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Novel carbazole-oxadiazoles were developed as new potential antibacterial agents to combat dreadful resistance. Some target compounds displayed predominant inhibitory effects on the tested Gram-positive and -negative bacteria, and carbazole-oxadiazoles

Inhibition of the bromodomain and extra-terminal (BET) family of adaptor proteins is an attractive strategy for targeting transcriptional regulation of key oncogenes, such as c-MYC. Starting with the screening hit 1, a combination of structure-activity relationship and protein structure-guided drug design led to the discovery of a differently oriented carbazole 9 with favorable binding to the tryptophan, proline, and phenylalanine (WPF) shelf conserved in the BET family. Identification of an additional lipophilic pocket and functional group optimization to optimize pharmacokinetic (PK) properties culminated in the discovery of 18 (BMS-986158) with excellent potency in binding and functional assays. On the basis of its favorable PK profile and robust in vivo activity in a panel of hematologic and solid tumor models, BMS-986158 was selected as a candidate for clinical evaluation.

Poly (ADP-ribose) polymerase (PARP) plays a significant role in DNA repair responses; therefore, this enzyme is targeted by PARP inhibitors in cancer therapy. Here we have developed a number of fused tetra- or pentacyclic dihydrodiazepinoindolone derivatives with excellent PARP enzymatic and cellular PARylation inhibition activities. These efforts led to the identification of pamiparib (BGB-290, 139), which displays excellent PARP-1 and PARP-2 inhibition with IC50 of 1.3 and 0.9 nM, respectively. In a cellular PARylation assay, this compound inhibits PARP activity with IC50 = 0.2 nM. Cocrystal of pamiparib shows similar binding sites with PARP with other PARP inhibitors, but pamiparib is not a P-gp substrate and shows excellent drug metabolism and pharmacokinetics (DMPK) properties with significant brain penetration (17-19%, mice). The compound is currently being investigated in phase III clinical trials as a maintenance therapy in platinum-sensitive ovarian cancer and gastric cancer.

Protein kinases C (PKCs) are a family of serine/threonine kinases involved in various cellular processes, including proliferation, differentiation, cell survival, and apoptosis. Here, we report the identification, structure-activity relationship (SAR), and 3D-QSAR studies of 69 natural indolocarbazoles, including 15 new compounds, from marine streptomyces strains. Interestingly, we found that the chair conformational isomer of 7-oxo-staurosporine (compound 15) inhibited PKCθ more potently than the corresponding boat isomer. An evaluation of kinase selectivity and antitumor efficacy revealed that 15 was a potent dual PKCθ/δ inhibitor and that it could efficiently inhibit tumor growth in pancreatic cancer (PC) by inducing cellular apoptosis and suppressing the NF-κB/p-P65 pathway. In addition, we demonstrated that overexpression of p-PKCδ and p-P65 was associated with poor survival rates in patients with PC, and p-PKCθ expression also showed significant positive correlations with p-PKCδ and p-P65 levels. Finally, the PC patient-derived xenograft model further confirmed the potential anti-PC efficacy of 15.

Antibiotic resistance has become one of the most urgently important problems facing healthcare providers. A novel series of dipicolylamine-containing carbazole amphiphiles with strong Zn

A series of novel anaplastic lymphoma kinase (ALK) degraders were designed and synthesized based on proteolysis-targeting chimera (PROTAC) technology by linking two alectinib analogs (36 and 37) with pomalidomide through linkers of different lengths and types. The most promising degrader 17 possessed a high ALK-binding affinity and potent antiproliferative activity in the ALK-dependent cell lines and did not exhibit obvious cytotoxicity in ALK fusion-negative cells. More importantly, the efficacy of compound 17 in a Karpas 299 xenograft mouse model was further evaluated based on its ALK-sustained degradation ability in vivo. The reduction in tumor weight in the compound 17-treated group (10 mg/kg/day, I.V.) reached 75.82%, while alectinib reduced tumor weight by 63.82% at a dose of 20 mg/kg/day (P.O.). Taken together, our findings suggest that alectinib-based PROTACs associated with the degradation of ALK may have promising beneficial effects for treating ALK-driven malignancies.

Development of neuroinflammation agents targeting the translocator protein (TSPO) has been hindered by a common single nucleotide polymorphism (A147T) at which TSPO ligands commonly lose affinity. To this end, carbazole acetamide scaffolds were synthesized and structure activity relationships elaborated to explore the requirements for high-affinity binding to both TSPO wild type (WT) and the polymorphic TSPO A147T. This study reports high binding affinity and nondiscriminating TSPO ligands.

A series of calothrixin B (2) analogues bearing substituents at the ‘E’ ring and their corresponding deoxygenated quinocarbazoles lacking quinone unit were synthesized. The cytotoxicities of calothrixins 1, 2, and 15b–p and quinocarbazole analogues were investigated against nine cancer cell lines. The quinocarbazoles 21a and 25a inhibited the catalytic activity of human topoisomerase II. The plasmid DNA cleavage abilities of calothrixins 1, 2, and 15b–p identified compound 15h causing DNA cleavage comparable to that of calothrixin A (1). Calothrixin A (1), 3-fluorocalothrixin 15h and 4-fluoroquinocarbazole 21b induced extensive DNA damage followed by apoptotic cell death. Spectral and plasmid unwinding studies demonstrated an intercalative mode of binding for quinocarbazoles. We identified two promising drug candidates, the 3-fluorocalothrixin B 15h with low toxicity in animal model and its deoxygenated derivative 4-fluoroquinocarbazole 21b as having potent cytotoxicity against NCI-H460 cell line with a G...

