Fabrizio Carta

Targeting tumor hypoxia: suppression of breast tumor growth and metastasis by novel carbonic anhydrase IX inhibitors.

Carbonic anhydrase IX (CAIX) is a hypoxia and HIF-1-inducible protein that regulates intra- and extracellular pH under hypoxic conditions and promotes tumor cell survival and invasion in hypoxic microenvironments. Interrogation of 3,630 human breast cancers provided definitive evidence of CAIX as an independent poor prognostic biomarker for distant metastases and survival. shRNA-mediated depletion of CAIX expression in 4T1 mouse metastatic breast cancer cells capable of inducing CAIX in hypoxia resulted in regression of orthotopic mammary tumors and inhibition of spontaneous lung metastasis formation. Stable depletion of CAIX in MDA-MB-231 human breast cancer xenografts also resulted in attenuation of primary tumor growth. CAIX depletion in the 4T1 cells led to caspase-independent cell death and reversal of extracellular acidosis under hypoxic conditions in vitro. Treatment of mice harboring CAIX-positive 4T1 mammary tumors with novel CAIX-specific small molecule inhibitors that mimicked the effects of CAIX depletion in vitro resulted in significant inhibition of tumor growth and metastasis formation in both spontaneous and experimental models of metastasis, without inhibitory effects on CAIX-negative tumors. Similar inhibitory effects on primary tumor growth were observed in mice harboring orthotopic tumors comprised of lung metatstatic MDA-MB-231 LM2-4(Luc+) cells. Our findings show that CAIX is vital for growth and metastasis of hypoxic breast tumors and is a specific, targetable biomarker for breast cancer metastasis.

Antiglaucoma carbonic anhydrase inhibitors: a patent review

Introduction: Glaucoma is one of the major causes of blindness, affecting together with age-related macular degeneration > 70 million people worldwide. One of the therapeutic options for its management is based on the inhibition of the metalloenyme carbonic anhydrase (CA, EC 4.2.1.1). CA inhibitors (CAIs) diminish intraocular pressure (IOP) by reducing the rate of bicarbonate formation and thus secretion of the aqueous humor. Areas covered: The main classes of clinically used antiglaucoma CAIs are the sulfonamides with systemic (acetazolamide, methazolamide, ethoxzolamide and dichlorophenamide) and topical (dorzolamide and brinzolamide) action. A patent literature review covering the period 2007 – 2013 is presented. Expert opinion: This review presents an overview of the patent literature in the CAI antiglaucoma drug design field during the past 6 years. Most of the patents deal with sulfonamide/sulfamide/sulfamate CAIs, sulfonamides incorporating NO-donating moieties, as well as hybrids incorporating sulfonamide and prostaglandin (PG) analogs, were also reported. There is an urgent need for new antiglaucoma CAIs/approaches to treat and diagnose this disease in the very near future, as the last drug which has been discovered in the field (latanoprost) dates back > 10 years ago.

Polyamines inhibit carbonic anhydrases by anchoring to the zinc-coordinated water molecule

Carbonic anhydrases (CAs, EC 4.2.1.1) are inhibited by sulfonamides, phenols, and coumarins. Polyamines such as spermine, spermidine, and many synthetic congeners are described to constitute a novel class of CA inhibitors (CAIs), interacting with the different CA isozymes with efficiency from the low nanomolar to millimolar range. The main structure-activity relationship for these CAIs have been delineated: the length of the molecule, number of amine moieties, and their functionalization are the main parameters controlling activity. The X-ray crystal structure of the CA II-spermine adduct allowed understanding of the inhibition mechanism. Spermine anchors to the nonprotein zinc ligand through a network of hydrogen bonds. Its distal amine moiety makes hydrogen bonds with residues Thr200 and Pro201, which further stabilize the adduct. Spermine binds differently compared to sulfonamides, phenols, or coumarins, rendering possible to develop CAIs with a diverse inhibition mechanism, profile, and selectivity for various isoforms.

