Potent Isomer Research Articles

Discovery of Novel MyD88 Inhibitor A5S to Alleviate Acute Lung Injury with Favorable Drug-like Properties.

Myeloid differentiation primary response 88 (MyD88) plays a central role in inflammatory responses and diseases. However, only a few inhibitors of MyD88 with some limits have been reported currently. Herein, we identified a lead compound (L7) through virtual screening and synthesized twenty-seven L7 derivatives. An optimal compound (A5) was determined through enzyme-linked immunosorbent assay (ELISA), 2,5-diphenyl-2H-tetrazolium bromide (MTT), and biolayer interferometry (BLI) assay. The potent isomer A5S showed a high MyD88 binding ability and exerted an anti-inflammatory effect through the NF-κB/MAPK pathway. A5S had good stability and safety, showed the highest distribution concentration in the lungs, and exhibited good therapeutic effects on LPS-induced and sepsis-induced ALI mouse models. Most importantly, A5S showed advantages in PK properties, and was identified as a promising MyD88 inhibitor with favorable drug-like properties, compared to the only approved MyD88 inhibitor, TJ-M2010-5, which is currently undergoing a Phase I study, and our previously reported MyD88 inhibitors LM8.

Stretching the structural envelope of imatinib to reduce β-amyloid production by modulating both β- and γ-secretase cleavages of APP.

We previously showed that the anticancer drug imatinib mesylate (IMT, trade name: Gleevec) and a chemically distinct compound, DV2-103 (a kinase-inactive derivative of the potent Abl and Src kinase inhibitor, PD173955) lower Aβ levels at low micromolar concentrations primarily through a lysosome-dependent mechanism that renders APP less susceptible to proteolysis by BACE1 without directly inhibiting BACE1 enzymatic activity, or broadly inhibiting the processing of other BACE1 substrates. Additionally, IMT indirectly inhibits γ-secretase and stimulates autophagy, and thus may decrease Aβ levels through multiple pathways. In two recent studies we demonstrated similar effects on APP metabolism caused by derivatives of IMT and DV2-103. In the present study, we synthesized and tested radically altered IMT isomers (IMTi's) that possess medium structural similarity to IMT. Independent of structural similarity, these isomers manifest widely differing potencies in altering APP metabolism. These will enable us to choose the most potent isomers for further derivatization.

Synthesis of the Most Potent Isomer of μ-Conotoxin KIIIA Using Different Strategies.

In the chemical synthesis of conotoxins with multiple disulfide bonds, the oxidative folding process can result in diverse disulfide bond connectivities, which presents a challenge for determining the natural disulfide bond connectivities and leads to significant structural differences in the synthesized toxins. Here, we focus on KIIIA, a μ-conotoxin that has high potency in inhibiting Nav1.2 and Nav1.4. The non-natural connectivity pattern (C1-C9, C2-C15, C4-C16) of KIIIA exhibits the highest activity. In this study, we report an optimized Fmoc solid-phase synthesis of KIIIA using various strategies. Our results indicate that free random oxidation is the simplest method for peptides containing triple disulfide bonds, resulting in high yields and a simplified process. Alternatively, the semi-selective strategy utilizing Trt/Acm groups can also produce the ideal isomer, albeit with a lower yield. Furthermore, we performed distributed oxidation using three different protecting groups, optimizing their positions and cleavage order. Our results showed that prioritizing the cleavage of the Mob group over Acm may result in disulfide bond scrambling and the formation of new isomers. We also tested the activity of synthesized isomers on Nav1.4. These findings provide valuable guidance for the synthesis of multi-disulfide-bonded peptides in future studies.

