Channeling Nicotinamide Phosphoribosyltransferase (NAMPT) to Address Life and Death

Nicotinamide phosphoribosyltransferase (NAMPT) catalyzes the rate-limiting step in NAD+ biosynthesis via salvage of NAM formed from catabolism of NAD+ by proteins with NADase activity (e.g., PARPs, SIRTs, CD38). Depletion of NAD+ in aging, neurodegeneration, and metabolic disorders is addressed by NAD+ supplementation. Conversely, NAMPT inhibitors have been developed for cancer therapy: many discovered by phenotypic screening for cancer cell death have low nanomolar potency in cellular models. No NAMPT inhibitor is yet FDA-approved. The ability of inhibitors to act as NAMPT substrates may be associated with efficacy and toxicity. Some 3-pyridyl inhibitors become 4-pyridyl activators or "NAD+ boosters". NAMPT positive allosteric modulators (N-PAMs) and boosters may increase enzyme activity by relieving substrate/product inhibition. Binding to a "rear channel" extending from the NAMPT active site is key for inhibitors, boosters, and N-PAMs. A deeper understanding may fulfill the potential of NAMPT ligands to regulate cellular life and death.

Structure-Guided Design and Synthesis of Pyridinone-Based Selective Bromodomain and Extra-Terminal Domain (BET)-First Bromodomain (BD1) Inhibitors

The bromodomain and extra-terminal domain (BET) proteins are epigenetic readers, regulating transcription via two highly homologous tandem bromodomains, BD1 and BD2. Clinical development of nonselective pan-BD BET inhibitors has been challenging, partly due to dose-limiting side effects such as thrombocytopenia. This has prompted the push for domain-selective BET inhibitors to achieve a more favorable therapeutic window. We report a structure-guided drug design campaign that led to the development of a potent BD1-selective BET inhibitor, 33 (XL-126), with a Kd of 8.9 nM and 185-fold BD1/BD2 selectivity. The high selectivity was first assayed by SPR, validated by a secondary time-resolved fluorescence energy transfer assay, and further corroborated by BROMOscan (∼57-373 fold selectivity). The cocrystal of 33 with BRD4 BD1 and BD2 demonstrates the source of selectivity: repulsion with His437 and lost binding with the leucine clamp. Notably, the BD1 selectivity of BET inhibitor 33 leads to both the preservation of platelets and potent anti-inflammatory efficacy.

Nicotinamide Phosphoribosyltransferase Positive Allosteric Modulators Attenuate Neuronal Oxidative Stress

Evidence supports boosting nicotinamide adenine dinucleotide (NAD+) to counteract oxidative stress in aging and neurodegenerative disease. One approach is to enhance the activity of nicotinamide phosphoribosyltransferase (NAMPT). Novel NAMPT positive allosteric modulators (N-PAMs) were identified. A cocrystal structure confirmed N-PAM binding to the NAMPT rear channel. Early hit-to-lead efforts led to a 1.88-fold maximum increase in the level of NAD+ in human THP-1 cells. Select N-PAMs were assessed for mitigation of reactive oxygen species (ROS) in HT-22 neuronal cells subject to inflammatory stress using tumor necrosis factor alpha (TNFα). N-PAMs that increased NAD+ more effectively in THP-1 cells attenuated TNFα-induced ROS more effectively in HT-22 cells. The most efficacious N-PAM completely attenuated ROS elevation in glutamate-stressed HT-22 cells, a model of neuronal excitotoxicity. This work demonstrates for the first time that N-PAMs are capable of mitigating elevated ROS in neurons stressed with TNFα and glutamate and provides support for further N-PAM optimization for treatment of neurodegenerative diseases.

Synthesis, Optimization, and Structure-Activity Relationships of Nicotinamide Phosphoribosyltransferase (NAMPT) Positive Allosteric Modulators (N-PAMs)

Depletion of nicotinamide adenine dinucleotide (NAD+) is associated with aging and disease, spurring the study of dietary supplements to replenish NAD+. The catabolism of NAD+ to nicotinamide (NAM) requires the salvage of NAM to replenish cellular NAD+, which relies on the rate-limiting enzyme nicotinamide phosphoribosyltransferase (NAMPT). Pharmacological activation of NAMPT provides an alternative to dietary supplements. Screening for activators of NAMPT identified small molecule NAMPT positive allosteric modulators (N-PAMs). N-PAMs bind to the rear channel of NAMPT increasing enzyme activity and alleviating feedback inhibition by NAM and NAD+. Synthesis of over 70 N-PAMs provided an excellent correlation between rear channel binding affinity and potency for enzyme activation, confirming the mechanism of allosteric activation via binding to the rear channel. The mechanism accounts for higher binding affinity leading to loss of efficacy. Enzyme activation translated directly to elevation of NAD+ measured in cells. Optimization led to an orally bioavailable N-PAM.

Inhibition of ACAT as a Therapeutic Target for Alzheimer's Disease Is Independent of ApoE4 Lipidation

APOE4, encoding apolipoprotein E4 (apoE4), is the greatest genetic risk factor for Alzheimer's disease (AD), compared to the common APOE3. While the mechanism(s) underlying APOE4-induced AD risk remains unclear, increasing the lipidation of apoE4 is an important therapeutic target as apoE4-lipoproteins are poorly lipidated compared to apoE3-lipoproteins. ACAT (acyl-CoA: cholesterol-acyltransferase) catalyzes the formation of intracellular cholesteryl-ester droplets, reducing the intracellular free cholesterol (FC) pool. Thus, inhibiting ACAT increases the FC pool and facilitates lipid secretion to extracellular apoE-containing lipoproteins. Previous studies using commercial ACAT inhibitors, including avasimibe (AVAS), as well as ACAT-knock out (KO) mice, exhibit reduced AD-like pathology and amyloid precursor protein (APP) processing in familial AD (FAD)-transgenic (Tg) mice. However, the effects of AVAS with human apoE4 remain unknown. In vitro, AVAS induced apoE efflux at concentrations of AVAS measured in the brains of treated mice. AVAS treatment of male E4FAD-Tg mice (5xFAD+/-APOE4+/+) at 6-8 months had no effect on plasma cholesterol levels or distribution, the original mechanism for AVAS treatment of CVD. In the CNS, AVAS reduced intracellular lipid droplets, indirectly demonstrating target engagement. Surrogate efficacy was demonstrated by an increase in Morris water maze measures of memory and postsynaptic protein levels. Amyloid-beta peptide (Aβ) solubility/deposition and neuroinflammation were reduced, critical components of APOE4-modulated pathology. However, there was no increase in apoE4 levels or apoE4 lipidation, while amyloidogenic and non-amyloidogenic processing of APP were significantly reduced. This suggests that the AVAS-induced reduction in Aβ via reduced APP processing was sufficient to reduce AD pathology, as apoE4-lipoproteins remained poorly lipidated.

Non-covalent inhibitors of thioredoxin glutathione reductase with schistosomicidal activity in vivo

Only praziquantel is available for treating schistosomiasis, a disease affecting more than 200 million people. Praziquantel-resistant worms have been selected for in the lab and low cure rates from mass drug administration programs suggest that resistance is evolving in the field. Thioredoxin glutathione reductase (TGR) is essential for schistosome survival and a validated drug target. TGR inhibitors identified to date are irreversible and/or covalent inhibitors with unacceptable off-target effects. In this work, we identify noncovalent TGR inhibitors with efficacy against schistosome infections in mice, meeting the criteria for lead progression indicated by WHO. Comparisons with previous in vivo studies with praziquantel suggests that these inhibitors outperform the drug of choice for schistosomiasis against juvenile worms.

Mechanism of Allosteric Modulation of Nicotinamide Phosphoribosyltransferase to Elevate Cellular NAD. Biochemistry 2023;62:923-933. [PMID: 36746631 DOI: 10.1021/acs.biochem.2c00655]

In aging and disease, cellular nicotinamide adenine dinucleotide (NAD+) is depleted by catabolism to nicotinamide (NAM). NAD+ supplementation is being pursued to enhance human healthspan and lifespan. Activation of nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting step in NAD+ biosynthesis, has the potential to increase the salvage of NAM. Novel NAMPT-positive allosteric modulators (N-PAMs) were discovered in addition to the demonstration of NAMPT activation by biogenic phenols. The mechanism of activation was revealed through the synthesis of novel chemical probes, new NAMPT co-crystal structures, and enzyme kinetics. Binding to a rear channel in NAMPT regulates NAM binding and turnover, with biochemical observations being replicated by NAD+ measurements in human cells. The mechanism of action of N-PAMs identifies, for the first time, the role of the rear channel in the regulation of NAMPT turnover coupled to productive and nonproductive NAM binding. The tight regulation of cellular NAMPT via feedback inhibition by NAM, NAD+, and adenosine 5'-triphosphate (ATP) is differentially regulated by N-PAMs and other activators, indicating that different classes of pharmacological activators may be engineered to restore or enhance NAD+ levels in affected tissues.

