CCK2 receptor antagonists potentiate pain relief by MOP receptor agonists. In an attempt to enhance this effect, we prepared bivalent ligands incorporating CCK2 receptor antagonist and MOP receptor agonist pharmacophores.9 Ligands with 16- to 22-atom spacers could simultaneously bind both receptors but provided no advantage in activity over individual ligands. We now examine the effect of these ligands on receptor internalization as a mechanism of receptor regulation. We prepared CHO cell lines expressing nonfluorescent halves (YN and YC) of yellow fluorescent protein attached to each receptor. Spatial approximation of constructs was needed to yield fluorescence. Monovalent MOP agonist 1 signaled normally and internalized the MOP receptor. Monovalent CCK2 antagonist 2 did not stimulate receptor internalization. In the dual receptor-bearing cells, bivalent ligands 3a–c capable of simultaneously binding both receptors resulted in cell surface fluorescence and internalization of the fluorescent complex in a time- and temperature-dependent manner. Bivalent ligand 4 with spacer too short to occupy both receptors simultaneously yielded no signal. Receptor tethering with appropriate bivalent ligands can down-regulate signaling by moving a nonactivated receptor into the endocytic pathway.

Some antipsychotic drugs are known to cause valvular heart disease by activating serotonin 5-HT2B receptors. We have developed and validated binary classification QSAR models capable of predicting potential 5-HT2B binders. The classification accuracies of the models to discriminate 5-HT2B actives from the inactives were as high as 80% for the external test set. These models were used to screen in silico 59,000 compounds included in the World Drug Index and 122 compounds were predicted as actives with high confidence. Ten of them were tested in radioligand binding assays and nine were found active suggesting a success rate of 90%. All validated binders were then tested in functional assays and one compound was identified as a true 5-HT2B agonist. We suggest that the QSAR models developed in this study could be used as reliable predictors to flag drug candidates that are likely to cause valvulopathy.

The binding of zonisamide to purified, recombinant monoamine oxidases (MAOs) has been investigated. It is a competitive inhibitor of human MAO B (Ki = 3.1 ± 0.3 μM), of rat MAO B (Ki = 2.9 ± 0.5 μM), and of zebrafish MAO (Ki = 30.8 ± 5.3 μM). No inhibition is observed with purified human or rat MAO A. The 1.8 Å structure of the MAO B complex demonstrates that it binds within the substrate cavity.

Novel derivatives of the clinically established anticancer drug oxaliplatin were synthesized. Cytotoxicity of the compounds was studied in six human cancer cell lines by means of the MTT assay. Additionally, most promising complexes were also investigated in cisplatin- and oxaliplatin-resistant human cancer cell models. The therapeutic efficacy in vivo was studied in the murine L1210 leukemia model. Most remarkably, {(1R,2R,4R)-4-methyl-1,2-cyclohexanediamine}oxalatoplatinum(II), comprising an equatorial methyl substituent at position 4 of the cyclohexane ring, was as potent as oxaliplatin in vitro but distinctly more effective in the L1210 model in vivo at the optimal dose. The advantage observed in the in vivo situation was mainly based on a more favorable therapeutic index. The maximum tolerated dose of the novel analogue was higher than that of oxaliplatin and caused a greater increase in life span (>200% versus 152%), with more animals experiencing long-term survival (5/6 versus 2/6). These data support further (pre)clinical development of the methyl-substituted oxaliplatin analogue with improved anticancer activity.

7,8-Dihydroxyflavone is a recently identified small molecular tropomyosin-receptor-kinase B (TrkB) agonist. Our preliminary structural activity relationship (SAR) study showed that the 7,8-dihydroxy groups are essential for the agonistic effect. To improve the lead compound's agonistic activity, we have conducted an extensive SAR study and synthesized numerous derivatives. We have successfully identified 4'-dimethylamino-7,8-dihydroxyflavone that displays higher TrkB agonistic activity than the lead. This novel compound also exhibits a more robust and longer TrkB activation effect in animals. Consequently, this new compound reveals more potent anti-apoptotic activity. Interestingly, chronic oral administration of 4'-dimethylamino-7,8-dihydroxyflavone and its lead strongly promotes neurogenesis in dentate gyrus and demonstrates marked antidepressant effects. Hence, our data support that the synthetic 4'-dimethylamino-7,8-dihydroxyflavone and its lead both are orally bioavailable TrkB agonists and possess potent antidepressant effects.