Whole-body inhalation exposure to 2-ethyltoluene for two weeks produced nasal lesions in rats and mice

Objective Ethyltoluenes are isolated during crude oil refinement for use in gasoline and commercial products and are ubiquitous in the environment. However, minimal toxicity data are available. Previously, we identified 2-ethyltoluene (2-ET) as the most potent isomer via nose-only inhalation exposure in rodents. Here, we expanded the hazard characterization of 2-ET in two rodent models using whole-body inhalation exposure and evaluated the role of prenatal exposure. Methods Time-mated Hsd:Sprague Dawley® SD® rats were exposed to 0, 150, 300, 600, 900, or 1200 ppm 2-ET via inhalation starting on gestation day 6 until parturition. Rat offspring (n = 8/exposure/sex) were exposed to the same concentrations as the respective dams for 2 weeks after weaning. Adult male and female B6C3F1/N mice (n = 5/exposure/sex) were exposed to the same concentrations for 2 weeks. Results and Discussion Exposure to ≥600 ppm 2-ET produced acute toxicity in rats and mice characterized by large decreases in survival, body weight, adverse clinical observations, and diffuse nasal olfactory epithelium degeneration (rats) or necrosis (mice). Due to the early removal of groups ≥600 ppm, most endpoint evaluations focused on lower exposure groups. In 150 and 300 ppm exposure groups, reproductive performance and littering were not significantly changed and body weights in exposed rats and mice were 9–18% lower than controls. Atrophy of the olfactory epithelium and nerves was observed in all animals exposed to 150 and 300 ppm. These lesions were more severe in mice than in rats. Conclusion Nasal lesions were observed in all animals after whole-body exposure up to 600 ppm 2-ET for 2 weeks. Future studies should focus on 2-ET metabolism and distribution to better understand species differences and refine hazard characterization of this understudied environmental contaminant.

Divergent Solid-Phase Synthesis and Biological Evaluation of Yaku'amide B and Its Seven E/Z Isomers.

Yaku'amide B (1) inhibits cancer cell growth through a unique mechanism of action. Compound 1 binds to mitochondrial Fo F1 -ATP synthase, inhibits ATP production, and enhances ATP hydrolysis. The presence of one (E)- and two (Z)-α,β-dehydroisoleucines (ΔIle) in the linear 13-mer sequence is the most unusual structural feature of 1. To uncover the biological importance of these residues, we synthesized 1 and its seven E/Z isomers 2-8 by devising a new divergent solid-phase strategy. Both the (E)- and (Z)-ΔIle residues were stereoselectively constructed by traceless Staudinger ligation on resin to ultimately deliver 1-8. All isomers 2-8 displayed effects on the inhibition of cell growth and ATP production, and enhanced ATP hydrolysis, thus indicating that 2-8 share the same mode of action as 1. The least potent isomer, 8, was isomeric at three ΔIle residues of the most potent 1. These findings together indicate that the E/Z stereochemistry of the three ΔIle residues controls the magnitude of the biological functions of 1.

Assessment of Ketamine and its Enantiomers in an Organophosphate-Based Rat Model for Features of Gulf War Illness

Approximately 33% of U.S. soldiers from the first Gulf War suffer from a multi-system disorder known as the Gulf War Illness (GWI). GW veterans suffer from a cluster of symptoms that prominently include fatigue and can include mood-related symptoms. Compared to traditional antidepressants, ketamine (KET) produces a fast-onset and long-lasting antidepressant response, but assessments of KET for GWI-related depression are lacking. The etiology of GWI is multi-factorial and exposure to organophosphates (OP) during deployment is one of the factors underlying GWI development. Here, male Sprague-Dawley rats were repeatedly exposed to an OP DFP and three months later these rats, when assessed on a battery of rodent behavioral assays, displayed signs consistent with aspects of GWI characteristics. When treated with a sub-anesthetic dose of KET (3, 5, or 10 mg/kg, i.p.), DFP-treated rats exhibited a significant improvement in immobility time, open-arm exploration, and sucrose consumption as early as 1 h and much of these effects persisted at 24-h post-KET injection. KET’s stereoisomers, R-KET and S-KET, also exhibited such effects in DFP rats, with R-KET being the more potent isomer. Our studies provide a starting point for further assessment of KET for GWI depression.

