Collaboration and knowledge integration for successful brain therapeutics - lessons learned from the pandemic

Brain diseases are a major cause of death and disability worldwide and contribute significantly to years of potential life lost. Although there have been considerable advances in biological mechanisms associated with brain disorders as well as drug discovery paradigms in recent years, these have not been sufficiently translated into effective treatments. This Special Article expands on Keystone Symposia's pre- and post-pandemic panel discussions on translational neuroscience research. In the article, we discuss how lessons learned from the COVID-19 pandemic can catalyze critical progress in translational research, with efficient collaboration bridging the gap between basic discovery and clinical application. To achieve this, we must place patients at the center of the research paradigm. Furthermore, we need commitment from all collaborators to jointly mitigate the risk associated with the research process. This will require support from investors, the public sector and pharmaceutical companies to translate disease mechanisms into world-class drugs. We also discuss the role of scientific publishing in supporting these models of open innovation. Open science journals can now function as hubs to accelerate progress from discovery to treatments, in neuroscience in particular, making this process less tortuous by bringing scientists together and enabling them to exchange data, tools and knowledge effectively. As stakeholders from a broad range of scientific professions, we feel an urgency to advance brain disease therapies and encourage readers to work together in tackling this challenge.

GNE-064: A Potent, Selective, and Orally Bioavailable Chemical Probe for the Bromodomains of SMARCA2 and SMARCA4 and the Fifth Bromodomain of PBRM1

Bromodomains are acetyllysine recognition domains present in a variety of human proteins. Bromodomains also bind small molecules that compete with acetyllysine, and therefore bromodomains have been targets for drug discovery efforts. Highly potent and selective ligands with good cellular permeability have been proposed as chemical probes for use in exploring the functions of many of the bromodomain proteins. We report here the discovery of a class of such inhibitors targeting the family VIII bromodomains of SMARCA2 (BRM) and SMARCA4 (BRG1), and PBRM1 (polybromo-1) bromodomain 5. We propose one example from this series, GNE-064, as a chemical probe for the bromodomains SMARCA2, SMARCA4, and PBRM1(5) with the potential for in vivo use.

Identification and characterization of second-generation EZH2 inhibitors with extended residence times and improved biological activity

The histone methyltransferase EZH2 has been the target of numerous small-molecule inhibitor discovery efforts over the last 10+ years. Emerging clinical data have provided early evidence for single agent activity with acceptable safety profiles for first-generation inhibitors. We have developed kinetic methodologies for studying EZH2-inhibitor-binding kinetics that have allowed us to identify a unique structural modification that results in significant increases in the drug-target residence times of all EZH2 inhibitor scaffolds we have studied. The unexpected residence time enhancement bestowed by this modification has enabled us to create a series of second-generation EZH2 inhibitors with sub-pM binding affinities. We provide both biophysical evidence validating this sub-pM potency and biological evidence demonstrating the utility and relevance of such high-affinity interactions with EZH2.

Design, Synthesis, and Pharmacological Evaluation of Second Generation EZH2 Inhibitors with Long Residence Time

Histone methyltransferase EZH2, which is the catalytic subunit of the PRC2 complex, catalyzes the methylation of histone H3K27-a transcriptionally repressive post-translational modification (PTM). EZH2 is commonly mutated in hematologic malignancies and frequently overexpressed in solid tumors, where its expression level often correlates with poor prognosis. First generation EZH2 inhibitors are beginning to show clinical benefit, and we believe that a second generation EZH2 inhibitor could further build upon this foundation to fully realize the therapeutic potential of EZH2 inhibition. During our medicinal chemistry campaign, we identified 4-thiomethyl pyridone as a key modification that led to significantly increased potency and prolonged residence time. Leveraging this finding, we optimized a series of EZH2 inhibitors, with enhanced antitumor activity and improved physiochemical properties, which have the potential to expand the clinical use of EZH2 inhibition.