Synthesis, Optimization, and Structure-Activity Relationships of Imidazo[1,2-a]pyrimidines as Inhibitors of Group 2 Influenza A Viruses

The influenza A virus (IAV) is a highly contagious virus that causes pandemics and seasonal epidemics, which are major public health issues. Current anti-influenza therapeutics are limited partly due to the continuous emergence of drug-resistant IAV strains; thus, there is an unmet need to develop novel anti-influenza therapies. Here, we present a novel imidazo[1,2-a]pyrimidine scaffold that targets group 2 IAV entry. We have explored three different regions of the lead compound, and we have developed a series of small molecules that have nanomolar activity against oseltamivir-sensitive and -resistant forms of group 2 IAVs. These small molecules target hemagglutinin (HA), which mediates the viral entry process. Mapping a known small-molecule-binding cavity of the HA structure with resistant mutants suggests that these molecules bind to that cavity and block HA-mediated membrane fusion.

Effect of a brain-penetrant selective estrogen receptor degrader (SERD) on binge drinking in female mice

Background

Greater circulating levels of the steroid hormone 17β‐estradiol (E2) are associated with higher levels of binge drinking in women. In female mice, estrogen receptors in the ventral tegmental area, a dopaminergic region of the brain involved in the motivation to consume ethanol, regulate binge‐like ethanol intake. We recently developed a brain‐penetrant selective estrogen receptor degrader (SERD), YL3‐122, that could be used to test the behavioral role of brain estrogen receptors. We hypothesized that treating female mice with this compound would reduce binge‐like ethanol drinking.

Methods

Female C57BL/6J mice were treated systemically with YL3‐122 and a related SERD with low brain penetrance, XR5‐27, and tested for binge‐like ethanol consumption in the drinking in the dark (DID) test. Mice were also tested for sucrose and water consumption and blood ethanol clearance after treatment with the SERDs. Finally, the effect of ethanol exposure on Esr1 gene expression was measured in the ventral tegmental area (VTA), prefrontal cortex (PFC), and ventral hippocampus (vHPC) of male and female mice by quantitative real‐time PCR after 4 DID sessions.

Results

YL3‐122 reduced ethanol consumption when mice were in diestrus but not estrus. YL3‐122 also decreased sucrose consumption but did not alter water intake or blood ethanol clearance. XR5‐27 did not affect any of these measures. Binge‐like ethanol drinking resulted in increased Esr1 transcript in the VTA of both sexes, male vHPC, and female PFC.

Conclusions

These results indicate that SERD treatment can decrease binge‐like ethanol drinking in female mice. Thus, it could be a novel strategy to reduce binge drinking in women, with the caveat that effectiveness may depend on menstrual cycle phase. In addition, Esr1 transcript is increased by binge ethanol exposure in both sexes but in a brain region‐specific manner.

MAP4K4 promotes pancreatic tumorigenesis via phosphorylation and activation of mixed lineage kinase 3

MAP4K4 is a Ste20 member and reported to play important roles in various pathologies, including in cancer. However, the mechanism by which MAP4K4 promotes pancreatic cancer is not fully understood. It is suggested that MAP4K4 might function as a cancer promoter via specific downstream target(s) in an organ-specific manner. Here we identified MLK3 as a direct downstream target of MAP4K4. The MAP4K4 and MLK3 associates with each other, and MAP4K4 phosphorylates MLK3 on Thr738 and increases MLK3 kinase activity and downstream signaling. The phosphorylation of MLK3 by MAP4K4 promotes pancreatic cancer cell proliferation, migration, and colony formation. Moreover, MAP4K4 is overexpressed in human pancreatic tumors and directly correlates with the disease progression. The MAP4K4-specific pharmacological inhibitor, GNE-495, impedes pancreatic cancer cell growth, migration, induces cell death, and arrests cell cycle progression. Additionally, the GNE-495 reduced the tumor burden and extended survival of the KPC mice with pancreatic cancer. The MAP4K4 inhibitor also reduced MAP4K4 protein expression, tumor stroma, and induced cell death in murine pancreatic tumors. These findings collectively suggest that MLK3 phosphorylation by MAP4K4 promotes pancreatic cancer, and therefore therapies targeting MAP4K4 might alleviate the pancreatic cancer tumor burden in patients.

Identification of a potent Nrf2 displacement activator among aspirin-containing prodrugs

Aspirin is a desired leaving group in prodrugs aimed at treatment of neurodegeneration and other conditions. A library of aspirin derivatives of various scaffolds potentially activating Nrf2 has been tested in Neh2-luc reporter assay which screens for direct Nrf2 protein stabilizers working via disruption of Nrf2-Keap1 interaction. Most aspirin prodrugs had a pro-alkylating or pro-oxidant motif in the structure and, therefore, were toxic at high concentrations. However, among the active compounds, we identified a molecule resembling a well-known Nrf2 displacement activator, bis-1,4-(4-methoxybenzenesulfonamidyl) naphthalene (NMBSA). The direct comparison of the newly identified compound with NMBSA and its improved analog in the reporter assay showed no quenching with N-acetyl cysteine, thus pointing to Nrf2 stabilization mechanism without cysteine alkylation. The potency of the newly identified compound in the reporter assay was much stronger than NMBSA, despite its inhibitory action in the commercial fluorescence polarization assay was observed only in the millimolar range. Molecular docking predicted that mono-deacetylation of the novel prodrug should generate a potent displacement activator. The time-course of reporter activation with the novel prodrug had a pronounced lag-period pointing to a plausible intracellular transformation leading to an active product. Treatment of the novel prodrug with blood plasma or cell lysate demonstrated stepwise deacetylation as judge by liquid chromatography-mass spectrometry (LC-MS). Hence, the esterase-catalyzed hydrolysis of the prodrug liberates only acetyl groups from aspirin moiety and generates a potent Nrf2 activator. The discovered mechanism of prodrug activation makes the newly identified compound a promising lead for future optimization studies.

Metabolomic analysis of a selective ABCA1 inducer in obesogenic challenge provides a rationale for therapeutic development

BACKGROUND

Therapeutic agents with novel mechanisms of action are needed to combat the growing epidemic of type 2 diabetes (T2D) and related metabolic syndromes. Liver X receptor (LXR) agonists possess preclinical efficacy yet produce side effects due to excessive lipogenesis. Anticipating that many beneficial and detrimental effects of LXR agonists are mediated by ABCA1 and SREPB1c expression, respectively, we hypothesized that a phenotypic optimization strategy prioritizing selective ABCA1 induction would identify an efficacious lead compound with an improved side effect profile over existing LXRβ agonists.

METHODS

We synthesized and characterized a novel small molecule for selective induction of ABCA1 vs. SREBP1c in vitro. This compound was evaluated in both wild-type mice and a high-fat diet (HFD) mouse model of obesity-driven diabetes through functional, biochemical, and metabolomic analysis.

FINDINGS

Six weeks of oral administration of our lead compound attenuated weight gain, glucose intolerance, insulin signaling deficits, and adiposity. Global metabolomics revealed suppression of gluconeogenesis, free fatty acids, and pro-inflammatory metabolites. Target identification linked these beneficial effects to selective LXRβ agonism and PPAR/RXR antagonism.

INTERPRETATION

Our observations in the HFD model, combined with the absence of lipogenesis and neutropenia in WT mice, support this novel approach to therapeutic development for T2D and related conditions.

Extending the Calpain-Cathepsin Hypothesis to the Neurovasculature: Protection of Brain Endothelial Cells and Mice from Neurotrauma

The calpain-cathepsin hypothesis posits a key role for elevated calpain-1 and cathepsin-B activity in the neurodegeneration underlying neurotrauma and multiple disorders including Alzheimer's disease (AD). AD clinical trials were recently halted on alicapistat, a selective calpain-1 inhibitor, because of insufficient exposure of neurons to the drug. In contrast to neuroprotection, the ability of calpain-1 and cathepsin-B inhibitors to protect the blood-brain barrier (BBB), is understudied. Since cerebrovascular dysfunction underlies vascular dementia, is caused by ischemic stroke, and is emerging as an early feature in the progression of AD, we studied protection of brain endothelial cells (BECs) by selective and nonselective calpain-1 and cathepsin-B inhibitors. We show these inhibitors protect both neurons and murine BECs from ischemia-reperfusion injury. Cultures of primary BECs from ALDH2 ^-/- mice that manifest enhanced oxidative stress were sensitive to ischemia, leading to reduced cell viability and loss of tight junction proteins; this damage was rescued by calpain-1 and cathepsin-B inhibitors. In ALDH2 ^-/- mice 24 h after mild traumatic brain injury (mTBI), BBB damage was reflected by significantly increased fluorescein extravasation and perturbation of tight junction proteins, eNOS, MMP-9, and GFAP. Both calpain and cathepsin-B inhibitors alleviated BBB dysfunction caused by mTBI. No clear advantage was shown by selective versus nonselective calpain inhibitors in these studies. The lack of recognition of the ability of calpain inhibitors to protect the BBB may have led to the premature abandonment of this therapeutic approach in AD clinical trials and requires further mechanistic studies of cerebrovascular protection by calpain-1 inhibitors.

