7-Azaindole-1-carboxamides as a new class of PARP-1 inhibitors.

7-Azaindole-1-carboxamides were designed as a new class of PARP-1 inhibitors. The compounds displayed a variable pattern of target inhibition profile that, in part, paralleled the antiproliferative activity in cell lines characterized by homologous recombination defects. A selected compound (1l; ST7710AA1) showed significant in vitro target inhibition and capability to substantially bypass the multidrug resistance mediated by Pgp. In antitumor activity studies against the MX1 human breast carcinoma growth in nude mice, the compound exhibited an effect similar to that of Olaparib in terms of tumor volume inhibition when used at a lower dose than the reference compound. Treatment was well tolerated, as no deaths or significant weight losses were observed among the treated animals.

Total synthesis of the natural product benzo[j]fluoranthene-4,9-diol: an approach to the synthesis of oxygenated benzo[j]fluoranthenes.

A synthetic sequence to the benzo[j]fluoranthene nucleus is described. Crucial steps of the procedure include a Suzuki coupling between appropriately substituted 2-bromo-acenaphthylene-1-carbaldehydes and 2-formylbenzeneboronates followed by McMurry ring closure. The synthesis represents a new approach to the benzo[j]fluoranthene ring system and specifically provides a method for the rapid preparation of differently substituted derivatives. Following this strategy, the first total synthesis of the recently isolated natural product benzo[j]fluoranthene-4,9-diol was carried out.

Identification of a novel arylpiperazine scaffold for fatty acid amide hydrolase inhibition with improved drug disposition properties.

We herein describe the systematic approach used to develop new analogues of compound 2, recently identified as a potent and selective fatty acid amide hydrolase (FAAH) inhibitor. Aiming at identifying new scaffolds endowed with improved drug disposition properties with respect to the phenylpyrrole-based lead, we subjected it to two different structural modification strategies. This process allowed the identification of derivatives 4b and 5c as potent, reversible and non-competitive FAAH inhibitors.

New retinoid derivatives as back-ups of Adarotene.

Adarotene belongs to the so-called class of atypical retinoids. The presence of the phenolic hydroxyl group on Adarotene structure allows a rapid O-glucuronidation as a major mechanism of elimination of the drug, favoring a fast excretion of its glucuronide metabolite in the urines. A series of ether, carbamate and ester derivatives was synthesized. All of them were studied and evaluated for their stability at different pH. The cytotoxic activity in vitro on NCI-H460 non-small cell lung carcinoma and A2780 ovarian tumor cell lines was also tested. A potential back-up of Adarotene has been selected to be evaluated in tumor models.

Synthesis and topoisomerase I inhibitory activity of a novel diazaindeno[2,1-b]phenanthrene analogue of Lamellarin D.

A novel 5-oxa-6a,8-diazaindeno[2,1-b]phenanthren-7-one scaffold was designed and synthesized as an active analogue of the cytotoxic marine alkaloid Lamellarin D. The design was based on molecular modeling of the site of interaction of Lamellarin D with DNA-topoisomerase I cleavable complex, whereas the synthesis capitalized on a simple Friedel-Crafts cyclization of indole to a ß-carbolinone nucleus. The product exhibited topoisomerase I poisoning activity and submicromolar cytotoxicity on human non-small cell lung cancer H460 cell line.

A new group of oxime carbamates as reversible inhibitors of fatty acid amide hydrolase.

A series of oxime carbamates have been identified as potent inhibitors of fatty acid amide hydrolase (FAAH), an important regulatory enzyme of the endocannabinoid signaling system. Kinetic analysis indicates that they behave as non-competitive, reversible inhibitors, and show remarkable selectivity for FAAH over the other components of the endocannabinoid system.

Natural and semisynthetic azaphilones as a new scaffold for Hsp90 inhibitors.

