Synthesis and carbonic anhydrase I, II, IX and XII inhibitory activity of sulfamates incorporating piperazinyl-ureido moieties

Chemistry of heterocycles as carbonic anhydrase inhibitors: A pathway to novel research in medicinal chemistry review

Nowadays, the scientific community has focused on dealing with different kinds of diseases by exploring the chemistry of various heterocycles as novel drugs. In this connection, medicinal chemists identified carbonic anhydrases (CA) as one of the biologically active targets for curing various diseases. The widespread distribution of these enzymes and the high degree of homology shared by the different isoforms offer substantial challenges to discovering potential drugs. Medicinal and synthetic organic chemists have been continuously involved in developing CA inhibitors. This review explored the chemistry of different heterocycles as CA inhibitors using the last 11 years of published research work. It provides a pathway for young researchers to further explore the chemistry of a variety of synthetic as well as natural heterocycles as CA inhibitors.

Pyrazole/pyrazoline as an excellent pharmacophore in the design of carbonic anhydrase inhibitors (2018-2022)

Carbonic anhydrase (CA) is a metalloenzyme that catalyzes the interconversion between carbon dioxide and water and dissociated ions of carbonic acid. In addition, CA performs various other functions in animals and plants, depending on the part of the living being. CAs have been found in almost all organisms. Besides, CAs are associated with several diseases, such as glaucoma, obesity, epilepsy, cancer, and so on. CAs are also involved in tumor cell growth and angiogenesis. Thus, inhibition of CA may be an attractive way of control of such diseases. Hence, CA inhibitors have been designed and developed to cure CA-associated diseases. Some examples of approved CA inhibitors are dorzolamide, methazolamide, brinzolamide, and dichlorphenamide. Furthermore, various heterocyclic scaffolds were utilized for the design of CA inhibitors. Among those, pyrazole/pyrazoline derivatives have exhibited greater potency toward CA inhibition. Hence, research that took place in the field of drug design and discovery of CA inhibition has been systematically reviewed and collated. Alongside, the structure-activity relationship has been described, followed by a description of the most potent molecules and their structural features.

A comparative study of the binding modes of SLC-0111 and its analogues in the hCA II and hCA IX active sites using QM/MM, molecular docking, MM-GBSA and MD approaches

Human carbonic anhydrase IX (hCA IX) is over-expressed in many tumor types and serves as an important target for the discovery of novel anticancer agents. However, development of compounds that can selectively inhibit hCA IX over its widespread cytosolic isoform human carbonic anhydrase II (hCA II) is a major challenge. This work focuses on recognizing the structural features of the hCA IX receptor that could help in achieving its selective inhibition. Tools such as protein structure alignment, rigid as well as flexible docking, QM/MM calculations and molecular dynamics simulations on SLC-0111, a selective hCA IX inhibitor, in complexation with each receptor, have been used to differentiate the receptor-ligand interactions in the two complexes. It is found that the ligand shows better binding to hCA IX due to stronger coordination to the Zn (II) ion. The ligand provides bidentate coordination through its negatively charged nitrogen and an oxygen of the sulfonamide zinc binding group. Binding energy calculations show that the potency of this ligand is due to the hydrophobic contacts, whereas the selectivity is due to the electrostatic interactions. Molecular docking and binding energy calculations for three different series of SLC-0111 analogs have identified a few molecules that show high potency and selectivity toward hCA IX. It is found that both hydrophobic and polar contacts contribute to the potency and selectivity of the ligands.