Systemic Candesartan Treatment Modulates Behavior, Synaptic Protein Levels, and Neuroinflammation in Female Mice That Express Human APOE4

Evidence suggests that angiotensin receptor blockers (ARBs) could be beneficial for Alzheimer’s disease (AD) patients independent of any effects on hypertension. However, studies in rodent models directly testing the activity of ARB treatment on behavior and AD-relevent pathology including neuroinflammation, Aβ levels, and cerebrovascular function, have produced mixed results. APOE4 is a major genetic risk factor for AD and has been linked to many of the same functions as those purported to be modulated by ARB treatment. Therefore, evaluating the effects of ARB treatment on behavior and AD-relevant pathology in mice that express human APOE4 could provide important information on whether to further develop ARBs for AD therapy. In this study, we treated female and male mice that express the human APOE4 gene in the absence (E4FAD−) or presence (E4FAD+) of high Aβ levels with the ARB prodrug candesartan cilexetil for a duration of 4 months. Compared to vehicle, candesartan treatment resulted in greater memory-relevant behavior and higher hippocampal presynaptic protein levels in female, but not male, E4FAD− and E4FAD+ mice. The beneficial effects of candesartan in female E4FAD− and E4FAD+ mice occurred in tandem with lower GFAP and Iba1 levels in the hippocampus, whereas there were no effects on markers of cerebrovascular function and Aβ levels. Collectively, these data imply that the effects of ARBs on AD-relevant pathology may be modulated in part by the interaction between APOE genotype and biological sex. Thus, the further development of ARBs could provide therapeutic options for targeting neuroinflammation in female APOE4 carriers.

Evidence for distinct mechanisms of small molecule inhibitors of filovirus entry

Many small molecules have been identified as entry inhibitors of filoviruses. However, a lack of understanding of the mechanism of action for these molecules limits further their development as anti-filoviral agents. Here we provide evidence that toremifene and other small molecule entry inhibitors have at least three distinctive mechanisms of action and lay the groundwork for future development of anti-filoviral agents. The three mechanisms identified here include: (1) direct binding to the internal fusion loop region of Ebola virus glycoprotein (GP); (2) the HR2 domain is likely the main binding site for Marburg virus GP inhibitors and a secondary binding site for some EBOV GP inhibitors; (3) lysosome trapping of GP inhibitors increases drug exposure in the lysosome and further improves the viral inhibition. Importantly, small molecules targeting different domains on GP are synergistic in inhibiting EBOV entry suggesting these two mechanisms of action are distinct. Our findings provide important mechanistic insights into filovirus entry and rational drug design for future antiviral development.

Discovery of Nonlipogenic ABCA1 Inducing Compounds with Potential in Alzheimer's Disease and Type 2 Diabetes

Selective liver X receptor (LXR) agonists have been extensively pursued as therapeutics for Alzheimer's disease and related dementia (ADRD) and, for comorbidities such as type 2 diabetes (T2D) and cerebrovascular disease (CVD), disorders with underlying impaired insulin signaling, glucose metabolism, and cholesterol mobilization. The failure of the LXR-focused approach led us to pursue a novel strategy to discover nonlipogenic ATP-binding cassette transporter A1 (ABCA1) inducers (NLAIs): screening for ABCA1-luciferase activation in astrocytoma cells and counterscreening against lipogenic gene upregulation in hepatocarcinoma cells. Beneficial effects of LXRβ agonists mediated by ABCA1 include the following: control of cholesterol and phospholipid efflux to lipid-poor apolipoproteins forming beneficial peripheral HDL and HDL-like particles in the brain and attenuation of inflammation. While rare, ABCA1 variants reduce plasma HDL and correlate with an increased risk of ADRD and CVD. In secondary assays, NLAI hits enhanced cholesterol mobilization and positively impacted in vitro biomarkers associated with insulin signaling, inflammatory response, and biogenic properties. In vivo target engagement was demonstrated after oral administration of NLAIs in (i) mice fed a high-fat diet, a model for obesity-linked T2D, (ii) mice administered LPS, and (iii) mice with accelerated oxidative stress. The lack of adverse effects on lipogenesis and positive effects on multiple biomarkers associated with T2D and ADRD supports this novel phenotypic approach to NLAIs as a platform for T2D and ADRD drug discovery.

Rapid Induction of the Unfolded Protein Response and Apoptosis by Estrogen Mimic TTC-352 for the Treatment of Endocrine-Resistant Breast Cancer

Patients with long-term estrogen-deprived breast cancer, after resistance to tamoxifen or aromatase inhibitors develops, can experience tumor regression when treated with estrogens. Estrogen's antitumor effect is attributed to apoptosis via the estrogen receptor (ER). Estrogen treatment can have unpleasant gynecologic and nongynecologic adverse events; thus, the development of safer estrogenic agents remains a clinical priority. Here, we study synthetic selective estrogen mimics (SEM) BMI-135 and TTC-352, and the naturally occurring estrogen estetrol (E₄), which are proposed as safer estrogenic agents compared with 17β-estradiol (E₂), for the treatment of endocrine-resistant breast cancer. TTC-352 and E₄ are being evaluated in breast cancer clinical trials. Cell viability assays, real-time PCR, immunoblotting, ERE DNA pulldowns, mass spectrometry, X-ray crystallography, docking and molecular dynamic simulations, live cell imaging, and Annexin V staining were conducted in 11 biologically different breast cancer models. Results were compared with the potent full agonist E₂, less potent full agonist E₄, the benchmark partial agonist triphenylethylene bisphenol (BPTPE), and antagonists 4-hydroxytamoxifen and endoxifen. We report ERα's regulation and coregulators' binding profiles with SEMs and E₄ We describe TTC-352's pharmacology as a weak full agonist and antitumor molecular mechanisms. This study highlights TTC-352's benzothiophene scaffold that yields an H-bond with Glu353, which allows Asp351-to-helix 12 (H12) interaction, sealing ERα's ligand-binding domain, recruiting E₂-enriched coactivators, and triggering rapid ERα-induced unfolded protein response (UPR) and apoptosis, as the basis of its anticancer properties. BPTPE's phenolic OH yields an H-Bond with Thr347, which disrupts Asp351-to-H12 interaction, delaying UPR and apoptosis and increasing clonal evolution risk.

Cortical Proteins Associated With Cognitive Resilience in Community-Dwelling Older Persons

Importance

Identifying genes and proteins for cognitive resilience (ie, targets that may be associated with slowing or preventing cognitive decline regardless of the presence, number, or combination of common neuropathologic conditions) provides a complementary approach to developing novel therapeutics for the treatment and prevention of Alzheimer disease and related dementias.

Objective

To identify proteins associated with cognitive resilience via a proteome-wide association study of the human dorsolateral prefrontal cortex.

Design, Setting, and Participants

This study used data from 391 community-dwelling older persons who participated in the Religious Orders Study and the Rush Memory and Aging Project. The Religious Orders Study began enrollment January 1, 1994, and the Rush Memory and Aging Project began enrollment September 1, 1997, and data were collected and analyzed through October 23, 2019.

Exposures

Participants had undergone annual detailed clinical examinations, postmortem evaluations, and tandem mass tag proteomics analyses.

Main Outcomes and Measures

The outcome of cognitive resilience was defined as a longitudinal change in cognition over time after controlling for common age-related neuropathologic indices, including Alzheimer disease, Lewy bodies, transactive response DNA-binding protein 43, hippocampal sclerosis, infarcts, and vessel diseases. More than 8000 high abundance proteins were quantified from frozen dorsolateral prefrontal cortex tissue using tandem mass tag and liquid chromatography-mass spectrometry.

