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1.  Design, Synthesis, and Characterization of α-Ketoheterocycles Additionally Targeting the Cytosolic Port Cys269 of Fatty Acid Amide Hydrolase 
Journal of medicinal chemistry  2014;57(3):1079-1089.
A series of α-ketooxazoles incorporating electrophiles at the C5 position of the pyridyl ring of 2 (OL-135) and related compounds were prepared and examined as inhibitors of fatty acid amide hydrolase (FAAH), additionally targeting the cytosolic port Cys269. From this series, a subset of the candidate inhibitors exhibited time-dependent FAAH inhibition and non-competitive irreversible inactivation of the enzyme, consistent with the targeted Cys269 covalent alkylation or addition, and maintained or enhanced the intrinsic selectivity for FAAH versus other serine hydrolases. A preliminary in vivo assessment demonstrates that these inhibitors raise endogenous brain levels of anandamide and other FAAH substrates upon intraperitoneal (i.p.) administration to mice with peak levels achieved within 1.5–3 h and that the elevations of the signaling lipids were maintained >6 h, indicating that the inhibitors effectively reach and remain active in the brain inhibiting FAAH for a sustained period.
doi:10.1021/jm401820q
PMCID: PMC3940414  PMID: 24456116
2.  Development of Selective Inhibitors for Aldehyde Dehydrogenases based on Substituted Indole-2,3-diones 
Journal of medicinal chemistry  2014;57(3):714-722.
Aldehyde dehydrogenases (ALDH) participate in multiple metabolic pathways and have been indicated to play a role in several cancerous disease states. Our laboratory is interested in developing novel and selective ALDH inhibitors. We looked to further work recently published by developing a class of isoenzyme selective inhibitors using a similar indole-2,3-diones that exhibit differential inhibition of ALDH1A1, ALDH2 and ALDH3A1. Kinetic and X-ray crystallography data suggest these inhibitors are competitive against aldehyde binding, forming direct interactions with active site cysteine residues. The selectivity is precise in that these compounds appear to interact directly with the catalytic nucleophile, Cys243, in ALDH3A1, but not in ALDH2. In ALDH2, the 3-keto group is surrounded by the adjacent Cys301/303. Surprisingly, the orientation of the interaction changes depending on the nature of the substitutions on the basic indole ring structure and correlates well with the observed structure-activity relationships for each ALDH isoenzyme.
doi:10.1021/jm401377v
PMCID: PMC3954746  PMID: 24444054
3.  Substituted 2-Phenyl-Imidazopyridines: A New Class of Drug Leads for Human African Trypanosomiasis 
Journal of medicinal chemistry  2014;57(3):828-835.
A phenotypic screen of a compound library for antiparasitic activity on Trypanosoma brucei, the causative agent of human African trypanosomiasis, led to the identification of substituted 2-(3-aminophenyl) oxazolopyridines as a starting point for hit-to-lead medicinal chemistry. A total of 110 analogues were prepared, which led to the identification of 64, a substituted 2-(3-aminophenyl) imidazopyridine. This compound showed antiparasitic activity in vitro with an EC50 of 2 nM and displayed reasonable drug-like properties when tested in a number of in vitro assays. The compound was orally bioavailable and displayed good plasma and brain exposure in mice. Compound 64 cured mice infected with Trypanosoma brucei when dosed orally down to 2.5 mg/kg. Given its potent anti-parasitic properties and its ease of synthesis, compound 64 represents a new lead for the development of drugs to treat human African trypanosomiasis.
doi:10.1021/jm401178t
PMCID: PMC3962778  PMID: 24354316
4.  Discovery of 8-Cyclopentyl-2-[4-(4-methyl-piperazin-1-yl)-phenylamino]-7-oxo-7,8- dihydro-pyrido[2,3-d]pyrimidine-6-carbonitrile (7x) as a Potent Inhibitor of Cyclin- Dependent Kinase 4 (CDK4) and AMPK-related Kinase 5 (ARK5) 
Journal of medicinal chemistry  2014;57(3):578-599.
