Silvia Salerno

Recent advances in the development of dual topoisomerase I and II inhibitors as anticancer drugs.

DNA topoisomerases (topos) are essential enzymes that regulate the topological state of DNA during cellular processes such as replication, transcription, recombination, and chromatin remodeling. Topoisomerase I (Topo I) is a ubiquitous nuclear enzyme which catalyzes the relaxation of superhelical DNA generating a transient single strand nick in the duplex, through cycles of cleavage and religation. Topoisomerase II (Topo II) mediates the ATP-dependent induction of coordinated nicks in both strands of the DNA duplex, followed by crossing of another double strand DNA through the transiently broken duplex. Although the biological functions of Topoisomerases are important for ensuing genomic integrity, the ability to interfere with enzymes or generate enzyme-mediated damage is an effective strategy for cancer therapy and, in this connection, DNA topos (I and II) proved to be the excellent targets of clinically significant classes of anticancer drugs. Actually, specific Topo I and Topo II inhibitors reversibly trap the enzyme-DNA complexes, thus converting Topos into physiological poisons, able to produce permanent DNA damage, which triggers cell death. Given that both enzymes are good targets, it would be desirable to jointly inhibit them, but use-limiting toxicity of sequential or simultaneous combinations of topo I and II poisons include severe to life-threatening neutropenia and anemia. Furthermore, the emergence of resistance phenomena to topo I inhibitors is often accompanied by a concomitant rise in the level of topo II expression and viceversa, leading to the failure of clinical therapies. In this regard, a single compound able to inhibit both Topo I and II may present the advantage of improving antitopoisomerase activity, with reduced toxic side effects, with respect to the combination of two inhibitors. Due to the high interest in such compounds, this review represents an update of previous works dealing with the development of dual Topo I and II inhibitors as novel anti-cancer agents. The newly collected derivatives have been described focusing attention on their chemical structures and their biological profiles.

Synthesis, in vitro antiproliferative activity and DNA-interaction of benzimidazoquinazoline derivatives as potential anti-tumor agents

The synthesis of benzimidazoquinazoline derivatives bearing different alkylamino side chains is reported. All new compounds tested by means of an in vitro assay exhibit antiproliferative activity toward human tumor cell lines. The cytotoxic effect depends on the type of side chain inserted in the planar nucleus and in some cases it is comparable to that of the well-known drug ellipticine. In order to understand the mechanism of action of these compounds, the interaction with DNA has been investigated. Linear flow dichroism measurements allowed us to verify the formation of a molecular complex with DNA and the corresponding geometry of interaction. Intrinsic binding constants have also been evaluated by performing fluorimetric titrations.

Synthesis, DNA binding and in vitro antiproliferative activity of purinoquinazoline, pyridopyrimidopurine and pyridopyrimidobenzimidazole derivatives as potential antitumor agents

Abstract In the search for new antitumor agents, 8,10-dimethylpurino[7,8-a]quinazoline-5,9, 11(6H,8H,10H)-triones 1 , 8,10-dimethylpyrido [2′,3′:4,5]pyrimido[1,2-f]purine-5,9,11 (6H,8H, 10H)-triones 2 , and 5,7-dihydro-5-oxopyrido[3′,2′:5,6]pyrimido[1,2-a]benzimidazoles 3 , a series of new planar heteropolycyclic compounds, were synthesized. The approach to understanding their structure-activity relationship involved a physico-chemical investigation of the binding process of these molecules to DNA, considered to be an important target for drug action, and an examination of their biological activity. Thermodynamic parameters of the DNA binding process, intrinsic binding constant and exclusion parameter were determined. The mode of interaction was additionally investigated by means of linear flow dichroism studies. Evaluation of the biological activity included cell growth inhibition in human tumoral cell lines and the ability to induce DNA cleavage in the presence of eukaryotic topoisomerase II. Only compounds of the purinoquinazoline series 1 , which are able to form a complex with DNA and to inhibit the topoisomerase II, show antiproliferative activity.

