Alessandra Montalbano

Novel 1H-Pyrrolo[2,3-b]pyridine Derivative Nortopsentin Analogues: Synthesis and Antitumor Activity in Peritoneal Mesothelioma Experimental Models

In this study, we describe the synthesis of new nortopsentin analogues, 1H-pyrrolo[2,3-b]pyridine derivatives and their biological effects in experimental models of diffuse malignant peritoneal mesothelioma (DMPM), a rare and rapidly fatal disease, poorly responsive to conventional therapies. The three most active compounds, 1f (3-[2-(5-fluoro-1-methyl-1H-indol-3-yl)-1,3-thiazol-4-yl]-1H-pyrrolo[2,3-b]pyridine), 3f (3-[2-(1H-indol-3-yl)-1,3-thiazol-4-yl]-1-methyl-1H-pyrrolo[2,3-b]pyridine), and 1l (3-[2-(5-fluoro-1-methyl-1H-indol-3-yl)-1,3-thiazol-4-yl]-1-methyl-1H-pyrrolo[2,3-b] pyridine), which were shown to act as cyclin-dependent kinase 1 inhibitors, consistently reduced DMPM cell proliferation and induced a caspase-dependent apoptotic response, with a concomitant reduction of the expression of the active Thr(34)-phosphorylated form of the antiapoptotic protein survivin. Moreover, the combined treatment of DMPM cells with 3f derivative and paclitaxel produced a synergistic cytotoxic effect, which was paralleled by an enhanced apoptotic response. In the mouse model, i.p. administration of 1f, 3f, and 1l derivatives was effective, resulting in a significant tumor volume inhibition of DMPM xenografts (range, 58-75%) at well-tolerated doses, and two complete responses were observed in each treatment group.

Pyrrolo[2,1-c][1,2,4]triazines from 2-diazopyrroles: synthesis and antiproliferative activity

Pyrrolo[2,1-c][1,2,4]triazines 4a-g were directly obtained from the reaction of 2-diazopyrroles 1a and b with the sodium salts of beta-diketones, beta-carbonitriles, and beta-dinitriles. Only when the 2-diazopyrroles were coupled with ethyl cyanoacetate, it was possible to isolate, together with the pyrrolotriazines, the intermediate hydrazones 3 which, in turn, cyclised to the title ring system. Pyrrolotriazines 4a-e were evaluated for cytotoxic activity against a panel of 60 human cancer cell lines by the National Cancer Institute and some of them demonstrated inhibitory effects in the growth of a wide range of cancer cell lines generally at 10(-5) M level and in some cases at micromolar concentrations.

Synthesis and Antitumor Activity of 3‐(2‐Phenyl‐1,3‐thiazol‐4‐yl)‐1H‐indoles and 3‐(2‐Phenyl‐1,3‐thiazol‐4‐yl)‐1H‐7‐azaindoles

Given the potent antimicrobial, antiviral, and antitumor activities of many natural products, there is an increasing interest in the synthesis of new molecules based on natural compound scaffolds. Based on a 2,4‐bis(3′‐indolyl)imidazole skeleton, two new series of phenylthiazolylindoles and phenylthiazolyl‐7‐azaindoles were obtained by Hantzsch reaction between substituted phenylthioamides and the α‐bromoacetyl derivatives. Some azaindole derivatives, tested at the National Cancer Institute against a panel of ∼60 tumor cell lines derived from nine human cancer cell types, showed inhibitory effects against all cell lines investigated at micromolar to nanomolar concentrations. Two of them exhibited a high affinity for CDK1, with IC50 values of 0.41 and 0.85 μM. These promising results will set the foundation for future investigations into the development of anticancer therapies.

Synthesis of a new class of pyrrolo[3,4-h]quinazolines with antimitotic activity

A new series of pyrrolo[3,4-h]quinazolines was conveniently prepared with a broad substitution pattern. A large number of derivatives was obtained and the cellular cytotoxicity was evaluated in vitro against 5 different human tumor cell lines with GI₅₀ values reaching the low micromolar level (1.3-19.8 μM). These compounds were able to induce cell death mainly by apoptosis through a mitochondrial dependent pathway. Selected compounds showed antimitotic activity and a reduction of tubulin polymerization in a concentration-dependent manner. Moreover, they showed anti-angiogenic properties since reduced in vitro endothelial cell migration and disrupted HUVEC capillary-like tube network in Matrigel.

Pyrrolo[3,2-h]quinazolines as photochemotherapeutic agents.

