Chapter 24. Inhibition of Matrix Metalloproteinases

Synthesis and evaluation of novel heterocyclic MMP inhibitors

A variety of novel heterocyclic compounds were synthesized and evaluated for MMP inhibition. Broad spectrum inhibition of MMPs 1, 2, 9, and 12 was found with pyridinone-based compounds while N-heterocyclic triazoles and tetrazoles were largely ineffective. A highly selective tetrazole inhibitor for MMP-2 was discovered.

Matrix metalloproteinases (MMPs): chemical-biological functions and (Q)SARs

Matrix metalloproteinases (MMPs) are a large family of calcium-dependent zinc-containing endopeptidases, which are responsible for the tissue remodeling and degradation of the extracellular matrix (ECM), including collagens, elastins, gelatin, matrix glycoproteins, and proteoglycan. They are regulated by hormones, growth factors, and cytokines, and are involved in ovarian functions. MMPs are excreted by a variety of connective tissue and pro-inflammatory cells including fibroblasts, osteoblasts, endothelial cells, macrophages, neutrophils, and lymphocytes. These enzymes are expressed as zymogens, which are subsequently processed by other proteolytic enzymes (such as serine proteases, furin, plasmin, and others) to generate the active forms. Matrix metalloproteinases are considered as promising targets for the treatment of cancer due to their strong involvement in malignant pathologies. Clinical/preclinical studies on MMP inhibition in tumor models brought positive results raising the idea that the development of strategies to inhibit MMPs may be proved to be a powerful tool to fight against cancer. However, the presence of an inherent flexibility in the MMP active-site limits dramatically the accurate modeling of MMP-inhibitor complexes. The interest in the application of quantitative structure-activity relationships (QSARs) has steadily increased in recent decades and we hope it may be useful in elucidating the mechanisms of chemical-biological interactions for this enzyme. In the present review, an attempt has been made to explore the in-depth knowledge from the classification of this enzyme to the clinical trials of their inhibitors. A total number of 92 QSAR models (44 published and 48 new formulated QSAR models) have also been presented to understand the chemical-biological interactions. QSAR results on the inhibition of various compound series against MMP-1, -2, -3, -7, -8, -9, -12, -13, and -14 reveal a number of interesting points. The most important of these are hydrophobicity and molar refractivity, which are the most important determinants of the activity.

Comparative studies of potential cancer biomarkers carbon-11 labeled MMP inhibitors (S)-2-(4'-[11C]methoxybiphenyl-4-sulfonylamino)-3-methylbutyric acid and N-hydroxy-(R)-2-[[(4'-[11C]methoxyphenyl)sulfonyl]benzylamino]-3-methylbutanamide