Acetic Acid Aldose Reductase Inhibitors Bearing a Five-Membered Heterocyclic Core with Potent Topical Activity in a Visual Impairment Rat Model

A number of 1,2,4-oxadiazol-5-yl-acetic acids and oxazol-4-yl-acetic acids were synthesized and tested for their ability to inhibit aldose reductase (ALR2). The oxadiazole derivatives, 7c, 7f, 7i, and 8h, 8i, proved to be the most active compounds, exhibiting inhibitory levels in the submicromolar range. In this series, the phenyl group turned out to be the preferred substitution pattern, as its lengthening to a benzyl moiety determined a general reduction of the inhibitory potency. The lead compound, 2-[3-(4-methoxyphenyl)-1,2,4-oxadiazol-5-yl]acetic acid, 7c, showed an excellent in vivo activity, proving to prevent cataract development in severely galactosemic rats when administered as an eye-drop solution in the precorneal region of the animals. Computational studies on the ALR2 inhibitors were performed to rationalize the structure-activity relationships observed and to provide the basis for further structure-guided design of novel ALR2 inhibitors.

Novel N2-substituted pyrazolo[3,4-d]pyrimidine adenosine A3 receptor antagonists: inhibition of A3-mediated human glioblastoma cell proliferation.

Adenosine induces glioma cell proliferation by means of an antiapoptotic effect, which is blocked by cotreatment with selective A(3) AR antagonists. In this study, a novel series of N(2)-substituted pyrazolo[3,4-d]pyrimidines 2a-u was developed as highly potent and selective A(3) AR antagonists. The most performing compounds were derivatives 2a (R(1) = CH(3) and R(2) = COC(6)H(5); K(i) 334, 728, and 0.60 nM at the human A(1), A(2A), and A(3) ARs, respectively) and 2b (R(1) = CH(3) and R(2) = COC(6)H(4)-4-OCH(3); K(i) 1037, 3179, and 0.18 nM at the human A(1), A(2A), and A(3) ARs, respectively), which counteracted the effect of the A(3) AR agonists Cl-IB-MECA and IB-MECA on human glioma U87MG cell proliferation. This effect was concentration-dependent, with IC(50) values comparable to A(3) AR binding affinity values of 2a and 2b, thereby suggesting that their effects were receptor-mediated. Furthermore, the antiproliferative activity of the new compounds was demonstrated to be mediated by the block of A(3) AR agonist activation of intracellular kinases ERK 1/2.

Exploiting the Pyrazolo[3,4-d]pyrimidin-4-one Ring System as a Useful Template To Obtain Potent Adenosine Deaminase Inhibitors

A number of pyrazolo[3,4-d]pyrimidin-4-ones bearing either alkyl or arylalkyl substituents in position 2 of the nucleus were synthesized and tested for their ability to inhibit adenosine deaminase (ADA) from bovine spleen. The 2-arylalkyl derivatives exhibited excellent inhibitory activity, showing Ki values in the nanomolar/subnanomolar range. The most active compound, 1-(4-((4-oxo-4,5-dihydropyrazolo[3,4-d]pyrimidin-2-yl)methyl)phenyl)-3-(4-(trifluoromethyl)phenyl)urea, 14d, was tested in rats with colitis induced by 2,4-dinitrobenzenesulfonic acid to assess its efficacy to attenuate bowel inflammation. The treatment with 14d induced a significant amelioration of both systemic and intestinal inflammatory alterations in animals with experimental colitis. Docking simulations of the synthesized compounds into the ADA catalytic site were also performed to rationalize the structure-activity relationships observed and to highlight the key pharmacophoric elements of these products, thus prospectively guiding the design of novel ADA inhibitors.