Results

There were 391 participants (273 women); their mean (SD) age was 79.7 (6.7) years at baseline and 89.2 (6.5) years at death. Eight cortical proteins were identified in association with cognitive resilience: a higher level of NRN1 (estimate, 0.140; SE, 0.024; P = 7.35 × 10-9), ACTN4 (estimate, 0.321; SE, 0.065; P = 9.94 × 10-7), EPHX4 (estimate, 0.198; SE, 0.042; P = 2.13 × 10-6), RPH3A (estimate, 0.148; SE, 0.031; P = 2.58 × 10-6), SGTB (estimate, 0.211; SE, 0.045; P = 3.28 × 10-6), CPLX1 (estimate, 0.136; SE, 0.029; P = 4.06 × 10-6), and SH3GL1 (estimate, 0.179; SE, 0.039; P = 4.21 × 10-6) and a lower level of UBA1 (estimate, -0.366; SE, 0.076; P = 1.43 × 10-6) were associated with greater resilience.

Conclusions and Relevance

These protein signals may represent novel targets for the maintenance of cognition in old age.

Pharmacology and Molecular Mechanisms of Clinically Relevant Estrogen Estetrol and Estrogen Mimic BMI-135 for the Treatment of Endocrine-Resistant Breast Cancer

Long-term estrogen deprivation (LTED) with tamoxifen (TAM) or aromatase inhibitors leads to endocrine-resistance, whereby physiologic levels of estrogen kill breast cancer (BC). Estrogen therapy is effective in treating patients with advanced BC after resistance to TAM and aromatase inhibitors develops. This therapeutic effect is attributed to estrogen-induced apoptosis via the estrogen receptor (ER). Estrogen therapy can have unpleasant gynecologic and nongynecologic adverse events. Here, we study estetrol (E4) and a model Selective Human ER Partial Agonist (ShERPA) BMI-135. Estetrol and ShERPA TTC-352 are being evaluated in clinical trials. These agents are proposed as safer estrogenic candidates compared with 17β-estradiol (E2) for the treatment of endocrine-resistant BC. Cell viability assays, real-time polymerase chain reaction, luciferase reporter assays, chromatin immunoprecipitation, docking and molecular dynamics simulations, human unfolded protein response (UPR) RT2 PCR profiler arrays, live cell microscopic imaging and analysis, and annexin V staining assays were conducted. Our work was done in eight biologically different human BC cell lines and one human endometrial cancer cell line, and results were compared with full agonists estrone, E2, and estriol, a benchmark partial agonist triphenylethylene bisphenol (BPTPE), and antagonists 4-hydroxytamoxifen and endoxifen. Our study shows the pharmacology of E4 and BMI-135 as less-potent full-estrogen agonists as well as their molecular mechanisms of tumor regression in LTED BC through triggering a rapid UPR and apoptosis. Our work concludes that the use of a full agonist to treat BC is potentially superior to a partial agonist given BPTPE's delayed induction of UPR and apoptosis, with a higher probability of tumor clonal evolution and resistance. SIGNIFICANCE STATEMENT: Given the unpleasant gynecologic and nongynecologic adverse effects of estrogen treatment, the development of safer estrogens for endocrine-resistant breast cancer (BC) treatment and hormone replacement therapy remains a priority. The naturally occurring estrogen estetrol and Selective Human Estrogen-Receptor Partial Agonists are being evaluated in endocrine-resistant BC clinical trials. This work provides a comprehensive evaluation of their pharmacology in numerous endocrine-resistant BC models and an endometrial cancer model and their molecular mechanisms of tumor regression through the unfolded protein response and apoptosis.

Screening and Reverse-Engineering of Estrogen Receptor Ligands as Potent Pan-Filovirus Inhibitors

Filoviridae, including Ebola (EBOV) and Marburg (MARV) viruses, are emerging pathogens that pose a serious threat to public health. No agents have been approved to treat filovirus infections, representing a major unmet medical need. The selective estrogen receptor modulator (SERM) toremifene was previously identified from a screen of FDA-approved drugs as a potent EBOV viral entry inhibitor, via binding to EBOV glycoprotein (GP). A focused screen of ER ligands identified ridaifen-B as a potent dual inhibitor of EBOV and MARV. Optimization and reverse-engineering to remove ER activity led to a novel compound 30 (XL-147) showing potent inhibition against infectious EBOV Zaire (0.09 μM) and MARV (0.64 μM). Mutagenesis studies confirmed that inhibition of EBOV viral entry is mediated by the direct interaction with GP. Importantly, compound 30 displayed a broad-spectrum antifilovirus activity against Bundibugyo, Tai Forest, Reston, and Měnglà viruses and is the first submicromolar antiviral agent reported for some of these strains, therefore warranting further development as a pan-filovirus inhibitor.

Synthesis of α-Ketoamide-Based Stereoselective Calpain-1 Inhibitors as Neuroprotective Agents

Calpain inhibitors have been proposed as drug candidates for neurodegenerative disorders, with ABT-957 entering clinical trials for Alzheimer's disease and mild cognitive impairment. The structure of ABT-957 was very recently disclosed, and trials were terminated owing to inadequate CNS concentrations to obtain a pharmacodynamic effect. The multistep synthesis of an α-ketoamide peptidomimetic inhibitor series potentially including ABT-957 was optimized to yield diastereomerically pure compounds that are potent and selective for calpain-1 over papain and cathepsins B and K. As the final oxidation step, with its optimized synthesis protocol, does not alter the configuration of the substrate, the synthesis of the diastereomeric pair (R)-1-benzyl-N-((S)-4-((4-fluorobenzyl)amino)-3,4-dioxo-1-phenylbutan-2-yl)-5-oxopyrrolidine-2-carboxamide (1 c) and (R)-1-benzyl-N-((R)-4-((4-fluorobenzyl)amino)-3,4-dioxo-1-phenylbutan-2-yl)-5-oxopyrrolidine-2-carboxamide (1 g) was feasible. This allowed the exploration of stereoselective inhibition of calpain-1, with 1 c (IC₅₀ =78 nM) being significantly more potent than 1 g. Moreover, inhibitor 1 c restored cognitive function in amnestic mice.

Discovery and Structural Optimization of 4-(Aminomethyl)benzamides as Potent Entry Inhibitors of Ebola and Marburg Virus Infections

The recent Ebola epidemics in West Africa underscore the great need for effective and practical therapies for future Ebola virus outbreaks. We have discovered a new series of remarkably potent small molecule inhibitors of Ebola virus entry. These 4-(aminomethyl)benzamide-based inhibitors are also effective against Marburg virus. Synthetic routes to these compounds allowed for the preparation of a wide variety of structures, including a conformationally restrained subset of indolines (compounds 41-50). Compounds 20, 23, 32, 33, and 35 are superior inhibitors of Ebola (Mayinga) and Marburg (Angola) infectious viruses. Representative compounds (20, 32, and 35) have shown good metabolic stability in plasma and liver microsomes (rat and human), and 32 did not inhibit CYP3A4 nor CYP2C9. These 4-(aminomethyl)benzamides are suitable for further optimization as inhibitors of filovirus entry, with the potential to be developed as therapeutic agents for the treatment and control of Ebola virus infections.

Novel Pyrrolopyridone Bromodomain and Extra-Terminal Motif (BET) Inhibitors Effective in Endocrine-Resistant ER+ Breast Cancer with Acquired Resistance to Fulvestrant and Palbociclib

Acquired resistance to fulvestrant and palbociclib is a new challenge to treatment of estrogen receptor positive (ER+) breast cancer. ER is expressed in most resistance settings; thus, bromodomain and extra-terminal protein inhibitors (BETi) that target BET-amplified ER-mediated transcription have therapeutic potential. Novel pyrrolopyridone BETi leveraged novel interactions with L92/L94 confirmed by a cocrystal structure of 27 with BRD4. Optimization of BETi using growth inhibition in fulvestrant-resistant (MCF-7:CFR) cells was confirmed in endocrine-resistant, palbociclib-resistant, and ESR1 mutant cell lines. 27 was more potent in MCF-7:CFR cells than six BET inhibitors in clinical trials. Transcriptomic analysis differentiated 27 from the benchmark BETi, JQ-1, showing downregulation of oncogenes and upregulation of tumor suppressors and apoptosis. The therapeutic approach was validated by oral administration of 27 in orthotopic xenografts of endocrine-resistant breast cancer in monotherapy and in combination with fulvestrant. Importantly, at an equivalent dose in rats, thrombocytopenia was mitigated.