(S)-2-(4'-[11C]methoxybiphenyl-4-sulfonylamino)-3-methylbutyric acid ([11C]MSMA) and N-hydroxy-(R)-2-[[(4'-[11C]methoxyphenyl)sulfonyl]benzylamino]-3-methylbutanamide ([11C]CGS 25966), carbon-11 labeled matrix metalloproteinase (MMP) inhibitors, have been synthesized for evaluation as new potential positron emission tomography (PET) cancer biomarkers. [11C]MSMA was prepared by appropriate precursor (S)-2-(4'-hydroxybiphenyl-4-sulfonylamino)-3-methylbutyric acid tert-butyl ester, which was synthesized in eight steps from amino acid (L)-valine in 39.4% chemical yield. This precursor was labeled by [11C]methyl triflate through O-[11C]methylation method at the hydroxyl position of biphenol under basic conditions, followed by a quick acid hydrolysis and isolated by solid-phase extraction (SPE) purification to produce pure target compound [11C]MSMA in 35-55% radiochemical yield, based on 11CO2, decay corrected to end of bombardment (EOB), and 20-25 min synthesis time. [11C]CGS 25966 was prepared in our previous work starting from amino acid (D)-valine. The biodistribution of [11C]MSMA and [11C]CGS 25966 were determined at 45 min post iv injection in breast cancer animal models MCF-7's transfected with IL-1alpha implanted athymic mice and MDA-MB-435 implanted athymic mice. The results showed the uptakes of [11C]MSMA and [11C]CGS 25966 in these tumors were 0.95 and 0.42%dose/g in MCF-7's transfected with IL-1alpha implanted mice, 0.98 and 1.53%dose/g in MDA-MB-435 implanted mice, respectively; the ratios of tumor/muscle (T/M) and tumor/blood (T/B) were 1.21 and 1.09 (T/M, MCF-7's), 0.99 and 0.84 (T/B, MCF-7's), 1.38 and 1.27 (T/M, MDA-MB-435), 1.27 and 1.95 (T/B, MDA-MB-435), respectively. The micro-PET images of [11C]MSMA and [11C]CGS 25966 in both breast cancer athymic mice were acquired for 15 min from a MCF-7's transfected with IL-1alpha and/or MDA-MB-435 implanted mouse at 45 min post iv injection of 1 mCi of the tracer using a dedicated high resolution (<3 mm full-width at half-maximum) small FOV (field-of-view) PET imaging system, Indy-PET II scanner, developed in our laboratory, which showed both tumors were invisible with both tracers. The results were compared. From our results, we concluded that both [11C]MSMA and [11C]CGS 25966 might be unsuitable as PET tracers for cancer imaging.

New radioiodinated carboxylic and hydroxamic matrix metalloproteinase inhibitor tracers as potential tumor imaging agents

Several studies have demonstrated a positive correlation between tumor progression and expression of extracellular proteinases such as matrix metalloproteinases (MMPs). MMP-2 and MMP-9 have become attractive targets for cancer research because of their increased expression in human malignant tumor tissues of various organs, providing a target for medical imaging techniques. Radioiodinated carboxylic and hydroxamic MMP inhibitors 2-(4'-[(123)I]iodo-biphenyl-4-sulfonylamino)-3-(1H-indol-3-yl)-propionic acid (9) and 2-(4'-[(123)I]iodo-biphenyl-4-sulfonylamino)-3-(1H-indol-3-yl)-propionamide (11) were synthesized by electrophilic aromatic substitution of the tributylstannyl derivatives and resulted in radiochemical yields of 60% +/- 5% (n = 3) and 70% +/- 5% (n = 6), respectively. In vitro zymography and enzyme assays showed high inhibition capacities of the inhibitors on gelatinases. In vivo biodistribution showed no long-term accumulation in organs and the possibility to accumulate in the tumor. These results warrant further studies of radioiodinated carboxylic and hydroxamic MMP inhibitor tracers as potential SPECT tumor imaging agents.

Synthesis of radiolabeled biphenylsulfonamide matrix metalloproteinase inhibitors as new potential PET cancer imaging agents

Novel matrix metalloproteinase (MMP) inhibitor radiotracers, (S)-3-methyl-2-(2',3',4'-methoxybiphenyl-4-sulfonylamino)-butyric acid [(11)C]methyl ester (1a-c), (S)-3-methyl-2-(2',3',4'-fluorobiphenyl-4-sulfonylamino)-butyric acid [(11)C]methyl ester (1d-f), and (S)-3-methyl-2-(4'-nitrobiphenyl-4-sulfonylamino)-butyric acid [(11)C]methyl ester (1g), a series of substituted biphenylsulfonamide derivatives, have been synthesized for evaluation as new potential positron emission tomography (PET) cancer imaging agents.

Broad-spectrum matrix metalloproteinase inhibitor marimastat-induced musculoskeletal side effects in rats

OBJECTIVE

To characterize the clinical and histopathologic changes in a rat model of broad-spectrum matrix metalloproteinase (MMP)-induced musculoskeletal syndrome (MSS), and to facilitate research into the causes and treatments of MSS in humans.

