Identification of 2-acylaminothiophene-3-carboxamides as potent inhibitors of FLT3

A series of 2-acylaminothiophene-3-carboxamides has been identified which exhibit potent inhibitory activity against the FLT3 tyrosine kinase. Compound 44 inhibits the isolated enzyme (IC50 = 0.027 microM) and blocks the proliferation of MV4-11 cells (IC50 = 0.41 microM). Structure-activity relationship studies within this series are described in the context of a proposed binding model within the ATP binding site of the enzyme.     

N-[2-(1-cyclohexenyl)ethyl]-N'-[2-(5-bromopyridyl)]-thiourea and N'-[2-(1-cyclohexenyl)ethyl]-N'-[2-(5-chloropyridyl)]-thiourea as potent inhibitors of multidrug-resistant human immunodeficiency virus-1.

We have replaced the pyridyl ring of trovirdine with an alicyclic cyclohexenyl, adamantyl or cis-myrtanyl ring. Only the cyclohexenyl-containing thiourea compound N-[2-(1-cyclohexenyl)ethyl]-N'-[2-(5-bromopyridyl)]- thiourea (HI-346) (as well as its chlorine-substituted derivative N-[2-(1-cyclohexenyl)ethyl]-N'-[2-(5-chloropyridyl)]- thiourea/HI-445) showed RT inhibitory activity. HI-346 and HI-445 effectively inhibited recombinant RT with better IC50 values than other anti-HIV agents tested. The ranking order of efficacy in cell-free RT inhibition assays was: HI-346 (IC50 = 0.4 microM) > HI-445 (IC50 = 0.5 microM) > trovirdine (IC50 = 0.8 microM) > MKC-442 (IC5 = 0.8 microM) = delavirdine (IC50 = 1.5 microM) > nevirapine (IC50 = 23 microM). In accord with this data, both compounds inhibited the replication of the drug-sensitive HIV-1 strain HTLV(IIIB) with better IC50 values than other anti-HIV agents tested. The ranking order of efficacy in cellular HIV-1 inhibition assays was: HI-445 = HI-346 (IC50 = 3 nM) > MKC-442 (IC50 = 4 nM) = AZT (IC50 = 4 nM) > trovirdine (IC50 = 7 nM) > delavirdine (IC50 = 9 nM) > nevirapine (IC50 = 34 nM). Surprisingly, the lead compounds HI-346 and HI-445 were 3-times more effective against the multidrug resistant HIV-1 strain RT-MDR with a V106A mutation (as well as additional mutations involving the RT residues 74V,41L, and 215Y) than they were against HTLV(IIIB) with wild-type RT. HI-346 and HI-445 were 20-times more potent than trovirdine, 200-times more potent than AZT, 300-times more potent than MKC-442, 400-times more potent than delavirdine, and 5000-times more potent than nevirapine against the multidrug resistant HIV-1 strain RT-MDR. HI-445 was also tested against the RT Y181C mutant A17 strain of HIV-1 and found to be >7-fold more effective than trovirdine and >1,400-fold more effective than nevirapine or delavirdine. Similarly, both HI-346 and HI-445 were more effective than trovirdine, nevirapine, and delavirdine against the problematic NNI-resistant HIV-1 strain A17-variant with both Y181C and K103N mutations in RT, although their activity was markedly reduced against this strain. Neither compound exhibited significant cytotoxicity at effective concentrations (CC50 >100 microM). These findings establish the lead compounds HI-346 and HI-445 as potent inhibitors of drug-sensitive as well as multidrug-resistant stains of HIV-1.     

Synthesis, biochemical evaluation of a range of potent 4-substituted phenyl alkyl imidazole-based inhibitors of the enzyme complex 17alpha-Hydroxylase/17,20-Lyase (P45017alpha)

