Synthesis and cellular pharmacology studies of a series of 2-amino-3-aroyl-4-substituted thiophene derivatives.

Microtubules are dynamic structures that play a crucial role in cellular division and are recognized as an important target for cancer therapy. In search of new compounds with strong antiproliferative activity and simple molecular structure, we have synthesized four different series of compounds in which different substituents were linked to the 4- or 5-position of the 2-amino-3-(3',4',5'-trimethoxybenzoyl) thiophene system. When these compounds were analyzed in vitro for their inhibition of cell proliferation, the 4-aryl substituted derivatives had little activity. In contrast, the presence of a methylene, oxymethyl, aminomethyl or methylenepiperazino moiety between the aryl and the 4-position of the thiophene ring resulted in statistically significant improvement in activity relative to the 4-aryl substituted derivatives. It is noteworthy that the antiproliferative effects of the synthesized compounds were more pronounced against human Molt/4 and CEM as compared with murine L1210 and FM3A cells. The effects of a selected series of compounds on cell cycle progression correlated well with their strong antiproliferative activity and inhibition of tubulin polymerization. We found that the antiproliferative effects of the most active compounds were associated with increase of the proportion of cells in the G2/M and sub-G1 phases of the cell cycle. The structure-activity relationships observed in the series of compounds described here should permit the design of more active molecules.

Synthesis and biological evaluation of 2- and 3-aminobenzo[b]thiophene derivatives as antimitotic agents and inhibitors of tubulin polymerization.

Two new series of inhibitors of tubulin polymerization based on the 2-amino-3-(3,4,5-trimethoxybenzoyl)benzo[b]thiophene molecular skeleton and its 3-amino positional isomer were synthesized and evaluated for antiproliferative activity, inhibition of tubulin polymerization, and cell cycle effects. Although many more 3-amino derivatives have been synthesized so far, the most promising compound in this series was 2-amino-6-methyl-3-(3,4,5-trimethoxybenzoyl)benzo[b]thiophene, which inhibits cancer cell growth at subnanomolar concentrations and interacts strongly with tubulin by binding to the colchicine site.

Synthesis and biological evaluation of 2-(3',4',5'-trimethoxybenzoyl)-3-amino 5-aryl thiophenes as a new class of tubulin inhibitors.

2-(3',4',5'-Trimethoxybenzoyl)-3-amino-5-aryl/heteroaryl thiophene derivatives were synthesized and evaluated for antiproliferative activity, inhibition of tubulin polymerization, and cell cycle effects. SARs were elucidated with various substitutions on the aryl moiety 5-position of the thienyl ring. Substituents at the para-position of the 5-phenyl group showed antiproliferative activity in the order of F=CH(3) > OCH(3)=Br=NO(2) > CF(3)=I > OEt. Several of these compounds led to arrest of HL-60 cells in the G2/M phase of the cell cycle and induction of apoptosis.

Synthesis and biological evaluation of 2-amino-3-(3',4',5'-trimethoxybenzoyl)-5-aryl thiophenes as a new class of potent antitubulin agents.

A new series of compounds in which the 2-amino-5-chlorophenyl ring of phenstatin analogue 7 was replaced with a 2-amino-5-aryl thiophene was synthesized and evaluated for antiproliferative activity and for inhibition of tubulin polymerization and colchicine binding to tubulin. 2-Amino-3-(3',4',5'-trimethoxybenzoyl)-5-phenyl thiophene (9f) as well as the p-fluoro-, p-methyl-, and p-methoxyphenyl substituted analogues (9i, j, and l, respectively) displayed high antiproliferative activities with IC50 values from 2.5 to 6.5 nM against the L1210 and K562 cell lines. Compounds 9i and j were more active than combretastatin A-4 as inhibitors of tubulin polymerization. Molecular docking simulations to the colchicine site of tubulin were performed to determine the possible binding mode of 9i. The results obtained demonstrated that antiproliferative activity correlated well with the inhibition of tubulin polymerization and the lengthening of the G2/M phase of the cell cycle. Moreover, a good correlation was found between these inhibitory effects and the induction of apoptosis in cells treated with the compounds.