The inhibition of the mammalian soluble epoxide hydrolase (sEH) is a promising new therapy in the treatment of hypertension, inflammation and other disorders. However, the problems of limited water solubility, high melting point and low metabolic stability complicated the development of 1,3-disubstituted urea-based sEH inhibitors. The current study explored the introduction of the substituted piperazino group as the tertiary pharmacophore, which resulted in substantial improvements in pharmacokinetic parameters over previously reported 1-adamantyl-urea based inhibitors while retaining high potency. The SAR studies revealed that the meta- or para-substituted phenyl spacer, and N4-acetyl or sulfonyl substituted piperazine were optimal structures for achieving high potency and good physical properties. The 1-(4-(4-(4-acetylpiperazin-1-yl)butoxy)phenyl)-3-adamantan-1-yl urea (29c) demonstrated excellent in vivo pharmacokinetic properties in mice: T1/2 =14 h, Cmax = 84 nM and AUC = 40200 nM • min with an IC50 value of 7.0 nM against human sEH enzyme.

A new series of 3-ethynyl-1H–indazoles has been synthesized and evaluated in both biochemical and cell-based assays as potential kinase inhibitors. Interestingly, a selected group of compounds identified from this series exhibited low micromolar inhibition against critical components of the PI3K pathway, targeting PI3K, PDK1 and mTOR kinases. Combination of computational modeling and structure-activity relationships studies reveal a possible novel mode for PI3K inhibition, resulting in a PI3Kα isoform specific compound. Hence, by targeting the most oncogenic mutant isoform of PI3K, the compound displays anti-proliferative activity both in monolayer human cancer cell cultures and in three-dimensional tumor models. Because of its favorable physicochemical, in vitro ADME and drug-like properties, we propose that this novel ATP mimetic scaffold could result useful in deriving novel selecting and multi-kinase inhibitors for clinical use.

There is a need for different and better aids to tobacco product use cessation. Useful smoking cessation aids, bupropion (2) and varenicline (3), share some chemical features with 3-phenyltropanes (4), which have promise in cocaine dependence therapy. Here we report studies to generate and characterize pharmacodynamic features of 3-phenyltropane analogues. These studies extend our work on the multiple molecular target model for aids to smoking cessation. We identified several new 3-phenyltropane analogues that are superior to 2 in inhibition of dopamine, norepinephrine, and sometimes serotonin reuptake. All of these ligands also act as inhibitors of nicotinic acetylcholine receptor (nAChR) function with a selectivity profile that favors, like 2, inhibition of α3β4*-nAChR. Many of these ligands also block acute effects of nicotine-induced antinociception, locomotor activity, and hypothermia. Importantly, all except one of the analogues tested have better potencies in inhibition of nicotine conditioned place preference than 2. We have identified new compounds that have utility as research tools and possible promise for treatment of nicotine dependence.

Based on the structures and activities of our previously identified non-nucleoside reverse transcriptase inhibitors (NNRTIs), we designed and synthesized two sets of derivatives, diarylpyridines (A) and diarylanilines (B), and tested their anti-HIV-1 activity against infection by HIV-1 NL4-3 and IIIB in TZM-bl and MT-2 cells, respectively. The results showed that most compounds exhibited potent anti-HIV-1 activity with low nanomolar EC50 values, and some of them, such as 13m, 14c, and 14e, displayed high potency with subnanomolar EC50 values, which were more potent than etravirine (TMC125, 1) in the same assays. Notably, these compounds were also highly effective against infection by multi-RTI-resistant strains, suggesting a high potential to further develop these compounds as a novel class of NNRTIs with improved antiviral efficacy and resistance profile.

Gallium-68 is a generator-produced radionuclide for positron emission tomography (PET) that is being increasingly used for radiolabeling of tumor-targeting peptides. Compounds [68Ga]3 and [68Ga]6 are high-affinity, urea-based inhibitors of the prostate-specific membrane antigen (PSMA) that were synthesized in decay-uncorrected yields ranging from 60 – 70% and radiochemical purities of more than 99%. Compound [68Ga]3 demonstrated 3.78 ± 0.90 percent injected dose per gram of tissue (%ID/g) within PSMA+ PIP tumor at 30 min post-injection, while [68Ga]6 showed a two hour PSMA+ PIP tumor uptake value of 3.29 ± 0.77%ID/g. Target (PSMA+ PIP) to non-target (PSMA− flu) ratios were 4.6 and 18.3, respectively, at those time points. Both compounds delineated tumor clearly by small animal PET. The urea series of imaging agents for PSMA can be radiolabeled with 68Ga, a cyclotron-free isotope useful for clinical PET studies, with maintenance of target specificity.