The success of imatinib, a BCR-ABL inhibitor for the treatment of chronic myelogenous leukemia, has created a great impetus for the development of additional kinase inhibitors as therapeutic agents. However, the complexity of cancer has led to recent interest in polypharmacological approaches for developing multi kinase inhibitors with low toxicity profiles. With this goal in mind, we analyzed more than 150 novel cyano pyridopyrimidine compounds and identified structure activity relationship trends that can be exploited in the design of potent kinase inhibitors. One compound, 8-Cyclopentyl-2-[4-(4-methyl-piperazin-1-yl)-phenylamino]-7-oxo-7,8-dihydro-pyrido[2,3-d]pyrimidine-6-carbonitrile (7x) was found to be the most active, inducing apoptosis of tumor cells at a concentration of approximately 30–100nM. In vitro kinase profiling revealed that 7x is a multi-kinase inhibitor with potent inhibitory activity against the CDK4/CYCLIN D1 and ARK5 kinases. Here, we report the synthesis, structure activity relationship, kinase inhibitory profile, in vitro cytotoxicity and in vivo tumor regression studies by this lead compound.
doi:10.1021/jm401073p
PMCID: PMC3983396  PMID: 24417566
5.  Exploiting an Allosteric Binding Site of PRMT3 Yields Potent and Selective Inhibitors 
Journal of medicinal chemistry  2013;56(5):2110-2124.
Protein arginine methyltransferases (PRMTs) play an important role in diverse biological processes. Among the nine known human PRMTs, PRMT3 has been implicated in ribosomal biosynthesis via asymmetric dimethylation of the 40S ribosomal protein S2 and in cancer via interaction with the DAL-1 tumor suppressor protein. However, few selective inhibitors of PRMTs have been discovered. We recently disclosed the first selective PRMT3 inhibitor, which occupies a novel allosteric binding site and is noncompetitive with both the peptide substrate and cofactor. Here we report comprehensive structure–activity relationship studies of this series, which resulted in the discovery of multiple PRMT3 inhibitors with submicromolar potencies. An X-ray crystal structure of compound 14u in complex with PRMT3 confirmed that this inhibitor occupied the same allosteric binding site as our initial lead compound. These studies provide the first experimental evidence that potent and selective inhibitors can be created by exploiting the allosteric binding site of PRMT3.
doi:10.1021/jm3018332
PMCID: PMC4319713  PMID: 23445220
6.  Selective ALDH3A1 inhibition by benzimidazole analogs increase mafosfamide sensitivity in cancer cells 
Journal of medicinal chemistry  2014;57(2):449-461.
Aldehyde dehydrogenase enzymes irreversibly oxidize aldehydes generated from metabolism of amino acids, fatty acids, food, smoke, additives and xenobiotic drugs. Cyclophosphamide is one such xenobiotic used in cancer therapies. Upon activation, cyclophosphamide forms an intermediate, aldophosphamide, which can be detoxified to carboxyphosphamide by aldehyde dehydrogenases (ALDH), especially ALDH1A1 and ALDH3A1. Consequently, selective inhibition of ALDH3A1 could increase chemosensitivity toward cyclophosphamide in ALDH3A1 expressing tumors. Here, we report detailed kinetic and structural characterization of a highly selective sub-micromolar inhibitor of ALDH3A1, 1-[(4-fluorophenyl)sulfonyl]-2-methyl-1H-benzimidazole, (CB7, IC50 of 0.2 µM). CB7 does not inhibit ALDH1A1, ALDH1A2, ALDH1A3, ALDH1B1 or ALDH2 activity. Structural, kinetic and mutagenesis study show that CB7 binds to the aldehyde binding pocket of ALDH3A1. ALDH3A1-expressing lung adenocarcinoma and glioblastoma cell lines are sensitized toward mafosfamide (MF) treatment in the presence analogs of CB7 whereas primary lung fibroblasts lacking ALDH3A1 expression, are not.
doi:10.1021/jm401508p
PMCID: PMC3988914  PMID: 24387105
7.  Correction 
Journal of medicinal chemistry  2013;56(21):8953.
doi:10.1021/jm401535f
PMCID: PMC4301842
8.  Toward Orthopoxvirus Countermeasures: A Novel Heteromorphic Nucleoside of Unusual Structure 
Journal of medicinal chemistry  2006;49(14):4052-4054.