Novel combretastatin analogues endowed with antitumor activity.

We studied the anticancer activity of a series of new combretastatin derivatives with B-ring modifications. The structure-activity relationship (SAR) information confirmed the importance of cis-stereochemistry and of a phenolic moiety in B-ring. We selected the benzo[b]thiophene and benzofuran combretastatin analogues 11 (ST2151) and 13 (ST2179) and their phosphate prodrugs (29 and 30) for their high antitumor activity in in vitro and in vivo models. Cell exposure to IC50 of 11, 13, and CA-4 led to the arrest of various cell types in the G2/M phase of the cell cycle and induction of apoptosis. Mainly, 11 and 13 induced the formation of multinucleated cells with abnormal chromatin distribution, with only a minimal effect on the microtubule organization, with respect to CA-4. Interestingly, both the pharmacokinetic profile of 29 and its in vivo antitumor effect and those of 30, active even after oral administration, suggest additional pharmacological differences between these compounds and CA-4P.

Synthesis and biological characterization of [3H] (2-amino-4,5,6,7-tetrahydrobenzo[b]thiophen-3-yl)-(4-chlorophenyl)-methanone, the first radiolabelled adenosine A1 allosteric enhancer.

Among the adenosine A(1) allosteric enhancers reported so far, compound (2-amino-4,5,6,7-tetrahydrobenzo[b]thiophen-3-yl)-(4-chlorophenyl)-methanone 1 (named T-62) has shown biological properties similar to those of PD 81,723, the reference A(1) allosteric enhancer and it has been more fully pharmacologically investigated. The preparation of the radiolabelled form of compound 1 and its characterization by saturation binding experiments are reported. These studies allowed us to demonstrate for the first time the existence of a specific, allosteric site on the A(1) receptor.

Synthesis, radiolabeling, and preliminary biological evaluation of [3H]-1-[(S)-N,O-bis-(isoquinolinesulfonyl)-N-methyl-tyrosyl]-4-(o-tolyl)-piperazine, a potent antagonist radioligand for the P2X7 receptor.

The design, synthesis, and preliminary biological evaluation of the first potent radioligand antagonist for the P2X(7) receptor, named [(3)H]-1-[(S)-N,O-bis-(isoquinolinesulfonyl)-N-methyl-tyrosyl]-4-(o-tolyl)-piperazine (compound 13), are reported. This compound bound to human P2X(7) receptors expressed in HEK transfected cells with K(D) and B(max) value of 3.46+/-0.1 nM and 727+/-73 fmol/mg of protein, respectively. The high affinity and facile labeling makes it a promising radioligand for a further characterization of P2X(7) receptor subtype.

Synthesis of 2-amino-3-heteroaroylthiophenes and evaluation of their activity as potential allosteric enhancers at the human A1 receptor.

2-Amino-3-benzoylthiophenes are allosteric enhancers of agonist binding to the adenosine A(1) receptor. New compounds bearing an heteroaroyl instead of the benzoyl moiety at the 3-position of the thiophene were synthesized. The phenyl ring was replaced with heterocycles that possess heteroatoms able to form hydrogen bonds (2-furanyl, 2-benzofuranyl, 2-pyridinyl in compounds 2-13) or with a thienyl moiety as isoster of the phenyl ring (2-thienyl, 3-thienyl and 5-halo-2-thienyl in compounds 14-29). The effect of several alkyl substituents at positions 4 and 5 of the thiophene ring to increase enhancer activity was determined. The ability of the new molecules to reduce the cAMP content in CHO cells expressing the human adenosine A(1) receptor was evaluated. Compounds 2-13 with hydrogen bond-forming heteroatoms did not show significant activity as allosteric enhancers. On the other hand, compounds 15-16 and 19-20 with an unsubstituted thienyl moiety as replacement for the phenyl ring were nearly as efficacious as PD 81,723, the prototypical A(1) allosteric enhancer. Alkyl substituents at positions 4 and 5 of the thiophene ring were tolerated while a substituted piperidine ring was not tolerated. We conclude that hydrogen bonds could not be formed in the domain of the receptor that accommodates the phenyl ring of 2-amino-3-benzoylthiophene derivatives, indicating that this domain is hydrophobic.