Mixed lineage kinase 3 inhibition induces T cell activation and cytotoxicity

Mixed lineage kinase 3 (MLK3), also known as MAP3K11, was initially identified in a megakaryocytic cell line and is an emerging therapeutic target in cancer, yet its role in immune cells is not known. Here, we report that loss or pharmacological inhibition of MLK3 promotes activation and cytotoxicity of T cells. MLK3 is abundantly expressed in T cells, and its loss alters serum chemokines, cytokines, and CD28 protein expression on T cells and its subsets. MLK3 loss or pharmacological inhibition induces activation of T cells in in vitro, ex vivo, and in vivo conditions, irrespective of T cell activating agents. Conversely, overexpression of MLK3 decreases T cell activation. Mechanistically, loss or inhibition of MLK3 down-regulates expression of a prolyl-isomerase, Ppia, which is directly phosphorylated by MLK3 to increase its isomerase activity. Moreover, MLK3 also phosphorylates nuclear factor of activated T cells 1 (NFATc1) and regulates its nuclear translocation via interaction with Ppia, and this regulates T cell effector function. In an immune-competent mouse model of breast cancer, MLK3 inhibitor increases Granzyme B-positive CD8+ T cells and decreases MLK3 and Ppia gene expression in tumor-infiltrating T cells. Likewise, the MLK3 inhibitor in pan T cells, isolated from breast cancer patients, also increases cytotoxic CD8+ T cells. These results collectively demonstrate that MLK3 plays an important role in T cell biology, and targeting MLK3 could serve as a potential therapeutic intervention via increasing T cell cytotoxicity in cancer.

Characterization of Lead Compounds Targeting the Selenoprotein Thioredoxin Glutathione Reductase for Treatment of Schistosomiasis

Schistosomiasis is a widespread human parasitic disease currently affecting over 200 million people. Chemotherapy for schistosomiasis relies exclusively on praziquantel. Although significant advances have been made in recent years to reduce the incidence and intensity of schistosome infections, these gains will be at risk should drug-resistant parasites evolve. Thioredoxin glutathione reductase (TGR) is a selenoprotein of the parasite essential for the survival of schistosomes in the mammalian host. Several high-throughput screening campaigns have identified inhibitors of Schistosoma mansoni TGR. Follow up analyses of select active compounds form the basis of the present study. We identified eight compounds effective against ex vivo worms. Compounds 1-5 are active against all major species and development stages. The ability of these compounds to target immature worms is especially critical because praziquantel is poorly active against this stage. Compounds 1-5, 7, and 8 displayed schistosomicidal activity even after only 1 h incubation with the worms. Compounds 1-4 meet or exceed standards set by the World Health Organization for leads for schistosomiasis therapy activity. The mechanism of TGR inhibition was studied further with wild-type and mutant TGR proteins. Compounds 4-6 were found to induce an nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity in TGR, leading to the production of superoxide and hydrogen peroxide. Collectively, this effort has identified several active compound series that may serve as the basis for the development of new schistosomicidal compounds.

G1T48, an oral selective estrogen receptor degrader, and the CDK4/6 inhibitor lerociclib inhibit tumor growth in animal models of endocrine-resistant breast cancer

Purpose

The combination of targeting the CDK4/6 and estrogen receptor (ER) signaling pathways with palbociclib and fulvestrant is a proven therapeutic strategy for the treatment of ER-positive breast cancer. However, the poor physicochemical properties of fulvestrant require monthly intramuscular injections to patients, which limit the pharmacokinetic and pharmacodynamic activity of the compound. Therefore, an orally available compound that more rapidly reaches steady state may lead to a better clinical response in patients. Here, we report the identification of G1T48, a novel orally bioavailable, non-steroidal small molecule antagonist of ER.

Methods

The pharmacological effects and the antineoplastic mechanism of action of G1T48 on tumors was evaluated using human breast cancer cells (in vitro) and xenograft efficacy models (in vivo).

Results

G1T48 is a potent and efficacious inhibitor of estrogen-mediated transcription and proliferation in ER-positive breast cancer cells, similar to the pure antiestrogen fulvestrant. In addition, G1T48 can effectively suppress ER activity in multiple models of endocrine therapy resistance including those harboring ER mutations and growth factor activation. In vivo, G1T48 has robust antitumor activity in a model of estrogen-dependent breast cancer (MCF7) and significantly inhibited the growth of tamoxifen-resistant (TamR), long-term estrogen-deprived (LTED) and patient-derived xenograft tumors with an increased response being observed with the combination of G1T48 and the CDK4/6 inhibitor lerociclib.

Conclusions

These data show that G1T48 has the potential to be an efficacious oral antineoplastic agent in ER-positive breast cancer.

Electronic supplementary material

The online version of this article (10.1007/s10549-020-05575-9) contains supplementary material, which is available to authorized users.

Optimization of 4-Aminopiperidines as Inhibitors of Influenza A Viral Entry That Are Synergistic with Oseltamivir

Vaccination is the most prevalent prophylactic means for controlling seasonal influenza infections. However, an effective vaccine usually takes at least 6 months to develop for the circulating strains. Therefore, new therapeutic options are needed for the acute treatment of influenza infections to control this virus and prevent epidemics/pandemics from developing. We have discovered fast-acting, orally bioavailable acylated 4-aminopiperidines with an effective mechanism of action targeting viral hemagglutinin (HA). Our data show that these compounds are potent entry inhibitors of influenza A viruses. We present docking studies that suggest an HA binding site for these inhibitors on H5N1. Compound 16 displayed a significant decrease of viral titer when evaluated in the infectious assays with influenza virus H1N1 (A/Puerto Rico/8/1934) or H5N1 (A/Vietnam/1203/2004) strains and the oseltamivir-resistant strain with the most common H274Y mutation. In addition, compound 16 showed significant synergistic activity with oseltamivir in vitro.

Interaction of oxidative stress and neurotrauma in ALDH2-/- mice causes significant and persistent behavioral and pro-inflammatory effects in a tractable model of mild traumatic brain injury

Oxidative stress induced by lipid peroxidation products (LPP) accompanies aging and has been hypothesized to exacerbate the secondary cascade in traumatic brain injury (TBI). Increased oxidative stress is a contributor to loss of neural reserve that defines the ability to maintain healthy cognitive function despite the accumulation of neuropathology. ALDH2^−/− mice are unable to clear aldehyde LPP by mitochondrial aldehyde dehydrogenase-2 (Aldh2) detoxification and provide a model to study mild TBI (mTBI), therapeutic interventions, and underlying mechanisms. The ALDH2^−/− mouse model presents with elevated LPP-mediated protein modification, lowered levels of PSD-95, PGC1-α, and SOD-1, and mild cognitive deficits from 4 months of age. LPP scavengers are neuroprotective in vitro and in ALDH2^−/− mice restore cognitive performance. A single-hit, closed skull mTBI failed to elicit significant effects in WT mice; however, ALDH2^−/− mice showed a significant inflammatory cytokine surge in the ipsilateral hemisphere 24 h post-mTBI, and increased GFAP cleavage, a biomarker for TBI. Known neuroprotective agents, were able to reverse the effects of mTBI. This new preclinical model of mTBI, incorporating significant perturbations in behavior, inflammation, and clinically relevant biomarkers, allows mechanistic study of the interaction of LPP and neurotrauma in loss of neural reserve.

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ALDH2^−/− mice have elevated brain LPP adducts and mild cognitive impairment.

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The effects of a “2nd hit” via LPS are exacerbated by LPP in vitro and in vivo.

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ALDH2^−/− mice + mTBI show amplified/prolonged cognitive deficits and neuroinflammation.

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This new preclinical model for mTBI supports a role for LPP in reduced neural reserve.

Ectopic suicide inhibition of thioredoxin glutathione reductase

Selective suicide inhibitors represent a seductively attractive approach for inactivation of therapeutically relevant enzymes since they are generally devoid of off-target toxicity in vivo. While most suicide inhibitors are converted to reactive species at enzyme active sites, theoretically bioactivation can also occur in ectopic (secondary) sites that have no known function. Here, we report an example of such an "ectopic suicide inhibition", an unprecedented bioactivation mechanism of a suicide inhibitor carried out by a non-catalytic site of thioredoxin glutathione reductase (TGR). TGR is a promising drug target to treat schistosomiasis, a devastating human parasitic disease. Utilizing hits selected from a high throughput screening campaign, time-resolved X-ray crystallography, molecular dynamics, mass spectrometry, molecular modeling, protein mutagenesis and functional studies, we find that 2-naphtholmethylamino derivatives bound to this novel ectopic site of Schistosoma mansoni (Sm)TGR are transformed to covalent modifiers and react with its mobile selenocysteine-containing C-terminal arm. In particular, one 2-naphtholmethylamino compound is able to specifically induce the pro-oxidant activity in the inhibited enzyme. Since some 2-naphtholmethylamino analogues show worm killing activity and the ectopic site is not conserved in human orthologues, a general approach to development of novel and selective anti-parasitic therapeutics against schistosoma is proposed.

