powerful than compound 3 (IC50 = 900 nM). Furthermore, when compared to the reference inhibitor 1 (IC50 = 111 nM), the use of a C17-spiranic E-ring made it possible to introduce differently the hydrophobic nonyl side chain, without reducing the inhibitory activity.

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.

Secosteroid-quinoline hybrids as new anticancer agents

An elegant approach to unknown secosteroid-quinoline hybrids is disclosed. A series of 13,17-secoestra-1,3,5(10)-trien-17-oic acid [N'-(iso)quinolylmethylene]hydrazides was prepared and these novel type of secosteroids was screened for antiproliferative activity against estrogen-responsive human breast cancer cell line MCF-7. Most of the synthesized compounds showed a cytotoxic effect superior to that of reference drug cisplatin; the lead compound exhibits the highest activity with the IC₅₀ value of about 0.8 μM and is 7 times more active than cisplatin. A high selectivity index was observed for the hit 13,17-secoestra-1,3,5(10)-trien-17-oic acid [N'-quinolylmethylene]hydrazides 2a and 2c. Compounds 2a and 2c evaluated in luciferase reporter assays exhibited high antiestrogenic potency which was superior to that of tamoxifen. These hit compounds were characterized by high activity against MCF-7 cells that retained towards multidrug-resistant NCI/ADR-RES cells.

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.

Microwave-enhanced synthesis of 26-amino-22-oxocholestanes and their cytotoxic activity

The synthesis of a series of 26-amino-22-oxocholestanes derived from diosgenin was accomplished via the substitution of an iodine atom at C-26 by primary and secondary amines. The reactions were conducted in refluxing acetonitrile and through microwave-assisted heating. The latter shows significant improvements in terms of reaction times going from hours to a few minutes or even seconds for completion. Only one of the selected amines, 4-aminourazole, did not yield the substitution product and the imine formation pathway was investigated instead, achieving the 26-iminourazole-22-oxocholestane. All the final products have been characterized and the cytotoxic activity of three of them has been evaluated in SiHa, MCF-7 and MDA tumor cell lines by the sulforhodamine B assay.

Coupling of Heteroaryl Halides with Chlorodifluoroacetamides and Chlorodifluoroacetate by Nickel Catalysis

A nickel-catalyzed cross-coupling of heteroaryl halides with chlorodifluoroacetamides and chlorodifluoroacetate has been developed. The combination of NiCl₂  ⋅ DME with 4,4'-diNon-bpy, co-ligand PPh₃ , and additive LiCl renders the catalytic system efficient for the synthesis of medicinal interest heteroaryldifluoroacetamides. The application of the method leads to short and highly efficient synthesis of biologically active molecules, providing a facile route for applications in medicinal chemistry and agrochemistry.

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.

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.

Synthesis, NMR Characterization, and Antileukemic Activity of N-Nonanoylpiperazinyl-5α-Androstane-3α,17β-Diol A-Ring Derivatives

The combination of an androstane-3,17-diol nucleus and a 2β-N-alkylamidopiperazino sidechain is important for the anticancer activity of a new family of steroid derivatives. As the structure-activity relationship studies have so far been limited to the beta orientation of the substituent at position 2 of the steroid nucleus, a series of analogs (compounds 1–4) were synthesized to investigate the impact on biological activity of A-ring substitution. Nuclear magnetic resonance (NMR) analysis, especially using a series of 2D experiments, such as correlation spectroscopy (COSY), homonuclear Overhauser effect spectroscopy (NOESY), heteronuclear single-quantum correlation (HSQC), and heteronuclear multiple-bond correlation (HMBC) provided crucial information that was found essential in confirming the sidechain position and orientation of compounds 1–4. Assessment of their antiproliferative activity on leukemia HL-60 cells confirmed the best efficiency of the 2β-sidechain/3α-OH orientation (compound 1) compared to the other configurations tested (compounds 2–4).