METHODS

Male Lewis rats weighing 150-180 gm were administered 10-30 mg of the broad-spectrum MMP inhibitor marimastat over a 2-week period via surgically implanted subcutaneous osmotic pumps. The animals were monitored and scored for the onset and severity of MSS, using clinical and histologic parameters.

RESULTS

Marimastat-treated rats exhibited various clinical signs, including compromised ability to rest on their hind feet, high-stepping gait, reluctance or inability to move, and hind paw swelling. Histologically, marimastat-treated rat joints were characterized by soft tissue and bone changes, such as increased epiphyseal growth plate, synovial hyperplasia, and increased cellularity in the joint capsule and extracapsular ligaments. The severity of MSS, as judged by clinical criteria (2 blinded observers using 3 clinical parameters), paw volume, and histologic score, was nearly identical. The observed changes were indistinguishable from those reported for primate models and mimic MSS in humans.

CONCLUSION

This simple and sensitive model of MSS is an attractive alternative for studying the pathology of MSS.

Design and synthesis of sulfur based inhibitors of matrix metalloproteinase-1

Fibroblast collagenase (MMP-1), a member of the matrix metalloproteinases family, is believed to be a pathogenesis of arthritis, by cleaving triple-helical type II collagen in cartilage. From the similarity of the active site zinc binding mode with hydroxamate, we designed and synthesized alpha-mercaptocarbonyl possessing compounds (3-5), which incorporated various peptide sequences as enzyme recognition sites. The P4-P1 peptide incorporating compound (3) exhibited as potent inhibition as the hydroxamate (1) and the carboxylate (2) type inhibitors, with an IC50 of 10(-6) M order against MMP-1. But the inhibitor (3) related compounds (6-8) displayed decreased or no inhibitory potencies. These results suggest that the existence of both the carbonyl and thiol groups might be critical for the inhibition, and the distance between the two functional groups is important for inhibitory potency. For Pn' peptide incorporating compounds (4a-k), except for 4h and 4k, all compounds showed IC50 values under sub-nanomolar. Among them, for potent inhibition, Leu was better than Phe and Val as the P1' amino acid, and the P2' position amino acid was necessary, and preferentially Phe. Insertion of the Pn peptide into 4d or 4k, giving compounds 5a-c, did not increase the activities of 4d and 4k. Substitution of the mercapto group with other functional groups lost the activity of compound 4a. The stereochemical preference at the thiol-attached position was also determined by preparation of both isomers of 4a. It was found that the S configuration compound (36b) is approximately 100 times more potent than the corresponding R-isomer (36a).

Design and synthesis of carboxylate inhibitors for matrix metalloproteinases

A series of carboxylate compounds were prepared from N(alpha)-substituted 2,3-diaminopropionic acid and were tested for efficacy as matrix metalloproteinase (MMP) inhibitors. During modeling of the initial compound 10a, we utilized three-dimensional structure modeling software (InsightII/Discover Ver. 2.98). Some of the prepared carboxylate derivatives, such as carbamate compounds (12c,d, 22) and sulfonamide compounds (14b,c), proved to be effective MMP-1 inhibitors (with IC50 values of a 10(-6) M order), depending on the substituent at the N(alpha)-position of 2,3-diaminopropionic acid. Some of them were also evaluated for inhibition of stromelysin-1 (MMP-3), and the sulfonamide compound 14c exceeded the lead compound 5b in its MMP-3 inhibitory potency. For the carbamate compounds, we investigated the minimum molecular size at which the MMP-1 inhibitory potency was maintained, and found that this was P3-P1' compound 10b.

