Benzoxepinones: A new isoform-selective class of tumor associated carbonic anhydrase inhibitors

Investigation of novel alkyl/benzyl (4-sulphamoylphenyl)carbamimidothioates as carbonic anhydrase inhibitors

A library of novel alkyl/benzyl (4-sulphamoylphenyl)carbamimidothioates was synthesised by selective S-alkylation of the easily accessible 4-thioureidobenzenesulphonamide. The compounds were assayed as inhibitors of four human (h) carbonic anhydrase isoforms hCA I, II, VII, and XIII, as well as three bacterial enzymes belonging to the β-CA class, MscCA from Mammaliicoccus (Staphylococcus) sciuri and StCA1 and StCA2, from Salmonella enterica (serovar Typhimurium). Most compounds investigated here exhibited moderate to low nanomolar inhibition constants against hCA I, II, and VII. The cytosolic hCA XIII was also inhibited by these compounds, but not as effective as hCA I, II, and VII. Several compounds were very effective against MscCA and StCA1. StCA2 was less inhibited compared to MscCA and StCA1. Some compounds showed considerable selectivity for inhibiting some CA isoforms. They may thus be considered as interesting starting points for the discovery and development of novel therapeutic agents belonging to this class of enzyme inhibitors.

Derivatives of 4-methyl-1,2,3-benzoxathiazine 2,2-dioxide as selective inhibitors of human carbonic anhydrases IX and XII over the cytosolic isoforms I and II

A series of 4-methyl-1,2,3-benzoxathiazine-2,2-dioxides with various substituents in 5, 6 or 7 positions was obtained from corresponding 2'-hydroxyacetophenones in their reaction with sulphamoyl chloride. 6- and 7-aryl substituted 4-methyl-1,2,3-benzoxathiazine-2,2-dioxides were obtained from aryl substituted 2'-hydroxyacetophenonesprepared from 4- or 5-bromo-2'-hydroxyacetophenones via two-step protocol. 4-Methyl-1,2,3-benzoxathiazine-2,2-dioxides were investigated as inhibitors of four human (h) carbonic anhydrase (hCA, EC 4.2.1.1) isoforms, off-target cytosolic hCA I and II, and target transmembrane, tumour-associated hCA IX and XII. Twenty derivatives of 4-methyl-1,2,3-benzoxathiazine 2,2-dioxide were obtained. With one exception (compound2a), they mostly act as nanomolar inhibitors of target hCA IX and XII. Basically, all screened compounds express none or low inhibitory properties towards off-target hCA I. hCA II is inhibited in micromolar range. Overwhelming majority of 4-methyl-1,2,3-benzoxathiazine 2,2-dioxides express excellent selectivity towards CA IX/XII over hCA I as well as very good selectivity towards CA IX/XII over hCA II.

A simple yet multifaceted 90 years old, evergreen enzyme: Carbonic anhydrase, its inhibition and activation

Advances in the carbonic anhydrase (CA, EC 4.2.1.1) research over the last three decades are presented, with an emphasis on the deciphering of the activation mechanism, the development of isoform-selective inhibitors/ activators by the tail approach and their applications in the management of obesity, hypoxic tumors, neurological conditions, and as antiinfectives.

Design, synthesis, and structure-activity studies of new rhodanine derivatives as carbonic anhydrase II, IX inhibitors

Rhodanine and its derivatives are an important class of heterocycles with diverse biological properties, including anticancer, antibacterial, and anti-mycobacterial activities. In the present work, four series of new Rhodanine derivatives were synthesized and evaluated for their inhibitory activity against carbonic anhydrase I, II, IX, and XII isoforms. Interestingly, the tested compounds exhibited good inhibitory activity against the cytosolic isoform human carbonic anhydrase (hCA) II and tumor-associated hCA IX. While the Rhodanine-benzylidene derivatives (3a-l) and Rhodanine-hydrazine derivatives (6a-e) are found to be selective against hCA II, the Rhodanine-N-carboxylate derivatives (8a-d) are found to be highly selective toward hCA IX. The Rhodanine-linked isoxazole and 1,2,4-oxadiazole derivatives (8ba, 8da, and 8db) exhibited inhibitory activity against hCA II and hCA IX. Among the tested compounds, 3b, 3j, 6d, and 8db were found to inhibit hCA II with Ki values of 9.8, 46.4, 7.7, and 4.7 µM, respectively. Furthermore, their mechanism of action is supported by molecular docking studies. Notably, the synthesized Rhodanine derivatives belong to a nonsulfonamide class of carbonic anhydrase inhibitors.