Synthesis of 17β-hydroxysteroid dehydrogenase type 10 steroidal inhibitors: Selectivity, metabolic stability and enhanced potency

17beta-Hydroxysteroid dehydrogenase type 10 (17β-HSD10) is the only mitochondrial member of 17β-HSD family. This enzyme can oxidize estradiol (E2) into estrone (E1), thus reducing concentration of this neuroprotective steroid. Since 17β-HSD10 possesses properties that suggest a possible role in Alzheimer's disease, its inhibition appears to be a therapeutic strategy. After we identified the androsterone (ADT) derivative 1 as a first steroidal inhibitor of 17β-HSD10, new analogs were synthesized to increase the metabolic stability, to improve the selectivity of inhibition over 17β-HSD3 and to optimize the inhibitory potency. From six D-ring derivatives of 1 (17-CO), two compounds (17β-H/17α-OH and 17β-OH/17α-CCH) were more metabolically stable and did not inhibit the 17β-HSD3. Moreover, solid phase synthesis was used to extend the molecular diversity on the 3β-piperazinylmethyl group of the steroid base core. Eight over 120 new derivatives were more potent inhibitors than 1 for the transformation of E2 to E1, with the 4-(4-trifluoromethyl-3-methoxybenzyl)piperazin-1-ylmethyl-ADT (D-3,7) being 16 times more potent (IC₅₀ = 0.14 μM). Finally, D-ring modification of D-3,7 provided 17β-OH/17α-CCH derivative 25 and 17β-H/17α-OH derivative 26, which were more potent inhibitor than 1 (1.8 and 2.4 times, respectively).

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.

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.

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

Anticancer structure-activity relationship studies on aminosteroid (5α-androstane) derivatives have emerged with a promising lead candidate: RM-133 (2β-[1-(quinoline-2-carbonyl)pyrrolidine-2-carbonyl]-N-piperazine-5α-androstane-3α,17β-diol), which possesses high in vitro and in vivo activities against several cancer cells, and selectivity over normal cells. However, the relatively weak metabolic stability of RM-133 has been a drawback to its progression toward clinical trials. We investigated the replacement of the androstane backbone by a more stable mestranol moiety. The resulting compound, called RM-581 ({4-[17α-ethynyl-17β-hydroxy-3-methoxyestra-1,3,5(10)-trien-2-yl]piperazin-1-yl}[(2S)-1-(quinolin-2-ylcarbonyl)pyrrolidin-2-yl]methanone), was synthesized efficiently in only five steps from commercially available estrone. In comparison with RM-133, RM-581 was found to be twice as metabolically stable, retains potent cytotoxic activity in breast cancer MCF-7 cell culture, and fully blocks tumor growth in a mouse xenograft model of breast cancer. Advantageously, the selectivity over normal cells has been increased with this estrane version of RM-133. In fact, RM-581 showed a better selectivity index (15.3 vs. 3.0) for breast cancer MCF-7 cells over normal breast MCF-10A cells, and was found to be nontoxic toward primary human kidney proximal tubule cells at doses reaching 50 μm.

Explorative study on the anticancer activity, selectivity and metabolic stability of related analogs of aminosteroid RM-133

RM-133 is a key representative of a new family of aminosteroids reported as potent anticancer agents. Although RM-133 produced interesting results in 4 mouse xenograft cancer models when injected subcutaneously, it needs to be improved to increase its in vivo potency. Thus, to obtain an analog of RM-133 with a better drug potential, a structure-activity relationship study was conducted by synthesizing eleven RM-133-related compounds and addressing their antiproliferative activity on 3 human cancer cells (HL-60, OVCAR-3 and PANC-1) and 3 human normal cell lines (primary ovary, pancreas and renal proximal tubule) as well as their metabolic stability in human liver microsomes. When the 2β-tertiary amine of RM-133 was transformed into a salt or moved to position 3β, the anticancer activity was lost. Modifying the orientation of the side chain of RM-133 increased anticancer activity and selectivity, but led to a drastic loss of stability. The protection of the 3α-hydroxyl of RM-133 by the formation of an ester or a carbamate stabilized the molecule against the phase I metabolic enzymes without affecting its anticancer activity. In comparison to RM-133, the 3-dimethylcarbamate derivative 3 is more selective for cancer cells over normal cells and is much more stable in liver microsomes. Those results support the use of a pro-drug strategy targeting the 3α-hydroxyl of RM-133 as an approach to improve its drug properties. The work presented will enable the development of an optimized anticancer drug of the aminosteroid family that is suitable for a future phase I clinical trial.