International audience; We report the synthesis and metabolic and biological evaluation of a series of 17 novel heterocyclic derivatives of isocombretastatin-A4 (iso-CA-4) and their structure-activity relationships. Among these derivatives, the most active compound, 4f, inhibited the growth of a panel of seven cancer cell lines with an IC50 in the low nanomolar range. In addition, 4f showed interesting activity against CA-4-resistant colon-carcinoma cells and multidrug-resistant leukemia cells. It also induced G2/M cell-cycle arrest. Structural data indicated binding of 4f to the colchicine site of tubulin, likely preventing the curved-to-straight tubulin structural changes that occur during microtubule assembly. Also, 4f disrupted the blood-vessel-like assembly formed by human umbilical-vein endothelial cells in vitro, suggesting its function as a vascular-disrupting agent. An in vitro metabolism study of 4f showed its high human-microsomal stability in comparison with that of iso-CA-4. The physicochemical properties of 4f may be conducive to CNS permeability, suggesting that this compound may be a possible candidate for the treatment of glioblastoma.

Sirtuin 1 (SIRT1) is a class III histone deacetylase that plays significant roles in the regulation of lifespan, metabolism, memory, and circadian rhythms and in the mechanisms of many diseases. However, methods of monitoring the pharmacodynamics of SIRT1-targeted drugs are limited to blood sampling because of the invasive nature of biopsies. For the noninvasive monitoring of the spatial and temporal dynamics of SIRT1 expression−activity in vivo by PET−CT−MRI, we developed a novel substrate-type radio-tracer, [18F]-2-fluorobenzoylaminohexanoicanilide (2-[18F]-BzAHA). PET−CT−MRI studies in rats demonstrated increased accumulation of 2-[18F]BzAHA-derived radioactivity in the hypothalamus, hippocampus, nucleus accumbens, and locus coeruleus, consistent with autoradiographic and immunofluorescent (IMF) analyses of brain-tissue sections. Pretreatment with the SIRT1 specific inhibitor, EX-527 (5 mg/kg, ip), resulted in about a 20% reduction of 2-[18F]BzAHA-derived-radioactivity accumulation in these structures. In vivo imaging of SIRT1 expression−activity should facilitate studies that improve the understanding of SIRT1-mediated regulation in the brain and aid in the development and clinical translation of SIRT1-targeted therapies.

Downregulating transcription of the oncogene c-MYC is a feasible strategy for cancer therapy. Stabilization of the G-quadruplex structure present in the c-MYC promoter can suppress c-MYC transcription. Thus, far, several ligands targeting this structure have been developed. However, most have shown no selectivity for the c-MYC G-quadruplex over other G-quadruplexes, leading to uncertain side effects. In this study, through structural modification of aryl-substituted imidazole/carbazole conjugates, a brand-new, four-leaf clover-like ligand called IZCZ-3 was found to preferentially bind and stabilize the c-MYC G-quadruplex. Further intracellular studies indicated that IZCZ-3 provoked cell cycle arrest and apoptosis and thus inhibited cell growth, primarily by blocking c-MYC transcription through specific targeting of the promoter G-quadruplex structure. Notably, IZCZ-3 effectively suppressed tumor growth in a mouse xenograft model. Accordingly, this work provides an encouraging example of a selective small molecule that can target one particular G-quadruplex structure, and the selective ligand might serve as an excellent anticancer agent.

Dysregulation of anaplastic lymphoma kinase (ALK) has been detected in nonsmall cell lung cancer (NSCLC) in the form of EML4-ALK fusion. Secondary mutations opposing activity of the first-generation ALK inhibitor crizotinib came into existence, requiring mutation-targeting drug discovery for the powerful second-line treatment. In this study, we report 4-phenoxyquinoline-based inhibitors that overcome crizotinib resistance to ALK L1196M, discovered by the fragment-growing strategy. The protonation of 4-aminoquinoline core could interrupt the ability the N atom of quinoline to act as a hydrogen bond acceptor; therefore, the pKa and calculated ionization pH values of relevant pyridine-based core moieties were carefully analyzed. The replacement of amine linkage with ether resulted in single-digit nanomolar range inhibitors. The inhibitors exhibited significant antiproliferative effects on H2228 CR crizotinib-resistant cells by decreasing PI3K/AKT and MAPK signaling. This work constitutes the first example for systematic investigation of the effect of ionization pH on activity in this system.

(−)-P7C3-S243 is a neuroprotective aminopropyl carbazole with improved druglike properties compared with previously reported compounds in the P7C3 class. It protects developing neurons in a mouse model of hippocampal neurogenesis and protects mature neurons within the substantia nigra in a mouse model of Parkinson’s disease. A short, enantioselective synthesis provides the neuroprotective agent in optically pure form. It is nontoxic, orally bioavailable, metabolically stable, and able to cross the blood–brain barrier. As such, it represents a valuable lead compound for the development of drugs to treat neurodegenerative diseases and traumatic brain injury.

Carvedilol is a uniquely effective drug for the treatment of cardiac arrhythmias in patients with heart failure. This activity is in part because of its ability to inhibit store-overload-induced calcium release (SOICR) through the RyR2 channel. We describe the synthesis, characterization, and bioassay of ca. 100 compounds based on the carvedilol motif to identify features that correlate with and optimize SOICR inhibition. A single-cell bioassay was employed on the basis of the RyR2-R4496C mutant HEK-293 cell line in which calcium release from the endoplasmic reticulum through the defective channel was measured. IC50 values for SOICR inhibition were thus obtained. The compounds investigated contained modifications to the three principal subunits of carvedilol, including the carbazole and catechol moieties, as well as the linker chain containing the β-amino alcohol functionality. The SAR results indicate that significant alterations are tolerated in each of the three subunits.