4-chloro-orto-cresol activates ryanodine receptor more selectively and potently than 4-chloro-meta-cresol

In this study we performed the comprehensive pharmacological analysis of two stereoisomers of 4-chloro-meta-cresol (4CMC), a popular ryanodine receptor (RyR) agonist used in muscle research. Experiments investigating the Ca2+-releasing action of the isomers demonstrated that the most potent isomer was 4-chloro-orto-cresol (4COC) (EC50 = 55 ± 14 μM), although 3-chloro-para-cresol (3CPC) was more effective, as it was able to induce higher magnitude of Ca2+ flux from isolated terminal cisterna vesicles. Nevertheless, 3CPC stimulated the hydrolytic activity of the sarcoplasmic reticulum ATP-ase (SERCA) with an EC50 of 91 ± 17 μM, while 4COC affected SERCA only in the millimolar range (IC50 = 1370 ± 88 μM). IC50 of 4CMC for SERCA pump was 167 ± 8 μM, indicating that 4CMC is not a specific RyR agonist either, as it activated RyR in a similar concentration (EC50 = 121 ± 20 μM).Our data suggest that the use of 4COC might be more beneficial than 4CMC in experiments, when Ca2+ release should be triggered through RyRs without influencing SERCA activity.

Ginsenoside Rg3 stereoisomers differentially inhibit vascular smooth muscle cell proliferation and migration in diabetic atherosclerosis.

Ginsenoside 20(R/S)‐Rg3, as a natural peroxisome proliferator‐activated receptor gamma (PPARγ) ligand, has been reported to exhibit differential biological effects. It is of great interest to understand the stereochemical selectivity of 20(R/S)‐Rg3 and explore whether differential PPARγ activation by Rg3 stereoisomers, if it exists, could lead to differential physiological outcome and therapeutic effects in diabetic atherosclerosis. Here, we investigated the binding modes of 20(R/S)‐Rg3 stereoisomers in the PPARγ ligand‐binding domain (PPARγ‐LBD) using molecular modelling and their effects on smooth muscle cell proliferation and migration induced by advanced glycation end products (AGEs). The results revealed that 20(S)‐Rg3 exhibited stronger antiproliferative and antimigratory effects due to stronger PPARγ activation. To validate the in vitro results, we used a mice model with diabetic atherosclerosis and obtained that 20(S)‐Rg3 markedly reduced the plaque size secondary to reducing the proliferation and migration of VSMCs, while the plaques were more stable due to improvements in other plaque compositions. The results shed light on the structural difference between Rg3 stereoisomers that can lead to significant differential physiological outcome, and the (S)‐isomer seems to be the more potent isomer to be developed as a promising drug for diabetic atherosclerosis.

Comparative inhalation toxicity of ethyltoluene isomers in rats and mice

The C9 alkylbenzenes, composed mostly of ethyltoluenes and trimethylbenzenes, comprise 75–90% of the naphtha fraction of crude oil. Occupational and environmental exposure to C9 alkylbenzenes occur via inhalation. We conducted short-term inhalation studies on the ethyltoluene isomers (2-, 3- or 4-) to select one isomer for more comprehensive studies. Male Hsd:Sprague Dawley rats and female B6C3F1/N mice (n = 10) were exposed by nose-only inhalation to 2-, 3- or 4-ethyltoluene (0, 1000 or 2000 ppm) or cumene (a reference compound: 0, 500 or 1000 ppm) 3 h/day, 5 days/week, for 2 weeks. Clinical observations included abnormal gait and delayed righting reflex. Rats and mice exposed to 2000 ppm 2-ethyltoluene and mice exposed to 2000 ppm 4-ethyltoluene were euthanized early in moribund condition; no exposure-related deaths were observed with 3-ethyltoluene or cumene. Histopathology of selected tissues revealed that the nose and liver (rats and mice) and lung (mice only) to be toxicity targets. In the mouse lung, all compounds except 4-ethyltoluene produced bronchial and bronchiolar hyperplasia. In rats and mice, 2-ethyltoluene was the only compound to produce lesions in the nose and liver: in mice, squamous metaplasia and neutrophilic inflammation of the respiratory epithelium and atrophy and degeneration of the olfactory epithelium were observed in the nose and centrilobular hypertrophy and necrosis were observed in the liver. In rats, 2-ethyltoluene exposure produced atrophy of the olfactory epithelium in the nose and centrilobular necrosis in the liver. Based on mortality, body weight effects and histopathology, the 2-ethyltoluene isomer was the most potent isomer.