Tricyclic sulfonamides incorporating benzothiopyrano[4,3-c]pyrazole and pyridothiopyrano[4,3-c]pyrazole effectively inhibit α- And β-carbonic anhydrase: X-ray crystallography and solution investigations on 15 isoforms

Carbonic anhydrases (CAs, EC 4.2.1.1) are ubiquitous isozymes involved in crucial physiological and pathological events, representing the targets of inhibitors with several therapeutic applications. In this connection, we report a new class of carbonic anhydrase inhibitors, based on the thiopyrano-fused pyrazole scaffold to which a pendant 4-sulfamoylphenyl moiety was attached. The new sulfonamides 3a-e were designed as constrained analogues of celecoxib and valdecoxib. The most interesting feature of sulfonamides 3 was their predominantly strong inhibition of human (h) CA I and II, as well as those of the mycobacterial β-class enzymes (Rv1284, Rv3273, and Rv3588c), whereas their inhibitory action against hCA III, IV, VA, VB, VI, VII, IX, XII, XIII, and XIV was found to be at least 2 orders of magnitude lower. X-ray crystallography and structural superposition studies made it possible to explain the very distinct inhibition profile of the tricyclic sulfonamides, different from those of celecoxib and valdecoxib.

Arylsulfonamide inhibitors of aggrecanases as potential therapeutic agents for osteoarthritis: Synthesis and biological evaluation

Aggrecanases, in particular aggrecanase-2 (ADAMTS-5), are considered the principal proteases responsible for aggrecan degradation in osteoarthritis. For this reason, considerable effort has been put on the discovery and development of aggrecanase inhibitors able to slow down or halt the progression of osteoarthritis. We report herein the synthesis and biological evaluation of a series of arylsulfonamido-based hydroxamates as aggrecanase inhibitors. Compound 18 was found to have a nanomolar activity for ADAMTS-5, ADAMTS-4 and MMP-13 and high selectivity over MMP-1 and MMP-14. Furthermore, this compound proved to be effective in blocking ex vivo cartilage degradation without having effect on cell cytotoxicity.

Phenylpyrazolo[1,5-a]quinazolin-5(4H)-one: a suitable scaffold for the development of noncamptothecin topoisomerase I (Top1) inhibitors.

In search for a novel chemotype to develop topoisomerase I (Top1) inhibitors, the pyrazolo[1,5-a]quinazoline nucleus, structurally related to the indenoisoquinoline system precursor of well-known Top1 poisons, was variously decorated (i.e., a substituted phenyl ring at 2- or 3-position, a protonable side chain at 4- or 5-position), affording a number of Top1 inhibitors with cleavage patterns common to CPT and MJ-III-65. SARs data were rationalized by means of an advanced docking protocol.

Synthesis and biological activity of 1,4-dihydrobenzothiopyrano[4,3-c]pyrazole derivatives, novel pro-apoptotic mitochondrial targeted agents.

This study reports the synthesis of a number of 1- and 2-phenyl derivatives of the 1,4-dihydrobenzothiopyrano[4,3-c]pyrazole nucleus, which were obtained by the reaction of the versatile 7-substituted 2,3-dihydro-3-hydroxymethylene-4H-1-benzothiopyran-4-ones with hydrazine and substituted phenylhydrazines. The antiproliferative activity of the synthesized compounds was evaluated by an in vitro assay on human tumor cell lines (HL-60 and HeLa) and showed a significant capacity of the 7-methoxy-substituted benzothiopyrano[4,3-c]pyrazoles 3b-d, carrying the pendant phenyl group in the 1-position, to inhibit cell growth. Investigation of the mechanism of action indicated the induction of the mitochondrial permeability transition (MPT) as the molecular event responsible for the inhibition of cell growth. This phenomenon is related to the ability of the test compounds to cause a rapid Ca2+-dependent and cyclosporin A-sensitive collapse of the transmembrane potential (DeltaPsi) and matrix swelling. All this leads to the release of caspase activators, such as cytochrome c (cyt c) and apoptosis-inducing factor (AIF), which trigger the pro-apoptotic pathway leading to DNA fragmentation.