The sirtuin SIRT1 is a NAD(+)-dependent histone deacetylase, a Sir2 family member, and one of seven human sirtuins. Sirtuins are conserved from archaea to mammals and regulate transcription, genome stability, longevity, and metabolism. SIRT1 regulates transcription via deacetylation of transcription factors such as PPARγ, NFκB, and the tumor suppressor protein p53. EX527 (27) is a nanomolar SIRT1 inhibitor and a micromolar SIRT2 inhibitor. To elucidate the mechanism of SIRT inhibition by 27, we determined the 2.5 Å crystal structure of the SIRT1 catalytic domain (residues 241-516) bound to NAD(+) and the 27 analogue compound 35. 35 binds deep in the catalytic cleft, displacing the NAD(+) nicotinamide and forcing the cofactor into an extended conformation. The extended NAD(+) conformation sterically prevents substrate binding. The SIRT1/NAD(+)/35 crystal structure defines a novel mechanism of histone deacetylase inhibition and provides a basis for understanding, and rationally improving, inhibition of this therapeutically important target by drug-like molecules.

Bruton’s tyrosine kinase (BTK) belongs to the TEC family of nonreceptor tyrosine kinases and plays a critical role in multiple cell types responsible for numerous autoimmune diseases. This article will detail the structure–activity relationships (SARs) leading to a novel second generation series of potent and selective reversible carbazole inhibitors of BTK. With an excellent pharmacokinetic profile as well as demonstrated in vivo activity and an acceptable safety profile, 7-(2-hydroxypropan-2-yl)-4-[2-methyl-3-(4-oxo-3,4-dihydroquinazolin-3-yl)phenyl]-9H-carbazole-1-carboxamide 6 (BMS-935177) was selected to advance into clinical development.

Recently, covalent drugs have attracted great interest in the drug discovery community, with successful examples that have demonstrated their therapeutic effects. Here, we focus on the covalent inhibition of the fatty acid amide hydrolase (FAAH), which is a promising strategy in the treatment of pain and inflammation. Among the most recent and potent FAAH inhibitors (FAAHi), there are the cyclic piperidine and piperazine aryl ureas. FAAH hydrolyzes efficiently the amide bond of these compounds, forming a covalent enzymeinhibitor adduct. To rationalize this experimental evidence, we performed an extensive computational analysis centered on piperidine-based PF750 (1) and piperazine-based JNJ1661010 (2), two potent lead compounds used to generate covalent inhibitors as clinical candidates. We found that FAAH induces a distortion of the amide bond of the piperidine and piperazine aryl ureas. Quantum mechanics/molecular mechanics ΔELUMOHOMO energies indicate that the observed enzymeinduced distortion of the amide bond favors the formation of a covalent FAAHinhibitor adduct. These findings could help in the rational structure-based design of novel covalent FAAHi.

9-Substituted 6,6-dimethyl-11-oxo-6,11-dihydro-5H-benzo[b]carbazoles were discovered as highly selective and potent anaplastic lymphoma kinase (ALK) inhibitors by structure-based drug design. The high target selectivity was achieved by introducing a substituent close to the E(0) region of the ATP binding site, which has a unique amino acid sequence. Among the identified inhibitors, compound 13d showed highly selective and potent inhibitory activity against ALK with an IC(50) value of 2.9 nM and strong antiproliferative activity against KARPAS-299 with an IC(50) value of 12.8 nM. The compound also displayed significant antitumor efficacy in an established ALK fusion gene-positive anaplastic large-cell lymphoma (ALCL) xenograft model in mice without body weight loss.

The kinesin spindle protein (KSP) is a mitotic kinesin involved in the establishment of a functional bipolar mitotic spindle during cell division. It is considered to be an attractive target for cancer chemotherapy with reduced side effects. Based on natural product scaffold-derived fused indole-based inhibitors and known biphenyl-type KSP inhibitors, various carboline and carbazole derivatives were synthesized and biologically evaluated. β-Carboline and lactam-fused carbazole derivatives exhibited remarkably potent KSP inhibitory activity and mitotic arrest in prometaphase with formation of an irregular monopolar spindle. The planar tri- and tetracyclic analogs inhibited KSP ATPase in an ATP-competitive manner just like biphenyl-type inhibitors.

Mitotic kinesin spindle protein (KSP) is involved in the assembly of the bipolar spindle during cell division. On the basis of a common 2,3-fused indole substructure within the complex frameworks of terpendole E and other KSP inhibitors, the carbazoles with a bulky alkyl group were identified as a novel KSP inhibitory scaffold. Additionally, among several naturally occurring cell growth inhibitors with 2,3-fused indole structures, beta-carboline alkaloids, harman and harmine, showed moderate inhibition of KSP.

Structure-activity relationship studies were carried out by chemical modification of manzamine A (1), 8-hydroxymanzamine A (2), manzamine F (14), and ircinal isolated from the sponge Acanthostrongylophora. The derived analogues were evaluated for antimalarial, antimicrobial, and antineuroinflammatory activities. Several modified products exhibited potent and improved in vitro antineuroinflammatory, antimicrobial, and antimalarial activity. 1 showed improved activity against malaria compared to chloroquine in both multi- and single-dose in vivo experiments. The significant antimalarial potential was revealed by a 100% cure rate of malaria in mice with one administration of 100 mg/kg of 1. The potent antineuroinflammatory activity of the manzamines will provide great benefit for the prevention and treatment of cerebral infections (e.g., Cryptococcus and Plasmodium). In addition, 1 was shown to permeate across the blood-brain barrier (BBB) in an in vitro model using a MDR-MDCK monolayer. Docking studies support that 2 binds to the ATP-noncompetitive pocket of glycogen synthesis kinase-3beta (GSK-3beta), which is a putative target of manzamines. On the basis of the results presented here, it will be possible to initiate rational drug design efforts around this natural product scaffold for the treatment of several different diseases.