Two privileged drug scaffolds have been hybridized to create the novel heteromorphic nucleoside 5-(2-amino-3-cyano-5-oxo-5,6,7,8-tetrahydro-4H-chromen-4-yl)-1-(2-deoxypentofuranosyl)pyrimidine-2,4-(1H,3H)-dione (2). Compound 2 inhibited the replication of two orthopoxviruses, vaccinia virus (VV) (EC50 = 4.6 ± 2.0 μM), and cowpox virus (CV) (EC50 = 2.0 ± 0.3 μM). Compound 2 exhibited reduced activity against a thymidine kinase (TK) negative strain of CV, implying a requirement for 5′-monophosphorylation for antiorthopoxvirus activity. Compound 2 was efficiently phosphorylated by VV TK, establishing that VV TK is more promiscuous than previously believed.
doi:10.1021/jm060404n
PMCID: PMC4298854  PMID: 16821766
9.  Synthesis and Biological Evaluation of Pentacyclic Strychnos Alkaloids as Selective Modulators of the ABCC10 (MRP7) Efflux Pump 
Journal of medicinal chemistry  2014;57(24):10383-10390.
The selective modulation of ABC efflux pumps overexpressed in multidrug resistant cancers (MDR) and attendant resensitization to chemotherapeutic agents represents a promising strategy for treating cancer. We have synthesized four novel pentacyclic Strychnos alkaloids alstolucines B (2), F (3), A (5), and N-demethylalstogucine (4), in addition to known Strychnos alkaloid echitamidine (16), and evaluated compounds 1–3, 5 in biochemical assays with ABCC10 and P-gp. Alstolucines B (2) and F (3) inhibited ABCC10 ATPase activity at 12.5 μM without affecting P-gp function; moreover, they resensitized ABCC10-transfected cell lines to paclitaxel at 10 μM. Altogether, the alstolucines represent promising lead candidates in the development of modulators of ABCC10 for MDR cancers overexpressing this pump.
doi:10.1021/jm501189p
PMCID: PMC4281106  PMID: 25419978
total synthesis; Strychnos alkaloids; ABCC10; multidrug resistance protein 7; multidrug resistance; resensitization
10.  Development of Organometallic S6K1 Inhibitors 
Journal of medicinal chemistry  2014;58(1):305-314.
Aberrant activation of S6 kinase 1 (S6K1) is found in many diseases, including diabetes, aging, and cancer. We developed ATP competitive organometallic kinase inhibitors, EM5 and FL772, which are inspired by the structure of the pan-kinase inhibitor staurosporine, to specifically inhibit S6K1 using a strategy previously used to target other kinases. Biochemical data demonstrate that EM5 and FL772 inhibit the kinase with IC50 value in the low nanomolar range at 100 μM ATP and that the more potent FL772 compound has a greater than 100-fold specificity over S6K2. The crystal structures of S6K1 bound to staurosporine, EM5, and FL772 reveal that the EM5 and FL772 inhibitors bind in the ATP binding pocket and make S6K1-specific contacts, resulting in changes to the p-loop, αC helix, and αD helix when compared to the staurosporine-bound structure. Cellular data reveal that FL772 is able to inhibit S6K phosphorylation in yeast cells. Together, these studies demonstrate that potent, selective, and cell permeable S6K1 inhibitors can be prepared and provide a scaffold for future development of S6K inhibitors with possible therapeutic applications.
doi:10.1021/jm5011868
PMCID: PMC4289024  PMID: 25356520
11.  Neurosteroid Analogues. 18. Structure–Activity Studies of ent-Steroid Potentiators of γ-Aminobutyric Acid type A Receptors and Comparison of Their Activities with Those of Alphaxalone and Allopregnanolone 
Journal of medicinal chemistry  2013;57(1):171-190.
A model of the alignment of neurosteroids and ent-neurosteroids at the same binding site on γ-aminobutyric acid type A (GABAA) receptors was evaluated for its ability to identify the structural features in ent-neurosteroids that enhance their activity as positive allosteric modulators of this receptor. Structural features that were identified included: 1) a ketone group at position C-16; 2) an axial 4α-OMe group and 3) a C-18 methyl group. Two ent-steroids were identified that were more potent than the anesthetic steroid alphaxalone in their threshold for and duration of loss of the righting reflex in mice. In tadpoles, loss of righting reflex for these two ent-steroids occurs with EC50 values similar to those found for allopregnanolone. The results indicate that ent-steroids have considerable potential to be developed as anesthetic agents as and drugs to treat brain disorders that are ameliorated by positive allosteric modulators of GABAA receptor function.
doi:10.1021/jm401577c
PMCID: PMC3951241  PMID: 24328079
12.  Synthesis and Cytostatic Evaluation of 4-N-Alkanoyl and 4-N-Alkyl Gemcitabine Analogues 
Journal of medicinal chemistry  2013;57(1):191-203.