A series of mold metabolites of Ascomycetes, structurally belonging to the class of azaphilones, were found to inhibit the heat shock protein Hsp90. In particular, bulgarialactone B was tested for its binding to Hsp90 using surface plasmon resonance and limited proteolysis assays and for its effects on Hsp90 client proteins expression in a series of human tumor cell lines. This compound showed high affinity for Hsp90, interacting with the 90-280 region of the N-terminal domain and down-regulated the Hsp90 client proteins Raf-1, survivin, Cdk4, Akt, and EGFR. Bulgarialactone B and other natural azaphilones showed antiproliferative activity in a panel of human tumor cell lines; their conversion into semisynthetic derivatives by reaction with primary amines increased the antiproliferative activity. Preliminary results indicated in vivo activity of bulgarialactone B against an ascitic ovarian carcinoma xenograft, thus supporting the therapeutic potential of this novel series of Hsp90 inhibitors.

Synthesis and antifungal activity of 2-hydroxy-4,5-methylenedioxyaryl ketones as analogues of kakuol.

In a study aiming to determine the structural elements essential to the antifungal activity of kakuol, we synthesized a series of 2-hydroxy-4,5-methylenedioxyaryl ketones, and we assayed their in vitro antifungal activity. The most sensitive target organisms to the action of these class of compounds were Phytophthora infestans, Phytium ultimum, Cercospora beticola, Cladosporium cucumerinum, and Rhizoctonia solani. Most of the analogs showed a remarkable in vitro activity, and some of them appeared significantly more effective than the natural product. The biological activity was mainly affected by introducing structural modification on the carbonyl moiety of the natural-product molecule. In particular, compound 5a, bearing a C=C bond conjugated to the C=O group, was found active with a MIC value of 10 microg ml(-1) against Cladosporium cucumerinum. The results suggest that 2-hydroxy-4,5-methylenedioxyaryl ketones can be considered promising candidates in the development of new antifungal compounds.

Optimized synthesis and enhanced efficacy of novel triplex-forming camptothecin derivatives based on gimatecan.

Sequence-specific camptothecins are useful tools to inhibit specifically gene expression. The camptothecins are attached to the 3' end of triplex-forming oligonucleotides (TFO), sequence-specific DNA ligands that position the camptothecin moiety exclusively in proximity to their binding site. We studied here different gimatecan derivatives or analogues, a potent lipophilic camptothecin compound in clinical trials. We optimized the synthesis procedure in order to increase the yields and the purity and obtain the conjugates on a large scale. The greatly improved synthesis is now based on the conjugation of a bromoalkyl analogue of gimatecan to the 3' phosphorothioate of the TFO. We showed that the most efficient conjugate, both in vitro and in HeLa cells, bears the TFO on position 7 of the gimatecan analogue, and it is more efficient than the previous camptothecin conjugates. In addition, the gimatecan-like moiety at the 3' end of the TFO protects from nuclease degradation.

Preclinical profile of antitumor activity of a novel hydrophilic camptothecin, ST1968.

ST1968 is a novel hydrophilic camptothecin (CPT) derivative of the 7-oxyiminomethyl series. Because ST1968 retained ability to form remarkably stable cleavable complexes, this study was done to investigate its preclinical profile of antitumor activity in a large panel of human tumor models, including irinotecan-resistant tumors. Although less potent than SN38 in vitro, i.v. administered ST1968 caused a marked tumor inhibition, superior to that of irinotecan, in most tested models. ST1968 exhibited an impressive activity against several tumors including models of ovarian and colon carcinoma in which a high rate of cures was observed. In the most responsive tumors, complete and persistent tumor regressions were achieved even with low suboptimal doses. Even tumors derived from intrinsically resistant cells exhibited a significant responsiveness. Histologic analysis of treated tumors supports a contribution of both proapoptotic and antiangiogenic effects to ST1968 antitumor efficacy. A study done in yeast cells transformed with CPT-resistant mutant forms of topoisomerase I documented that, in contrast to other tested CPT, ST1968 was active against yeasts expressing the mutant K720E enzyme. Based on its outstanding efficacy superior to that of irinotecan and of its good therapeutic index, ST1968 has been selected for clinical development.