DNA minor groove binders as potential antitumor and antimicrobial agents.

DNA minor groove binders constitute an important class of derivatives in anticancer therapy. Some of these compounds form noncovalent complexes with DNA (e.g., distamycin A, Hoechst 33258, and pentamidine) while others DNA-binding compounds (such as CC-1065) cause cleavages in the DNA backbone. In this article, we have reviewed the minor groove binders currently in preclinical evaluation in the last years. Diarylamidines such as DAPI, berenil, and pentamidine; bis-benzimidazoles such as Hoechst 33258; ecteinascidins, pyrrololo [2,1-c]-[1,4]-benzodiazepines (PBDs), CC-1065, and distamycins are the classes discussed in this review article. A special section has been dedicated to hybrid molecules resulted by the combination of two minor groove binders, especially for derivatives of naturally occurring antitumor agents, such as anthramycin or the alkylating unit of the antibiotic CC-1065, and distamycin frames.

Design, synthesis and in vitro cytotoxicity of a cis-dichloroplatinum (II) complex linked to the minor groove binder stallimycin.

Two potentially hydrophilic platinum (II) complexes 10 and 11 bound to the minor groove binder stallimycin (distamycin A, CAS 636-47-5) by L-cysteine and D,L-2,3-diaminopropionic acid have been synthesized. The in vitro cytotoxicity of both these complexes was evaluated against several cell lines. None of the synthesized platinum complexes showed greater activity than that of cisplatin (cis-DDP, 1) (CAS 15663-27-1). Interestingly, the free ligands 6 and 9 were more active than the related platinum complexes 10 and 11, respectively, with respect to RAJI, CCRF-CEM and MOLT-4 human leukaemia cell lines.

Synthesis and biological effects of novel 2-amino-3-naphthoylthiophenes as allosteric enhancers of the A1 adenosine receptor.