Inhibition Studies on Human and Mycobacterial Carbonic Anhydrases with N-((4-Sulfamoylphenyl)carbamothioyl) Amides

A library of structurally diverse N-((4-sulfamoylphenyl)carbamothioyl) amides was synthesized by selective acylation of easily accessible 4-thioureidobenzenesulfonamide with various aliphatic, benzylic, vinylic and aromatic acyl chlorides under mild conditions. Inhibition of three α-class cytosolic human (h) carbonic anhydrases (CAs) (EC 4.2.1.1); that is, hCA I, hCA II and hCA VII and three bacterial β-CAs from Mycobacterium tuberculosis (MtCA1-MtCA3) with these sulfonamides was thereafter investigated in vitro and in silico. Many of the evaluated compounds displayed better inhibition against hCA I (K_I = 13.3-87.6 nM), hCA II (K_I = 5.3-384.3 nM), and hCA VII (K_I = 1.1-13.5 nM) compared with acetazolamide (AAZ) as the control drug (K_I values of 250, 12.5 and 2.5 nM, respectively, against hCA I, hCA II and hCA VII). The mycobacterial enzymes MtCA1 and MtCA2 were also effectively inhibited by these compounds. MtCA3 was, on the other hand, poorly inhibited by the sulfonamides reported here. The most sensitive mycobacterial enzyme to these inhibitors was MtCA2 in which 10 of the 12 evaluated compounds showed K_Is (K_I, the inhibitor constant) in the low nanomolar range.

Synthesis, characterizations of aryl-substituted dithiodibenzothioate derivatives, and investigating their anti-Alzheimer's properties

The main objective of the present study was to synthesize potential inhibitor/activators of AChE and hCA I-II enzymes, which are thought to be directly related to Alzheimer's disease. Dithiodibenzothioate compounds were synthesized by thioesterification. Six different thiolate compounds produced were characterized by ¹H-, ¹³C-NMR, FT-IR, LC-MS/MS methods. HOMO-LUMO calculations and electronic properties of all synthesized compounds were comprehensively illuminated with a semi-empirical molecular orbital (SEMO) package for organic and inorganic systems using Austin Model 1 (AM1)-Hamiltonian as implemented in the VAMP module of Materials Studio. In addition, the inhibition effects of these compounds for AChE and hCA I-II in vitro conditions were investigated. It was revealed that TE-1, TE-2, TE-3, TE-4, TE-5, and TE-6 compounds inhibited the AChE under in vitro conditions. TE-1 compound activated the enzyme hCA I while TE-2, TE-3 TE-4 compounds inhibited it. TE-5 and TE-6, on the other hand, did not exhibit a regular inhibition profile. Similarly, TE-1 activated the hCA II enzyme whereas TE-2, TE-3, TE-4, and TE-5 compounds inhibited it. TE-6 compound did not have a consistent inhibition profile for hCA II. Docking studies were performed with the compounds against AChE and hCA I-II receptors using induced-fit docking method. Molecular Dynamics (MD) simulations for best effective three protein-ligand couple were conducted to explore the binding affinity of the considered compounds in semi-real in-silico conditions. Along with the MD results, TE-1-based protein complexes were found more stable than TE-5. Based on these studies, TE-1 compound could be considered as a potential drug candidate for AD.Communicated by Ramaswamy H. Sarma.