Selectivity of inhibition of matrix metalloproteases MMP-3 and MMP-2 by succinyl hydroxamates and their carboxylic acid analogues is dependent on P3' group chirality

Structure-activity relationships are described for a series of succinyl hydroxamic acids 1a-o and their carboxylic acid analogues 2a-o as inhibitors of matrix metalloproteases MMP-3 and MMP-2. For this series (P1' = (CH2)3Ph, P2' = t-Bu) selectivity for the inhibition of MMP-2 was found to be strongly dependent on P3'.

P1, P2'-linked macrocyclic amine derivatives as matrix metalloproteinase inhibitors

A novel series of 13- and 14-membered macrocyclic amines was developed by linking the P1 and P2' groups. The synthesis entails stereoselective Frater alkylation to install the anti-succinate configuration and macrocyclic amination via nucleophilic displacement. This strategy resulted in a new class of conformationally constrained inhibitors that are potent and selective for MMP-8 and 9 over MMP-1 and 3.

Small molecule inhibitors of tumor-promoted angiogenesis, including protein tyrosine kinase inhibitors

Angiogenesis is an exciting and promising new area of research. The concept that tumor cells are absolutely dependent upon neovascularization to grow and metastasize has opened the door to a multitude of new approaches and targets for developing anticancer therapies. These potential new antiangiogenic therapies offer the possibility for improved efficacy and reduced toxicity relative to conventional cancer treatments without the possibility of drug resistance. In particular, reports of small molecule inhibitors of tumor-promoted angiogenesis are appearing ever more frequently in the scientific literature. For this reason, the major focus of this review will be to cover small molecule inhibitors of tumor-promoted angiogenesis. The present review concentrates on selected literature, principally from mid-1996 to mid-1998, where there are sufficient biological data to support claims of antiangiogenic activities by small molecules. In addition, a historical background is presented and some of the important issues related to this field are discussed within.

Discovery of a novel series of selective MMP inhibitors: identification of the gamma-sulfone-thiols

We have discovered a new series of potent MMP Inhibitors that are selective for MMP-13 over MMP-1 incorporating a gamma-sulfone thiol.

First hydroxamate inhibitors for carboxypeptidase A. N-acyl-N-hydroxy-beta-phenylalanines

A series of N-acyl-N-hydroxy-beta-Phe were designed, synthesized, and shown to have potent inhibitory activity for carboxypeptidase A (CPA). They are the first examples of CPA inhibitors having a hydroxamate functionality.

Inhibition of adamalysin II and MMPs by phosphonate analogues of snake venom peptides

Phosphonate analogues of the peptidomimetic N-(Furan-2-yl)carbonyl-Leu-Trp-OH were prepared with the goal of evaluating the effect of phosphonate for carboxylate replacement on binding with snake venom metalloproteinases and MMPs. N-(Furan-2-yl)carbonyl-Leu-L-Trp(P)-(OH)2 showed a 75-fold increase of the inhibiting activity against adamalysin II, a snake venom metalloproteinase structurally related to MMPs and TACE. Both the phosphonate and carboxylate peptidomimetics fit into the active site adopting a retrobinding mode and provide the structural base for a new class of metalloproteinases inhibitors.

NMR screening in drug discovery

NMR methods in drug discovery have traditionally been used to obtain structural information for drug targets or target-ligand complexes. Recently, it has been shown that NMR may be used as an alternative approach for identification of ligands that bind to protein drug targets, shifting the emphasis of many NMR laboratories towards screening and design of potential drug molecules, rather than structural characterization.

