Inhibition of carbonic anhydrase isoforms I, II, IX and XII with Schiff’s bases incorporating iminoureido moieties

Constitutional Dynamic Inhibition/Activation of Carbonic Anhydrases

In this review we consider one important member of the metalloenzymes family, the carbonic anhydrase (CA), involved in the treatment of several common diseases. Different approaches have emerged to regulate the activity of CA, mostly acting on the inner catalytic active site or outer microenvironment of the enzyme, leading to inhibition or activation of CA. In recent years, gradually increased attention has focused on the adoption of constitutional dynamic chemistry (CDC) strategies for the screening and discovery of potent inhibitors or activators. The participation of reversible covalent bonds enabled the enzyme itself to select the optimal ligands obtained from diverse building blocks with comparatively higher degree of variety, resulting in the fittest recognition of enzyme ligands from complex dynamic systems. With the increasing implementation of CDC for enzyme targets, it shows great potential for drug discovery or CO₂ capture applications.

Design and synthesis of benzenesulfonamide-linked imidazo[2,1-b][1,3,4]thiadiazole derivatives as carbonic anhydrase I and II inhibitors

A novel series of imidazothiadiazole-linked benzenesulfonamide derivatives (5a-t) was synthesized and subjected for screening against the four physiologically and pharmacologically relevant human carbonic anhydrase (hCA) isoforms: hCA I, II, VA, and IX. The compounds selectively inhibited hCA I and II over hCA VA and IX. Furthermore, among the two cytosolic isoforms, hCA II was more effectively inhibited as compared with hCA I. The most active compounds were 5o with K i  = 0.246 µM and 5p with K i  = 0.376 µM against hCA II, whereas compound 5f showed good inhibition against both hCA I and II with K i  = 0.493 and 0.4 µM, respectively. This class of underexplored sulfonamides may be used to design isoform-selective CA inhibitors targeting enzymes of medicinal chemistry interest.

Investigation of in vitro and in silico effects of some novel carbazole Schiff bases on human carbonic anhydrase isoforms I and II

Carbonic anhydrases (CAs, EC4.2.1.1) are metalloenzymes that catalyse reversible hydration reaction of carbon dioxide to bicarbonate and protons. In recent years, there has been a great interest in inhibitors/activators of carbonic anhydrase isoenzymes. Therefore, we investigated the effects of four different carbazole Schiff base derivatives, which are believed to have a potential to be used as a drug, on human carbonic anhydrase (hCA) isoenzymes I and II under in vitro conditions. The IC₅₀ values of carbazole Schiff base derivatives were found to be in the range of 32.09-151.2 μM for hCA isoenzyme I and 21.82-40.54 μM for hCA isoenzyme II. Among all compounds, (E)-3-(((9-Octyl-9H-carbazole-3-yl)imino)methyl)benzene-1,2-diol (C3) had the strongest inhibitory effect on hCA isoenzyme II. It was determined that 2,3,4-trimethoxy and 4-hydroxy phenyl containing carbazole compounds have selective inhibition against hCA II isoenzyme. Docking studies were performed against hCA I and II receptors using induced-fit docking method. The compounds had affinity scores varying from -7.74 ± 0.27 to -6.27 ± 0.07 kcal/mol for hCA I and from -8.04 ± 0.17 to -7.27 ± 0.18 kcal/mol for hCA II.Communicated by Ramaswamy H. Sarma.

Design, synthesis and molecular modelling studies of some pyrazole derivatives as carbonic anhydrase inhibitors

In this study, newly synthesised compounds 6, 8, 10 and other compounds (1-5, 7 and 9) and their inhibitory properties against the human isoforms hCA I and hCA II were reported for the first time. Compounds 1-10 showed effective inhibition profiles with KI values in the range of 5.13-16.9 nM for hCA I and of 11.77-67.39 nM against hCA II, respectively. Molecular docking studies were also performed with Glide XP to get insight into the inhibitory activity and to evaluate the binding modes of the synthesised compounds to hCA I and II. More rigorous binding energy calculations using MM-GBSA protocol which agreed well with observed activities were then performed to improve the docking scores. Results of in silico calculations showed that all compounds obey drug likeness properties. The new compounds reported here might be promising lead compounds for the development of new potent inhibitors as alternatives to classical hCA inhibitors.

Progress in the development of human carbonic anhydrase inhibitors and their pharmacological applications: Where are we today?