Design and Synthesis of Basic Selective Estrogen Receptor Degraders for Endocrine Therapy Resistant Breast Cancer

The clinical steroidal selective estrogen receptor (ER) degrader (SERD), fulvestrant, is effective in metastatic breast cancer, but limited by poor pharmacokinetics, prompting the development of orally bioavailable, nonsteroidal SERDs, currently in clinical trials. These trials address local breast cancer as well as peripheral metastases, but patients with brain metastases are generally excluded because of the lack of blood-brain barrier penetration. A novel family of benzothiophene SERDs with a basic amino side arm (B-SERDs) was synthesized. Proteasomal degradation of ERα was induced by B-SERDs that achieved the objectives of oral and brain bioavailability, while maintaining high affinity binding to ERα and both potency and efficacy comparable to fulvestrant in cell lines resistant to endocrine therapy or bearing ESR1 mutations. A novel 3-oxyazetidine side chain was designed, leading to 37d, a B-SERD that caused endocrine-resistant ER+ tumors to regress in a mouse orthotopic xenograft model.

Correction to Design, Synthesis, and Biological Evaluation of Tetrahydroisoquinoline-Based Histone Deacetylase 8 Selective Inhibitors

[This corrects the article DOI: 10.1021/acsmedchemlett.7b00126.].

Pharmacological manipulation of cGMP and NO/cGMP in CNS drug discovery

The development of small molecule modulators of NO/cGMP signaling for use in the CNS has lagged far behind the use of such clinical agents in the periphery, despite the central role played by NO/cGMP in learning and memory, and the substantial evidence that this signaling pathway is perturbed in neurodegenerative disorders, including Alzheimer's disease. The NO-chimeras, NMZ and Nitrosynapsin, have yielded beneficial and disease-modifying responses in multiple preclinical animal models, acting on GABA_A and NMDA receptors, respectively, providing additional mechanisms of action relevant to synaptic and neuronal dysfunction. Several inhibitors of cGMP-specific phosphodiesterases (PDE) have replicated some of the actions of these NO-chimeras in the CNS. There is no evidence that nitrate tolerance is a phenomenon relevant to the CNS actions of NO-chimeras, and studies on nitroglycerin in the periphery continue to challenge the dogma of nitrate tolerance mechanisms. Hybrid nitrates have shown much promise in the periphery and CNS, but to date only one treatment has received FDA approval, for glaucoma. The potential for allosteric modulation of soluble guanylate cyclase (sGC) in brain disorders has not yet been fully explored nor exploited; whereas multiple applications of PDE inhibitors have been explored and many have stalled in clinical trials.

Activation of Nrf2 and Hypoxic Adaptive Response Contribute to Neuroprotection Elicited by Phenylhydroxamic Acid Selective HDAC6 Inhibitors

Activation of HIF-1α and Nrf2 is a primary component of cellular response to oxidative stress, and activation of HIF-1α and Nrf2 provides neuroprotection in models of neurodegenerative disorders, including ischemic stroke, Alzheimer's and Parkinson's diseases. Screening a library of CNS-targeted drugs using novel reporters for HIF-1α and Nrf2 elevation in neuronal cells revealed histone deacetylase (HDAC) inhibitors as potential activators of these pathways. We report the identification of phenylhydroxamates as single agents exhibiting tripartite inhibition of HDAC6, inhibition of HIF-1 prolyl hydroxylase (PHD), and activation of Nrf2. Two superior tripartite agents, ING-6 and ING-66, showed neuroprotection against various cellular insults, associated with stabilization of both Nrf2 and HIF-1, and expression of their respective target genes in vitro and in vivo. Discovery of the innate ability of phenylhydroxamate HDAC inhibitors to activate Nrf2 and HIF provides a novel route to multifunctional neuroprotective agents and cautions against HDAC6 selective inhibitors as chemical probes of specific HDAC isoform function.

Time-Gated Luminescence Detection of Enzymatically Produced Hydrogen Sulfide: Design, Synthesis, and Application of a Lanthanide-Based Probe

Hydrogen sulfide (H₂S) is now recognized as an important gaseous transmitter that is involved in a variety of biological processes. Here, we report the design and synthesis of a luminescent lanthanide biosensor for H₂S, LP2-Cu(II)-Ln(III), a heterobinuclear metal complex that uses Cu(II) decomplexation to control millisecond-scale-lifetime-Tb(III)- or Eu(III)-emission intensity. LP2-Cu(II)-Ln(III) responded rapidly, selectively, and with high sensitivity to aqueous H₂S. The probe's potential for biological applications was verified by measuring the H₂S generated by the slow-releasing chemical-sulfide-donor GYY4147, by cystathionine γ-lyase (CSE), and by Na₂S-stimulated HeLa cells.

Design, Synthesis, Molecular Modeling, and Biological Evaluation of Novel Amine-based Histone Deacetylase Inhibitors

Histone deacetylases (HDACs) are promising drug targets for a variety of therapeutic applications. Herein we describe the design, synthesis, biological evaluation in cellular models of cancer, and preliminary drug metabolism and pharmacokinetic studies (DMPK) of a series of secondary and tertiary N-substituted 7-aminoheptanohydroxamic acid-based HDAC inhibitors. Introduction of an amino group with one or two surface binding groups (SBGs) yielded a successful strategy to develop novel and potent HDAC inhibitors. The secondary amines were found to be generally more potent than the corresponding tertiary amines. Docking studies suggested that the SBGs of tertiary amines cannot be favorably accommodated at the gorge region of the binding site. The secondary amines with naphthalen-2-ylmethyl, 5-phenylthiophen-2-ylmethyl, and 1H-indol-2-ylmethyl (2 j) substituents exhibited the highest potency against class I HDACs: HDAC1 IC50 39-61 nm, HDAC2 IC50 260-690 nm, HDAC3 IC50 25-68 nm, and HDAC8 IC50 320-620 nm. The cytotoxicity of a representative set of secondary and tertiary N-substituted 7-aminoheptanoic acid hydroxyamide-based inhibitors against HT-29, SH-SY5Y, and MCF-7 cancer cells correlated with their inhibition of HDAC1, 2, and 3 and was found to be similar to or better than that of suberoylanilide hydroxamic acid (SAHA). Compounds in this series increased the acetylation of histones H3 and H4 in a time-dependent manner. DMPK studies indicated that secondary amine 2 j is metabolically stable and has plasma and brain concentrations >23- and >1.6-fold higher than the IC50 value for class I HDACs, respectively. Overall, the secondary and tertiary N-substituted 7-aminoheptanoic acid hydroxyamide-based inhibitors exhibit excellent lead- and drug-like properties and therapeutic capacity for cancer applications.

2-Arylidene Hydrazinecarbodithioates as Potent, Selective Inhibitors of Cystathionine γ-Lyase (CSE)

Hydrogen sulfide is produced from l-cysteine by the action of both cystathionine γ-lyase (CSE) and cystathionine β-synthase (CBS) and increasingly has been found to play a profound regulatory role in a range of physiological processes. Mounting evidence suggests that upregulation of hydrogen sulfide biosynthesis occurs in several disease states, including rheumatoid arthritis, hypertension, ischemic injury, and sleep-disordered breathing. In addition to being critical tools in our understanding of hydrogen sulfide biology, inhibitors of CSE hold therapeutic potential for the treatment of diseases in which increased levels of this gasotransmitter play a role. We describe the discovery and development of a novel series of potent CSE inhibitors that show increased activity over the benchmark inhibitor and, importantly, display high selectivity for CSE versus CBS.

Design, Synthesis, and Biological Evaluation of Tetrahydroisoquinoline-Based Histone Deacetylase 8 Selective Inhibitors

Histone deacetylase 8 (HDAC8) is a promising drug target for multiple therapeutic applications. Here, we describe the modeling, design, synthesis, and biological evaluation of a novel series of C1-substituted tetrahydroisoquinoline (TIQ)-based HDAC8 inhibitors. Minimization of entropic loss upon ligand binding and use of the unique HDAC8 "open" conformation of the binding site yielded a successful strategy for improvement of both HDAC8 potency and selectivity. The TIQ-based 3g and 3n exhibited the highest 82 and 55 nM HDAC8 potency and 330- and 135-fold selectivity over HDAC1, respectively. Selectivity over other class I isoforms was comparable or better, whereas inhibition of HDAC6, a class II HDAC isoform, was below 50% at 10 μM. The cytotoxicity of 3g and 3n was evaluated in neuroblastoma cell lines, and 3n displayed concentration-dependent cytotoxicity similar to or better than that of PCI-34051. The selectivity of 3g and 3n was confirmed in SH-SY5Y cells as both did not increase the acetylation of histone H3 and α-tubulin. Discovery of the novel TIQ chemotype paves the way for the development of HDAC8 selective inhibitors for therapeutic applications.