A prodrug strategy was applied to guanidino-containing analogs to increase oral absorption via hPEPT1 and hVACVase. L-Valine, L-isoleucine and L-phenylalanine esters of [3-(hydroxymethyl)phenyl]guanidine (3-HPG) were synthesized and evaluated for transport and activation. In HeLa/hPEPT1 cells, Val-3-HPG and Ile-3-HPG exhibited high affinity to hPEPT1 (IC50: 0.65 and 0.63 mM, respectively), and all three L-amino acid esters showed higher uptake (2.6- to 9-fold) than the parent compound 3-HPG. Val-3-HPG and Ile-3-HPG demonstrated remarkable Caco-2 permeability enhancement, and Val-3-HPG exhibited comparable permeability to valacyclovir. In rat perfusion studies, Val-3-HPG and Ile-3-HPG permeabilities were significantly higher than 3-HPG, and exceeded/matched the high-permeability standard metoprolol, respectively. All the L-amino acid 3-HPG esters were effectively activated in HeLa and Caco-2 cell homogenates, and were found to be good substrates of hVACVase (kcat/Km in mM−1·s−1: Val-3-HPG, 3370; Ile-3-HPG, 1580; Phe-3-HPG, 1660). In conclusion, a prodrug strategy is effective at increasing the intestinal permeability of polar guanidino analogs via targeting hPEPT1 for transport and hVACVase for activation.

A series of 1,3-disubstituted ureas possessing a piperidyl moiety has been synthesized to investigate their structure-activity relationships as inhibitors of the human and murine soluble epoxide hydrolase (sEH). Oral administration of thirteen 1-aryl-3-(1-acylpiperidin-4-yl)urea inhibitors in mice revealed substantial improvements in pharmacokinetic parameters over previously reported 1-adamantyl-urea based inhibitors. For example, 1-(1-(cyclopropanecarbonyl)piperidin-4-yl)-3-(4-(trifluoromethoxy)phenyl)urea (52) showed a 7-fold increase in potency, a 65-fold increase in Cmax† and a 3300 fold increase in AUC over its adamantane analogue 1-(1-adamantyl)-3-(1-propionylpiperidin-4-yl)urea (2). This novel sEH inhibitor showed a 1000 fold increase in potency when compared to morphine by reducing hyperalgesia as measured by mechanical withdrawl threshold using the in vivo carrageenan induced inflammatory pain model.

Fragment-based lead design (FBLD) has been used to identify new metal-binding groups for metalloenzyme inhibitors. When screened at 1 mM, a chelator fragment library (CFL-1.1) of 96 compounds produced hit rates ranging from 29–43% for five matrix metalloproteases (MMPs), 24% for anthrax lethal factor (LF), 49% for 5-lipoxygenase (5-LO), and 60% for tyrosinase (TY). The ligand efficiencies (LE) of the fragment hits are excellent, in the range of 0.4–0.8 kcal/mol. The MMP enzymes all generally elicit the same chelators as hits from CFL-1.1; however, the chelator fragments that inhibit structurally unrelated metalloenzymes (LF, 5-LO, TY) vary considerably. To develop more advanced hits, one hit from CFL-1.1, 8-hydroxyquinoline, was elaborated at four different positions around the ring system to generate new fragments. 8-Hydroxyquinoline fragments substituted at either the 5- or 7-positions gave potent hits against MMP-2, with IC50 values in the low micromolar range. The 8-hydroxyquinoline represents a promising, new chelator scaffold for the development of MMP inhibitors that was discovered by use of a metalloprotein-focused chelator fragment library.

The design, synthesis, and evaluation of a new series of hexahydrofuropyran-derived HIV-1 protease inhibitors are described. We have designed a stereochemically defined hexahydrofuropyranol-derived urethane as the P2-ligand. The current ligand is designed based upon the X-ray structure of 1a-bound HIV-1 protease. The synthesis of (3aS,4S,7aR)-hexahydro-2H-furo[2,3-b] pyran-4-ol (−)-7 was carried out in optically active form. Incorporation of this ligand provided inhibitor 35a, which has shown excellent enzyme inhibitory activity and antiviral potency. Our structure activity studies have indicated that the stereochemistry and the position of oxygens in the ligand are important to the observed potency of the inhibitor. Inhibitor 35a has maintained excellent potency against multidrug-resistant HIV-1 variants. An active site model of 35a was created based upon the X-ray structure of 1b-bound HIV-1 protease. The model offers molecular insights regarding ligand-binding site interactions of the hexahydrofuropyranol-derived novel P2-ligand.