Solid-phase synthesis of libraries of ethynylated aminosteroid derivatives as potential antileukemic agents

Steroids possessing an ethynyl group at position 17α (tertiary alcohols) are well known to be more stable than their non-ethynyl analogs (secondary alcohols). To facilitate the development of new drugs with better metabolic stability, we developed a new diethylsilyl acetylenic linker allowing us to rapidly synthesize libraries of ethynylated steroid derivatives using a solid-phase strategy. To illustrate its usefulness, this linker was used to expand the molecular diversity of a lead compound having a hydroxy acetylenic pattern and to potentially find new compounds with interesting cytotoxic activity against leukemia cell lines. Herein, we report the chemical synthesis and the characterization of three libraries of ethynylated aminosteroid derivatives using the diethylacetylenic linker. We discuss their antiproliferative activities obtained in 2 leukemia cell lines (HL-60 and Jurkat), which results provided new structure-activity relationships. We also identified a new promising aminosteroid derivative with an azetidine moiety (compound B1) inhibiting 60% and 75% of HL-60 and Jurkat cell proliferation, respectively, at 1 μM. More generally, these results validate the use of a diethylsilyl acetylenic linker for researchers interested in generating libraries of alcohol derivatives with better stability and drug profile.

The Aminosteroid Derivative RM-133 Shows In Vitro and In Vivo Antitumor Activity in Human Ovarian and Pancreatic Cancers

Ovarian and pancreatic cancers are two of the most aggressive and lethal cancers, whose management faces only limited therapeutic options. Typically, these tumors spread insidiously accompanied first with atypical symptoms, and usually shift to a drug resistance phenotype with the current pharmaceutical armamentarium. Thus, the development of new drugs acting via a different mechanism of action represents a clear priority. Herein, we are reporting for the first time that the aminosteroid derivative RM-133, developed in our laboratory, displays promising activity on two models of aggressive cancers, namely ovarian (OVCAR-3) and pancreatic (PANC-1) cancers. The IC₅₀ value of RM-133 was 0.8 μM and 0.3 μM for OVCAR-3 and PANC-1 cell lines in culture, respectively. Based on pharmacokinetic studies on RM-133 using 11 different vehicles, we selected two main vehicles: aqueous 0.4% methylcellulose:ethanol (92:8) and sunflower oil:ethanol (92:8) for in vivo studies. Using subcutaneous injection of RM-133 with the methylcellulose-based vehicle, growth of PANC-1 tumors xenografted to nude mice was inhibited by 63%. Quite interestingly, RM-133 injected subcutaneously with the methylcellulose-based or sunflower-based vehicles reduced OVCAR-3 xenograft growth by 122% and 100%, respectively. After the end of RM-133 treatment using the methylcellulose-based vehicle, OVCAR-3 tumor growth inhibition was maintained for ≥ 1 week. RM-133 was also well tolerated in the whole animal, no apparent sign of toxicity having been detected in the xenograft studies.

Chemical synthesis, cytotoxicity, selectivity and bioavailability of 5α-androstane-3α,17β-diol derivatives

Aminosteroid derivatives represent a new family of compounds with promising antiproliferative activity over different cancer cell lines. Among all the aminosteroid derivatives synthesised in our laboratory, we have identified E-37P as one of the more potent when tested in vitro. Unfortunately, the pharmacokinetic properties of E-37P decrease its effectiveness when tested in vivo. To improve the bioavailability and increase the efficiency of aminosteroid E-37P, two series of analog compounds were synthesised by classic chemical synthesis, they were then characterized, and the concentration that inhibits 50% of cell proliferation (IC50) was determined on different cell lines. RM-133, a 5α-androstane-3α,17β-diol derivative with a quinoline nucleus at the end of the piperazine-proline side-chain at position 2β and an ethinyl at position 17α, showed very good antiproliferative activity among the five cancer cell lines studied (IC50=0.1, 0.1, 0.1, 2.0 and 1.1 μM for HL-60, MCF-7, T-47D, LNCaP and WEHI-3, respectively). Moreover, the plasmatic concentration of RM-133 at 3h, when injected subcutaneously in rats, was 2.3-fold higher than that of E-37P (151 vs 64.8 ng/mL). Furthermore, RM-133 weakly inhibited the two representative liver enzymes, CYP3A4 and CYP2D6, indicating a very low risk of drug-drug interactions. The cytotoxicity of RM-133 against normal cells was tested on peripheral blood lymphocytes (PBL) obtained from different donors and previously activated with phytohemagglutinin-L. PBL responded differently to treatment with RM-133, we observed a stimulation of cell proliferation and/or cytotoxicity in a dose-dependent manner. Based on these results, additional studies are currently underway to evaluate the selectivity of our lead compound against normal cell lines in a more detailed fashion.