The optimization of the dihydronaphthyl[3,4-a]pyrrolo[3,4-c]carbazole-5-one R(2) and R(12) positions led to the identification of the first MLK1 and MLK3 subtype-selective inhibitors within the MLK family. Compounds 14 (CEP-5104) and 16 (CEP-6331) displayed good potency for MLK1 and MLK3 inhibition with a greater than 30- to 100-fold selectivity for related family members MLK2 and DLK. Compounds 14 and 16 were orally active in vivo in a mouse MPTP biochemical efficacy model that was comparable to the first-generation pan-MLK inhibitor 1 (CEP-1347). The MLK1 structure-activity relationships were supported by the first-reported X-ray crystal structure of MLK1 bound with 16.

Pyrrolo[2,3- a]carbazole derivatives were synthesized, and their effects on CDK1/cyclinB activity were evaluated. The most potent and efficacious inhibitor was found to be ethyl 9-chloro-1H-pyrrolo[2,3-alpha]carbazole-2-carboxylate (1e), exhibiting an IC50 in the low micromolar range and leading to 90% at higher concentrations. Using a computational model for CDK1-1e, binding we have observed that 1e exhibited two likely binding modes in the ATP-binding cleft that involve interactions with Lys130, Thr14, and Asp146 of the enzyme.

In the course of structure-activity relationship studies on granulatimide analogues, new pyrrolo[3,4-c]carbazoles in which the imidazole heterocycle has been replaced by a five- or a six-membered ring bearing one or two carbonyl functions have been synthesized. Their checkpoint kinase 1 (Chk1) inhibitory properties and their in vitro antiproliferative activities toward three tumor cell lines-murine leukemia L1210 and human colon carcinoma HT29 and HCT116 have been determined. The results of molecular modeling in the ATP binding pocket of Chk1 are described. Among the newly synthesized compounds, compounds 13 and 16, in which the imidazole was replaced by a quinone and a hydroquinone and which bear a hydroxy group on the indole moiety, are the most potent Chk1 inhibitors in this series with IC50 values of 27 and 23 nM, respectively.

Some 3,3-dimethyl-1-(3-naphthylpropyl)piperidine and 1-cyclohexyl-4-(3-naphthylpropyl)piperazine derivatives, structurally containing naphthol as a fluorescent moiety, were prepared for being potentially used as fluorescent sigma ligands. Structurally related analogs were also prepared, where the naphthalene nucleus was replaced by the fluorescent carbazole moiety and chain length was varied. For all compounds the in vitro affinities toward sigma receptors and Delta8-Delta7 sterol isomerase site were measured, and the fluorescent properties were determined. Compound 19 gave the best results both for sigma receptor affinities (sigma1, Ki = 6.78 nM and sigma2, Ki = 26.4 nM) and fluorescence features; thus, it was chosen for in vitro saturation binding analysis at sigma receptors. The good results obtained in such assay suggested that the fluorescent compound 19 could be used instead of a radioligand in "green" binding assays.

Indole-3-carbinol (I3C) is a naturally occurring anticancer agent and has entered clinical trials for cancer prevention. However, the clinical development of I3C has been impeded by its poor metabolic profile. The active components of I3C were used to develop a novel class of indole analogs to optimize I3C's anticancer actions, including blocking growth factor-stimulated Akt activation. The most promising of these analogs, SR13668, exhibited potent oral anticancer activity against various cancers and no significant toxicity.

Structural modification of the indolecarbazole natural product (+)K-252a identified structural requirements for MLK activity and a novel series of potent fused pyrrolocarbazole MLK1/3 inhibitors. The SAR revealed that the lactam regiochemistry, the shape of the heterocycle, and aryl rings B and F are important to MLK activity. Heteroatom and alkyl replacement of the N-12 and/or N-13 indole nitrogen atoms identified the nonplanar dihydronaphthyl[3,4-a]pyrrolo[3,4-c]carbazole-7-one (8) and corresponding 5,7-dione (7) as potent cell-permeable MLK1/3 family-selective leads with in vitro activity comparable to that of (+)K-252a and determined them to be 2- to 3-fold more potent than the aglycone natural product K-252c.

Checkpoint kinase 1 (ChK1) plays a key role in the DNA damage response, facilitating cell-cycle arrest to provide sufficient time for lesion repair. This leads to the hypothesis that inhibition of ChK1 might enhance the effectiveness of DNA-damaging therapies in the treatment of cancer. Lead compound 1 (GNE-783), the prototype of the 1,7-diazacarbazole class of ChK1 inhibitors, was found to be a highly potent inhibitor of acetylcholine esterase (AChE) and unsuitable for development. A campaign of analogue synthesis established SAR delineating ChK1 and AChE activities and allowing identification of new leads with improved profiles. In silico docking using a model of AChE permitted rationalization of the observed SAR. Compounds 19 (GNE-900) and 30 (GNE-145) were identified as selective, orally bioavailable ChK1 inhibitors offering excellent in vitro potency with significantly reduced AChE activity. In combination with gemcitabine, these compounds demonstrate an in vivo pharmacodynamic effect and are efficacious in a mouse p53 mutant xenograft model.