Couplings of gemcitabine with the functionalized carboxylic acids (C9-C13) or reactions of 4-N-tosylgemcitabine with the corresponding alkyl amines afforded 4-N-alkanoyl and 4-N-alkyl gemcitabine derivatives. The analogues with a terminal hydroxyl group on the alkyl chain were efficiently fluorinated under conditions that are compatible with protocols for 18F labeling. The 4-N-alkanoylgemcitabines showed potent cytostatic activities in the low nM range against a panel of tumor cell lines while cytotoxicity of the 4-N-alkylgemcitabines were in the low μM range. The cytotoxicity for the 4-N-alkanoylgemcitabine analogues were reduced approximately by two orders of magnitude in the 2′-deoxycytidine kinase (dCK)-deficient CEM/dCK- cell line whereas cytotoxicity of the 4-N-alkylgemcitabines were only 2-5 times lower. None of the compounds acted as efficient substrates for cytosolic dCK, and therefore, the 4-N-alkanoyl analogues need to be converted first to gemcitabine to display a significant cytostatic potential, while 4-N-alkyl derivatives attain the modest activity without “measurable” conversion to gemcitabine.
doi:10.1021/jm401586a
PMCID: PMC3918440  PMID: 24341356
13.  Design of an Amide N-glycoside Derivative of β-Glucogallin: A Stable, Potent, and Specific Inhibitor of Aldose Reductase 
Journal of medicinal chemistry  2013;57(1):71-77.
β-glucogallin (BGG), a major component of the Emblica officinalis medicinal plant, is a potent and selective inhibitor of aldose-reductase (AKR1B1). New linkages (ether/triazole/amide) were introduced via high yielding, efficient syntheses to replace the labile ester, and an original 2-step (90%) preparation of BGG was developed. Inhibition of AKR1B1was assessed in vitro and using transgenic lens organ cultures, which identified the amide linked glucoside (BGA) as a stable, potent and selective lead therapeutic toward the treatment of diabetic eye disease.
doi:10.1021/jm401311d
PMCID: PMC3956592  PMID: 24341381
14.  δ-Thiolactones as prodrugs of thiol-based glutamate carboxypeptidase II (GCPII) inhibitors 
Journal of medicinal chemistry  2013;57(1):243-247.
δ-Thiolactones derived from thiol-based glutamate carboxypeptidase II (GCPII) inhibitors were evaluated as prodrugs. In rat liver microsomes, 2-(3-mercaptopropyl)pentanedioic acid (2-MPPA, 1) was gradually produced from 3-(2-oxotetrahydro-thiopyran-3-yl)propionic acid (5), a thiolactone derived from 1. Compound 1 was detected in plasma at concentrations well above its IC50 value for GCPII following oral administration of 5 in rats. Consistent with the oral plasma pharmacokinetics, thiolactone 5 exhibited efficacy in a rat model of neuropathic pain following oral administration.
doi:10.1021/jm401703a
PMCID: PMC3932958  PMID: 24354364
15.  A peripherally selective diphenyl purine antagonist of the CB1 receptor 
Journal of medicinal chemistry  2013;56(20):8066-8072.
Antagonists of the CB1 receptor can be useful in the treatment of several diseases including obesity, diabetes, and liver disease. However, to date, the only clinically approved CB1 receptor antagonist, rimonabant, was withdrawn due to adverse CNS related side effects such as depression and suicidal ideation. Since rimonabant’s withdrawal, several groups have begun pursuing peripherally selective CB1 antagonists. These compounds are expected to be devoid of undesirable CNS related effects but maintain efficacy through antagonism of peripherally expressed CB1 receptors within target tissues. Reported here are our latest results toward development of a peripherally selective analog of the diphenyl purine CB1 antagonist otenabant 1. Compound 9 (N-{1-[8-(2-Chlorophenyl)-9-(4-chlorophenyl)-9H-purin-6-yl]piperidin-4-yl}pentanamide) is a potent, orally absorbed antagonist of the CB1 receptor that is >50-fold selective for CB1 over CB2, highly selective for the periphery in a rodent model, and without efficacy in a series of in vivo assays designed to evaluate its ability to mitigate the central effects of Δ9-THC through the CB1 receptor.
doi:10.1021/jm401129n
PMCID: PMC4281022  PMID: 24041123
CB1; peripheral; antagonist; cannabinoid; topological polar surface area
16.  Controlled-Deactivation Cannabinergic Ligands 
Journal of medicinal chemistry  2013;56(24):10142-10157.