Optimization of 3-Pyrimidin-4-yl-oxazolidin-2-ones as Allosteric and Mutant Specific Inhibitors of IDH1.

High throughput screening and subsequent hit validation identified 4-isopropyl-3-(2-((1-phenylethyl)amino)pyrimidin-4-yl)oxazolidin-2-one as a potent inhibitor of IDH1R132H. Synthesis of the four separate stereoisomers identified the (S,S)-diastereomer (IDH125, 1f) as the most potent isomer. This also showed reasonable cellular activity and excellent selectivity vs IDH1wt. Initial structure-activity relationship exploration identified the key tolerances and potential for optimization. X-ray crystallography identified a functionally relevant allosteric binding site amenable to inhibitors, which can penetrate the blood-brain barrier, and aided rational optimization. Potency improvement and modulation of the physicochemical properties identified (S,S)-oxazolidinone IDH889 (5x) with good exposure and 2-HG inhibitory activity in a mutant IDH1 xenograft mouse model.

Delta- and gamma-tocotrienol isomers are potent in inhibiting inflammation and endothelial activation in stimulated human endothelial cells

BackgroundTocotrienols (TCTs) are more potent antioxidants than α-tocopherol (TOC). However, the effectiveness and mechanism of the action of TCT isomers as anti-atherosclerotic agents in stimulated human endothelial cells under inflammatory conditions are not well established.Aims1) To compare the effects of different TCT isomers on inflammation, endothelial activation, and endothelial nitric oxide synthase (eNOS). 2) To identify the two most potent TCT isomers in stimulated human endothelial cells. 3) To investigate the effects of TCT isomers on NFκB activation, and protein and gene expression levels in stimulated human endothelial cells.MethodsHuman umbilical vein endothelial cells were incubated with various concentrations of TCT isomers or α-TOC (0.3–10 µM), together with lipopolysaccharides for 16 h. Supernatant cells were collected and measured for protein and gene expression of cytokines (interleukin-6, or IL-6; tumor necrosis factor-alpha, or TNF-α), adhesion molecules (intercellular cell adhesion molecule-1, or ICAM-1; vascular cell adhesion molecule-1, or VCAM-1; and e-selectin), eNOS, and NFκB.Resultsδ-TCT is the most potent TCT isomer in the inhibition of IL-6, ICAM-1, VCAM-1, and NFκB, and it is the second potent in inhibiting e-selectin and eNOS. γ-TCT isomer is the most potent isomer in inhibiting e-selectin and eNOS, and it is the second most potent in inhibiting is IL-6, VCAM-1, and NFκB. For ICAM-1 protein expression, the most potent is δ-TCT followed by α-TCT. α- and β-TCT inhibit IL-6 at the highest concentration (10 µM) but enhance IL-6 at lower concentrations. γ-TCT markedly increases eNOS expression by 8–11-fold at higher concentrations (5–10 µM) but exhibits neutral effects at lower concentrations.Conclusionδ- and γ-TCT are the two most potent TCT isomers in terms of the inhibition of inflammation and endothelial activation whilst enhancing eNOS, possibly mediated via the NFκB pathway. Hence, there is a great potential for TCT isomers as anti-atherosclerotic agents.

α-Tocopherol suppresses antiangiogenic effect of δ-tocotrienol in human umbilical vein endothelial cells