The bacterial DNA replication machinery presents new targets for the development of antibiotics acting via novel mechanisms. One such target is the protein–protein interaction between the DNA sliding clamp and the conserved peptide linear motifs in DNA polymerases. We previously established that binding of linear motifs to the Escherichia coli sliding clamp occurs via a sequential mechanism that involves two subsites (I and II). Here, we report the development of small-molecule inhibitors that mimic this mechanism. The compounds contain tetrahydrocarbazole moieties as “anchors” to occupy subsite I. Functional groups appended at the tetrahydrocarbazole nitrogen bind to a channel gated by the side chain of M362 and lie at the edge of subsite II. One derivative induced the formation of a new binding pocket, termed subsite III, by rearrangement of a loop adjacent to subsite I. Discovery of the extended binding area will guide further inhibitor development.

Up-regulation of a disintegrin and metalloproteinase 10 (ADAM10) to prevent the formation of β-amyloid (Aβ) peptides might be a promising strategy to treat Alzheimer's disease (AD). RNA G-quadruplex motif within the 5'-UTR of the ADAM10 mRNA is an inhibitory element for ADAM10 translation. Thus, mitigation of the suppressive effect of this motif using an RNA G-quadruplex-forming G-rich sequence (QGRS) binder might be a new approach for AD therapy. Herein, a series of new methylquinolinium derivatives were synthesized and screened by surface plasmon resonance (SPR) and the dual-luciferase reporter assay. Among them, compound 24 showed selective affinity for the QGRS of ADAM10 and could strongly up-regulate the translation of it. Moreover, treatment with 24 led to a significant increase of the secretion of sAPPα, consequently decreasing the Aβ40 in cellular. These results illustrate that the interaction between the RNA QGRS and a small molecule may be a new molecular strategy to modulate the translation of ADAM10.

Two series of carbazole sulfonamides related to Combretastatin A4 (1) were synthesized and evaluated for antiproliferative activity. Thirteen of the 26 new sulfonamides exhibited IC(50) values of

Rebeccamycin analogues containing uncommon sugars and substitutions on the imide nitrogen have been synthesized. Their cytotoxicities were tested in colon cancer and leukemia cells. Their ability to target topoisomerase I was examined using the in vivo complex of the topoisomerase bioassay in Hela cells. Compared with aglycon 1, the modified compounds with various sugar moieties showed more potent cytotoxicities and topo I targeting ability. In addition, the rebeccamycin analogues with various uncommon sugars showed distinct cytotoxicities and topo I targeting activities. The activity of compounds with 2-deoxyglucose (8 and 9) > compounds with 2,6-deoxyglucose (5 and 6) > compounds with 2,3,6-deoxyglucose (10). Furthermore, the anticancer activity of compounds correlated with their ability to target endogenous topo I. These results suggest that the sugar moiety, especially the 2-OH and 6-OH group of the sugar, rather than the modifications in imide structure on the indolocarbazole ring, is a key element for its activity.

A series of fluoroglycosylated fluoroindolocarbazoles was examined with respect to their topoisomerase I activity, cytotoxicity, and selectivity. The lead clinical candidate from this series, BMS-250749, displays broad spectrum antitumor activity superior to CPT-11 against some preclinical xenograft models, including curative antitumor activity against Lewis lung carcinoma.

We report the efficient synthesis involving palladium-catalyzed reactions and biological evaluation of new naphthocarbazoles designed as potential anticancer agents. The use of 5- and 6-benzyloxyindoles generated three substitution sites which were successively exploited to introduce several hydrophilic side chains. The cytotoxicity of the newly designed compounds was evaluated on three cell lines. Several compounds showed a marked cytotoxicity with IC(50) values in the sub-micromolar range. This is the case for the 3-hydroxy-naphthopyrrolocarbazoledione 37, bearing a dimethylaminoethyl side chain, which is extremely cytotoxic to L1210 and DU145 cells (IC(50): 36 nM, 108 nM) and induces an accumulation of L1210 cells in the G2+M phases of the cell cycle. Some of the most cytotoxic compounds were tested for inhibition of CDK-5, GSK-3 and topoisomerase I, and their interaction with DNA was also evaluated. Interaction with DNA was detected, suggesting that nucleic acids represent a privileged target for these molecules.

A series of potent vascular endothelial growth factor R2 (VEGF-R2) tyrosine kinase inhibitors from a new indenopyrrolocarbazole template is reported. The structure-activity relationships for a series of 9-alkoxymethyl-12-(3-hydroxypropyl)indeno[2,1-a]pyrrolo[3,4-c]carbazole-5-ones revealed an optimal R9 substitution with ethoxymethyl 19 (VEGF-R2 IC(50) = 4 nM) and isopropoxymethyl 21 (VEGF-R2 IC(50) = 8 nM) being the most potent inhibitors in the series. The VEGF-R2 activity was reduced appreciably by increasing the size of the R9 alkoxy group or by alpha-methyl branching adjacent to the ring. The combined R9 alkoxymethyl and N12 hydroxypropyl substitutions were required for potent VEGF-R2 activity, and the corresponding thioether analogues were weaker than their ether counterparts. Compound 21 (R9 isopropoxymethyl, CEP-5214) was identified as a potent, low-nanomolar pan inhibitor of human VEGF-R tyrosine kinases, displaying IC(50) values of 16, 8, and 4 nM for VEGF-R1/FLT-1, VEGF-R2/KDR, and VEGF-R3/FLT-4, respectively, with cellular activity equivalent to the isolated enzyme activity. Compound 21 exhibited good selectivity against numerous tyrosine and serine/threonine kinases including PKC, Tie2, TrkA, CDK1, p38, JNK, and IRK. To increase water solubility and oral bioavailability, the N,N-dimethylglycine ester 40 was prepared. In pharmacokinetic studies in mice and rats, increased plasma levels of 21 were observed after oral administration of 40. Compound 21 demonstrated significant in vivo antitumor activity in numerous tumor models and was advanced into phase I clinical trials as the water-soluble N,N-dimethylglycine ester prodrug 40 (CEP-7055).