Design and Synthesis of Styrenylcyclopropylamine LSD1 Inhibitors

Leveraging the catalytic machinery of LSD1 (KDM1A), a series of covalent styrenylcyclopropane LSD1 inhibitors were identified. These inhibitors represent a new class of mechanism-based inhibitors that target and covalently label the FAD cofactor of LSD1. The series was rapidly progressed to potent biochemical and cellular LSD1 inhibitors with good physical properties. This effort resulted in the identification of 34, a highly potent (<4 nM biochemical, 2 nM cell, and 1 nM GI50), and selective LSD1 inhibitor. In-depth kinetic profiling of 34 confirmed its covalent mechanism of action, validated the styrenylcyclopropane as an FAD-directed warhead, and demonstrated that the potency of this inhibitor is driven by improved non-covalent binding (K I). 34 demonstrated robust cell-killing activity in a panel of AML cell lines and robust antitumor activity in a Kasumi-1 xenograft model of AML when dosed orally at 1.5 mg/kg once daily.

Early Drug-Discovery Efforts towards the Identification of EP300/CBP Histone Acetyltransferase (HAT) Inhibitors

EP300 and CBP (KAT3A/3B) are two highly homologous, multidomain, epigenetic coregulators that play central roles in transcription through the acetylation of lysine residues on histones and other proteins. Both enzymes have been implicated in human diseases, especially cancer. From a high-throughput screen of 191 000 compounds searching for EP300/CBP histone acetyltransferase (HAT) inhibitors, 18 compounds were characterized by a suite of biochemical enzymatic assays and biophysical methods, including X-ray crystallography and native mass spectrometry. This work resulted in the discovery of three distinct mechanistic classes of EP300/CBP HAT inhibitors, including two classes not previously described. The profiles of an example of each class of inhibitor are described in detail. A subsequent medicinal chemistry effort led to the development of a novel class of orally bioavailable AcCoA-competitive EP300/CBP HAT inhibitors with in vivo activity. We believe that this work will prove to be a useful guide for other groups interested in the development of HAT inhibitors.

Mentoring Matters in Drug Discovery

Mentoring is an essential opportunity to be embraced by medicinal chemists seeking a gratifying career. In this Viewpoint, we highlight the importance of developing an intentional mindset about mentoring to achieve professional goals. The impact of mentoring is even more critical for underrepresented minorities in drug discovery and in particular for women aspiring to achieve leadership positions in the field.

GNE-886: A Potent and Selective Inhibitor of the Cat Eye Syndrome Chromosome Region Candidate 2 Bromodomain (CECR2)

The biological function of bromodomains, epigenetic readers of acetylated lysine residues, remains largely unknown. Herein we report our efforts to discover a potent and selective inhibitor of the bromodomain of cat eye syndrome chromosome region candidate 2 (CECR2). Screening of our internal medicinal chemistry collection led to the identification of a pyrrolopyridone chemical lead, and subsequent structure-based drug design led to a potent and selective CECR2 bromodomain inhibitor (GNE-886) suitable for use as an in vitro tool compound.

Identification of (R)-N-((4-Methoxy-6-methyl-2-oxo-1,2-dihydropyridin-3-yl)methyl)-2-methyl-1-(1-(1-(2,2,2-trifluoroethyl)piperidin-4-yl)ethyl)-1H-indole-3-carboxamide (CPI-1205), a Potent and Selective Inhibitor of Histone Methyltransferase EZH2, Suitable for Phase I Clinical Trials for B-Cell Lymphomas

Polycomb repressive complex 2 (PRC2) has been shown to play a major role in transcriptional silencing in part by installing methylation marks on lysine 27 of histone 3. Dysregulation of PRC2 function correlates with certain malignancies and poor prognosis. EZH2 is the catalytic engine of the PRC2 complex and thus represents a key candidate oncology target for pharmacological intervention. Here we report the optimization of our indole-based EZH2 inhibitor series that led to the identification of CPI-1205, a highly potent (biochemical IC₅₀ = 0.002 μM, cellular EC₅₀ = 0.032 μM) and selective inhibitor of EZH2. This compound demonstrates robust antitumor effects in a Karpas-422 xenograft model when dosed at 160 mg/kg BID and is currently in Phase I clinical trials. Additionally, we disclose the co-crystal structure of our inhibitor series bound to the human PRC2 complex.

