Novel antitumor indolizino[6,7-b]indoles with multiple modes of action: DNA cross-linking and topoisomerase I and II inhibition.

A series of bis(hydroxymethyl)indolizino[6,7-b]indoles and their bis(alkylcarbamates) were synthesized for antitumor studies. These agents were designed as hybrid molecules of ß-carboline (topoisomerase inhibition moiety) and bis(hydroxymethyl)pyrrole (DNA cross-linking moiety). The preliminary antitumor studies indicated that these agents exhibited significant cytotoxicity against a variety of human tumor cells in vitro. Treatment of human breast carcinoma MX-1 xenograft-bearing nude mice with compounds 18b and 28c achieved more than 99% tumor remission. We also observed that 18a displayed potent therapeutic efficacy against human lung adenocarcinoma A549 and colon cancer HT-29 xenografts. These results revealed that compound 18a was more potent than irinotecan against HT-29 cells and was as potent as irinotecan against A549 cells in xenograft models. Furthermore, we demonstrated that these derivatives possess multiple modes of action, such as induction of DNA cross-linking, inhibition of topoisomerase I and II, and cell-cycle arrest at the S-phase.

Evaluation of structurally diverse benzoazepines clubbed with coumarins as Mycobacterium tuberculosis agents.

Tuberculosis caused by Mycobacterium tuberculosis remains a leading cause of mortality worldwide into 21st century. In continuation with our anti-tuberculosis research programme, in this work, we have prepared molecularly diverse coumarins clubbed with benzothiazepines as well as its aza-analogues-benzodiazepines by molecular hybridization. The resulting compounds were screened for their M. tuberculosis activity against H(37) Rv strains using microplate alamar blue assay. Among the designed diversity, the compounds 5k, 5n and 5o were found significantly active in primary anti-tuberculosis assay at minimum inhibitory concentration <6.25 µm. Moreover, the IC(50) values of 5k and 5o in level-2 screening were observed as >10 µg/mL and 3.63 µg/mL, respectively. Design and synthesis of more focused library and its three-dimensional quantitative structure activity relationship analysis are underway.

Synthesis and antitumor evaluation of novel benzo[d]pyrrolo[2,1-b]thiazole derivatives.

A series of novel 2,3-bis(hydroxymethyl)benzo[d]pyrrolo[2,1-b]thiazoles and their bis(alkylcarbamate) derivatives were synthesized starting from benzothiazole via reaction with dimethyl acetylenedicarboxylate (DMAD)/tetra-fluoro boric acid, catalytic hydrogenation, and alkylcarbamoylation. The anti-proliferative activity of these agents against human leukemia and various solid tumor cell growth in vitro was studied. The structure-activity relationship studies revealed that the bis(alkylcarbamates) derivatives are generally more cytotoxic than the corresponding bis(hydroxymethyl) congeners in inhibiting human lymphoblastic leukemia CCRF-CEM and various human solid tumor cell growth in culture. These agents have no cross-resistance to taxol or vinblastine. Studies on the therapeutic effect against human breast carcinoma MX-1 xenograft showed that complete tumor remission (CR) were achieved by treating with C1-4'-F- or C1-4'-Cl-Ph-bis(i-propylcarbamates) derivatives (19b and 19c, respectively) and more than 99% tumor suppression by the corresponding bis(ethylcarbamates) 18b and 18c at the maximal tolerated dose. Alkaline agarose gel shifting assay revealed that the newly synthesized compounds are able to induce DNA interstrand cross-linking. The present studies generated a series of new potent DNA interstrand cross-linking agents, which have potential for further antitumor drug development.

Design, synthesis and antitumor evaluation of phenyl N-mustard-quinazoline conjugates.

A series of N-mustard-quinazoline conjugates was synthesized and subjected to antitumor studies. The N-mustard pharmacophore was attached at the C-6 of the 4-anilinoquinazolines via a urea linker. To study the structure-activity relationships of these conjugates, various substituents were introduced to the C-4 anilino moiety. The preliminary antitumor studies revealed that these agents exhibited significant antitumor activity in inhibiting various human tumor cell growths in vitro. Compounds 21b, 21g, and 21h were selected for further antitumor activity evaluation against human breast carcinoma MX-1 and prostate PC-3 xenograft in animal model. These agents showed 54-75% tumor suppression with low toxicity (5-7% body-weight changes). We also demonstrate that the newly synthesized compounds are able to induce DNA cross-linking through alkaline agarose gel shift assay and inhibited cell cycle arrest at G2/M phase.

Novel bifunctional alkylating agents, 5,10-dihydropyrrolo[1,2-b]isoquinoline derivatives, synthesis and biological activity.

A series of linear pyrrolo[1,2-b]isoquinoline derivatives was synthesized for antitumor evaluation. The preliminary antitumor studies reveal that both bis(hydroxymethyl) and their bis(alkylcarbamate) derivatives show significant antitumor activity in inhibiting various human tumor cell growth in vitro. 1,2-Bis(hydroxymethyl)-3-methyl-5,10-dihydropyrrolo[1,2-b]isoquinoline (20a) was selected for antitumor studies in animal models. The results show that this agent can induce complete tumor remission or significant suppression in nude mice bearing human breast (MX-1) xenograft and ovarian (SK-OV-3) xenografts, respectively. Alkaline agarose gel shifting assay showed that 20a is able to cross-link with DNA. Studies on the cell cycle inhibition revealed that this agent induces cell arrest at G2/M phase. The results warrant further antitumor investigation against other human tumor growth in animal models.