Preclinical Evaluation of Ureidosulfamate Carbonic Anhydrase IX/XII Inhibitors in the Treatment of Cancers

Carbonic anhydrases (CAs) are a family of enzymes involved in the pH regulation of metabolically active cells/tissues. Upregulation of the CAIX/XII isoforms is associated with hypoxic tumours and clinically linked with malignant progression, treatment resistance and poor prognosis. The elucidation of the crystal structure of the catalytic domains of CAIX/XII provided the basis for the generation of CAIX/XII selective inhibitors based on the sulfonamide, sulfamate and coumarins chemical structures. Ureido-substituted benzenesulfonamide CAIX/XII inhibitors have shown significant potential, with U-104 (SLC-0111) currently present in clinical Phase I/II. Ureido-substituted sulfamate CAIX/XII inhibitors have received less attention despite encouraging preclinical test results. In triple-negative breast cancer (TNBC), ureidosulfamates revealed a significant antitumour (FC9-398A) and antimetastatic potential (S4). In small cell lung cancer (SCLC), a cancer cell type very sensitive to a dysregulation in CAIX signaling, S4 treatment was particularly effective when combined with cisplatin with no evidence of acquired cisplatin-resistance. These successful anticancer strategies should provide a solid basis for future studies on ureido-substituted sulfamates.

Structure-activity relationship with pyrazoline-based aromatic sulfamates as carbonic anhydrase isoforms I, II, IX and XII inhibitors: Synthesis and biological evaluation

Four new series of aromatic sulfamates were synthesized and investigated for the inhibition of four human (h) isoforms of zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1), hCA I, II, IX, and XII. The reported derivatives, obtained by a sulfamoylation reaction of the corresponding phenolic precursors, bear 3,5-diarylpyrazoline moieties as spacers between the benzenesulfamate fragment which binds the zinc ion from the active site, and the tail of the inhibitor. Pyrazolines are biologically privileged scaffolds, endowed with versatile biological activity, such as an anti-proliferative action. The derivatives were tested for the inhibition of the cytosolic, hCA I and II (off target isoforms) and the trans-membrane, tumor-associated hCA IX and XII enzymes (anticancer drug targets). Generally, hCA I was not effectively inhibited, whereas many low nanomolar inhibitors were evidenced against hCA II (KIs in the range of 0.42-90.1 nM), IX (KIs in the range of 0.72-63.6 nM), and XII (KIs in the range of 0.88-85.2 nM). The best substitution fragments at the pyrazoline ring included for CA II a 4-sulfamic group on the 3-aryl and halogens on the 5-aryl or a methoxy group on the 3-aryl and a 4-sulfamate group on the 5-aryl; for CA IX and CA XII they included the sulfamic group on the 3- or 4-position of the 5-aryl and an electronwithdrawing group on the 4-postion of the 3-aryl ring.

Synthesis and in vitro evaluation of piperazinyl-ureido sulfamates as steroid sulfatase inhibitors

Two new piperazinyl-ureido single ring aryl sulfamate-based inhibitor series were designed against the emerging oncology drug target steroid sulfatase (STS), for which there are existing potent steroidal and non-steroidal agents in clinical trials. 4-(Piperazinocarbonyl)aminosulfamates (5-31) were obtained by reacting 4-hydroxyarylamines with phenylchloroformate, subsequent sulfamoylation of the resulting hydroxyarylcarbamates and coupling of the product with 1-substituted piperazines. Pyrimidinyl-piperazinourea sulfamates (35-42) were synthesized by pyrimidine ring closure of 4-Boc-piperazine-1-carboxamidine with 3-(dimethylamino)propenones, deprotection and coupling with the sulfamoylated building block. Target ureidosulfamates 5-31 and 35-42 were evaluated both as STS inhibitors in vitro using a lysate of JEG-3 human placenta choriocarcinoma cell line and in a whole cell assay. SAR conclusions were drawn from both series. In series 35-42 the best inhibitory activity is related to the presence of a benzofuryl on the pyrimidine ring. In series 5-31 the best inhibitory activity was shown by the ureas bearing 4-chlorophenyl, 3,4-dichlorophenyl groups or aliphatic chains at the piperazino 4-nitrogen displaying IC₅₀ in the 33-94 nM concentration range. Final optimization to the low nanomolar level was achieved through substitution of the arylsulfamate ring with halogens. Four halogenated arylsulfamates of high potency were achieved and two of these 19 and 20 had IC₅₀ values of 5.1 and 8.8 nM respectively and are attractive for potential in vivo evaluation and further development. We demonstrate the optimization of this new series to low nanomolar potency, employing fluorine substitution, providing potent membrane permeant inhibitors with further development potential indicating piperazinyl-ureido aryl sulfamate derivatives as an attractive new class of STS inhibitors.