Diving into the Water: Inducible Binding Conformations for BRD4, TAF1(2), BRD9, and CECR2 Bromodomains

The biological role played by non-BET bromodomains remains poorly understood, and it is therefore imperative to identify potent and highly selective inhibitors to effectively explore the biology of individual bromodomain proteins. A ligand-efficient nonselective bromodomain inhibitor was identified from a 6-methyl pyrrolopyridone fragment. Small hydrophobic substituents replacing the N-methyl group were designed directing toward the conserved bromodomain water pocket, and two distinct binding conformations were then observed. The substituents either directly displaced and rearranged the conserved solvent network, as in BRD4(1) and TAF1(2), or induced a narrow hydrophobic channel adjacent to the lipophilic shelf, as in BRD9 and CECR2. The preference of distinct substituents for individual bromodomains provided selectivity handles useful for future lead optimization efforts for selective BRD9, CECR2, and TAF1(2) inhibitors.

Regulatory T Cell Modulation by CBP/EP300 Bromodomain Inhibition

Covalent modification of histones is a fundamental mechanism of regulated gene expression in eukaryotes, and interpretation of histone modifications is an essential feature of epigenetic control. Bromodomains are specialized binding modules that interact with acetylated histones, linking chromatin recognition to gene transcription. Because of their ability to function in a domain-specific fashion, selective disruption of bromodomain:acetylated histone interactions with chemical probes serves as a powerful means for understanding biological processes regulated by these chromatin adaptors. Here we describe the discovery and characterization of potent and selective small molecule inhibitors for the bromodomains of CREBBP/EP300 that engage their target in cellular assays. We use these tools to demonstrate a critical role for CREBBP/EP300 bromodomains in regulatory T cell biology. Because regulatory T cell recruitment to tumors is a major mechanism of immune evasion by cancer cells, our data highlight the importance of CREBBP/EP300 bromodomain inhibition as a novel, small molecule-based approach for cancer immunotherapy.

Histone Modifications and Cancer

Histone posttranslational modifications represent a versatile set of epigenetic marks involved not only in dynamic cellular processes, such as transcription and DNA repair, but also in the stable maintenance of repressive chromatin. In this article, we review many of the key and newly identified histone modifications known to be deregulated in cancer and how this impacts function. The latter part of the article addresses the challenges and current status of the epigenetic drug development process as it applies to cancer therapeutics.

Discovery of Benzotriazolo[4,3-d][1,4]diazepines as Orally Active Inhibitors of BET Bromodomains

Inhibition of the bromodomains of the BET family, of which BRD4 is a member, has been shown to decrease myc and interleukin (IL) 6 in vivo, markers that are of therapeutic relevance to cancer and inflammatory disease, respectively. Herein we report substituted benzo[b]isoxazolo[4,5-d]azepines and benzotriazolo[4,3-d][1,4]diazepines as fragment-derived novel inhibitors of the bromodomain of BRD4. Compounds from these series were potent and selective in cells, and subsequent optimization of microsomal stability yielded representatives that demonstrated dose- and time-dependent reduction of plasma IL-6 in mice.

EZH2 inhibitor efficacy in non-Hodgkin's lymphoma does not require suppression of H3K27 monomethylation

The histone lysine methyltransferase (MT) Enhancer of Zeste Homolog 2 (EZH2) is considered an oncogenic driver in a subset of germinal center B-cell-like diffuse large B cell lymphoma (GCB-DLBCL) and follicular lymphoma due to the presence of recurrent, monoallelic mutations in the EZH2 catalytic domain. These genomic data suggest that targeting the EZH2 MT activity is a valid therapeutic strategy for the treatment of lymphoma patients with EZH2 mutations. Here we report the identification of highly potent and selective EZH2 small molecule inhibitors, their validation by a cellular thermal shift assay, application across a large cell panel representing various non-Hodgkin's lymphoma (NHL) subtypes, and their efficacy in EZH2mutant-containing GCB-DLBCL xenograft models. Surprisingly, our EZH2 inhibitors selectively affect the turnover of trimethylated, but not monomethylated histone H3 lysine 27 at pharmacologically relevant doses. Importantly, we find that these inhibitors are broadly efficacious also in NHL models with wild-type EZH2.