Atypical retinoids ST1926 and CD437 are S-phase-specific agents causing DNA double-strand breaks: significance for the cytotoxic and antiproliferative activity.

Retinoid-related molecules (RRM) are novel agents with tumor-selective cytotoxic/antiproliferative activity, a different mechanism of action from classic retinoids and no cross-resistance with other chemotherapeutics. ST1926 and CD437 are prototypic RRMs, with the former currently undergoing phase I clinical trials. We show here that ST1926, CD437, and active congeners cause DNA damage. Cellular and subcellular COMET assays, H2AX phosphorylation (gamma-H2AX), and scoring of chromosome aberrations indicate that active RRMs produce DNA double-strand breaks (DSB) and chromosomal lesions in NB4, an acute myeloid leukemia (AML) cell line characterized by high sensitivity to RRMs. There is a direct quantitative correlation between the levels of DSBs and the cytotoxic/antiproliferative effects induced by RRMs. NB4.437r blasts, which are selectively resistant to RRMs, do not show any sign of DNA damage after treatment with ST1926, CD437, and analogues. DNA damage is the major mechanism underlying the antileukemic activity of RRMs in NB4 and other AML cell lines. In accordance with the S-phase specificity of the cytotoxic and antiproliferative responses of AML cells to RRMs, increases in DSBs are maximal during the S phase of the cell cycle. Induction of DSBs precedes inhibition of DNA replication and is associated with rapid activation of ataxia telangectasia mutated, ataxia telangectasia RAD3-related, and DNA-dependent protein kinases with subsequent stimulation of the p38 mitogen-activated protein kinase. Inhibition of ataxia telangectasia mutated and DNA-dependent protein kinases reduces phosphorylation of H2AX. Cells defective for homologous recombination are particularly sensitive to ST1926, indicating that this process is important for the protection of cells from the RRM-dependent DNA damage and cytotoxicity.

Synthesis and cytotoxic activity of a new series of topoisomerase I inhibitors.

A series of structurally simple analogues of natural topopyrone C were synthesized and tested for cytotoxic and topoisomerase I inhibitory activities. The removal of the hydroxyl groups at the 5 and 9 positions resulted in an increased cytotoxic potency and ability to stabilize topoisomerase-mediated cleavage. In addition, the results suggest that some structural features, such as the pyrone ring and a polar group in position 11, are fundamental for topoisomerase I inhibitory effect. These structural requirements are also consistent with the cytotoxic activity.

Synthesis and cytotoxic activity of new 9-substituted camptothecins.

A series of novel 9-substituted camptothecins derived from 9-formylcamptothecin were synthesized. The aldehyde was obtained from 10-hydroxycamptothecin or, better, by total synthesis. The compounds showed antiproliferative activity higher than that of the reference compound topotecan. Modelling suggested the possibility of a favourable interaction of small and polar 9-substituents with the topoisomerase I-DNA complex, which is consistent with the higher activity of these derivatives with respect to the corresponding 7-substituted camptothecins.

Preclinical efficacy of ST1976, a novel camptothecin analog of the 7-oxyiminomethyl series.

In previous studies, we have documented the potential therapeutic advantages of camptothecin analogs modified at the 7-position, i.e., 7-oxyiminomethyl derivatives. The present study was performed to explore the therapeutic potential of novel hydrophilic derivatives of this series. With one exception (ST1976), the tested camptothecins exhibited a reduced antiproliferative activity and all compounds retained ability to stabilize the topoisomerase I-mediated cleavable complex. The two analogs (ST1976 and ST1968) characterized by the presence of a free amino group in the side chain also exhibited the formation of persistent cleavable complexes. The most potent compound, ST1976 (7-(4-aminobenzyl)oxyiminomethylcamptothecin), was selected for evaluation of its preclinical profile of antitumor activity in a large panel of human tumor xenografts. As expected on the basis of the introduction of a hydrophilic substituent, the novel camptothecin was a substrate for BCRP. However, in spite of an apparent recognition by BCRP, ST1976 was effective following oral administration. The antitumor activity was evaluated using various schedules and routes of administration (i.v. and p.o.). ST1976 exhibited a remarkable activity in all tested tumors and was effective in a number of tumors which are resistant to irinotecan. The biological and pharmacological profile of ST1976 supports the therapeutic potential of camptothecins containing hydrophilic substituents at the 7-position. On the basis of its excellent activity in preclinical models, ST1976 is a promising candidate for clinical development.