Sulfonamides incorporating piperazine bioisosteres as potent human carbonic anhydrase I, II, IV and IX inhibitors

Starting from the molecular simplification of (R) 4-(3,4-dibenzylpiperazine-1-carbonyl)benzenesulfonamide 9a, a compound endowed with selectivity for human Carbonic Anhydrase (hCA) IV, a series of piperazines and 4-aminopiperidines carrying a 4-sulfamoylbenzamide moiety as Zn-binding group have been designed and tested on human isoforms hCA I, II, IV and IX, using a stopped flow CO₂ hydrase assay. The aim of the work was to derive structure-activity relationships useful for designing isoform selective compounds. These structural modifications changed the selectivity profile of the analogues from hCA IV to hCA I and II, and improved potency. Several of the new compounds showed subnanomolar activity on hCA II. X-ray crystallography of ligand-hCAII complexes was used to compare the binding modes of the new piperazines and the previously synthesized 2-benzyl-piperazine analogues, explaining the inhibition profiles.

Sulfamates in drug design and discovery: Pre-clinical and clinical investigations

In the present article, we reviewed the sulfamate-containing compounds reported as bioactive molecules. The possible molecular targets of sulfamate derivatives include steroid sulfatase enzyme, carbonic anhydrases, acyl transferase, and others. Sulfamate derivatives can help treat hormone-dependent tumors including breast, prostate, and endometrial cancers, Binge eating disorder, migraine, glaucoma, weight loss, and epilepsy. Sulfamate derivatives can act also as calcium sensing receptor agonists and can aid in osteoporosis. Furthermore, acyl sulfamate derivatives can act as antibacterial agents against Gram-positive bacteria. A recent study revealed a new side effect of topiramate, a sulfamate-containing compound, which is sialolithiasis. The structural and biological characteristics of the reviewed compounds are presented in detail.

Enhancement of the tail hydrophobic interactions within the carbonic anhydrase IX active site via structural extension: Design and synthesis of novel N-substituted isatins-SLC-0111 hybrids as carbonic anhydrase inhibitors and antitumor agents

Herein we report the design and synthesis of novel N-substituted isatins-SLC-0111 hybrids (6a-f and 9a-l). A structural extension approach was adopted via N-alkylation and N-benzylation of isatin moiety to enhance the tail hydrophobic interactions within the carbonic anhydrase (CA) IX active site. Thereafter, a hybrid pharmacophore approach was utilized via merging the pharmacophoric elements of isatin and SLC-0111 in a single chemical framework. As planned, a substantial improvement of inhibitory profile of the target hybrids (K_Is: 4.7-86.1 nM) towards hCA IX in comparison to N-unsubstituted leads IVa-c (K_Is: 192-239 nM), was achieved. Molecular docking of the designed hybrids in CA IX active site unveiled, as planned, the ability of N-alkylated and N-benzylated isatin moieties to accommodate in a wide hydrophobic pocket formed by T73, P75, P76, L91, L123 and A128, establishing strong van der Waals interactions. Hybrid 6c displayed good anti-proliferative activity under hypoxic conditions towards breast cancer MDA-MB-231 and MCF-7 cell lines (IC₅₀ = 7.43 ± 0.28 and 12.90 ± 0.34 μM, respectively). Also, 6c disrupted the MDA-MB-231 cell cycle via alteration of the Sub-G₁ phase and arrest of G₂-M stage. Additionally, 6c displayed significant increase in the percent of annexinV-FITC positive apoptotic cells from 1.03 to 18.54%. Furthermore, 6c displayed potent VEGFR-2 inhibitory activity (IC₅₀ = 260.64 nM). Collectively, these data suggest 6c as a promising lead molecule for the development of effective anticancer agents.