Carbonic anhydrases (CAs, EC 4.2.1.1) are widely distributed metalloenzymes in both prokaryotes and eukaryotes. They efficiently catalyze the reversible hydration of carbon dioxide to bicarbonate and H⁺  ions and play a crucial role in regulating many physiological processes. CAs are well-studied drug target for various disorders such as glaucoma, epilepsy, sleep apnea, and high altitude sickness. In the past decades, a large category of diverse families of CA inhibitors (CAIs) have been developed and many of them showed effective inhibition toward specific isoforms, and effectiveness in pathological conditions in preclinical and clinical settings. The discovery of isoform-selective CAIs in the last decade led to diminished side effects associated with off-target isoforms inhibition. The many new classes of such compounds will be discussed in the review, together with strategies for their development. Pharmacological advances of the newly emerged CAIs in diseases not usually associated with CA inhibition (neuropathic pain, arthritis, cerebral ischemia, and cancer) will also be discussed.

Aryl-4,5-dihydro-1H-pyrazole-1-carboxamide Derivatives Bearing a Sulfonamide Moiety Show Single-digit Nanomolar-to-Subnanomolar Inhibition Constants against the Tumor-associated Human Carbonic Anhydrases IX and XII

A series of new 3-phenyl-5-aryl-N-(4-sulfamoylphenyl)-4,5-dihydro-1H-pyrazole-1-carboxamide derivatives was designed here, synthesized, and studied for carbonic anhydrase (CAs, EC 4.2.1.1) inhibitory activity against the human (h) isozymes I, II, and VII (cytosolic, off-target isoforms), and IX and XII (anticancer drug targets). Generally, CA I was not effectively inhibited, whereas effective inhibitors were identified against both CAs II (K_Is in the range of 5.2–233 nM) and VII (K_Is in the range of 2.3–350 nM). Nonetheless, CAs IX and XII were the most susceptible isoforms to this class of inhibitors. In particular, compounds bearing an unsubstituted phenyl ring at the pyrazoline 3 position showed 1.3–1.5 nM K_Is against CA IX. In contrast, a subset of derivatives having a 4-halo-phenyl at the same position of the aromatic scaffold even reached subnanomolar K_Is against CA XII (0.62–0.99 nM). Docking studies with CA IX and XII were used to shed light on the derivative binding mode driving the preferential inhibition of the tumor-associated CAs. The identified potent and selective CA IX/XII inhibitors are of interest as leads for the development of new anticancer strategies.

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.

Novel indolin-2-one-based sulfonamides as carbonic anhydrase inhibitors: Synthesis, in vitro biological evaluation against carbonic anhydrases isoforms I, II, IV and VII and molecular docking studies

Herein we present the design, synthesis, and biological evaluation of three different series of novel sulfonamides (3a-f, 6a-f and 9a-f) incorporating substituted indolin-2-one moieties (as tails) linked to benzenesulfonamide (as zinc anchoring moieties) through aminoethyl or (4-oxothiazolidin-2-ylidene)aminoethyl linkers. The synthesized sulfonamides were evaluated in vitro for their inhibitory activity against the following human (h) carbonic anhydrase (hCA, EC 4.2.1.1) isoforms, hCA I, II, IV and VII. All these isoforms were inhibited by the sulfonamides reported here in variable degrees. hCA I was inhibited with K_Is in the range of 42-8550.9 nM, hCA II in the range of 5.9-761 nM; hCA IV in the range of 4.0-2069.5 nM, whereas hCA VII in the range of 13.2-694 nM. Molecular docking studies were carried out for some of the tested compounds within the hCA II active site, allowed us to rationalize the obtained inhibition results.

Synthesis and inhibitory properties of some carbamates on carbonic anhydrase and acetylcholine esterase

A series of carbamate derivatives were synthesized and their carbonic anhydrase I and II isoenzymes and acetylcholinesterase enzyme (AChE) inhibitory effects were investigated. All carbamates were synthesized from the corresponding carboxylic acids via the Curtius reactions of the acids with diphenyl phosphoryl azide followed by addition of benzyl alcohol. The carbamates were determined to be very good inhibitors against for AChE and hCA I, and II isoenzymes. AChE inhibition was determined in the range 0.209-0.291 nM. On the other hand, tacrine, which is used in the treatment of Alzheimer's disease possessed lower inhibition effect (Ki: 0.398 nM). Also, hCA I and II isoenzymes were effectively inhibited by the carbamates, with inhibition constants (Ki) in the range of 4.49-5.61 nM for hCA I, and 4.94-7.66 nM for hCA II, respectively. Acetazolamide, which was clinically used carbonic anhydrase (CA) inhibitor demonstrated Ki values of 281.33 nM for hCA I and 9.07 nM for hCA II. The results clearly showed that AChE and both CA isoenzymes were effectively inhibited by carbamates at the low nanomolar levels.

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.