Synthesis and antifungal activity of a series of N-substituted [2-(2,4-dichlorophenyl)-3-(1,2,4-triazol-1-yl)]propylamines.

A series of N-mono- or N, N-disubstituted [2-(2,4-dichlorophenyl-3-(1,2,4-triazol-1-yl)]propylamines and N-[2-(2,4-dichlorophenyl-3-(1,2,4-triazol-1-yl)propyl]amides were synthesized and tested for their fungicidal activity in vitro and in vivo against a group of plant pathogenic fungi. Some compounds exhibited a fairly good in vitro activity. The replacement of the ether group of tetraconazole with a secondary or tertiary amino group leads to compounds that maintain the antifungal activity on several phytopathogenic fungi, provided that the substituents are not too bulky or lipophilic. The allyl, propargyl, and cyclopropyl groups appear particularly suitable. Although these compounds have some structural similarities with terbinafine and naftifine, which act as squalene epoxidase inhibitors, they maintain the usual mechanism of action of the other triazoles.

Synthesis and cytotoxic activity of polyamine analogues of camptothecin.

A number of derivatives of camptothecin with a polyamine chain linked to position 7 of camptothecin via an amino, imino, or oxyiminomethyl group were synthesized and tested for their biological activity. All compounds showed marked growth inhibitory activity against the H460 human lung carcinoma cell line. In particular, the iminomethyl derivatives where the amino groups of the chain were protected with Boc groups exhibited a high potency, with IC50 values of approximately 10(-8) M. The pattern of DNA cleavage in vitro and the persistence of the cleavable ternary complex drug-DNA-topoisomerase I observed with polyamine conjugates containing free amino groups support a contribution of specific drug interaction with DNA as a determinant of activity. Modeling of compound 7c in the complex with topoisomerase 1 and DNA is consistent with this hypothesis. The lack of a specific correlation between stabilization of the cleavable complex and growth inhibition likely reflects multiple factors including the cellular pharmacokinetic behavior related to the variable lipophilicity of the conjugate, and the nature and linkage of the polyamine moiety.

Synthesis and structure-activity relationships of a new series of retinoid-related biphenyl-4-ylacrylic acids endowed with antiproliferative and proapoptotic activity.

Atypical retinoids (AR) represent a class of proapoptotic agents with promising potential in the treatment of neoplastic diseases. In the present work 4'-hydroxybiphenyl-4-ylacrylic acids were studied as a novel series of AR. The synthesized compounds were evaluated for their antiproliferative activity in a human promyelocytic leukemia cell line (NB4) and in an ovarian carcinoma cell system including IGROV-1, carrying a functional wild-type p53, and a cisplatin-resistant subline, IGROV-1/Pt-1. The presence of a bulky lipophilic group at position 3' (adamantan-1-yl being the best) and the E configuration of the acrylic moiety appear essential for activity below 1 muM. No substitution on the rings or on the double bond improved the activity. A qualitative correlation between the log P and molecular volume of the 3'-substituent and the antiproliferative activity was found. From the study of a few selected compounds, it appears that the presence of the carboxylic group is an essential requirement for apoptogenic properties but not for antiproliferative activity, this being maintained in amide derivatives. On the other hand, compounds able to induce apoptosis produced a detectable level of genotoxic damage. This observation supports the hypothesis that the genotoxic stress is a critical event mediating apoptosis induction by compounds of this class. Among the compounds investigated, E-3-(3'-adamantan-1-yl-4'-hydroxybiphenyl-4-yl)acrylic acid (2) was chosen for further investigation.