We report the synthesis, biochemical evaluation and rationalisation of the inhibitory activity of a number of azole-based compounds as inhibitors of the two components of the cytochrome P-450 enzyme 17alpha-hydroxylase/17,20-lyase (P450(17alpha)), i.e. 17alpha-hydroxylase (17alpha-OHase) and 17,20-lyase (lyase). The results suggest that the compounds synthesised are potent inhibitors, with 7-phenyl heptyl imidazole (11) (IC(50)=320 nM against 17alpha-OHase and IC(50)=100 nM against lyase); 1-[7-(4-fluorophenyl) heptyl] imidazole (14) (IC(50)=170 nM against 17alpha-OHase and IC(50)=57 nM against lyase); 1-[5-(4-bromophenyl) pentyl] imidazole (19) (IC(50)=500 nM against 17alpha-OHase and IC(50)=58 nM against lyase) being the most potent inhibitors within the current study, in comparison to ketoconazole (KTZ) (IC(50)=3.76 microM against 17alpha-OHase and IC(50)=1.66 microM against lyase). Furthermore, consideration of the inhibitory activity against the two components shows that all of the compounds tested are less potent towards the 17alpha-OHase in comparison to the lyase component, a desirable property in the development of novel inhibitors of P450(17alpha). From the modelling of these compounds onto the novel substrate heme complex (SHC) for the overall enzyme complex, the length of the compound, along with its ability to undergo interaction with the active site corresponding to the C(3) area of the steroidal backbone, are suggested to play a key role in determining the overall inhibitory activity.     

Synthesis and anticancer evaluation of bis(benzimidazoles), bis(benzoxazoles), and benzothiazoles

Four classes of UK-1 analogues were synthesized and their cytotoxicity testing against human A-549, BFTC-905, RD, MES-SA, and HeLa carcinoma cell lines was determined. The results revealed that UK-1 and four of these analogues (15-18) are potent against the cancer cell lines. In particular, compound 16 is more potent than UK-1 against A-549 and HeLa cell lines, and compounds 15, 17, and 18 selectively exhibit potent cytotoxic activity against the BFTV-905 cells (IC50 9.6 microM), A-549 cells (IC50 6.6 microM), and MES-SA cells (IC50 9.2 microM), respectively.     

Exploration of biguanido–oxovanadium complexes as potent and selective inhibitors of protein tyrosine phosphatases

The inhibitory effects of three biguanido-oxovanadium complexes ([VO(L(1-3))(2)]·nH(2)O: HL(1) = metformin, HL(2) = phenformin, HL(3) = moroxydine) against four protein tyrosine phosphatases (PTPs) and an alkaline phosphatase (ALP) were investigated. The complexes display strong inhibition against PTP1B and TCPTP (IC(50), 80-160 nM), a bit weaker inhibition against HePTP (IC(50), 190-410 nM) and SHP-1(IC(50), 0.8-3.3 μM) and much weaker inhibition against ALP (IC(50), 17-35 μM). Complex 3 is about twofold less potent against PTP1B, TCPTP and HePTP than complexes 1 and 2, while complex 2 inhibits SHP-1 more strongly (about three to fourfold) than the other two complexes. These results suggest that the structures of the ligands slightly influence the potency and selectivity against PTPs. The complexes inhibit PTP1B and ALP with a typical competitive type.     

Urease and serine protease inhibitory alkaloids from Isatis tinctoria

Phytochemical investigations on the alkaloidal fraction of the whole plant of the Isatis tinctoria led to the isolation of the alkaloids 1-6., 3'-Hydroxyepiglucoisatisin (3), Epiglucoisatisin (2) were found to be potent urease inhibitors in a concentration-dependent manner with IC(50) values 25.63 +/- 0.74, 37.01 +/- 0.41 and 31.72 +/- 0.93, 47.33 +/- 0.31 microM against Bacillus pasteurii & Jack bean urease, respectively. Compounds 3 and 2 also showed potent inhibitory potential against alpha-chymotrypsin with IC(50) values of 23.40 +/- 0.21 and 27.45 +/- 0.23 microM, respectively.     

Synthesis, cytotoxicity, and anti-inflammatory evaluation of 2-(furan-2-yl)-4-(phenoxy)quinoline derivatives. Part 4