A Novel Strategy to Co-target Estrogen Receptor and Nuclear Factor κB Pathways with Hybrid Drugs for Breast Cancer Therapy

Nearly 75% of breast tumors express estrogen receptor (ER), and will be treated with endocrine therapy, such as selective estrogen receptor modulator (SERM), tamoxifen, or aromatase inhibitors. Despite their proven success, as many as 40-50% of ER+ tumors fail to respond to endocrine therapy and eventually recur as aggressive, metastatic cancers. Therefore, preventing and/or overcoming endocrine resistance in ER+ tumors remains a major clinical challenge. Deregulation or activation of the nuclear factor κB (NFκB) pathway has been implicated in endocrine resistance and poor patient outcome in ER+ tumors. As a consequence, one option to improve on existing anti-cancer treatment regimens may be to introduce additional anti-NFκB activity to endocrine therapy drugs. Our approach was to design and test SERM-fumarate co-targeting hybrid drugs capable of simultaneously inhibiting both ER, via the SERM, raloxifene, and the NFκB pathway, via fumarate, in breast cancer cells. We find that the hybrid drugs display improved anti-NFκB pathway inhibition compared to either raloxifene or fumarate. Despite some loss in potency against the ER pathway, these hybrid drugs maintain anti-proliferative activity in ER+ breast cancer cells. Furthermore, these drugs prevent clonogenic growth and mammosphere formation of ER+ breast cancer cells. As a proof-of-principle, the simultaneous inhibition of ER and NFκB via a single bifunctional hybrid drug may represent a viable approach to improve the anti-inflammatory activity and prevent therapy resistance of ER-targeted anti-cancer drugs.

Abstract P3-04-23: Combination therapy of targeted anticancer pathways and estrogen receptor ligands and their responses in de novo andtamoxifen resistant cell models

Approximately 75% of breast cancers are classified as Estrogen Receptor positive (ER+). Tamoxifen, a selective estrogen receptor modulator (SERM), is the standard of care for many of these ER+ breast cancer patients. Unfortunately, tamoxifen resistance occurs in almost 50% of patients within 5 years of treatment, and endocrine-independence accompanying resistance also negates the effects of aromatase inhibitors. Combination therapy is increasingly used in non-cytotoxic therapeutic approaches in many types of cancer. The potential exists that endocrine resistance can be lessened, eliminated, or overcome through targeted therapy in combination with endocrine therapy. Inhibition of kinase signaling (e.g. via CDK4/6 or PI3K) and other pathways (e.g. HSP90) are expected to be effective in combination with endocrine therapy. We have discovered a variety of ER ligands with potential as endocrine therapeutic agents, based upon a single chemical scaffold with a diverse set of pharmacological responses: including SERMs, selective ER downregulators (SERDs), selective estrogen mimics (SEMs), and selective human ER partial agonists (ShERPAs). To predict which agents in combination with these endocrine-targeted ligands would be of potential therapeutic benefit it was necessary to develop 3D spheroidal cultures of ER+ breast cancer cell lines: including endocrine-dependent lines; and cell lines made endocrine-independent either by extended exposure to tamoxifen or extended deprivation of estradiol. In contrast to 2D cultures, drug response in 3D spheroidal cell cultures was predictive of response to treatment in mouse xenograft studies. Growth of endocrine-dependent cell lines was, as expected, inhibited by SERDs; and endocrine-independent, tamoxifen-resistant cell lines were also sensitive to SERD treatment, although one cell line was largely resistant. Growth of all three tamoxifen-resistant cell lines was inhibited by SEMs/ShERPAs. Importantly, regardless of the type of endocrine therapeutic agent studied, concentrations leading to saturation of the target (ER) did not cause cell death. Equally, all endocrine therapies studied benefited from combination treatment with other agents, leading to enhanced cell death.

Citation Format: Gutgesell LM, Xiong R, Thatcher GRJ, Tonetti DA. Combination therapy of targeted anticancer pathways and estrogen receptor ligands and their responses in de novo andtamoxifen resistant cell models [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-04-23.

Novel Selective Estrogen Receptor Downregulators (SERDs) Developed against Treatment-Resistant Breast Cancer

Resistance to the selective estrogen receptor modulator tamoxifen and to aromatase inhibitors that lower circulating estradiol occurs in up to 50% of patients, generally leading to an endocrine-independent ER+ phenotype. Selective ER downregulators (SERDs) are able to ablate ER and thus, theoretically, to prevent survival of both endocrine-dependent and -independent ER+ tumors. The clinical SERD fulvestrant is hampered by intramuscular administration and undesirable pharmacokinetics. Novel SERDs were designed using the 6-OH-benzothiophene (BT) scaffold common to arzoxifene and raloxifene. Treatment-resistant (TR) ER+ cell lines (MCF-7:5C and MCF-7:TAM1) were used for optimization, followed by validation in the parent endocrine-dependent cell line (MCF-7:WS8), in 2D and 3D cultures, using ERα in-cell westerns, ERE-luciferase, and cell viability assays, with 2 (GDC-0810/ARN-810) used for comparison. Two BT SERDs with superior in vitro activity to 2 were studied for bioavailability and shown to cause regression of a TR, endocrine-independent ER+ xenograft superior to that with 2.

Targeting NO/cGMP Signaling in the CNS for Neurodegeneration and Alzheimer's Disease

cAMP-response element-binding protein (CREB) plays a central role in various aspects of central nervous system (CNS) function, ranging from the developmental stages to neuronal plasticity and survival in adult brain. Activation of CREB plays a crucial role in learning and memory and is at the convergence of multiple intracellular signaling cascades including CAMKII and MAPK. This review focuses on the important functions of nitric oxide (NO) in activating CREB via the NO receptor, soluble guanylyl cyclase (sGC), and production of the second messenger, cGMP. The involvement of the NO/cGMP signaling pathway in synaptic plasticity suggests several avenues for therapeutic intervention, and targeting early synaptic degeneration could be an attractive approach for the development of novel disease-modifying approaches to treat cognition and memory dysfunction in neurodegenerative diseases.

Synthesis and Characterization of an Aspirin-fumarate Prodrug that Inhibits NFκB Activity and Breast Cancer Stem Cells

Inflammation is a cancer hallmark that underlies cancer incidence and promotion, and eventually progression to metastasis. Therefore, adding an anti-inflammatory drug to standard cancer regiments may improve patient outcome. One such drug, aspirin (acetylsalicylic acid, ASA), has been explored for cancer chemoprevention and anti-tumor activity. Besides inhibiting the cyclooxygenase 2-prostaglandin axis, ASA's anti-cancer activities have also been attributed to nuclear factor ĸB (NFĸB) inhibition. Because prolonged ASA use may cause gastrointestinal toxicity, a prodrug strategy has been implemented successfully. In this prodrug design the carboxylic acid of ASA is masked and additional pharmacophores are incorporated. This protocol describes how we synthesized an aspirin-fumarate prodrug, GTCpFE, and characterized its inhibition of the NFĸB pathway in breast cancer cells and attenuation of the cancer stem-like properties, an important NFĸB-dependent phenotype. GTCpFE effectively inhibits the NFĸB pathway in breast cancer cell lines whereas ASA lacks any inhibitory activity, indicating that adding fumarate to ASA structure significantly contributes to its activity. In addition, GTCpFE shows significant anti-cancer stem cell activity by blocking mammosphere formation and attenuating the cancer stem cell associated CD44⁺CD24^- immunophenotype. These results establish a viable strategy to develop improved anti-inflammatory drugs for chemoprevention and cancer therapy.

Time-Gated Detection of Cystathionine γ-Lyase Activity and Inhibition with a Selective, Luminogenic Hydrogen Sulfide Sensor

Herein, we report the design, synthesis, and characterization of a lanthanide^III complex-based probe for the time-gated luminescence detection of hydrogen sulfide (H₂ S) in aqueous media. The probe's unique sensing mechanism relies on the selective reduction of azide to amine by sulfide, followed by intramolecular cyclization to form a quinolinone. The quinolinone is a sensitizer that absorbs near-UV light and transfers excitation energy to coordinated Tb^III or Eu^III ions to trigger a strong "turn-on" luminescence response with ms-scale lifetimes characteristic of lanthanide complexes. Using this probe, we developed a robust, high throughput screening (HTS) assay for detecting H₂ S generated by cystathionine γ-lyase (CSE), one of the main producers of H₂ S in mammalian cells. In a 240-compound screen to identify potential CSE inhibitors, the Eu^III analogue of the sensor showed a low false-positive rate and high Z'-factor (>0.7).