Matrix Metalloproteinases Produced by Rat IL-2-Activated NK Cells

We have previously documented that adoptively transferred IL-2-activated NK (A-NK) cells can accumulate within cancer metastases. Electron microscopic studies of pulmonary metastases have revealed that adoptively transferred A-NK cells that accumulate within metastases bind to endothelial cells and are able to traverse basement membranes. We have now extended these morphologic studies. We report that rat A-NK cells produce two matrix metalloproteinases: MMP-2 and MMP-9, as determined by SDS-PAGE gelatin zymography. These activities are inhibited following incubation with BB-94 (batimastat), a specific inhibitor of matrix metalloproteinases but not with 3,4-dichloroisocoumarin, an inhibitor of neutral serine proteases. The identity of MMP-2 was confirmed by Western blots using a polyclonal Ab against human MMP-2, whereas reverse transcriptase-PCR analysis of mRNA extracts of A-NK cells has confirmed the presence of MMP-9. In addition, we report for the first time that A-NK cells can migrate through a model basement membrane-like extracellular matrix. Moreover, the ability of A-NK cells to migrate through this model basement membrane was partially inhibited by BB-94; however, BB-94 has no effect on A-NK cell-mediated cytotoxicity, suggesting that matrix metalloproteinases do not contribute to cytolytic function of A-NK cells. In sum, our studies show that A-NK cells employ BB-94-inhibitable matrix metalloproteinases to degrade extracellular matrices. This suggests that matrix metalloproteinases may play a role in the accumulation of A-NK cells within cancer metastases.

IgE secretion is attenuated by an inhibitor of proteolytic processing of CD23 (Fc epsilonRII)

CD23, the low-affinity IgE receptor, is up-regulated on interleukin (IL)-4-stimulated B cells and monocytes, with a concomitant increase in the release of soluble fragments of CD23 (sCD23) into the medium by proteolytic processing of the surface-bound intact CD23. The effect of inhibition of the processing of CD23 on IgE production in human and mouse cells and in a mouse model in vivo was evaluated. CD23 processing to sCD23 from RPMI 8866 (a human Epstein-Barr virus-transformed B cell line) cell membranes was inhibited by a broad-spectrum matrix-metalloprotease inhibitor, batimastat, with an IC50 of 0.15 microM. Batimastat also inhibited CD23 processing in whole RPMI 8866 cells as well as in IL-4-stimulated purified human monocytes with similar IC50. Batimastat inhibited IgE production from IL-4/anti-CD40-stimulated human tonsil B cells as well as mouse splenic B cells in a manner consistent with inhibition of CD23 processing. Release of soluble fragments of CD23 in the cell supernatants of tonsil B cells was inhibited over the concentration range of 1-10 microM batimastat and intact cell surface CD23 was increased on mouse splenic B cells in the presence of these concentrations of batimastat. IgE production of IL-4-stimulated human peripheral blood mononuclear cells was also blocked by 1-10 microM batimastat, again with comparable inhibition of sCD23 release over the same concentration range. Finally, in a mouse model of IgE production, batimastat inhibited IgE production in response to ovalbumin challenge as determined by serum IgE levels. Taken together, the data support a role of CD23 in IgE production and point to CD23 processing to sCD23 as a therapeutically relevant control point in the regulation of IgE synthesis.

Non-peptidic cysteine derivatives as inhibitors of matrix metalloproteinases

By exploiting the thiol function of L-cysteine as a chelating group of the active-site zinc atom of matrix metalloproteinases (MMPs), N- and C-terminal derivatization of this amino acid with aliphatic and aromatic groups allowed us to explore the selectivity of the S and/or S' binding subsites of human neutrophil collagenase (MMP8) and stromelysin (MMP3). With N-benzyloxycarbonyl-L-cysteine-(2-phenyl)ethylamide a submicromolar inhibitor of MMP8 was discovered.

A new type of carboxypeptidase A inhibitors designed using an imidazole as a zinc coordinating ligand

2-(4-Imidazoyl)hydrocinnamic acid (1) and its congeners (2-4) having different length of alkyl chain spacers between the imidazole ring and the alpha-carbon to the carboxylate of 1 have been designed, synthesized and evaluated as inhibitors for carboxypeptidase A to show that they are competitive inhibitors for the enzyme. Inhibitor 1 was most potent having the Ki value of 0.8 microM. The present study demonstrates that imidazole ring is an effective zinc coordinating ligand that can be useful for the design of inhibitors for zinc proteases.