Seven pharmaceutical heparins were investigated by oligosaccharide mapping by digestion with heparin lyase 1, 2 or 3, followed by high performance liquid chromatography analysis. The structure of one of the prepared mapping standards, ΔUA-Gal-Gal-Xyl-O-CH2CONHCH2COOH, (where ΔUA is 4-deoxy-α-L-threo-hex-4-eno-pyranosyluronic acid, Gal is β-D-galactpyranose, and Xyl is β-D-xylopyranose) released from the linkage region using either heparin lyase 2 or heparin lyase 3 digestion, is reported for the first time. A size-dependent susceptibility of site cleaved by heparin lyase 3 was also observed. Heparin lyase 3 acts on the under sulfated domains of the heparin chain and does not cleave the linkages within heparin’s antithrombin III binding site. Thus, a novel low molecular weight heparin (LMWH) was afforded on heparin lyase 3 digestion of heparin due to this unique substrate specificity, which has anticoagulant activity comparable to that of currently available LMWH.

The lymphoid tyrosine phosphatase (Lyp, PTPN22) is a critical negative regulator of T cell antigen receptor (TCR) signaling. A single-nucleotide polymorphism (SNP) in the ptpn22 gene correlates with the incidence of various autoimmune diseases, including type 1 diabetes, rheumatoid arthritis, and systemic lupus erythematosus. Since the disease-associated allele is a more potent inhibitor of TCR signaling, specific Lyp inhibitors may become valuable in treating autoimmunity. Using a structure-based approach, we synthesized a library of 34 compounds that inhibited Lyp with IC50 values between 0.27 and 6.2 μM. A reporter assay was employed to screen for compounds that enhanced TCR signaling in cells, and several inhibitors displayed a dose-dependent, activating effect. Subsequent probing for Lyp's direct physiological targets by immunoblot analysis confirmed the ability of the compounds to inhibit Lyp in T cells. Selectivity profiling against closely related tyrosine phosphatases and in silico docking studies with the crystal structure of Lyp yielded valuable information for the design of Lyp-specific compounds.

Proteasome inhibitors have potential for the treatment of cervical cancer. We describe the synthesis and biological characterization of a new series of 1,3-diphenylpropen-1-one (chalcone)-based derivatives lacking the boronic acid moieties of the previously reported chalcone-based proteasome inhibitor 3,5-bis-(4-boronic acid-benzylidene)-1-methyl-piperidin- 4-one and bearing a variety of amino acid substitutions on the amino-group of the 4-piperidone. Our lead compound 2 (RA-1) inhibits proteasomal activity and has improved dose-dependent anti-proliferative and pro-apoptotic properties in cervical cancer cells containing human papillomavirus. Further, it induces synergistic killing of cervical cancer cell lines when tested in combination with an FDA approved proteasome inhibitor. Exploration of the potential mechanism of proteasomal inhibition by our lead compound using in silico docking studies suggests that the carbonyl group of its oxopiperidine moiety is susceptible to nucleophilic attack by the γ-hydroxy threonine side chain within the catalytic sites of the proteasome.

Libraries of novel trisubstituted benzimidazoles were created through rational drug design. A good number of these benzimidazoles exhibited promising MIC values in the range of 0.5-6 μg/mL (2-15 μM) for their antibacterial activity against Mtb H37Rv strain. Moreover, five of the lead compounds also exhibited excellent activity against clinical Mtb strains with different drug-resistance profiles. All lead compounds do not show appreciable cytotoxicity (IC50 >200 μM) against Vero cells, which inhibit Mtb FtsZ assembly in a dose dependent manner. The two lead compounds unexpectedly showed enhancement of the GTPase activity of Mtb FtsZ. The result strongly suggests that the increased GTPase activity destabilizes FtsZ assembly leading to efficient inhibition of FtsZ polymerization and filament formation. The TEM and SEM analyses of Mtb FtsZ and Mtb cells, respectively, treated with a lead compound strongly suggest that lead benzimidazoles have a novel mechanism of action on the inhibition of Mtb FtsZ assembly and Z-ring formation.

The modification of 3′-((2-cyclopentyl-6,7-dimethyl-1-oxo-2,3-dihydro-1H-inden-5-yloxy)methyl)biphenyl-4-carboxylic acid (BINA, 1) by incorporating heteroatoms into the structure and replacing the cyclopentyl moiety led to the development of new mGluR2 positive allosteric modulators (PAMs) with optimized potency and superior drug-like properties. These analogues are more potent than 1 in vitro, and are highly selective for mGluR2 vs. other mGluR subtypes. They have significantly improved pharmacokinetic (PK) properties, with excellent oral bioavailability and brain penetration. The benzisothiazol-3-one derivative 14 decreased cocaine self-administration in rats, providing proof-of-concept for the use of mGluR2 PAMs for the treatment of cocaine dependence.