Recently, tocotrienol (T3), a less well-known form of vitamin E, has gained attention as a potent hypocholesterolemic, anticancer and antiangiogenic agent. However, tocopherol (Toc), a commonly consumed form of vitamin E, has been reported to inhibit T3’s effects (hypocholesterolemic and anticancer activity). There has been no report on Toc’s effect on the antiangiogenic action of T3 during cotreatment. The aim of this study is to determine if and to what extent Toc affects the antiangiogenic effects of δ-T3 (the most potent isomer). This was achieved through cotreatment of human umbilical vein endothelial cells (HUVECs) with δ-T3 and Toc (α-, β-, γ- and δ-isomers). Toc, especially α-Toc, attenuated δ-T3-induced cytotoxicity and tube degradation in cotreated HUVECs, while α-Toc treatments did not exhibit any effects. A rat aortic ring assay also showed inhibition of δ-T3’s antiangiogenic effects by α-Toc. Further, in HUVEC study, cell cycle arrest and proapoptotic gene expression (p21, p27, caspase-3 and caspase-9) which were induced by δ-T3 were decreased by α-Toc treatment. α-Toc also suppressed δ-T3-induced dephosphorylation of vascular endothelial growth factor receptor 2 and Akt pathway proteins. Additionally, uptake of δ-T3 into HUVECs was decreased by α-Toc. Here we demonstrate that α-Toc not only has little antiangiogenic effect on endothelial cells but also reduces the antiangiogenic effects of δ-T3 through modulation of its cellular uptake and of relevant signal transduction pathways. Understanding T3’s antiangiogenic effects and interaction with Toc is important for developing medical applications.

Isomer-specific comparisons of the hydrolysis of synthetic pyrethroids and their fluorogenic analogues by esterases from the cotton bollworm Helicoverpa armigera

The low aqueous solubility and chiral complexity of synthetic pyrethroids, together with large differences between isomers in their insecticidal potency, have hindered the development of meaningful assays of their metabolism and metabolic resistance to them. To overcome these problems, Shan and Hammock (2001) [7] therefore developed fluorogenic and more water-soluble analogues of all the individual isomers of the commonly used Type 2 pyrethroids, cypermethrin and fenvalerate. The analogues have now been used in several studies of esterase-based metabolism and metabolic resistance. Here we test the validity of these analogues by quantitatively comparing their hydrolysis by a battery of 22 heterologously expressed insect esterases with the hydrolysis of the corresponding pyrethroid isomers by these esterases in an HPLC assay recently developed by Teese et al. (2013) [14]. We find a strong, albeit not complete, correlation (r = 0.7) between rates for the two sets of substrates. The three most potent isomers tested were all relatively slowly degraded in both sets of data but three esterases previously associated with pyrethroid resistance in Helicoverpa armigera did not show higher activities for these isomers than did allelic enzymes derived from susceptible H. armigera. Given their amenability to continuous assays at low substrate concentrations in microplate format, and ready detection of product, we endorse the ongoing utility of the analogues in many metabolic studies of pyrethroids.

Pure Diastereomers of a Tranylcypromine-Based LSD1 Inhibitor: Enzyme Selectivity and In-Cell Studies.

The pure four diastereomers (11a-d) of trans-benzyl (1-((4-(2-aminocyclopropyl)phenyl)amino)-1-oxo-3-phenylpropan-2-yl)carbamate hydrochloride 11, previously described by us as LSD1 inhibitor, were obtained by enantiospecific synthesis/chiral HPLC separation method. Tested in LSD1 and MAO assays, 11b (S,1S,2R) and 11d (R,1S,2R) were the most potent isomers against LSD1 and were less active against MAO-A and practically inactive against MAO-B. In cells, all the four diastereomers induced Gfi-1b and ITGAM gene expression in NB4 cells, accordingly with their LSD1 inhibition, and 11b and 11d inhibited the colony forming potential in murine promyelocytic blasts.