A number of 2-(furan-2-yl)-4-phenoxyquinoline derivatives have been synthesized and evaluated for anti-inflammatory evaluation. 4-[(2-Furan-2-yl)quinolin-4-yloxy]benzaldehyde (8), with an IC(50) value of 5.0 microM against beta-glucuronidase release, was more potent than its tricyclic furo[2,3-b]quinoline isomer 3a (>30 microM), its 4'-COMe counterpart 7 (7.5 microM), and its oxime derivative 13a (11.4 microM) and methyloxime derivative 13b (>30 microM). For the inhibition of lysozyme release, however, oxime derivative 12a (8.9 microM) and methyloxime derivative 12b (10.4 microM) are more potent than their ketone precursor 7 and their respective tricyclic furo[2,3-b]quinoline counterparts 4a and 4b. Among them, 4-[4-[(2-furan-2-yl)-quinolin-4-yloxy]phenyl]but-3-en-2-one (10) is the most active against lysozyme release with an IC(50) value of 4.6 microM, while 8 is the most active against beta-glucuronidase release with an IC(50) value of 5.0 microM. (E)-1-[3-[(2-Furan-2-yl)quinolin-4-yloxy]phenyl] ethanone oxime (11a) is capable of inhibiting both lysozyme and beta-glucuronidase release with IC(50) values of 7.1 and 9.5 microM, respectively. For the inhibition of TNF-alpha formation, 1-[3-[(2-furan-2-yl)quinolin-4-yloxy]phenyl]ethanone (6) is the most potent with an IC(50) value of 2.3 microM which is more potent than genistein (9.1 microM). For the inhibitory activity of fMLP-induced superoxide anion generation, 11a (2.7 microM), 11b (2.8 microM), and 13b (2.2 microM) are three of the most active. None of above compounds exhibited significant cytotoxicity.     

Discovery of novel Cobactin-T based matrix metalloproteinase inhibitors via a ring closing metathesis strategy

The discovery of potent N-hydroxyl caprolactam matrix metalloproteinase (MMP) inhibitors (6) based on the natural product Cobactin-T (2) is described. The synthetic method, which utilizes the ring closing metathesis reaction, is compatible to provide complementary (R) and (S) enantiomers. These compounds tested against MMP-2 and 9, show that the R stereochemistry (i.e., 16), which is opposite for that found in the natural product Cobactin-T is >1000-fold more active with IC(50) values of 0.2-0.6nM against both enzymes. The variation in the incorporation of the sulfonamide enzyme recognition element (Ar(2)XAr(1)SO(2)N(R(1)), 6), along with alterations in the RCM/double bond chemistry (R(2)) provided a series of sub nanomolar MMP inhibitors. For example, compounds 16 and 34 were found to be the most potent with IC(50) values against MMP-2 and MMP-9 found to be between 0.2 and 0.6nM with 34 being the most potent compound discovered (MMP-2 IC(50)=0.39nM and MMP-9 IC(50)=0.22nM). Compounds 16 and 34 showed acceptable drug-like properties in vivo with compound 34 showing oral bioavailability.     

C(4)-alkyl substituted furanyl cyclobutenediones as potent, orally bioavailable CXCR2 and CXCR1 receptor antagonists

A novel series of cyclobutenedione centered C(4)-alkyl substituted furanyl analogs was developed as potent CXCR2 and CXCR1 antagonists. Compound 16 exhibits potent inhibitory activities against IL-8 binding to the receptors (CXCR2 Ki=1 nM, IC(50)=1.3 nM; CXCR1 Ki=3 nM, IC(50)=7.3 nM), and demonstrates potent inhibition against both Gro-alpha and IL-8 induced hPMN migration (chemotaxis: CXCR2 IC(50)=0.5 nM, CXCR1 IC(50)=37 nM). In addition, 16 has shown good oral pharmacokinetic profiles in rat, mouse, monkey, and dog.     

Discovery of potent and selective succinyl hydroxamate inhibitors of matrix metalloprotease-3 (stromelysin-1)

Structure activity relationships are described for a series of succinyl hydroxamic acids 4a-o as potent and selective inhibitors of matrix metalloprotease-3 (stromelysin-1). Optimisation of P1' and P3' groups gave compound 4j (MMP-3 IC50=5.9nM) which was >140-fold less potent against MMP-1 (IC50=51,000nM), MMP-2 (IC50=1790nM), MMP-9 (IC50=840nM) and MMP-14 (IC50=1900nM).     

Antimalarial activity of thioacridone compounds related to the acronycine alkaloid

A series of thioacridone compounds that were previously shown to have DNA binding interaction, were screened for antimalarial activity. The new compounds were assessed for in vitro antimalarial activity against a chloroquine sensitive (D10) strain of the malaria parasite Plasmodium falciparum, using a lactate dehydrogenase (PfLDH) assay. In the series, the IC(50) values ranged from 0.4 to 27 microg/ml. 1-(2-Dimethylaminoethylamino)-9(10H)-thioacridone was found to be the most potent against P. falciparum (D10) with an IC(50) value of 0.4 microg/ml. This compound was also evaluated against a South African chloroquine resistant (RSA 11) P. falciparum strain and was found to have an IC(50) value of 1 microg/ml, compared with 0.16 microg/ml for chloroquine. Quantitative structure-activity relationships of this series were also investigated and a multiple linear regression r(2) of 0.58 was found for the best fit equation. The most potent compound, 1-(2-dimethylaminoethylamino)-9(10H)-thioacridone, was docked into the chloroquine binding site of PfLDH and it was found that the slightly lower activity of this compound, compared with chloroquine, is likely due to steric interference within a restricted binding pocket.     