A novel series of N1-methyl-(2-phenylindol-3-yl)glyoxylamides 19–31, designed in accordance with our previously reported pharmacophore/topological model, showed high affinity for the 18 kDa translocator protein (TSPO) and paved the way for developing a new radiolabeled probe. Thus ligand 31, N,N-di-n-propyl-(N1-methyl-2-(4'-nitrophenyl)indol-3-yl)glyoxylamide, featuring the best combination of affinity and lipophilicity, was labeled with carbon-11 for evaluation with positron emission tomography (PET) in monkey. After intravenous injection, [11C]31 entered brain to give a high proportion of TSPO-specific binding. These findings augur well for the future application of [11C]31 in humans. Consequently, the binding of 31 to human TSPO was tested on samples of brain membranes from deceased subjects who through ethically-approved in vitro study had previously been established to be high-affinity binders (HABs), mixed-affinity binders (MABs) or low-affinity binders (LABs) for the known TSPO ligand, PBR28 (2). 31 showed high affinity for HABs, MABs and LABs. In conclusion, [11C]31 represents a promising new chemotype for developing novel TSPO radioligands as biomarkers of neuroinflammation.

An SAR study on the Dmt-substituted enkephalin-like tetrapeptide with a N-phenyl-N-piperidin-4-yl propionamide moiety at C-terminal was performed, and has resulted in highly potent ligands at μ and δ opioid receptors. In general, ligands with the substitution of D-Nle2 and halogenation of the aromatic ring of Phe4 showed highly increased opioid activities. Ligand 6 with good biological activities in vitro demonstrated potent in vivo antihyperalgesic and antiallodynic effects in the tail-flick assay.

The C-X-C chemokine receptor type 4 (CXCR4)/stromal cell derived factor-1 (SDF-1 or CXCL12) interaction and the resulting cell signaling cascade play a key role in metastasis and inflammation. Based on the previously published CXCR4 antagonist 5 (WZ811), a series of novel non-peptidic anti-CXCR4 small molecules have been designed and synthesized to improve potency. Following a structure-activity profile around 5, more advanced compounds in the N, N'-(1, 4-phenylenebis(methylene)) dipyrimidin-2-amines series were discovered and shown to possess higher CXCR4 binding potential and specificity than 5. Compound 26 (508MCl) is the leading compound, and exhibits subnanomolar potency in three in vitro assays including competitive binding, Matrigel invasion, and Gαi cyclic adenosine monophosphate (cAMP) modulation signaling. Furthermore, compound 26 displays promising effects by interfering with CXCR4 function in three mouse models: paw inflammation, Matrigel plug angiogenesis, and uveal melanoma micrometastasis. These data demonstrate that dipyrimidine amines are unique CXCR4 antagonists with high potency and specificity.

The isolation of 2-bromo-1-hydroxyphenazine from a marine Streptomyces sp., strain CNS284, and its activity against NFκB, suggested that a short and flexible route for the synthesis of this metabolite and a variety of phenazine analogues be developed. Numerous phenazines were subsequently prepared and evaluated as inducers of quinone reductase 1 (QR1) and inhibitors of quinone reductase 2 (QR2), NF-κB, and inducible nitric oxide synthase (iNOS). Several of the active phenazine derivatives displayed IC50 values vs. QR1 induction and QR2 inhibition in the nanomolar range, suggesting they may find utility as cancer chemopreventive agents.

Inhibition of intestinal carboxylesterases may allow modification of the pharmacokinetics/pharmacodynamic profile of existing drugs by altering half-life or toxicity. Since previously identified diaryl ethane-1,2-dione inhibitors are decidedly hydrophobic, a modified dione scaffold was designed and elaborated into a >300 member library, which was subsequently screened to establish the SAR for esterase inhibition. This allowed the identification of single digit nanomolar hiCE inhibitors that showed improvement in both selectivity and measured solubility.

Indenoisoquinoline topoisomerase I (Top1) inhibitors are a novel class of anticancer agents. Modifications of the indenoisoquinoline A, B and D rings have been extensively studied in order to optimize Top1 inhibitory activity and cytotoxicity. To improve understanding of the forces that stabilize drug-Top1-DNA ternary complexes, the five-membered cyclopentadienone C-ring of the indenoisoquinoline system was replaced by six-membered nitrogen heterocyclic rings, resulting in dibenzo[c,h][1,6]naphthyridines that were synthesized by a novel route and tested for Top1 inhibition. This resulted in several compounds that have unique DNA cleavage site selectivities and potent antitumor activities in a number of cancer cell lines.