Benzenesulfonamides Incorporating Hydantoin Moieties Effectively Inhibit Eukaryoticand Human Carbonic Anhydrases

A series of novel 1-(4-benzenesulfonamide)-3-alkyl/benzyl-hydantoin derivatives were synthesized and evaluated for the inhibition of eukaryotic and human carbonic anhydrases (CAs, EC 4.2.1.1). The prepared compounds were screened for their hCA inhibitory activities against three cytosolic isoforms as well as two β-CAs from fungal pathogens. The best inhibition was observed against hCA II and VII as well as Candida glabrata enzyme CgNce103. hCA I and Malassezia globosa MgCA enzymes were, on the other hand, less effectively inhibited by these compounds. The inhibitory potency of these compounds against CAs was found to be dependent on the electronic and steric effects of substituent groups on the N3-position of the hydantoin ring, which included alkyl, alkenyl and substituted benzyl moieties. The interesting results against CgNce103 make the compounds of interest for investigations in vivo as potential antifungals.

Phosphine-Mediated Sequential [2+4]/[2+3] Annulation to Construct Pyrroloquinolines

A domino [2+4]/[2+3] sequential annulation reaction of MBH carbonates with N-unprotected indoles has been developed to provide various pyrroloquinoline derivatives in ≤94% yield and 20:1 dr. The reaction could be either mediated by stoichiometric PCy₃ or catalyzed by R₃PO via P^III/P^V═O redox cycling in the presence of phenylsilane. This method assembles polycyclic 1,7-fused indoles in one step diastereoselectively.

What do cellular responses to acidity tell us about cancer?

The notion that invasive cancer is a product of somatic evolution is a well-established theory that can be modelled mathematically and demonstrated empirically from therapeutic responses. Somatic evolution is by no means deterministic, and ample opportunities exist to steer its trajectory towards cancer cell extinction. One such strategy is to alter the chemical microenvironment shared between host and cancer cells in a way that no longer favours the latter. Ever since the first description of the Warburg effect, acidosis has been recognised as a key chemical signature of the tumour microenvironment. Recent findings have suggested that responses to acidosis, arising through a process of selection and adaptation, give cancer cells a competitive advantage over the host. A surge of research efforts has attempted to understand the basis of this advantage and seek ways of exploiting it therapeutically. Here, we review key findings and place these in the context of a mathematical framework. Looking ahead, we highlight areas relating to cellular adaptation, selection, and heterogeneity that merit more research efforts in order to close in on the goal of exploiting tumour acidity in future therapies.

Base-Free Catalytic Wittig-/Cross-Coupling Reaction Sequence as Short Synthetic Strategy for the Preparation of Highly Functionalized Arylbenzoxepinones

The facile synthesis of highly functionalized building blocks with potential biological activity is of great interest to medicinal chemistry. The benzoxepinone core structures commonly exhibit biological activity. Thus, a short and efficient synthetic route towards benzoxepine containing scaffold, which enables late stage modification was developed. Namely, base-free catalytic Wittig reactions enabled the synthesis of bromobenzoxepinones from readily available starting materials. Subsequent, Suzuki–Miyaura and Stille reactions proved to be suitable methods to access a variety of benzoxepinone diaryl derivatives by late stage modification in only three steps. This three-step reaction sequence is suitable for high throughput applications and gives facile access to highly complex molecular structures, which are suitable for further functionalization. The antiproliferative properties of selected arylbenzoxepinones­ were tested in vitro on monolayer tumor cell line A549. Notably, in this initial screening, these compounds were found to be active in the micromolar range.

Pd-catalysed general access to 7-membered N/O-heterocyclic compounds as potential agents against inflammation

A Pd-catalysed regioselective synthesis of 4,5-disubstituted 7-membered N/O-heterocycles was achieved via the 7-endo-dig cyclization followed by C-C bond formation of 2-(1-alkynyl)phenylacetamide. The ligand/additive free cascade reaction proceeded in the presence of PdCl₂ in aqueous MeCN when the separate and individual use of methyl vinyl ketone and allyl bromide generally afforded an O- and N-heterocycle, respectively. The pharmacological assay was performed to identify the first example of a 1H-benzo[d]azepin-2(3H)-one based novel inhibitor of PDE4B.