Structural requirement of chalcones for the inhibitory activity of interleukin-5

Novel chalcones were found as potent inhibitors of interleukin (IL)-5. 1-(2-Benzyloxy-6-hydroxyphenyl)-3-(4-hydroxyphenyl)-2-propen-1-one (2b, 78.8% inhibition at 50microM, IC(50)=25.3microM) was initially identified as a potent inhibitor of IL-5. This shows the compatible activity with budesonide or sophoricoside. To identify structural requirements, 26 chalcones were prepared and their inhibitory activities were tested against IL-5. Among them, compound 4-[(E)-3-(2-cyclohexylmethoxy-6-hydroxyphenyl)-3-oxoprop-1-enyl]benzenesulfonamide (2w, 99.5% inhibition at 50microM, IC(50)=1.8microM) shows the most potent activity. The important structural requirements of these chalcone analogs exhibiting the inhibitory activity against IL-5 were recognized as the following. (1) The hydrophobic group such as benzyloxy or cyclohexylmethoxy at 6-position of A ring is necessary. (2) The existence of phenolic hydroxyl at 6-position of A ring is critical. (3) Propenone unit as alpha,beta-unsaturated ketone is essential. (4) Electron withdrawing groups with hydrogen acceptor property at 4-position of B ring enhance the activity and quantitative structure-activity relationship of 2 regarding these substituents was determined.     

CCR5 receptor antagonists: discovery and SAR of novel 4-hydroxypiperidine derivatives

The guanylhydrazone of 2-(4-chlorobenzyloxy)-5-bromobenzaldehyde, 1, with an IC(50) of 840 nM against the CCR5 receptor was identified using high-throughput screening. Optimization efforts led to the discovery of a novel piperidine series of CCR5 antagonists. In particular, the 4-hydroxypiperidine derivative, 6k, had improved potency against CCR5, and was a starting point for further optimization. SAR elaboration using parallel synthesis led to the identification of 10h, a potent CCR5 antagonist with an IC(50) of 11 nM.     

The antiplasmodial activity of norcantharidin analogs

The antiplasmodial activities of sixty norcantharidin analogs were tested in vitro against a chloroquine sensitive (D6, Sierra Leone) and chloroquine resistant (W2) strains of Plasmodium falciparum. Forty analogs returned IC(50) values <500 μM against at least one of the P. falciparum strains examined. The ring open compound 24 ((1S,4R)-3-(allylcarbamoyl)-7-oxabicyclo[2.2.1]heptane-2-carboxylic acid) is the most active aliphatic analog (D6 IC(50)=3.0±0.0 and W2 IC(50)=3.0±0.8 μM) with a 20-fold enhancement relative to norcantharidin. Surprisingly, seven norcantharimides also displayed good antiplasmodial activity with the most potent, 5 returning D6=8.9±0.9 and W2 IC(50)=12.5±2.2 μM, representing a fivefold enhancement over norcantharidin.     

Bicyclams, Selective Antagonists of the Human Chemokine Receptor CXCR4, Potently Inhibit Feline Immunodeficiency Virus Replication