There is compelling evidence that Bax channel activity stimulates cytochrome c release leading ultimately to cell death, which is a key event in ischemic injuries and neurodegenerative diseases. Here 3,6-dibromocarbazole piperazine derivatives of 2-propanol are described as the first small and potent modulators of the cytochrome c release triggered by Bid-induced Bax activation in a mitochondrial assay. Furthermore, a mechanism of action is proposed, and fluorescent derivatives allowing the localization of such inhibitors are reported.

Rebeccamycin analogues containing one azaindole unit, with and without a methyl group on the imide nitrogen and with the sugar moiety coupled either to the indole nitrogen or to the azaindole nitrogen were synthesized. To increase the solubility and induce stronger interactions with the target macromolecules, a bromo or nitro substitutent was introduced on the indole unit. The DNA binding and topoisomerase I inhibition properties were investigated together with the antiproliferative activities toward nine tumor cell lines. In addition, the effect of the compounds on the cell cycle of L1210 leukemia cells was examined. The nonaza analogues were found to be cytotoxic against all cell lines of the panel whereas the aza-analogues showed a selective action toward certain cell lines. They strongly inhibited the proliferation of SK-N-MC neuroblastoma, A431 epidermoid carcinoma and NCI-H69 small cell lung carcinoma cells, but showed little or no cytotoxic effect against IGROV ovary carcinoma, HT29 colon carcinoma, and A549 non small cell lung carcinoma cells. Whatever their cytotoxicity profile, all compounds induce similar cell cycle effects, with a marked G2+M block observed with L1210 leukemia cells. The data suggest that the molecular mechanism of action of the aza-analogue derivatives is different from that of rebeccamycin.

The hypothesis that antagonists of the neuropeptide Y5 receptor would provide safe and effective appetite suppressants for the treatment of obesity has prompted vigorous research to identify suitable compounds. We discovered a series of acylated aminocarbazole derivatives (e.g., 3a) that are potent and selective Y5 antagonists, representing interesting starting points but suffering from poor bioavailability and concerns about potential toxicity as a consequence of the embedded aminocarbazole fragment. It proved relatively easy to improve the drug metabolism and pharmacokinetic (DMPK) properties by variation of the side chain (as in 4a) but difficult to eliminate the aminocarbazole fragment. For compounds in this series to have the potential to be drugs, we believed that both the compound itself and the component aniline must be free of mutagenic activity. Parallel structure-activity relationship studies looking at the effects of ring substitution have proved that it is possible by incorporation of a 4-methyl substituent to produce carbazole ureas with potent Y5 activity, comprised of carbazole anilines that in themselves are devoid of mutagenic activity in the Ames test. Compound 4o (also known as NPY5RA-972) is highly selective with respect to Y1, Y2, and Y4 receptors (and also to a diverse range of unrelated receptors and enzymes), with an excellent DMPK profile including central nervous system penetration. NPY5RA-972 (4o) is a highly potent Y5 antagonist in vivo but does not block neuropeptide Y-induced feeding nor does it reduce feeding in rats, suggesting that the Y5 receptor alone has no significant role in feeding in these models.

Two series of pentacyclic carbazolones, 22 and 23, have been synthesized utilizing a facile intramolecular Dielsminus signAlder reaction and are allosteric modulators at muscarinic acetylcholine receptors. Their affinities and cooperativities with acetylcholine and the antagonist N-methylscopolamine (NMS) at M(1)minus signM(4) receptors have been analyzed and compared. All of the synthesized compounds are negatively cooperative with acetylcholine. In contrast, the majority of the compounds exhibit positive cooperativity with NMS, particularly at M(2) and M(4) receptors. The subtype selectivity, in terms of affinity, was in general M(2)M(1)M(4)M(3). The largest increases in affinity produced by a single substitution of the core structure were given by the 1-OMe (22b) and 1-Cl (22d) derivatives. The position of the N in the ring did not appear to be important for binding affinity or cooperativity. Two compounds 22y and 23i, both trisubstituted analogues, were the most potent compounds synthesized, with dissociation constants of 30minus sign100 nM for the M(2) NMS-liganded and unliganded receptor, respectively. The results indicate that the allosteric site, like the primary binding site, is capable of high-affinity interactions with molecules of relatively low molecular weight.

Synthesis and structure-activity relationships of tricyclic alpha-ethoxy-phenylpropionic acid derivatives guided by in vitro PPARalpha and PPARgamma transactivation data and computer modeling led to the identification of the novel carbazole analogue, 3q, with dual PPARalpha (EC(50) = 0.36 microM) and PPARgamma (EC(50) = 0.17 microM) activity in vitro. Ten days treatment of db/db mice with 3q improved the insulin sensitivity, as measured by OGTT, better than that seen with both pioglitazone and rosiglitazone treatment, suggesting in vivo PPARgamma activity. Likewise, 3q lowered plasma triglycerides and cholesterol in high cholesterol fed rats after 4 days treatment, indicating in vivo PPARalpha activity. Investigations of the pharmacokinetics of selected compounds suggested that extended drug exposure improved the in vivo activity of in vitro active compounds.