Dithiocarbamates strongly inhibit carbonic anhydrases and show antiglaucoma action in vivo

A series of dithiocarbamates were prepared by reaction of primary/secondary amines with carbon disulfide in the presence of bases. These compounds were tested for the inhibition of four human (h) isoforms of the zinc enzyme carbonic anhydrase, CA (EC 4.2.1.1), hCA I, II, IX, and XII, involved in pathologies such as glaucoma (CA II and XII) or cancer (CA IX). Several low nanomolar inhibitors targeting these CAs were detected. The X-ray crystal structure of the hCA II adduct with morpholine dithiocarbamate evidenced the inhibition mechanism of these compounds, which coordinate to the metal ion through a sulfur atom from the dithiocarbamate zinc-binding function. Some dithiocarbamates showed an effective intraocular pressure lowering activity in an animal model of glucoma.

Antiobesity carbonic anhydrase inhibitors: a literature and patent review

Introduction: Obesity is ranked as one of the top 10 global health problems and the major concern deriving from it is the exposure of the population to a vast array of chronic pathologies such as cardiovascular and musculoskeletal disorders, type 2 diabetes, cancer, such as colon, breast and endometrial cancer, together with psychological disorders derived from this condition. The discovery that the clinically used anticonvulsants topiramate (TPM) and zonisamide (ZNS) induced weight loss in obese, epileptic patients, afforded the validation of the mitochondrial carbonic anhydrases (CAs, EC 4.2.1.1) VA and VB as targets for the development of antiobesity drugs. Areas covered: This review deals with the scientific and patent literature regarding obesity or obesity-related pathologies, being particularly focused on the use of carbonic anhydrase inhibitors (CAI) such as TPM and ZNS which inhibit the de novo lipogenesis. Expert opinion: There is an urgent need of new drugs for the treatment of obesity. The identification that the mitochondrial CAs are implicated in the de novo lipogenesis allowed to consider selective inhibitors of such enzymes as useful for the development of new antiobesity drugs. Actually TPM was approved 1 year ago for this therapy, whereas ZNS is also an effective such agent. These compounds are the lead molecules in this field and an intense research is on the way in order to develop new compounds based on the selective inhibition of mitochondrial CA isoforms.

Sulfonamides: a patent review (2008 – 2012)

Introduction: The primary sulfonamide moiety is present in many clinically used drugs, such as diuretics (furosemide, indapamide, chlorthalidone, thiazides); carbonic anhydrase (CA) inhibitors (CAIs) (including acetazolamide, dichlorophenamide, dorzolamide and brinzolamide); antiepileptics (zonisamide and sulthiame); the antipsychotic sulpiride and the cycloxygenase 2 (COX2) inhibitors celecoxib and valdecoxib. Recently, novel drugs have been launched, such as apricoxib and pazopanib, which also incorporate this group. Areas covered: The article presents the main classes of sulfonamides investigated between 2008 and 2012. Specifically, the authors review the scientific and patent literature on CAIs, COX2 inhibitors, pazopanib and its congeners, which are multi-targeted receptor tyrosine kinase inhibitor of VEGFR-1, VEGFR-2, VEGFR-3, PDGFR-a/β, and c-kit. Expert opinion: Most patents deal with sulfonamide CAIs incorporating NO-donating moieties as antiglaucoma agents, or with compounds targeting the tumor-associated isoforms CA IX/XII. The antidandruff actions of sulphonamides, which inhibit yeast CAs, were also claimed. Apricoxib (a COX2 inhibitor) and pazopanib, a tyrosine kinase inhibitor, show significant antitumor activity and several patents deal with these drugs. There is a constant need of novel sulfonamides to act as selective antiglaucoma drugs (targeting CA II), as antitumor agents/diagnostic tools (targeting CA IX/XII), and to treat and diagnose other disease. This privileged structural motif is likely to be present in other drugs in the future.