We report an approach for obtaining novel cannabinoid analogs with controllable deactivation and improved druggability. Our design involves the incorporation of a metabolically labile ester group at the 2'-position on a series of (−)-Δ8-THC analogs. We have sought to introduce benzylic substituents alpha to the ester group which affect the half-lives of deactivation through enzymatic activity while enhancing the affinities and efficacies of individual ligands for the CB1 and CB2 receptors. The 1'-(S)-methyl, 1'-gem-dimethyl and 1'-cyclobutyl analogs exhibit remarkably high affinities for both CB receptors. The novel ligands are susceptible to enzymatic hydrolysis by plasma esterases in a controllable manner while their metabolites are inactive at the CB receptors. In further in vitro and in vivo experiments key analogs were shown to be potent CB1 receptor agonists and exhibit CB1-mediated hypothermic and analgesic effects.
doi:10.1021/jm4016075
PMCID: PMC3905450  PMID: 24286207
17.  Discovery of 5-substituted pyrrolo[2,3-d]pyrimidine antifolates as dual acting inhibitors of glycinamide ribonucleotide formyltransferase and 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase in de novo purine nucleotide biosynthesis: implications of inhibiting 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase to AMPK activation and anti-tumor activity 
Journal of medicinal chemistry  2013;56(24):10016-10032.
We synthesized 5-substituted pyrrolo[2,3-d]pyrimidine antifolates (compounds 5–10) with 1 to 6 bridge carbons and a benozyl ring in the side chain as antitumor agents. Compound 8 with a 4-carbon bridge was the most active analog and potently inhibited proliferation of folate receptor (FR) α-expressing Chinese hamster ovary and KB human tumor cells. Growth inhibition was reversed completely or in part by excess folic acid, indicating that FRα is involved in cellular uptake, and resulted in S-phase accumulation and apoptosis. Anti-proliferative effects of compound 8 toward KB cells were protected by excess adenosine but not thymidine, establishing de novo purine nucleotide biosynthesis as the targeted pathway. However, 5-aminoimidazole-4-carboxamide (AICA) protection was incomplete, suggesting inhibition of both AICA ribonucleotide formyltransferase (AICARFTase) and glycinamide ribonucleotide formyltransferase (GARFTase). Inhibition of GARFTase and AICARFTase by compound 8 was confirmed by cellular metabolic assays and resulted in ATP pool depletion. To our knowledge, this is the first example of an antifolate that acts as a dual inhibitor of GARFTase and AICARFTase as its principal mechanism of action.
doi:10.1021/jm401328u
PMCID: PMC3917155  PMID: 24256410
18.  Optimization of Antitumor Modulators of Pre-mRNA Splicing 
Journal of medicinal chemistry  2013;56(24):10033-10044.
The spliceosome regulates pre-mRNA splicing, which is a critical process in normal mammalian cells. Recently recurrent mutations in numerous spliceosomal proteins have been associated with a number of cancers. Previously natural product antitumor agents have been shown to interact with one of the proteins that is subject to recurrent mutations (SF3B1). We report the optimization of a class of tumor-selective spliceosome modulators, which demonstrate significant in vivo antitumor activity. This optimization culminated in the discovery of sudemycin D6, which shows potent cytotoxic activity in the melanoma line SK-MEL-2 (IC50= 39 nM) and other tumor lines, including: JeKo-1 (IC50= 26 nM), HeLa (IC50= 50 nM), and SK-N-AS (IC50= 81 nM). We also report improved processes for the synthesis of these compounds. Our work supports the idea that sudemycin D6 is worthy of further investigation as a novel preclinical anticancer agent with application in the treatment of numerous human cancers.
doi:10.1021/jm401370h
PMCID: PMC3932738  PMID: 24325474
19.  Synthesis and Structure Activity Relationship of 3-Hydroxypyridin-2-thione Based Histone Deacetylase Inhibitors 
Journal of medicinal chemistry  2013;56(24):9969-9981.