The aberrant activation of STAT3 occurs in many human cancers and promotes tumor progression. Phosphorylation of a tyrosine at amino acid Y705 is essential for the function of STAT3. Synthesized carbazole derived with fluorophore compound 12 was discovered to target STAT3 phosphorylation. Compound 12 was found to inhibit STAT3-mediated transcription as well as to reduce IL-6 induced STAT3 phosphorylation in cancer cell lines expressing both elevated and low levels of phospho-STAT3 (Y705). Compound 12 potently induced apoptosis in a broad number of TNBC cancer cell lines in vitro and was effective at inhibiting the in vivo growth of human TNBC xenograft tumors (SUM149) without any observed toxicity. Compound 12 also effectively inhibited the growth of human lung tumor xenografts (A549) harboring aberrantly active STAT3. In vitro and in vivo studies showed that the inhibitory effects of 12 on phospho-STAT3 were through up-regulation of the protein–tyrosine phosphatase PTPN6. Our present studies strongly support the continued preclinical evaluation of compound 12 as a potential chemotherapeutic agent for TNBC and cancers with constitutive STAT3 signaling.

Previously we discovered a tricyclic indoline, N-[2-(6-bromo-4-methylidene-2,3,4,4a,9,9a-hexahydro-1H-carbazol-4a-yl)ethyl]-4-chlorobenzene-1-sulfonamide (1, Of1), from bioinspired synthesis of a highly diverse polycyclic indoline alkaloid library, that selectively resensitizes methicillin-resistant Staphylococcus aureus strains to β-lactam antibiotics. Herein, we report a thorough structure–activity relationship investigation of 1, which identified regions of 1 that tolerate modifications without compromising activity and afforded the discovery of a more potent analogue with reduced mammalian toxicity.

Rebeccamycin derivatives represent a promising class of antitumor agents. In this series, two glycosylated indolocarbazoles, NB-506 and NSC-655649, are currently undergoing clinical trials. Their anticancer activities are associated with their capacities to interact with DNA and to inhibit DNA topoisomerases. Previous studies revealed that the planar indolocarbazole chromophore can intercalate into DNA, locating the appended carbohydrate residue in one of the two helical grooves, probably the minor groove as is the case with the anthracyclines and other DNA-binding antibiotics. The sugar residue contributes significantly to the DNA binding free energy of NB-506. However, the exact positioning of the glycosyl residue of rebeccamycin derivatives in the drug-DNA complex remains poorly understood. To better understand how glycosylated indolocarbazoles interact with DNA, we investigated the interaction of a rebeccamycin derivative (85) bearing a 2'-amino group on the sugar residue. We show that the presence of the 2'-amino function permits the formation of covalent drug-DNA complexes in the presence of formaldehyde. Complementary biochemical and spectroscopic measurements attest that 85 reacts covalently with the 2-amino group of guanines exposed in the minor groove of the double helix, as is the case with daunomycin. In contrast to daunomycin, 85 also forms cross-links with an oligonucleotide containing only A.T base pairs. The covalent binding to A.T base pairs was detected using a gel mobility shift assay and was independently confirmed by thermal denaturation studies and by fluorescence measurements using a series of synthetic polynucleotides. The HCHO-mediated alkylation reaction of the drug with A.T base pairs apparently involves the 6-amino group of adenines exposed in the major groove whereas the covalent attachment to G.C base pairs implicates the 2-amino group of guanines situated in the opposite minor groove. Therefore, the results suggest that either the drug is able to switch grooves in response to sequence or it can simultaneously bind to both the minor and major grooves of the double helix. This study will help to guide the rational design of new DNA-binding antitumor indolocarbazole drugs and also provides a general experimental approach for probing minor versus major groove interactions between small molecules and DNA.

9-[3-(cis-3,5-Dimethyl-1-piperazinyl)propyl]carbazole (rimcazole) has been characterized as a sigma receptor antagonist that binds to the dopamine transporter with moderate affinity (K(i) = 224 nM). Although the binding affinities at the dopamine transporter of rimcazole and cocaine are comparable, rimcazole only depressed locomotor activity in mice and antagonized the stimulant effects produced by cocaine. The neurochemical mechanisms underlying the attenuation of cocaine's effects are not understood, although interaction at a low affinity site/state of the dopamine transporter has been suggested. To explore further this class of compounds, a series of rimcazole analogues was designed and synthesized. Displacement of [(3)H]WIN 35,428 binding at the dopamine transporter in rat caudate-putamen revealed that aromatic substitutions on rimcazole were not well tolerated, generally, with significant reductions in affinity for the 3,6-dibromo (5; K(i) = 3890 nM), 1,3, 6-tribromo (6; K(i) = 30300 nM), 3-amino (8; K(i) = 2400 nM), and 3, 6-dinitro (9; K(i) = 174000 nM) analogues. The N-phenylpropyl group was the only terminal piperazine nitrogen substituent that retained moderate affinity at the dopamine transporter (11; K(i) = 263 nM). Analogues in which the carbazole ring was replaced with a freely rotating diphenylamine moiety were also prepared. Although the diphenylamino analogue in which the terminal piperazine nitrogen was unsubstituted, as in rimcazole, demonstrated relatively low binding affinity at the dopamine transporter (24; K(i) = 813 nM), the N-phenylpropyl analogue was found to have the highest affinity for the dopamine transporter within the series (25; K(i) = 61.0 nM). All of the analogues that had affinity for the dopamine transporter inhibited [(3)H]dopamine uptake in synaptosomes, and potencies for these two effects showed a positive correlation (r(2) = 0.7731, p = 0.0018). Several of the analogues displaced [(3)H]paroxetine from serotonin transporters with moderate to high affinity, with the N-phenylpropyl derivative (11) having the highest affinity (K(i) = 44.5 nM). In contrast, none of the analogues recognized the norepinephrine transporter with an affinity of1.3 microM. Binding affinities for sigma(1) and sigma(2) receptors were also determined, and several of the compounds were more potent than rimcazole with affinities ranging from 97 nM to6 microM at sigma(1) sites and 145 to 1990 nM at sigma(2) sites. The compound with the highest affinity (25) at sigma(1) sites was also the compound with highest affinity at the dopamine transporter. These novel rimcazole analogues may provide important tools with which to characterize the relationship between the low affinity site or state of the dopamine transporter, sigma receptors, and their potential roles in modulating cocaine's psychostimulant actions.