Specific inhibition of carbonic anhydrase IX activity enhances the in vivo therapeutic effect of tumor irradiation

BACKGROUND AND PURPOSE Carbonic anhydrase (CA) IX expression is increased upon hypoxia and has been proposed as a therapeutic target since it has been associated with poor prognosis, tumor progression and pH regulation. The aim of this study was to evaluate the antitumor activity of a high CAIX-affinity indanesulfonamide (11c) combined with irradiation, compared with the general CA inhibitor acetazolamide (AZA). MATERIAL AND METHODS HT-29 carcinoma cells with or without (genetic knockdown, KD) CAIX expression were incubated with 11c/AZA under different oxygen levels and proliferation, apoptosis and radiosensitivity were evaluated. 11c/AZA was administered intravenously (1×/day; 5 days) to tumor-bearing mice and tumor irradiation (10 Gy) was performed at day 3 of the injection period. Tumor growth and potential treatment toxicity were monitored (3×/week). RESULTS Treatment with 11c/AZA alone resulted in tumor regression, which was further increased in CAIX expressing cells by combining 11c with irradiation. AZA demonstrated also an additional effect in the KD tumors when combined with irradiation. CAIX inhibition in vitro significantly reduced proliferation and increased apoptosis upon hypoxia exposure without affecting intrinsic radiosensitivity. CONCLUSIONS Specific inhibition of CAIX activity enhanced the effect of tumor irradiation and might, therefore, be an attractive strategy to improve overall cancer treatment.

Dithiocarbamates strongly inhibit the β-class carbonic anhydrases from Mycobacterium tuberculosis

A series of N-mono- and N,N-disubstituted dithiocarbamates have been investigated as inhibitors of two β-carbonic anhydrases (CAs, EC 4.2.1.1) from the bacterial pathogen Mycobacterium tuberculosis, mtCA 1 (Rv1284) and mtCA 3 (Rv3273). Both enzymes were inhibited with efficacies between the subnanomolar to the micromolar one, depending on the substitution pattern at the nitrogen atom from the dithiocarbamate zinc-binding group. Aryl, arylalkyl-, heterocyclic as well as aliphatic and amino acyl such moieties led to potent mtCA 1 and 3 inhibitors in both the N-mono- and N,N-disubstituted dithiocarbamate series. This new class of β-CA inhibitors may have the potential for developing antimycobacterial agents with a diverse mechanism of action compared to the clinically used drugs for which many strains exhibit multi-drug/extensive multi-drug resistance.

Dithiocarbamates: a new class of carbonic anhydrase inhibitors. Crystallographic and kinetic investigations

The zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1) is inhibited by several classes of zinc-binders (sulfonamides, sulfamates, and sulfamides) as well as by compounds which do not interact with the metal ion (phenols, polyamines and coumarins). Here we report a new class of potent CA inhibitors which bind the zinc ion: the dithiocarbamates (DTCs). They coordinate to the zinc ion from the enzyme active site in monodentate manner and establish many favorable interactions with amino acid residues nearby. Several low nanomolar CA I, II and IX inhibitors were detected.

Novel therapies for glaucoma: A patent review 2007 - 2011

Introduction: Glaucoma affects a large number of people, and therapies for its management are based on the use of adrenergic agonist/antagonists, carbonic anhydrase (CA) inhibitors and prostaglandin (PG) analogs. However, no new drugs have been launched on the market, although some new drug classes, such as 5-hydroxy-tryptamine (5HT2) agonists and rho kinase inhibitors entered into advanced clinical investigations. Areas covered: The main classes of clinically used antiglaucoma drugs, as well as potential new targets (e.g., 5HT2 agonist, rho kinase inhibitor, RNA interference), are reviewed. A patent literature review covering the period 2007 – 2011 is presented. Expert opinion: Most of the patents deal with sulfonamide CA inhibitors incorporating nitric oxide donating moieties or with PG analogs based on the latanoprost scaffold. The PG analogs are the predominant patented compounds. Several new potential targets emerged (e.g., rho kinase inhibitors), but no such derivatives progressed to the clinic due to adverse effects. There is an urgent need of new antiglaucoma drugs/approaches to treat and diagnose this disease in the very near future.