Discovery, design, and synthesis of indole-based EZH2 inhibitors

The discovery and optimization of a series of small molecule EZH2 inhibitors is described. Starting from dimethylpyridone HTS hit (2), a series of indole-based EZH2 inhibitors were identified. Biochemical potency and microsomal stability were optimized during these studies and afforded compound 22. This compound demonstrates nanomolar levels of biochemical potency (IC50=0.002 μM), cellular potency (EC50=0.080 μM), and afforded tumor regression when dosed (200 mpk SC BID) in an EZH2 dependent tumor xenograft model.

Development of methyl isoxazoleazepines as inhibitors of BET

In this report we detail the evolution of our previously reported thiophene isoxazole BET inhibitor chemotype exemplified by CPI-3 to a novel bromodomain selective chemotype (the methyl isoxazoleazepine chemotype) exemplified by carboxamide 23. The methyl isoxazoleazepine chemotype provides potent inhibition of the bromodomains of the BET family, excellent in vivo PK across species, low unbound clearance, and target engagement in a MYC PK-PD model.

A practical synthesis of indoles via a Pd-catalyzed C-N ring formation

A method for the synthesis of N-functionalized C2-/C3-substituted indoles via Pd-catalyzed C-N bond coupling of halo-aryl enamines is described. The general strategy utilizes a variety of amines and β-keto esters which are elaborated into halo-aryl enamines as latent precursors to indoles. The preferred conditions comprising the RuPhos precatalyst and RuPhos in the presence of NaOMe in 1,4-dioxane tolerate a variety of substituents and are scalable for the construction of indoles in multigram quantities.

Discovery and Optimization of Tetramethylpiperidinyl Benzamides as Inhibitors of EZH2

The identification and development of a novel series of small molecule Enhancer of Zeste Homologue 2 (EZH2) inhibitors is described. A concise and modular synthesis enabled the rapid development of structure-activity relationships, which led to the identification of 44 as a potent, SAM-competitive inhibitor of EZH2 that dose-dependently decreased global H3K27me3 in KARPAS-422 lymphoma cells.

Identification of EZH2 and EZH1 small molecule inhibitors with selective impact on diffuse large B cell lymphoma cell growth

The histone methyltransferase enhancer of Zeste homolog 2 (EZH2) is a candidate oncogene due to its prevalent overexpression in malignant diseases, including late stage prostate and breast cancers. The dependency of cancer cells on EZH2 activity is also predicated by recurrent missense mutations residing in the catalytic domain of EZH2 that have been identified in subtypes of diffuse large B cell lymphoma, follicular lymphoma and melanoma. Herein, we report the identification of a highly selective small molecule inhibitor series of EZH2 and EZH1. These compounds inhibit wild-type and mutant versions of EZH2 with nanomolar potency, suppress global histone H3-lysine 27 methylation, affect gene expression, and cause selective proliferation defects. These compounds represent a structurally distinct EZH2 inhibitor chemotype for the exploration of the role of Polycomb Repressive Complex 2-mediated H3K27 methylation in various biological contexts.

Discovery, Design, and Optimization of Isoxazole Azepine BET Inhibitors

The identification of a novel series of small molecule BET inhibitors is described. Using crystallographic binding modes of an amino-isoxazole fragment and known BET inhibitors, a structure-based drug design effort lead to a novel isoxazole azepine scaffold. This scaffold showed good potency in biochemical and cellular assays and oral activity in an in vivo model of BET inhibition.