Bicyclams are low-molecular-weight anti-human immunodeficiency virus (HIV) agents that have been shown to act as potent and selective CXC chemokine receptor 4 (CXCR4) antagonists. Here, we demonstrate that bicyclams are potent inhibitors of feline immunodeficiency virus (FIV) replication when evaluated in Crandell feline kidney (CRFK) cells. With a series of bicyclam derivatives, 50% inhibitory concentrations (IC50s) against FIV were obtained in this cell system that were comparable to those obtained for HIV-1 IIIB replication in the human CD4(+) MT-4 T-cell line. The bicyclams were also able to block FIV replication in feline thymocytes, albeit at higher concentrations than in the CRFK cells. The prototype bicyclam AMD3100, 1-1'-[1,4-phenylene-bis(methylene)]-bis(1,4,8, 11-tetraazacyclotetradecane), was only fourfold less active in feline thymocytes (IC50, 62 ng/ml) than in CRFK cells (IC50, 14 ng/ml). AMD2763, 1,1'-propylene-bis(1,4,8, 11-tetraazacyclotetradecane), which is a less potent CXCR4 antagonist, was virtually inactive against FIV in feline thymocytes (IC50, >66.5 microgram/ml), while it was clearly active in CRFK cells (IC50, 0.9 microgram/ml). The CXC chemokine stromal-cell-derived factor 1alpha had anti-FIV activity in CRFK cells (IC50, 200 ng/ml) but not in feline thymocytes (IC50, >2.5 microgram/ml). When primary FIV isolates were evaluated for their drug susceptibility in feline thymocytes, the bicyclams AMD3100 and its Zn2+ complex, AMD3479, inhibited all six primary isolates at equal potency. The marked susceptibility of FIV to the bicyclams suggests that FIV predominantly uses feline CXCR4 for entering its target cells.     

Antioxidative activities of novel diphenylalkyl piperazine derivatives with high affinities for the dopamine transporter

A new series of diphenylalkyl piperazine derivatives with high affinities for the dopamine transporter (DAT), which were modified at both the diphenylalkyl moiety and the phenyl ring in the phenylamino moiety of 1-[4,4-bis(4-fluorophenyl)butyl]-4-[2-hydroxy-3-(phenylamino)propyl]piperazine 1, was evaluated for their inhibitory activities against auto-oxidative lipid peroxidation in canine brain homogenates. Some of these were approximately equivalent in activity to alpha-tocopherol as a potent antioxidant with IC(50) values of low micromolar order, and the 4-hydroxyphenyl derivative 11 showed the most potent antioxidative activity with an IC(50) value of 0.32 microM, exhibiting approximately 5-fold more potent activity than alpha-tocopherol. The structure-activity relationship (SAR) studies of the antioxidative activity of these derivatives are presented.     

Inhibitors of HCV NS5B polymerase: synthesis and structure-activity relationships of N-1-heteroalkyl-4-hydroxyquinolon-3-yl-benzothiadiazines

N-1-Alkylamino and N-1-alkyloxy-4-hydroxyquinolon-3-yl benzothiadiazines were synthesized and evaluated as inhibitors of genotype 1 HCV polymerase. The N-1-alkyloxy derivatives were not potent inhibitors, however N-1-alkylamino derivatives displayed comparable potency to carbon analogs. Analogs with aliphatic substituents were significantly more potent than those with benzylic substituents against genotype 1a polymerase. The most potent inhibitors contained small alkyl or carbocyclic substituents and exhibited IC50's of 50-100 and 200-400 nM against genotype 1b and 1a HCV polymerase, respectively.     

Tetraketones: a new class of tyrosinase inhibitors

Twenty-eight tetraketones (1-28) with variable substituents at C-7 were synthesized and evaluated as tyrosinase inhibitors. Remarkably compounds 25 (IC(50)=2.06 microM), 11 (IC(50)=2.09 microM), 15 (IC(50)=2.61 microM), and 27 (IC(50)=3.19 microM) were found to be the most active compounds of the series, even better than both standards kojic acid (IC(50)=16.67 microM) and L-mimosine (IC(50)=3.68 microM). This study may lead to the discovery of therapeutically potent agents against clinically very important dermatological disorders including hyperpigmentation as well as skin melanoma.     

Modified norcantharidins; synthesis, protein phosphatases 1 and 2A inhibition, and anticancer activity

Fourteen modified norcantharidin analogues have been synthesised and screened for their ability to inhibit the serine/threonine protein phosphatases 1 and 2A. The most potent compounds found were 10 (PP1 IC(50)=13+/-5 microM; PP2A IC(50)=7+/-3 microM) and 16 (PP1 IC(50)=18+/-8 microM; PP2A IC(50)=3.2+/-0.4 microM). Overall, only analogues possessing at least one acidic residue at the former anhydride warhead displayed any PP1 or PP2A inhibitory action. The ability of these analogues to inhibit PP1 and PP2A correlates well with their observed anti-cancer activity against a panel of five cancer cell lines: A2780 (human ovarian carcinoma), G401 (human kidney carcinoma), HT29 (human colorectal carcinoma), H460 (human lung carcinoma) and L1210 (murine leukemia).