Chiral HPLC Method for the Novel Triazole Antitubercular Compound MSDRT 12

Cyclohex-3-enyl(5-phenyl-4H-1,2,4-triazol-3-yl)methanol (MSDRT 12) is a novel triazole-based antitubercular compound with two chiral centres. Evaluation of the enantio-specific antitubercular activity has established that the stereoisomer 3 of MSDRT12 (Isomer 3) was the most potent isomer with a minimum inhibitory concentration of 0.78 μg/mL. The other stereoisomers show negligible or no activity. A sensitive, simple, specific, precise and accurate chiral chromatographic method for the direct analysis of the four stereoisomers of MSDRT 12 and the active Isomer 3 has been developed and validated. The method has also been validated for analysing the stereoisomeric impurities Isomer 1, Isomer 2 and Isomer 4 in the active Isomer 3. The separation of the four stereoisomers of MSDRT 12 was achieved using an immobilized polysaccharide-based column, Chiralpak ID with amylose tris(3-chlorophenylcarbamate) as the chiral selector. The separation was performed using a mixture of n-hexane, isopropyl alcohol, ethanol and diethylamine (60:35:5:0.1 v/v/v/v) at a flow rate of 1 mL/min. The method offers excellent separation of the four stereoisomers with resolution more than 1.5 and tailing factor <1.5. The standard curves were linear over the concentration range 5–500 μg/mL and 0.40–505 μg/mL for MSDRT 12 and Isomer 3, respectively. Excellent linearity in the range 0.4–5 μg/mL was obtained for Isomer 1, Isomer 2 and Isomer 4 and these stereoisomeric impurities could be accurately and precisely quantified at a level of 0.1 % of the active isomer.

Isolation and Evaluation of the Enantiospecific Antitubercular Activity of a Novel Triazole Compound

Cyclohex-3-enyl(5-phenyl-4H-1,2,4-triazol-3-yl)methanol (MSDRT 12) is a novel triazole-based antitubercular compound with two chiral centers. To evaluate the enantiospecific antitubercular activity, the four stereoisomers were isolated using preparative chiral chromatography and the individual stereoisomers were evaluated using the resazurin microtiter assay method (REMA) and a microbroth dilution technique against the Mycobacterium tuberculosis H37Rv strain. Isomer III of MSDRT 12 was found to be the most potent with a minimum inhibitory concentration (MIC) of 0.78 μg/mL, Isomer II had a MIC of 12.5 μg/mL, and isomers I and IV showed no activity. The diastereomeric mixture of MSDRT 12 showed a MIC of 3.125 μg/mL and isoniazid, used as the standard drug, showed a MIC of 0.4 μg/mL. This confirms the necessity of screening individual enantiomers for their pharmacological activity early in the discovery phase to identify the most potent isomer for further development efforts.

The Sweetness Concentration‐Response of R,R‐Monatin, a Naturally Occurring High‐Potency Sweetener

Monatin, known by the common and usual name arruva, is a zero-calorie, high-potency sweetener naturally occurring in the plant Sclerochiton ilicifolius A.Meeuse. The sweetness concentration-response (C-R) behavior of the most potent isomer (R,R-) in room-temperature (21 °C) water was determined using two-alternative forced choice discrimination tests with a minimum of 69 tasters. Results were processed by a method previously published to obtain isosweet concentrations of sucrose for 8 monatin concentrations up to 240 mg/L. These were used to construct a C-R plot. The equation for the resultant hyperbolic curve relating sucrose equivalent (SE,%) to monatin concentration ([monatin], mg/L) was SE = 26.7 ×[monatin]/(69.6 +[monatin]). R,R-monatin has a potency above 3000 at 5% sucrose equivalent, making it one of the most potently sweet naturally occurring substances known. Monatin is a naturally occurring, zero-calorie, high-potency sweetener. We have measured the sweetness of monatin over a range of concentrations. This information will help developers of zero-, low- and reduced-calorie products formulate with monatin.

Free radical scavenging activity of conjugated linoleic acid as single or mixed isomers

Context: Conjugated linoleic acids (CLAs) are a mixture of positional and geometric isomers of linoleic acid (LA) and believed to have many positive biological activities.Objective: The present study was undertaken to assess the antioxidant activity of cis-9, trans-11 and trans-10, cis-12 as single or mixed CLA isomers at two ratios, 1:6 and 1:13 (trans-10, cis-12/cis-9, trans-11).Materials and methods: A microplate reader was used to determine the free radical scavenging properties of CLAs against DPPH radical in ethanol.Results: The kinetic reactions of CLA-DPPH• showed that all tested CLAs have exerted radical scavenging activities in a dose-dependent manner and observed to immediately react and quench DPPH radicals at all tested levels and no lag phase was noticed in CLA-DPPH• reactions. The median inhibitory concentration (IC50) value for cis-9, trans-11 CLA was observed to be more effective than other tested CLA. Total antioxidant capacity (TAC) of all tested CLAs were less effective radical scavengers as compared to vitamin E and butylated hydroxytoluene, although all tested CLAs were quenched a high amount (P < 0.05) of DPPH free radicals.Discussion and conclusion: All tested CLAs have the ability to directly react and quench DPPH free radicals in ethanol. Furthermore, trans-10, cis-12 CLA has greater maximal efficacy than other tested CLAs as free radical scavenger, while cis-9, trans-11 CLA is the most potent isomer to directly react and quench free radicals at low concentrations in the system, suggesting that the free radical scavenging activity of CLA isomers may contribute to their diverse biological activities.