Abstract 4621: The histone methyltransferase EZH2 catalytic activity is required for cell growth in diffuse large B-cell lymphoma

Lysine methyltransferases and demethylases were identified as transcriptional co-regulators functioning by either preserving particular chromatin methylation states or by controlling placement and removal of histone lysine methylation marks to promote dynamic changes in gene expression. The development of small molecule methyltransferase and demethylase inhibitors provides a novel approach to affect the regulation of transcription, and thus potentially allowing interference with aberrant transcriptional programs as observed, for instance, in cancer.

Enhancer of Zeste Homolog 2 (EZH2), the major histone H3 lysine 27 (K27) methyltransferase, is widely implicated in tumor progression. The presence of a recurrent mutation of a single tyrosine residue in the EZH2 catalytic domain in germinal center B-cell like diffuse large B-cell lymphoma (GCB-DLBCL) and follicular lymphoma suggests that these cancers might be dependent on altered EZH2 molecular function, the mutation facilitating the conversion of an H3K27 di-methylated to a tri-methylated state. Inhibition of the EZH2 catalytic activity will provide a new therapeutic approach to treat human cancers, especially lymphomas carrying activating mutations.

Constellation has identified, characterized and optimized potent, selective and reversible EZH2 small molecule inhibitors as well as studied the biological impact of such inhibition. We find that pharmacological inhibition of EZH2 causes selective cell viability defects with cell lines harboring EZH2 mutations being the most sensitive. Our EZH2 inhibitors potently engage the target in vivo and exhibit efficacy in lymphoma xenograft models. Genome-wide mapping of EZH2 and H3K27me3 sites in the absence and presence of the compound revealed that the EZH2 inhibitor caused significant changes to the local chromatin modification landscape, however only a subset of these alterations translated into gene expression changes. The discovery of additional contexts that define sensitivity to EZH2 inhibitors will be discussed.

Citation Format: James E. Audia, Patrick Trojer, Shivani Garapaty, Fei Lan, Vidya Balasubramanian, Eric Chan, Charles Hatton, Robert Campbell, Richard Cummings, Emmanuel Normant, Barbara Bryant, Brian Albrecht, Jean Christophe Harmange, Les Dakin, Victor Gehling, Chris Nasveschuk, Rishi Vaswani, Andrew Cook. The histone methyltransferase EZH2 catalytic activity is required for cell growth in diffuse large B-cell lymphoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4621. doi:10.1158/1538-7445.AM2013-4621

Robust central reduction of amyloid-β in humans with an orally available, non-peptidic β-secretase inhibitor

According to the amyloid cascade hypothesis, cerebral deposition of amyloid-β peptide (Aβ) is critical for Alzheimer's disease (AD) pathogenesis. Aβ generation is initiated when β-secretase (BACE1) cleaves the amyloid precursor protein. For more than a decade, BACE1 has been a prime target for designing drugs to prevent or treat AD. However, development of such agents has turned out to be extremely challenging, with major hurdles in cell penetration, oral bioavailability/metabolic clearance, and brain access. Using a fragment-based chemistry strategy, we have generated LY2811376 [(S)-4-(2,4-difluoro-5-pyrimidin-5-yl-phenyl)-4-methyl-5,6-dihydro-4H-[1,3]thiazin-2-ylamine], the first orally available non-peptidic BACE1 inhibitor that produces profound Aβ-lowering effects in animals. The biomarker changes obtained in preclinical animal models translate into man at doses of LY2811376 that were safe and well tolerated in healthy volunteers. Prominent and long-lasting Aβ reductions in lumbar CSF were measured after oral dosing of 30 or 90 mg of LY2811376. This represents the first translation of BACE1-driven biomarker changes in CNS from preclinical animal models to man. Because of toxicology findings identified in longer-term preclinical studies, this compound is no longer progressing in clinical development. However, BACE1 remains a viable target because the adverse effects reported here were recapitulated in LY2811376-treated BACE1 KO mice and thus are unrelated to BACE1 inhibition. The magnitude and duration of central Aβ reduction obtainable with BACE1 inhibition positions this protease as a tractable small-molecule target through which to test the amyloid hypothesis in man.