Pattern of antitumor activity of a novel camptothecin, ST1481, in a large panel of human tumor xenografts.

PURPOSE: ST1481 is the lead compound of a novel series of 7-modified camptothecins, the 7-oxyimino methyl derivatives, characterized by potent topoisomerase I inhibition and cytotoxic activity. Based on its therapeutic efficacy in a human non-small cell lung carcinoma model and its favorable pharmacological profile, the novel analogue was selected for further preclinical development. EXPERIMENTAL DESIGN: We investigated the growth-inhibitory effects of ST1481 and topotecan, used as a reference compound, in a panel of human tumor cell lines of various tumor types (ovarian carcinoma, glioblastoma, osteosarcoma, and melanoma), including sublines with acquired resistance to cisplatin. We explored the antitumor efficacy in a large panel of human tumor xenografts, with particular reference to intrinsically resistant tumor types, using oral administration and an intermittent treatment schedule. RESULTS: ST1481 showed a potent antiproliferative activity with comparable effects in all tested cell lines. Only U-87-MG glioma cells were less sensitive, presumably as a consequence of the efficiency of the S-phase checkpoint. ST1481 produced a remarkable antitumor effect (tumor volume inhibition > 85%) in 16 of 18 examined models, with an appreciable rate of complete tumor regressions in 11 of 18 models (despite the nonoptimal intermittent treatment schedule). The most impressive antitumor effects were observed against lung carcinoma, melanoma, and osteosarcoma models, as documented by the high rate of complete responses (up to 100%). The efficacy of ST1481 was significantly superior to that of topotecan in 9 of 17 tumors. The novel drug was also markedly effective against slowly growing tumors (A549 lung carcinoma and HT29 colon carcinoma) when a daily protracted treatment was used to fully exploit the therapeutic potential of camptothecins. CONCLUSIONS: The unusual potency of ST1481 in a variety of tumor cell lines suggests the ability of the drug to overcome several resistance factors. The profile of antitumor efficacy further supports the therapeutic interest in the novel analogue and provides a rational basis for clinical evaluation in selected tumor types.

General pseudoreceptor model for sweet compounds: a semiquantitative prediction of binding affinity for sweet-tasting molecules.

The chemical structures of sweet compounds are very different, ranging from sugars to amino acids and peptides or other compounds such as saccharin. The biological mechanism underlying the generation of sweet taste is still unknown, although in the past few years much research has provided evidence for the existence of a true chemoreception process, mediated by receptor proteins on the taste buds. In particular, the initial step of the process involves the reversible binding of the sweet compounds to their receptor(s). In this work, we have investigated this binding via a pseudoreceptor model, which has been developed using a training set of 24 compounds belonging to different families including sugars, peptides, and other intensive sweeteners. This model provided a correlation coefficient (r(2)) of 0.985 between the calculated and the experimental free energies of binding, which are related to the molar relative sweetness, for the training set and is able to predict semiquantitatively free energies of ligand binding for an independent set of five test ligand molecules within 0.3-2.1 kcal mol(-1) of the experimental values.

A novel atypical retinoid endowed with proapoptotic and antitumor activity.

The novel atypical retinoid E-3-(4'-hydroxy-3'-adamantylbiphenyl-4-yl)acrylic acid (ST1926, 4) exhibited a potent antiproliferative activity on a large panel of human tumor cells. Despite almost complete loss of ability to activate RARs, the compound was an effective apoptosis inducer and surprisingly produced DNA damage, that likely contributes to the proapoptotic activity. Following oral administration, 4 was well tolerated and caused tumor growth inhibition in the ovarian carcinoma, A2780/DX, and in the human melanoma, MeWo, growing in nude mice, thus supporting the therapeutic interest of the novel agent.