We have previously identified 3-hydroxypyridin-2-thione (3HPT) as a novel zinc binding group for histone deacetylase (HDAC) inhibition. Early structure activity relationship (SAR) studies led to various small molecules possessing selective inhibitory activity against HDAC6 or HDAC8 but are devoid of HDAC1 inhibition. To further delineate the depth of the SAR of 3HPT-derived HDAC inhibitors (HDACi), we have extended the SAR studies to include the linker region and the surface recognition group to optimize the HDAC inhibition. The current efforts resulted in the identification of two lead compounds 10d and 14e with potent HDAC6 and HDAC8 activities, but that are inactive against HDAC1. These new HDACi possess anti-cancer activities against various cancer cell lines including Jurkat J-γ1 against which SAHA and the previously disclosed 3HPT-derived HDACi were inactive.
doi:10.1021/jm401225q
PMCID: PMC4029159  PMID: 24304348
20.  N- vs. C-Domain Selectivity of Catalytic Inactivation of Human Angiotensin Converting Enzyme by Lisinopril-Coupled Transition Metal Chelates 
Journal of medicinal chemistry  2013;56(24):9826-9836.
The N- and C-terminal domains of human somatic Angiotensin I Converting Enzyme (sACE-1) demonstrate distinct physiological functions, with resulting interest in the development of domain-selective inhibitors for specific therapeutic applications. Herein, the activity of lisinopril-coupled transition metal chelates were tested for both reversible binding and irreversible catalytic inactivation of sACE-1. C/N domain binding selectivity ratios ranged from 1 to 350, while rates of irreversible catalytic inactivation of the N- and C-domains were found to be significantly greater for the N-domain, suggesting a more optimal orientation of the M-chelate-lisinopril complexes within the active site of the N-domain of sACE-1. Finally, the combined effect of binding selectivity and inactivation selectivity was assessed for each catalyst (double-filter selectivity factors), and several catalysts were found to cause domain-selective catalytic inactivation. The results of this study demonstrate the ability to optimize the target selectivity of catalytic metallopeptides through both binding and orientation factors (double-filter effect).
doi:10.1021/jm4009345
PMCID: PMC4052451  PMID: 24228790
catalytic inactivation; domain selectivity; double-filter effect; metallopeptide; metal chelate; lisinopril; angiotensin converting enzyme
21.  Design and Synthesis of 1-(3-(dimethylamino)propyl)-1-(4-fluorophenyl)-1,3-dihydroisobenzofuran-5-carbonitrile (Citalopram) Analogues as Novel Probes for the Serotonin Transporter S1 and S2 Binding Sites 
Journal of medicinal chemistry  2013;56(23):9709-9724.
The serotonin transporter (SERT) is the primary target for antidepressant drugs. The existence of a high affinity primary orthosteric binding site (S1) and a low affinity secondary site (S2) has been described and their relation to antidepressant pharmacology has been debated. Herein, structural modifications to the N-, 4, 5, and 4’-positions of (±)citalopram (1) are reported. All of the analogues were SERT-selective and demonstrated that steric bulk was tolerated at the SERT S1 site, including two dimeric ligands (15 and 51.) In addition, 8 analogues were identified with similar potencies to S-1 for decreasing the dissociation of [3H]S-1 from the S1 site, via allosteric modulation at S2. Both dimeric compounds had similar affinities for the SERT S1 site (Ki=19.7 and 30.2 nM, respectively), whereas only the N-substituted analogue, 51, was as effective as S-1 in allosterically modulating the binding of [3H]S-1 via S2.
doi:10.1021/jm4014136
PMCID: PMC3894853  PMID: 24237160
22.  SAR Studies on Trisubstituted Benzimidazoles as Inhibitors of Mtb FtsZ for the Development of Novel Antitubercular Agents 
Journal of medicinal chemistry  2013;56(23):9756-9770.
FtsZ, an essential protein for bacterial cell division, is a highly promising therapeutic target, especially for the discovery and development of new-generation anti-TB agents. Following up the identification of two lead 2,5,6-trisubstituted benzimidazoles, 1 and 2, targeting Mtb-FtsZ in our previous study, an extensive SAR study for optimization of these lead compounds was performed through systematic modification of the 5 and 6 positions. This study has successfully led to the discovery of a highly potent advanced lead 5f (MIC 0.06 µg/mL) and several other compounds with comparable potencies. These advanced lead compounds possess a dimethylamino group at the 6 position. The functional groups at the 5 position exhibit substantial effects on the antibacterial activity as well. In vitro experiments such as the FtsZ polymerization inhibitory assay and TEM analysis of Mtb-FtsZ treated with 5f and others indicate that Mtb-FtsZ is the molecular target for their antibacterial activity.
doi:10.1021/jm401468w
PMCID: PMC3933301  PMID: 24266862
Mycobacterium tuberculosis; Antibacterial; Benzimidazoles; FtsZ; Structure-activity relationship
23.  Developing Bivalent Ligands to Target CUG Triplet Repeats, the Causative Agent of Myotonic Dystrophy Type 1 
Journal of medicinal chemistry  2013;56(23):9471-9481.