Abstract B188: Inhibition of Notch signaling for the treatment of cancer

The Notch pathway is a highly conserved signaling system that plays an important role in development and tissue homeostasis. While Notch mutations are well characterized and implicated in hematological malignancies such as T-cell acute lymphoblastic leukemia, in solid tumors ligand or receptor over-expression may lead to enhanced/sustained Notch function, triggering increased tumor cell proliferation/survival, angiogenesis and tumor formation. In order to delineate an oncogenic role of activated Notch in tumors of epithelial origin, we carried out a series of in-vitro and in-vivo studies. We demonstrated that the activated Notch1 receptor (a - secretase-dependent Notch1 E with the transmembrane domain and a-secretase-independent constitutively activated Notch1 intracellular fragment) can transform normal rat cells, RK3E. These transformed cells formed colonies in soft agar, confirming their anchorage-independent growth potential, and when implanted subcutaneously, formed tumors in athymic nude mice. Inhibition of Notch signaling through a small molecule inhibitor of -secretase, a key regulator of Notch processing, may provide an attractive targeted cancer therapeutic strategy. We have identified and characterized a novel small molecule that is an exquisitely potent inhibitor of Notch signaling in tumor cell lines and endothelial cells with an IC50 ranging from 0.005 nM to 20 nM. The Notch inhibitor meets all pharmacokinetic criteria in pre-clinical species. In a xenograft tumor model, the novel compound inhibited Notch cleavage in a dose-dependent manner at 6 hours after a single oral dose. This inhibition of Notch cleavage resulted in the induction of apoptosis (as measured by activated caspase-3 levels) that was statistically significant at 24 hours after a single oral dose of 3 mg/kg. Analysis of tumors from animals treated with the Notch inhibitor revealed inhibition of angiogenesis through formation of leaky vasculature which may also contribute to observed anti-tumor activity. Furthermore, Notch inhibition produced tumor regression in the Notch-dependent tumor models. Anti-tumor activity was also observed in several human xenograft tumors of epithelial origin. To mitigate mucoid gasteroentropathy due to Notch inhibition, PK/PD data were incorporated in devising dosing strategies that identified an optimal intermittent dosing schedule without negatively impacting efficacy. Furthermore, the mucoid gastroentropathy was also mitigated by the prophylactic administration of dexamethasone without negatively impacting Notch inhibitor mediated efficacy. In summary, we have characterized an orally bio-available small molecule Notch inhibitor that may provide therapeutic benefit to cancer patients.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):B188.

[3H]LY334370, a novel radioligand for the 5-HT1F receptor. I. In vitro characterization of binding properties

[(3)H]LY334370 was developed as a radioligand to study the characteristics of this compound's interaction with the 5-HT(1F) receptor. Monovalent or divalent cations did not enhance the binding of [(3)H]LY334370 to the cloned human 5-HT(1F) receptor. In the presence of MgCl(2), the time to reach equilibrium was approximately 2 h, while in its absence equilibrium was reached in less than 1 h. [(3)H]LY334370 had high affinity for the cloned human 5-HT(1F) receptor (K(d)=0.446 nM) and the 5-HT(1F) receptor in rat brain (K(d)=0.388 nM). The expression density of 5-HT(1F) receptors, as determined by binding to homogenates of cortical regions from rat, was low (B(max)=79.1 fmol/mg protein). There was a statistically significant correlation between the apparent pK(i) for inhibition of [(3)H]LY334370 binding and the pEC(50) for stimulation of [(35)S]GTPgammaS binding to homogenates of cells expressing the cloned human 5-HT(1F) receptor. In addition, there was a statistically significant correlation between the apparent pK(i) for inhibition of [(3)H]LY334370 binding to the cloned human 5-HT(1F) receptor and the pID(50) for inhibition of trigeminal nerve stimulated dural plasma protein extravasation in the guinea pig. The conclusion from these studies is that [(3)H]LY334370 is a high affinity radioligand which can be used for the study of the 5-HT(1F) receptor in rat brain or in cells transformed with the human 5-HT(1F) receptor.