Diarylpropionitrile (DPN) Enantiomers: Synthesis and Evaluation of Estrogen Receptor β-Selective Ligands

Two estrogen receptor (ER) subtypes, ERα and ERβ, mediate the actions of estrogens in diverse reproductive and nonreproductive target tissues. ER subtype-selective ligands, which bind to and activate these subtypes differentially, have proved to be useful in elucidating which actions of estrogens proceed through ERα vs ERβ. Some of these ligands show potential as novel therapeutic agents. Diarylpropionitrile (DPN), an ERβ selective ligand that we developed, is a chiral molecule, but it has been studied almost exclusively as the racemic mixture (rac-DPN, 1). Herein we report the development of an efficient enantioselective synthesis of the two isomers, R-DPN (3) and S-DPN (2), and we have compared the in vitro ligand binding affinities, coactivator binding affinities, recruitment potencies, and cellular transcriptional potencies of these isomers. Both enantiomers show a very high affinity and potency preference for ERβ over ERα, typically in the range of 80-300-fold. Although the enantioselectivity is only modest (3-4-fold), the R-enantiomer is the higher affinity and more potent isomer. While ERβ can be effectively and selectively stimulated by rac-DPN or by either R-DPN or S-DPN, R-DPN might be the preferred member of this isomeric series for biological studies of ERβ function.

Abstract 1732: Synthesis and evaluation of NSC23925 isomers to reverse multidrug resistance in cancer

Abstract The eventual development of multidrug resistance (MDR) during the course of chemotherapy treatment is a fundamental obstacle associated with cancer care. Prior studies have identified NSC23925 ((2-(4-methoxyphenyl)-4-quinolinyl) (2-piperidinyl) methanol)) to be a small molecule agent that reverses MDR in cancer cells. Analysis of the structure of NSC23925 indicates that NSC23925 has two chiral centers which lead to 4 different stereo-isomers (erythro-7a, threo-7b, threo-9a and erythro-9b). Each isomer may or may not have distinct bio-activity from the others. In this study, we synthesized all four isomers of NSC23925 and analyzed by liquid chromatography-mass spectrometry (LCMS, HPLC-MS). Structure and activity relationships for reversing MDR in several MDR human cancer cell lines were evaluated by MTT assay. We observed that compound erythro-9b (NSC23925-9b) is the most potent isomer on reversing drug resistance, threo-7b and threo-9a also showed modest but lesser activity, and Erythro-7a showed the least potency. NSC23925-9b is able to reverse MDR in several drug resistant cell lines expressing Pgp in vitro, including ovarian, breast, colon, and sarcoma cancer cell lines. NSC23925-9b was able to re-sensitize these cell lines to paclitaxel, doxorubicin, vincristine and ET-743 with no effect on cell sensitivity to cisplatin, topotecan and methotrexate. NSC23925-9b was unable to reverse drug resistance in non-Pgp expressing drug resistant cell lines. Furthermore, NSC23925-9b significantly enhanced in vivo antitumor activity of paclitaxel in MDR ovarian cancer cell line SKOV-3TR xenograft models, without significant increasing the level of paclitaxel toxicity. In conclusion, these results demonstrated that NSC23925-9b and derivatives of this compound may hold therapeutic value in the treatment of MDR dependent cancers. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1732. doi:10.1158/1538-7445.AM2011-1732