Reconsidering anion inhibitors in the general context of drug design studies of modulators of activity of the classical enzyme carbonic anhydrase

Inorganic anions inhibit the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1) generally by coordinating to the active site metal ion. Cyanate was reported as a non-coordinating CA inhibitor but those erroneous results were subsequently corrected by another group. We review the anion CA inhibitors (CAIs) in the more general context of drug design studies and the discovery of a large number of inhibitor classes and inhibition mechanisms, including zinc binders (sulphonamides and isosteres, dithiocabamates and isosteres, thiols, selenols, benzoxaboroles, ninhydrins, etc.); inhibitors anchoring to the zinc-coordinated water molecule (phenols, polyamines, sulfocoumarins, thioxocoumarins, catechols); CAIs occluding the entrance to the active site (coumarins and derivatives, lacosamide), as well as compounds that bind outside the active site. All these new chemotypes integrated with a general procedure for obtaining isoform-selective compounds (the tail approach) has resulted, through the guidance of rigorous X-ray crystallography experiments, in the development of highly selective CAIs for all human CA isoforms with many pharmacological applications.

A novel class for carbonic anhydrases inhibitors and evaluation of their non-zinc binding

In this study, 23 different imidazole derivatives were synthesized, and the inhibitory properties of these derivatives against carbonic anhydrase I and II isoenzymes were investigated for the first time. The inhibition concentrations of the imidazole derivatives were found to be in the range of 2.89-115.5 nM. Docking studies examined the binding properties of the imidazole derivatives, and the structure-activity relationship is discussed. Theoretical calculations showed that the binding mode of the imidazole ring was non-zinc binding.

Discovery of Potent Carbonic Anhydrase Inhibitors as Effective Anticonvulsant Agents: Drug Design, Synthesis, and In Vitro and In Vivo Investigations

Two sets of benzenesulfonamide-based effective human carbonic anhydrase (hCA) inhibitors have been developed using the tail approach. The inhibitory action of these novel molecules was examined against four isoforms: hCA I, hCA II, hCA VII, and hCA XII. Most of the molecules disclosed low to medium nanomolar range inhibition against all tested isoforms. Some of the synthesized derivatives selectively inhibited the epilepsy-involved isoforms hCA II and hCA VII, showing low nanomolar affinity. The anticonvulsant activity of selected sulfonamides was assessed using the maximal electroshock seizure (MES) and subcutaneous pentylenetetrazole (sc-PTZ) in vivo models of epilepsy. These potent CA inhibitors effectively inhibited seizures in both epilepsy models. The most effective compounds showed long duration of action and abolished MES-induced seizures up to 6 h after drug administration. These sulfonamides were found to be orally active anticonvulsants, being nontoxic in neuronal cell lines and in animal models.

Carbonic Anhydrase Inhibitors Targeting Metabolism and Tumor Microenvironment

The tumor microenvironment is crucial for the growth of cancer cells, triggering particular biochemical and physiological changes, which frequently influence the outcome of anticancer therapies. The biochemical rationale behind many of these phenomena resides in the activation of transcription factors such as hypoxia-inducible factor 1 and 2 (HIF-1/2). In turn, the HIF pathway activates a number of genes including those involved in glucose metabolism, angiogenesis, and pH regulation. Several carbonic anhydrase (CA, EC 4.2.1.1) isoforms, such as CA IX and XII, actively participate in these processes and were validated as antitumor/antimetastatic drug targets. Here, we review the field of CA inhibitors (CAIs), which selectively inhibit the cancer-associated CA isoforms. Particular focus was on the identification of lead compounds and various inhibitor classes, and the measurement of CA inhibitory on-/off-target effects. In addition, the preclinical data that resulted in the identification of SLC-0111, a sulfonamide in Phase Ib/II clinical trials for the treatment of hypoxic, advanced solid tumors, are detailed.