An expanded CUG repeat transcript (CUGexp) is the causative agent of myotonic dystrophy type 1 (DM1) by sequestering muscleblind-like 1 protein (MBNL1), a regulator of alternative splicing. Based on a ligand (1) that was previously reported to be active in an in vitro assay, we present the synthesis of a small library containing ten dimeric ligands (4-13) that differ in length, composition and attachment point of the linking chain. The oligoamino linkers gave a greater gain in affinity for CUG RNA and were more effective when compared to oligoether linkers. The most potent in vitro ligand (9) was shown to be aqueous-soluble and both cell- and nucleus-permeable displaying almost complete dispersion of MBNL1 ribonuclear foci in a DM1 cell model. Direct evidence for the bioactivity of 9 was observed in its ability to disperse ribonuclear foci in individual live DM1 model cells using time-lapse confocal fluorescence microscopy.
doi:10.1021/jm400794z
PMCID: PMC3925341  PMID: 24188018
24.  Characterization of a Novel Alpha-Conotoxin TxID from Conus textile that Potently Blocks rat Alpha3beta4 Nicotinic Acetylcholine Receptors 
Journal of medicinal chemistry  2013;56(23):9655-9663.
The α3β4 nAChRs are implicated in pain sensation in the PNS and addiction to nicotine in the CNS. We identified an α-4/6-conotoxin (CTx) TxID from Conus textile. The new toxin consists of 15 amino acid residues with two disulfide bonds. TxID was synthesized using solid phase methods and the synthetic peptide was functionally tested on nAChRs heterologously expressed in Xenopus laevis oocytes. TxID blocked rat α3β4 nAChRs with a 12.5 nM IC50, which places it amongst the most potent α3β4 nAChR antagonists. TxID also blocked the closely related α6/α3β4 with a 94 nM IC50 but showed little activity on other nAChR subtypes. NMR analysis showed that two major structural isomers exist in solution, one of which adopts a regular α-CTx fold but with different surface charge distribution to other 4/6 family members. α-CTx TxID is a novel tool with which to probe the structure and function of α3β4 nAChRs.
doi:10.1021/jm401254c
PMCID: PMC4033315  PMID: 24200193
α-CTx; α3β 4 nAChRs; potent antagonist; NMR
25.  Explorations of Substituted Urea Functionality for Discovery of New Activators of the Heme Regulated Inhibitor Kinase 
Journal of medicinal chemistry  2013;56(23):9457-9470.
Heme-regulated inhibitor kinase (HRI), an eukaryotic translation initiation factor 2 alpha (eIF2α) kinase, plays critical roles in cell proliferation, differentiation, and adaptation to cytoplasmic stress. HRI is also a critical modifier of hemoglobin disorders such as β-thalassemia. We previously identified N,N′-diarylureas as potent activators of HRI suitable for studying biology of this important kinase. To expand the repertoire of chemotypes that activate HRI we screened a ~1,900 member N,N′-disubstituted urea library in the surrogate eIF2α phosphorylation assay identifying N-aryl,N′-cyclohexylphenoxyurea as a promising scaffold. We validated hit compounds as a bona-fide HRI activators in secondary assays and explored contributions of substitutions on the N-aryl and N′-cyclohexylphenoxy groups to their activity by studying focused libraries of complementing analogs. We tested these N-aryl,N′-cyclohexylphenoxyureas in the surrogate eIF2α phosphorylation and cell proliferation assays, demonstrating significantly improved bioactivities and specificities. We consider these compounds to represent lead candidates for the development of potent and specific HRI activators.
doi:10.1021/jm400793v
PMCID: PMC3938169  PMID: 24261904
SAR study; N,N′-disubstituted ureas; inhibition of translation initiation; ternary complex; phosphorylation of eIF2α

Results 1-25 (1225)