Gabriella Vitale

Synthesis and in vitro antitumor activity of new quinoxaline derivatives

A series of novel 5,7-diamino-3-phenyl-2-benzylamino, 2-phenoxy, and 2-thiophenyl substituted quinoxalines has been designed, synthesized and evaluated for their in vitro antitumor activity towards cell lines of nine different types of human cancers. Some of these compounds exhibited inhibitory effects on the growth of a wide range of cancer cell lines generally at 10(-6) M, in some cases at 10(-7) M and 10(-8) M concentrations. Within this series the benzylamino quinoxaline derivatives 1b-7b were the most active, whereas compound 2c showed the highest MG_MD value (-5.66).

Quinoxaline chemistry: Part 13: 3-carboxy-2-benzylamino-substituted quinoxalines and N -[4-[(3-carboxyquinoxalin-2-yl) aminomethyl]benzoyl]- L -glutamates: synthesis and evaluation of in vitro anticancer activity

Among a new series of 28 3-carboxy or carbethoxy quinoxalines bearing a substituted benzylamino or N-[4-(aminomethyl)benzoyl]glutamate group on position 2 of the ring and various substituents at C-6, 7 positions, 21 were selected at the National Cancer Institute for evaluation of their in vitro anticancer activity. The results obtained seem to confirm that the carboxy or carbethoxy group on position 3 is not helpful, with a few exceptions, for the anticancer activity.

Quinoxaline chemistry. Part 11. 3-Phenyl-2[phenoxy- and phenoxymethyl]-6(7) or 6,8-substituted quinoxalines and N-[4-(6(7)-substituted or 6,8-disubstituted-3-phenylquinoxalin-2-yl)hydroxy or hydroxymethyl] benzoylglutamates. Synthesis and evaluation of in vitro anticancer activity and enzymatic inhibitory activity against dihydrofolate reductase and thymidylate synthase.

Twenty-four out of twenty-nine quinoxalines were selected at the National Cancer Institute, Bethesda, Md, USA, for in vitro anticancer screening. Among these, 10 derivatives exhibited high values of percent tumor growth inhibition at a concentration of 10(-4) M in all cancer cell lines. Four of these compounds maintained these values at 10(-5) M, whereas a certain number exhibited significant values of percent inhibition at the most diluted concentrations (10(-8)-10(-6) M). Inhibitory activity against dihydrofolate reductase (DHFR) (bovine and rat liver) was determined for the most active compounds. This test showed that this type of quinoxaline exhibited an appreciable activity in comparison with the previously described aza analogues. In the other test (Lactobacillus casei, thymidylate synthase (TS), human HTS) no or poor activity was detected in both series of compounds.

Quinoxaline chemistry: Part 9: Quinoxaline analogues of trimetrexate (TMQ) and 10-propargyl-5,8-dideazafolic acid (CB 3717) and its precursors: synthesis and evaluation of in vitro anticancer activity

Eighteen quinoxalines bearing a methyleneanilino or methyleneaminobenzoylglutamate group on position 6 of the ring and various lipophilic substituents on positions 2 and 3 were prepared in order to discover if their structural analogy with both trimetrexate (TMQ) and 10-propargyl-5,8-dideazafolic acid (CB 3717) might display in vitro anticancer activity. Among these, 12 compounds were selected at the National Cancer Institute, Bethesda, MD, USA; they exhibited moderate (4b,d,i,l,m and 8) to strong (4f,h and 5a,e) cell-growth inhibition at a concentration of 10(-4) M. Interesting selectivities were also recorded between 10(-8) and 10(-6) M. These analogues proved to be less potent inhibitors of tumor cells than other classical and non-classical antifolate analogues previously described by us.

Collateral sensitivity to novel thymidylate synthase inhibitors correlates with folate cycle enzymes impairment in cisplatin-resistant human ovarian cancer cells

The cytotoxicity of two novel folate cycle inhibitors with quinoxalinic structure, 3-methyl-7-trifluoromethyl-2(R)-[3,4,5-trimethoxyanilino]-quinoxaline (453R) and 3-piperazinilmethyl-2[4(oxymethyl)-phenoxy]quinoxaline (311S), was tested against a panel of both cisplatin(cDDP)-sensitive and -resistant carcinoma cell lines. Interestingly, the cisplatin-resistant human ovarian line, C13 cells, exhibited collateral sensitivity towards the two compounds when compared to its sensitive parental 2008 cells. In this resistant line, which showed elevated expression of the folate cycle enzymes, thymidylate synthase (TS) and dihydrofolate reductase (DHFR), due to cisplatin-resistance phenotype, collateral sensitivity correlated with the greater reduction of enzyme expression. In addition, TS and DHFR expression of the other resistant lines, the human ovarian carcinoma A2780/CP cells and the human breast cancer MDA/CH cells, were decreased in accordance with the similar sensitivity or the low level of cross-resistance to these compounds in comparison to their respective parental lines. Noteworthy, unlike 5-fluorouracil, both drugs reduced the level of TS without inducing ternary complex formation with the co-substrate and the nucleotide analogue. Median effect analysis of the interactive effects of cisplatin with the two quinoxalines mainly showed additive or synergistic cell killing, depending on schedules of drug combinations. In particular, synergistic effects were more often obtained, even on the resistant cells, when cisplatin was added at the beginning of the treatment. These results indicate that, despite the possibility of other mechanisms being involved, inhibition of TS cycle enzymes plays an important role in the pharmacology of these compounds, which might also represent a useful component in drug treatment protocols against cDDP-resistant cells.