In the course of structure-activity relationships on rebeccamycin analogues, a series of compounds bearing a halogenoacetyl substituent were synthesized with the expectation of increasing the interaction with DNA, possibly via covalent reaction with the double helix. Two rebeccamycin analogues bearing an acetyl instead of a bromoacetyl substituent were prepared to gain an insight into the role of the halogen atom. The new compounds show very little effect on protein kinase C and no covalent reaction with DNA was detected. However, the drugs behave as typical topoisomerase I poisons, and they are significantly more toxic toward P388 leukemia cells than to P388/CPT5 cells resistant to camptothecin. The introduction of a bromo- or chloro-acetyl substituent does not affect the capacity of the drug to interfere with topoisomerase I either in vitro or in cells. One of the bromoacetyl derivatives, compound 8, is the most cytotoxic rebeccamycin derivative among the hundred of derivatives we have synthesized to date. In addition, we determined the antimicrobial activities against two Gram-positive bacteria, Bacillus cereus and Streptomyces chartreusis, and against the Gram-negative bacterium Escherichia coli. The effect of the drugs on Candida albicans yeast growth and their anti-HIV-1 activities were also measured.

As a part of studies on structure-activity relationships, several potential topoisomerase I inhibitors were prepared. Different analogues of the antitumor antibiotic rebeccamycin substituted on the imide nitrogen with a methyl group were synthesized. These compounds bore either the sugar residue of rebeccamycin, with or without the chlorine atoms on the indole moieties, or modified sugar residues (galactopyranosyl, glucopyranosyl, or fucopyranosyl) linked to the aglycone via a beta- or alpha-N-glycosidic bond. Their inhibitory properties toward protein kinase C, topoisomerase I, and topoisomerase II were examined, and their DNA-binding properties were investigated. Their in vitro antitumor activities against murine B16 melanoma and P388 leukemia cells were determined. Their antimicrobial activities were tested against Gram-positive bacteria Bacillus cereus and Streptomyces chartreusis, Gram-negative bacterium Escherichia coli, and yeast Candida albicans. These compounds are inactive toward topoisomerase II but inhibit topoisomerase I. A substitution with a methyl group on the imide nitrogen led to a loss of proteine kinase C inhibition in the maleimide indolocarbazole series but did not prevent topoisomerase I inhibition. Compounds possessing a beta-N-glycosidic bond, which fully intercalated into DNA, were more efficient at inhibiting topoisomerase I than their analogues with an alpha-N-glycosidic bond; however, both were equally toxic toward P388 leukemia cells. Dechlorinated rebeccamycin possessing a methyl group on the imide nitrogen was about 10 times more efficient in terms of cytotoxicity and inhibition of topoisomerase I than the natural metabolite.

A series of 6-(alkylamino)-9-alkylpurines was synthesized and evaluated for the property of antagonizing the behavioral effects in animals of the dopamine agonist apomorphine. This model for identifying potential antipsychotic agents is based on the hypothesis that agents that antagonize apomorphine-induced aggressive behavior in rats and apomorphine-induced climbing in mice, but that do not block stereotyped behavior, could have an antipsychotic effect in humans without producing extrapyramidal side effects. The antiaggressive-behavior activity of lead compound 1 (6-(dimethylamino)-9-(3-phenylalaninamidobenzyl)-9H-purine) was improved 48-fold with 6-(cyclopropylamino)-9-(cyclopropylmethyl)-2-(trifluoromethyl)-9H- purine (80) (po ED50 of 2 mg/kg), which was obtained through an iterative sequence of structure--activity relationship studies that encompassed evaluation of the effects of structure variations at the purine 9-, 6-, and 2-positions. Potency was enhanced with a 9-cyclopropyl group, the duration of action was improved with the 6-(cyclopropylamino) substituent, potency was further enhanced with an N-formyl prodrug, and an agent with reduced cardiovascular effect emerged with the 2-trifluoromethyl purine 80. This potential antipsychotic agent was not developed further due to undesirable effects on the stomach.

A series of 3,9 disubstituted [(alkylthio)methyl]- and (alkoxymethyl)-K-252a derivatives was synthesized with the aim of enhancing and separating the neurotrophic properties from the undesirable NGF (trk A kinase) and PKC inhibitory activities of K-252a. Data from this series reveal that substitution in the 3- and 9-positions of K-252a with these groups reduces trk A kinase inhibitory properties approximately 100- to500-fold while maintaining or in certain cases enhancing the neurotrophic activity. From this research, 3,9-bis[(ethylthio)methyl]-K-252a (8) was identified as a potent and selective neurotrophic agent in vitro as measured by enhancement of choline acetyltransferase activity in embryonic rat spinal cord and basal forebrain cultures. Compound 8 was found to have weak kinase inhibitory activity for trk A, protein kinase C1 protein kinase A, and myosin light chain kinase. On the basis of the in vitro profile, 8 was evaluated in in vivo models suggestive of neurological diseases. Compound 8 was active in preventing degeneration of cholinergic neurons of the nucleus basalis magnocellularis (NBM) and reduced developmentally programmed cell death (PCD) of female rat spinal nucleus of the bulbocavernosus motoneurons and embryonic chick lumbar motoneurons.