Heteroanalogues of angelicin, pyrrolo[3,2‐h]quinazolines, were synthesized with the aim of obtaining new potent photochemotherapeutic agents. Many derivatives caused a significant decrease in cell proliferation in several human tumor cell lines after irradiation with UVA light (GI50=15.2–0.2 μM). Their phototoxicity effected apoptosis in Jurkat cells with the involvement of mitochondria (as determined by the loss of mitochondrial membrane potential and production of reactive oxygen species) and lysosomes. The phototoxicity of these compounds could be explained by lipid peroxidation.

Pyrrolo[3,4-h]quinolinones a new class of photochemotherapeutic agents

Pyrrolo[3,4-h]quinolin-2-ones were synthesized as nitrogen isosters of the angular furocoumarin angelicin, with the aim of obtaining new photochemotherapeutic agents with increased antiproliferative activity and lower undesired toxic effects. A versatile synthetic pathway was approached to allow the isolation of derivatives of the new ring system with a good substitution pattern on the pyrrole moiety. Photobiological screenings of the new compounds revealed a potent phototoxic effect and a great UVA dose dependence, reaching IC(50) values at submicromolar level. The induced cellular photocytotoxicity was related to apoptosis with the involvement of mitochondria and lysosomes, alteration of cell cycle profile and membrane lipid peroxidation.

Synthesis and Antiproliferative Activity of Substituted 3[2-(1H-indol-3-yl)- 1,3-thiazol-4-yl]-1H-pyrrolo[3,2-b]pyridines, Marine Alkaloid Nortopsentin Analogues

A large number of indolyl-4-azaindolyl thiazoles, nortopsentin analogues, were conveniently synthesized. The antiproliferative activity of the new derivatives was examined against four human tumor cell lines with different histologic origin. Seven derivatives consistently reduced the growth of the experimental models independently of TP53 gene status and exhibited the highest activity against the malignant peritoneal mesothelioma (STO) cell line. The most active compound of this series acts as a CDK1 inhibitor, and was found to cause cell cycle arrest at G2/M phase, to induce apoptosis by preventing the phosphorylation of survivin in Thr(34) and to increase the cytotoxic activity of paclitaxel in STO cells.

Synthesis and antiproliferative activity of thiazolyl-bis-pyrrolo[2,3-b]pyridines and indolyl-thiazolyl-pyrrolo[2,3-c]pyridines, nortopsentin analogues

Two new series of nortopsentin analogues, in which the imidazole ring of the natural product was replaced by thiazole and indole units were both substituted by 7-azaindole moieties or one indole unit was replaced by a 6-azaindole portion, were efficiently synthesized. Compounds belonging to both series inhibited the growth of HCT-116 colorectal cancer cells at low micromolar concentrations, whereas they did not affect the viability of normal-like intestinal cells. A compound of the former series induced apoptosis, evident as externalization of plasma membrane phosphatidylserine (PS), and changes of mitochondrial trans-membrane potential, while blocking the cell cycle in G2/M phase. In contrast, a derivative of the latter series elicited distinct responses in accordance with the dose. Thus, low concentrations (GI30) induced morphological changes characteristic of autophagic death with massive formation of cytoplasmic acid vacuoles without apparent loss of nuclear material, and with arrest of cell cycle at the G1 phase, whereas higher concentrations (GI70) induced apoptosis with arrest of cell cycle at the G1 phase.

Synthesis of pyrrolo[3,2-h]quinolinones with good photochemotherapeutic activity and no DNA damage.

In the search for new photochemotherapeutic agents, a series of derivatives of the ring system pyrrolo[3,2-h]quinoline--bioisosters of the angular furocoumarin angelicin--were synthesized through a four-step synthetic approach, in reasonable overall yields. Eight of the synthesized derivatives showed a remarkable phototoxicity against a panel of four human tumor cell lines and a great dose UV-A dependence, reaching IC₅₀ values at submicromolar level. The mode of cellular death photoinduced by pyrrolo[3,2-h]quinolines was evaluated through a series of flow cytometric analysis and other tests were performed to clarify their mechanism of action.

New tricyclic systems of biological interest. Annelated 1,2,3-triazolo[1,5-a]pyrimidines through domino reaction of 3-azidopyrroles and methylene active nitriles

Anionic hetero-domino reaction of 3-azidopyrroles and acetonitriles constitutes the synthetic entry to annelated 1,2,3-triazolo[1,5-a]pyrimidines. Upon slight variations of the experimental conditions the method is of general application either with 2 or 4 substituted pyrroles. Thus derivatives of the new ring system pyrrolo[2,3-e][1,2,3]triazolo[1,5-a]pyrimidine, isomers of the previously synthesized pyrrolo[3,4-e][1,2,3]triazolo[1,5-a]pyrimidine, were prepared in high yields. The condensed pyrrolo-triazolo-pyrimidines, although only moderately active, can be used as model for the design of DNA-interactive compounds.