2-Benzylpiperazine: A new scaffold for potent human carbonic anhydrase inhibitors. Synthesis, enzyme inhibition, enantioselectivity, computational and crystallographic studies and in vivo activity for a new class of intraocular pressure lowering agents

Two series of 2-benzylpiperazines have been prepared and tested for the inhibition of physiologically relevant isoforms of human carbonic anhydrases (hCA, EC 4.2.1.1). The new compounds carry on one nitrogen atom of the piperazine ring a sulfamoylbenzamide group as zinc-binding moiety, and different alkyl/acyl/sulfonyl groups on the other nitrogen. Regio- and stero-isomers are described. The majority of these compounds showed Ki values in the low-medium nanomolar range against hCA I, II and IV, but not IX. In many instances interaction with the enzyme was enantioselective. The binding mode has been studied by means of X-ray crystallography and molecular modelling. Two compounds, evaluated in rabbit models of glaucoma, were able to significantly reduce intraocular pressure, making them interesting candidates for further studies.

Synthesis and biological evaluation of novel pyrazoline-based aromatic sulfamates with potent carbonic anhydrase isoforms II, IV and IX inhibitory efficacy

Herein we report the synthesis of a new series of aromatic sulfamates designed considering the sulfonamide COX-2 selective inhibitors celecoxib and valdecoxib as lead compounds. These latter were shown to possess important human carbonic anhydrase (CA, EC 4.2.1.1) inhibitory properties, with the inhibition of the tumor-associated isoform hCA IX likely being co-responsible of the celecoxib anti-tumor effects. Bioisosteric substitution of the pyrazole or isoxazole rings from these drugs with the pyrazoline one was considered owing to the multiple biological activities ascribed to this latter heterocycle and paired with the replacement of the sulfonamide of celecoxib and valdecoxib with its equally potent bioisoster sulfamate. The synthesized derivatives were screened for the inhibition of four human carbonic anhydrase isoforms, namely hCA I, II, IV, and IX. All screened sulfamates exhibited great potency enhancement in inhibiting isoform II and IV, widely involved in glaucoma (K_Is in the range of 0.4-12.4 nM and 17.7 and 43.3 nM, respectively), compared to the lead compounds, whereas they affected the tumor-associated hCA IX as potently as celecoxib.

Carbonic anhydrase inhibitors: a review on the progress of patent literature (2011-2016)

INTRODUCTION

A large area of carbonic anhydrase (CA) research focuses on the inhibition of human CA IX and CA XII, as these isoforms have been designated as biomarkers and therapeutic targets for various cancer types.

AREAS COVERED

Recently, the majority of CA inhibitor (CAI) patents cover compound design, synthesis, and delivery methods for the treatment of glaucoma and cancer. The analysis of included patents highlights the need for isoform specific inhibitors. This review covers the patents of medically relevant carbonic anhydrase inhibitors between 2011-2016.

EXPERT OPINION

The improvement of structure-based drug design methods and access to the crystal structures of human CA isoforms have improved inhibitor development. This progress can be observed in relation to the selective inhibition of CA IX for cancer treatments, with one inhibitor in clinical trials. However, the design of nonclassical CAIs is essential to further improve isoform specificity and prevent sulfur allergies.

Amido/ureidosubstituted benzenesulfonamides-isatin conjugates as low nanomolar/subnanomolar inhibitors of the tumor-associated carbonic anhydrase isoform XII

By using a molecular hybridization approach, two series of amido/ureidosubstituted benzenesulfonamides incorporating substituted-isatin moieties were synthesized. The prepared derivatives were in vitro evaluated for their inhibitory activity against human carbonic anhydrase (hCA, EC 4.2.1.1) I, II (cytosolic) and IX, XII (transmembrane, tumor-associated) isoforms. All these isoforms were inhibited in variable degrees by the sulfonamides reported here. hCA I was inhibited with KIs in the range of 7.9-894 nM, hCA II in the range of 7.5-1645 nM (with one compound having a KI > 10 μM); hCA IX in the range of 5.0-240 nM, whereas hCA XII in the range of 0.47-2.83 nM. As all these isoforms are involved in various pathologies, in which their inhibition can be exploited therapeutically, the derivatives reported here may represent interesting extensions to the field of CA inhibitors of the sulfonamide type.