Quinoxaline chemistry: Part 10: Quinoxaline 10-oxa-analogues of trimetrexate (TMQ ) and of 5,8-dideazafolic acid: synthesis and evaluation of in vitro anticancer activity

Among twenty-eight novel compounds (twenty-two 2,3-disubstituted-6-[(substituted-phenoxy)methyl-quinoxalines and six 4-[(2,3-disubstituted-quinoxalin-6-yl)methoxy]benzoylglutamates ) only thirteen were selected at NCI for evaluation of their in vitro anticancer activity. The results have shown that compounds 3l,c,b,e and 4b were endowed with significantly high values of percent tumor growth inhibition on several tumor cell lines at 10(-4) M, while compound 3t was characterized by a high selectivity, being still strongly inhibiting on three cell lines at 10(-5) M. Comparison of the presently observed activity with that of the previously described aza-analogues confirms that the effected isosteric substitution is highly valuable in some cases.

5-Acetyl-2-arylbenzimidazoles as antiviral agents. Part 4

Within a project aimed at discovering new Flaviviridae inhibitors, new variously substituted 2-phenylbenzimidazoles were synthesized and evaluated in cell-based assays for cytotoxicity and antiviral activity against viruses representatives of the three genera of the Flaviviridae family, i.e.: Pestivirus (BVDV), Flavivirus (YFV) and Hepacivirus (HCV). Title compounds were also tested against RNA viruses representative of other single-stranded, positive-sense (ssRNA(+)) negative-sense (RNA(-)), or double-stranded (dsRNA) genomes, as well as against representatives of two DNA virus families. Nine compounds showed activity against BVDV (EC(50) = 0.8-8.0 μM), compound 31 being the most potent (EC(50) = 0.80 μM) and selective (SI = CC(50)/EC(50) = >100). When tested in an HCV replicon assay, compound 31 resulted again the most potent, displaying an EC(50) value of 1.11 μM and an SI of 100. Besides inhibiting BVDV, two compounds (35 and 38) showed a moderate activity also against YFV (EC(50) = 13 μM). Interestingly, 35 was moderately active also against RSV (EC(50) = 25 μM).

Quinoxaline chemistry: Part 12: 3-carboxy-2[phenoxy]-6(7)substituted quinoxalines and N -[4-(6(7) substituted-3-carboxyquinoxalin-2-yl)hydroxybenzoylglutamates: synthesis and evaluation of in vitro anticancer activity

Thirty quinoxalines bearing a substituted phenoxy or hydroxybenzoylglutamate group on position 2, a carboethoxy or carboxy group on position 3 and a trifluoromethyl group on position 6 or 7 of the heterocycle were prepared in order to evaluate the in vitro anticancer activity. Screening over 21 compounds selected at the National Cancer Institute (Bethesda, MD) showed that only few derivatives exhibited a moderate growth inhibition activity on various tumor panel cell lines at 10(-4) molar concentration. The acid derivatives showed no growth inhibition activity. The results obtained in this series seem to indicate that in general carboxy or carboethoxy groups close to O-link with phenyl or benzoyl glutamates on position 2 are detrimental for anticancer activity.

2-Arylbenzimidazoles as Antiviral and Antiproliferative Agents-Part 1

Being involved in an anti-Flaviviridae Project, and because of the role played by benzimidazole derivatives as promising inhibitors of the HCV helicase and RNA polymerase, as well as of the Zn finger transcription factor, we synthesized a new series of 2-arylbenzimidazoles and evaluated them for antiviral activity, as well as for antiproliferative activity. Compounds were tested in cell-based assays against viruses representative of: i) two of the three genera of the Flaviviridae family, i.e. Flaviviruses and Pestiviruses; ii) other RNA virus families, such as Retroviridae, Picornaviridae, Paramyxoviridae, Rhabdoviridae and Reoviridae; iii) two DNA virus families (Herpesviridae and Poxviridae). Compounds 15, 28 and 29 resulted moderately active only against Yellow Fever Virus (a Flavivirus) (range 6-27 microM), whereas none of the title benzimidazoles showed any antiviral activity at concentrations not cytotoxic for the resting cell monolayers. Compounds were also tested for antiproliferative activity against a panel of exponentially growing cell lines derived from human haematological and solid tumors. Several new benzimidazoles turned out active. Among them, compound 27 was the most potent against human haematologic and solid tumor cells and turned out to be as potent as Etoposide and more potent than 6-mercaptopurine (6-MP), used as reference antitumor agents.

Styrylbenzimidazoles. Synthesis and Biological Activity - Part 3

As a follow up of an anti-Flaviviridae project, a new series of variously substituted 2-styryl-benzimidazoles were synthesized and tested in vitro for biological activity. Compounds were tested in cell-based assays against viruses representative of: i) two of the three genera of the Flaviviridae family, i.e. Pestiviruses and Flaviviruses; ii) other RNA virus families, such as Retroviridae, Picornaviridae, Paramyxoviridae, Rhabdoviridae and Reoviridae; iii) two DNA virus families (Herpesviridae and Poxviridae) as well as for cytotoxicity tests, run in parallel with antiviral assays,against MDBK, BHK and Vero 76 cells. In the series examined, new leads emerged against BVDV, CVB-2 and RSV. Compounds 11, 12, 17, 18, 24, 31 exhibited anti-BVDV activity in the concentration range 1.7-16 microM; among them, compound 17 was the most active, with an EC(50) = 1.7 microM. Compounds 18 and 21 were equally active against CVB-2, with EC(50) values of 7 - 8 microM, while the derivative 30 was active against RSV with EC(50)= 1 microM and represents a new lead compound.