[3H]LY334370, a novel radioligand for the 5-HT1F receptor. II. Autoradiographic localization in rat, guinea pig, monkey and human brain

LY334370 is a high affinity, selective agonist at the 5-HT(1F) receptor. On this basis, the tritiated compound was examined for its utility in autoradiography to localize the 5-HT(1F) receptor in rat and guinea pig brain regions. Specific 5-HT(1F) receptor binding in rat brain was found in layers 4-5 of all cortical regions examined, as well as olfactory bulb and tubercle, nucleus accumbens, caudate putamen, parafascicular nucleus of the thalamus, medial mammillary nucleus, the CA3 region of the hippocampus, subiculum, and several amygdaloid nuclei. In guinea pig brain, the [(3)H]LY334370 binding sites were found at highest density in claustrum, but also in a layer of the cortex, caudate putamen, nucleus accumbens, thalamus, and medial mammillary nucleus. Some species differences in the distribution of the 5-HT(1F) receptor were noted. Side by side comparison of rat brain autoradiography with [(3)H]LY334370 and [(3)H]sumatriptan showed labeling in the same brain regions. Preliminary binding studies in rhesus monkey and human brain sections showed [(3)H]LY334370 binding in cortical layers 4-5, subiculum (in the monkey), and the granule cell layer of the cerebellum. These findings suggest a discrete localization of the 5-HT(1F) receptor in the rat, guinea pig, monkey and human brain, and confirms the utility of [(3)H]LY334370 as a potential tool to explore further the localization and possible functions of the 5-HT(1F) receptor.

In vivo assessment of brain interstitial fluid with microdialysis reveals plaque-associated changes in amyloid-beta metabolism and half-life

Soluble amyloid-beta (Abeta) peptide converts to structures with high beta-sheet content in Alzheimer's disease (AD). Soluble Abeta is released by neurons into the brain interstitial fluid (ISF), in which it can convert into toxic aggregates. Because assessment of ISF Abeta levels may provide unique insights into Abeta metabolism and AD, an in vivo microdialysis technique was developed to measure it. Our Abeta microdialysis technique was validated ex vivo with human CSF and then in vivo in awake, freely moving mice. Using human amyloid precursor protein (APP) transgenic mice, we found that, before the onset of AD-like pathology, ISF Abeta in hippocampus and cortex correlated with levels of APP in those tissues. After the onset of Abeta deposition, significant changes in the ISF Abeta40/Abeta42 ratio developed without changes in Abeta1-x. These changes differed from changes seen in tissue lysates from the same animals. By rapidly inhibiting Abeta production, we found that ISF Abeta half-life was short ( approximately 2 hr) in young mice but was twofold longer in mice with Abeta deposits. This increase in half-life, without an increase in steady-state levels, suggests that inhibition of Abeta synthesis reveals a portion of the insoluble Abeta pool that is in dynamic equilibrium with ISF Abeta. This now measurable in vivo pool is a likely target for new diagnostic and therapeutic strategies.

Neurogenic dural protein extravasation induced by meta-chlorophenylpiperazine (mCPP) involves nitric oxide and 5-HT2B receptor activation

The compound m-chlorophenylpiperazine (mCPP), which is known to trigger migraine-like head pain in some subjects, was evaluated for its ability to induce dural plasma protein extravasation (PPE) in guinea pigs. Intravenous mCPP dose-dependently increased PPE. This effect was inhibited by non-selective 5-HT2 receptor antagonists (methysergide, LY53857, LY215840), by a peripherally restricted 5-HT2 receptor antagonist (xylamidine) and by a 5-HT2B selective receptor antagonist (LY202146). These data suggests that peripheral 5-HT2B receptors mediate mCPP-induced PPE. The nitric oxide synthase inhibitor L-NAME and 5-HT1 agonist sumatriptan also blocked mCPP-induced PPE, suggesting a role for nitric oxide (NO) and the trigeminal system, respectively. NO release has been linked to activation of the 5-HT2B receptor on the vascular endothelium. However, LY202146 did not block PPE induced by electrical stimulation of the trigeminal ganglion. These data are consistent with activation of peripheral 5-HT2B receptors initiating PPE and the theory that selective 5-HT2B antagonists might be effective prophylactic therapies for migraine.