Abstract 3485: Estrogen receptor ligands and their responses in de novo and tamoxifen resistant cell models

Approximately 75% of breast cancer incidences are Estrogen Receptor positive (ER+). Tamoxifen, a selective estrogen receptor modulator (SERM), is the standard of care for many of these ER+ breast cancer patients. Unfortunately, tamoxifen resistance occurs in almost 50% of patients within 5 years of treatment, and endocrine-independence accompanying resistance negates the effects of aromatase inhibitors. Paradoxically, estradiol (E2) has shown clinical efficacy in patients with resistant breast cancer. Understanding the antiproliferative role of E2 and ER signaling in resistant ER+ cell lines is essential to gain a better understanding of paradoxical clinical efficacy and for the appropriate biomarker-assisted selection of endocrine therapy for various stages of ER+ breast cancer. We have discovered ER ligands, based upon a single chemical scaffold with a diverse set of pharmacological responses, which can be used to better understand the role of ER signaling in resistance and therapy: selective ER modulators (SERMs), selective ER downregulators (SERDs), selective estrogen mimics (SEMs), and selective human ER partial agonists (ShERPAs). These compounds were initially classified using an ERE luciferase reporter assay and affinity for ER confirmed by biochemical assays. The effects of these novel ER-directed chemical probes on cell viability were further examined in multiple 2D and 3D spheroid models of tamoxifen resistance. Finally, ERα localization upon administration of these ligands in tamoxifen-sensitive and tamoxifen-resistant cells was studied. While SERDs and SEMs showed growth inhibition in tamoxifen resistant cell lines, both molecules had different responses and mechanisms of growth inhibition. ERα was localized to extranuclear sites upon administration of E2, SEMs, and ShERPAs, an observation specific to the resistant phenotype and mechanistically associated with spheroid disintegration. SERDs inhibited the antiproliferative actions of E2, but were antiproliferative in resistant cell lines. Further dissection of the role of ER in resistance and survival is needed to define the appropriate ER-directed, endocrine therapy in ER+ breast cancer.

Citation Format: Lauren M. Gutgesell, Gregory R. J. Thatcher, Hitisha Patel, Rui Xiong. Estrogen receptor ligands and their responses in de novo and tamoxifen resistant cell models. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3485.

Abstract 4716: Dimethyl fumarate impairs breast cancer growth and inhibits the nuclear factor κB pathway in breast cancer cells by covalent modification of p65

Despite major advances in breast cancer treatment, successful therapy outcome is limited to early detection of cancer at the primary organ. Therapy options for aggressive, advanced stage, metastatic and recurring cancers are limited and this translates to poor patient outcome contributing to over 40,000 deaths each year in the United States. A key underlying factor of aggressive breast cancers is activation of the inflammatory nuclear factor κB (NFκB) pathway because it promotes numerous phenotypes such as cell survival, migration, invasion, angiogenesis, stem cell-like properties, and resistance to therapy. Therefore, adding an anti-inflammatory/anti-NFκB agent to breast cancer treatment would be beneficial, but no such drug is approved as either a mono- or adjuvant therapy. One option is Tecfidera® (dimethyl fumarate, DMF), the anti-inflammatory drug already in clinical use for multiple schlerosis. DMF is neuroprotective and is proposed to act via inhibition of the NFκB and activation of Nrf2 pathway. Most importantly, DMF has a proven safety in humans. This makes DMF an attractive candidate for NFκB inhibition in breast cancer therapy. Moreover, its therapeutic potential in treating breast cancer has yet to be explored.

We find that DMF inhibits proliferation of breast cancer cells in vitro. In addition, DMF abrogates mammosphere formation, a functional measure of cancer stem cell (CSC) properties. This prompted us to examine its activity in a murine breast cancer xenograft model. We find that DMF (30mg/kg daily) significantly impairs MDA-MB-231 tumor growth in athymic nude mice. As an anti-inflammatory agent, we show that DMF effectively blocks NFκB activity in multiple breast cancer cell lines. Mechanistically, DMF prevents p65 nuclear translocation and attenuates its DNA binding activity, but has no effect on upstream proteins in the NFκB pathway. Dimethyl succinate, the inactive analog of DMF that lacks the electrophilic double bond of fumarate, is unable to inhibit NFκB activity. Also, the cell permeable thiol, N-acetyl L-cysteine, reverses DMF's inhibition of the NFκB pathway, supporting the notion that the electrophile, DMF, acts via covalent modification. To determine whether DMF directly interacts with p65, we synthesized and used a novel chemical probe of DMF by incorporating an alkyne functionality, and found that DMF covalently modifies p65 at the cysteine 38 residue.

Altogether, these results establish DMF as a safe and effective NFκB inhibitor in breast cancer cells and elucidate its mechanism of action. These in addition to DMF's anti-tumor activity support the advancement of DMF as a therapeutic option to treat aggressive breast cancers in the clinic.

Citation Format: Irida Kastrati, Marton I. Siklos, Esther L. Calderon-Gierszal, Gregory R. J. Thatcher, Jonna Frasor. Dimethyl fumarate impairs breast cancer growth and inhibits the nuclear factor κB pathway in breast cancer cells by covalent modification of p65. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4716.

Prodrugs Bioactivated to Quinones Target NF-κB and Multiple Protein Networks: Identification of the Quinonome

Electrophilic reactive intermediates resulting from drug metabolism have been associated with toxicity and off-target effects and in some drug discovery programs trigger NO-GO decisions. Many botanicals and dietary supplements are replete with such reactive electrophiles, notably Michael acceptors, which have been demonstrated to elicit chemopreventive mechanisms; and Michael acceptors are gaining regulatory approval as contemporary cancer therapeutics. Identifying protein targets of these electrophiles is central to understanding potential therapeutic benefit and toxicity risk. NO-donating NSAID prodrugs (NO-NSAIDs) have been the focus of extensive clinical and preclinical studies in inflammation and cancer chemoprevention and therapy: a subset exemplified by pNO-ASA, induces chemopreventive mechanisms following bioactivation to an electrophilic quinone methide (QM) Michael acceptor. Having previously shown that these NO-independent, QM-donors activated Nrf2 via covalent modification of Keap-1, we demonstrate that components of canonical NF-κB signaling are also targets, leading to the inhibition of NF-κB signaling. Combining bio-orthogonal probes of QM-donor ASA prodrugs with mass spectrometric proteomics and pathway analysis, we proceeded to characterize the quinonome: the protein cellular targets of QM-modification by pNO-ASA and its ASA pro-drug congeners. Further comparison was made using a biorthogonal probe of the "bare-bones", Michael acceptor, and clinical anti-inflammatory agent, dimethyl fumarate, which we have shown to inhibit NF-κB signaling. Identified quinonome pathways include post-translational protein folding, cell-death regulation, protein transport, and glycolysis; and identified proteins included multiple heat shock elements, the latter functionally confirmed by demonstrating activation of heat shock response.

A multifunctional therapeutic approach to disease modification in multiple familial mouse models and a novel sporadic model of Alzheimer's disease

Background

Clinical failures singularly targeting amyloid-β pathology indicate a critical need for alternative Alzheimer’s disease (AD) therapeutic strategies. The mixed pathology reported in a large population of AD patients demands a multifunctional drug approach. Since activation of cAMP response element binding protein (CREB) plays a crucial role in synaptic strengthening and memory formation, we retooled a clinical drug with known neuroprotective and anti-inflammatory activity to activate CREB, and validated this novel multifunctional drug, NMZ, in 4 different mouse models of AD.

Results

NMZ was tested in three mouse models of familial AD and one model of sporadic AD. In 3 × Tg hippocampal slices, NMZ restored LTP. In vivo, memory was improved with NMZ in all animal models with robust cognitive deficits. NMZ treatment lowered neurotoxic forms of Aβ in both APP/PS1 and 3 × Tg transgenic mice while also restoring neuronal plasticity biomarkers in the 3 × Tg mice. In EFAD mice, incorporation of the major genetic AD risk factor, hAPOE4, did not mute the beneficial drug effects. In a novel sporadic mouse model that manifests AD-like pathology caused by accelerated oxidative stress in the absence of any familial AD mutation, oral administration of NMZ attenuated hallmark AD pathology and restored biomarkers of synaptic and neuronal function.

Conclusions

The multifunctional approach, embodied by NMZ, was successful in mouse models of AD incorporating Aβ pathology (APP/PS1), tau pathology (3xTg), and APOE4, the major human genetic risk factor for AD (EFAD). The efficacy observed in a novel model of sporadic AD (Aldh2^−/−) demonstrates that the therapeutic approach is not limited to rare, familial AD genetic mutations. The multifunctional drug, NMZ, was not designed directly to target Aβ and tau pathology; however, the attenuation of this hallmark pathology suggests the approach to be a highly promising, disease-modifying strategy for AD and mixed pathology dementia.