The current study describes the synthesis and biological evaluation of a novel series of 2-amino-3-naphthoylthiophenes, with variable modifications at the 4- and 5-position of the thiophene as well as the naphthoyl ring. Allosteric enhancer activity was measured in several ways: (1) evaluating the effect on forskolin-stimulated cAMP accumulation in the presence of an A(1)-adenosine agonist (CPA) in Chinese hamster ovary (CHO) cells expressing the cloned human A(1)-adenosine receptor (hA(1)AR); (2) ability of these compounds to displace the binding of [(3)H]DPCPX, [(3)H]ZM 241385, and [(3)H]MRE 3008F20 to the ligand binding site of CHO cells expressing the hA(1), hA(2A), and hA(3) adenosine receptors, respectively; (3) effect on the binding of [(3)H]CCPA to membranes from CHO cells expressing hA(1)AR, to rat brain and human cortex membrane preparations containing native adenosine A(1) receptors; (4) kinetics of the dissociation of [(3)H]CCPA from CHO-hA1 membranes. The pharmacological assays compared the various activities to that of the reference compound PD 81,723 (compound 1). Several compounds appeared to be better than PD 81,723 to enhance the effect of CPA (and thus reduce cAMP content) in the CHO:hA(1) assay. The effect of these compounds at a concentration of 10 microM was slightly greater than that of the same concentration of the PD 81,723 and substantially greater than that of PD 81,723 when responses to 1 microM of each compound were compared. These include compounds 23, 25-29, 31-34, 38, 39, 43, and 58. Cycloalkylthiophenes tended to be more potent then their 4,5-dimethyl analogues, and in the series of cycloalkylthiophenes, tetrahydrobenzo[b]thiophene derivatives appeared to be more potent than the dihydrocyclopentadien[b]thiophene counterparts. Some of the most potent compounds were tested at a concentration of 10 microM for their affinity as competitors to the antagonist binding site of CHO cells expressing hA(1), hA(2A), and hA(3) adenosine receptors. None inhibited binding at the hA(2A)AR, but most of them inhibited binding to the hA(1)AR to varying extents (0-19%) as well as to the hA(3)AR to a substantial degree (0-57%). At a concentration of 10 microM, the compounds 31, 34, 37, 38, and 39 were more active than PD 81,723 to increase the binding of [(3)H]CCPA to CHO:hA(1), human brain and rat cortex membranes. Compound 37 was the most active compound increasing the binding to CHO:hA(1), human brain, and rat cortex membranes by 149, 43, and 27%, respectively (51, 15, and 22%, respectively, for PD 81,723). A good correlation was found between the increments [(3)H]CCPA binding to A(1) receptors expressed in different systems. Unlike the effect on agonist binding, the tested compounds did not increase the binding of the antagonist [(3)H]DPCPX on hCHO-A(1) membranes. Ligand dissociation studies revealed that two compounds (22 and 39) were more potent than 1 to slow the dissociation of [(3)H]CCPA from CHO:hA(1)AR membranes. No clear-cut structure-activity relationship can be observed based on data from the functional assay, but we have identified several compounds, in particular 37 and 39, which appeared to be more potent than 1 and that may be selected for further development.

Synthesis, biological activity and molecular modeling studies of 1,2,3,4-tetrahydroisoquinoline derivatives as conformationally constrained analogues of KN62, a potent antagonist of the P2X7-receptor containing a tyrosine moiety.

A new series of ring constrained analogues of the P2X7 receptor antagonist KN62 (1-[N,O-bis(1,5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4- phenylpiperazine, CAS 127191-97-3) containing the 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid core with S configuration in position 3 was synthesised and their antagonist activities were tested on human macrophage cells. While KN62 is a potent antagonist of the P2X7 receptor, these novel compounds are weak antagonists of the purinergic P2X7 receptor and only one compound (5) showed appreciable activity as P2X7 antagonist, which was 30 times weaker than that reported for KN62. Along with compound 5, the derivatives 11 and 25 were the most active inhibitors in this synthesised series. A molecular modeling study confirmed that an extended rather than folded conformation seems to be crucial for the antagonistic activity at the P2X7 receptor.

Antimicrobial and antitumor activity of N-heteroimmine-1,2,3-dithiazoles and their transformation in triazolo-, imidazo-, and pyrazolopirimidines.

The reaction of Appel's salt with o-amino nitrile heterocycles 10-19 gave the corresponding 4-chloro-5-heteroimmine-1,2,3-dithiazoles 20-29 which were evaluated for their antibacterial, antifungal and antitumor activity. Although all these N-heteroimines were devoid of significant antibacterial activity, they showed significant antifungal activity. Moreover, the same derivatives represent highly versatile intermediates in heterocyclic synthesis, in fact the pyrazoleimino dithiazoles 20-26 can be converted in one step into 2-cyano derivatives of the corresponding 4-methoxy-pyrazolo[3,4-d]pyrimidines 30-35 by sodium methoxide in refluxing methanol. This provides a general and attractive route to 4-methoxy-6-cyano pyrazolo[3,4-d]pyrimidines from 1-substituted 5-amino pyrazoles 10-19 in two simple steps. Finally, the isosteric replacement of the pyrazole ring atoms to give the imidazole[3,4-d]pyrimidine and triazole [4,5-d] pyrimidine ring systems was examined.