A series of C-terminal amino alcohol dipeptide A beta inhibitors

Potent, small molecule A beta inhibitors have been prepared that incorporate an alanine core bracketed by an N-terminal arylacetyl group and various C-terminal amino alcohols. The compounds exhibit stereospecific inhibition as demonstrated in an in vitro assay.

Comparison of the effects of serotonin selective, norepinephrine selective, and dual serotonin and norepinephrine reuptake inhibitors on lower urinary tract function in cats

Previous studies showed that the dual serotonin (5-hydroxytryptamine, 5-HT) and norepinephrine (NE) reuptake inhibitor, duloxetine, increases bladder capacity and urethral sphincter electromyographic (EMG) activity in a cat model of acetic acid-induced bladder irritation. The present study aimed to determine the relative importance of 5-HT versus NE reuptake inhibition for mediating these effects by examining drugs that are selective for either the 5-HT or NE system or both. Similar to duloxetine, venlafaxine (0.1 to 10 mg/kg), also a dual serotonin and norepinephrine reuptake inhibitor, produced marked increases in bladder capacity and EMG activity that were reversed by methiothepin (0.3 mg/kg). S-norfluoxetine (0.01 to 10 mg/kg), a serotonin selective reuptake inhibitor, produced small but significant increases in bladder capacity and EMG activity at doses of 3 and 10 mg/kg. Thionisoxetine (0.01 to 3.0 mg/kg), a NE selective reuptake inhibitor, produced no effects on bladder capacity or sphincter EMG activity. Surprisingly, co-administration of thionisoxetine and s-norfluoxetine up to doses of 1 mg/kg of each compound produced no effect on lower urinary tract function. These doses were the maximum that could be administered in combination due to drug-induced emergence of skeletal muscle activity in chloralose-anesthetized animals. These results indicate that there are unexplained pharmacological differences between the effects of single compounds that exhibit dual NE and 5-HT reuptake inhibition and a combination of compounds that exhibit selective NE and 5-HT reuptake inhibition on lower urinary tract function.

N-[3-(2-Dimethylaminoethyl)-2-methyl-1H- indol-5-yl]-4-fluorobenzamide: a potent, selective, and orally active 5-HT(1F) receptor agonist potentially useful for migraine therapy

Recent studies have demonstrated that selective 5-HT(1F) receptor agonists inhibit neurogenic dural inflammation, a model of migraine headache, indicating that these compounds may be effective therapies for the treatment of migraine pain. This communication describes the synthesis and discovery of a novel compound, N-[3-(2-(dimethylamino)ethyl)-2-methyl-1H-indol-5-yl]-4-fluorobenzamide (4), which possesses high binding affinity and selectivity at the 5-HT(1F) receptor relative to more than 40 other serotonergic and nonserotonergic receptors examined.

Functional gamma-secretase inhibitors reduce beta-amyloid peptide levels in brain

Converging lines of evidence implicate the beta-amyloid peptide (Ass) as causative in Alzheimer's disease. We describe a novel class of compounds that reduce A beta production by functionally inhibiting gamma-secretase, the activity responsible for the carboxy-terminal cleavage required for A beta production. These molecules are active in both 293 HEK cells and neuronal cultures, and exert their effect upon A beta production without affecting protein secretion, most notably in the secreted forms of the amyloid precursor protein (APP). Oral administration of one of these compounds, N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester, to mice transgenic for human APP(V717F) reduces brain levels of Ass in a dose-dependent manner within 3 h. These studies represent the first demonstration of a reduction of brain A beta in vivo. Development of such novel functional gamma-secretase inhibitors will enable a clinical examination of the A beta hypothesis that Ass peptide drives the neuropathology observed in Alzheimer's disease.