Broad antitumor and antiangiogenic activities of AG3340, a potent and selective MMP inhibitor undergoing advanced oncology clinical trials

Matrix metalloproteinase inhibition after myocardial infarction: a new approach to prevent heart failure?

Increased activity of matrix metalloproteinases (MMPs) has been implicated in numerous disease processes, including tumor growth and metastasis, arthritis, and periodontal disease. It is now becoming increasingly clear that extracellular matrix degradation by MMPs is also involved in the pathogenesis of cardiovascular disease, including atherosclerosis, restenosis, dilated cardiomyopathy, and myocardial infarction. Administration of synthetic MMP inhibitors in experimental animal models of these cardiovascular diseases significantly inhibits the progression of, respectively, atherosclerotic lesion formation, neointima formation, left ventricular remodeling, pump dysfunction, and infarct healing. This review focuses on the role of MMPs in cardiovascular disease, in particular myocardial infarction and the subsequent progression to heart failure. MMPs, which are present in the myocardium and capable of degrading all the matrix components of the heart, are the driving force behind myocardial matrix remodeling. The recent finding that acute pharmacological inhibition of MMPs or deficiency in MMP-9 attenuates left ventricular dilatation in the infarcted mouse heart led to the proposal that MMP inhibitors could be used as a potential therapy for patients at risk for the development of heart failure after myocardial infarction. Although these promising results encourage the design of clinical trials with MMP inhibitors, there are still several unresolved issues. This review describes the biology of MMPs and discusses new insights into the role of MMPs in several cardiovascular diseases. Attention will be paid to the central role of the plasminogen system as an important activator of MMPs in the remodeling process after myocardial infarction. Finally, we speculate on the use of MMP inhibitors as potential therapy for heart failure.

Angiogenesis and melanoma

Angiogenesis is a process that is central to tumor growth and survival. This process is stimulated by a variety of intrinsic growth factors such as vascular endothelial growth factor, basic and acid fibroblast growth factor, and platelet-derived endothelial growth factor, among others. The process of neo-angiogenesis has been shown to be key in the proliferation of melanoma, and primarily believed to be so in the metastatic process. Biologic markers of angiogenesis are being evaluated for correlations with prognosis and biologic behavior of the tumor. These markers may also indicate susceptibility to targeted therapy. Interruption of the tumor-sustaining process of angiogenesis has become a major focus of anticancer drug development. Promising agents are in both preclinical and clinical development. Several may prove to be clinically important.

Antiangiogenic agents and their promising potential in combined therapy

One of the most promising strategies for treating cancer is the addition of antiangiogenic therapy to therapeutic regimens. Angiogenesis, or the growth of new blood vessels from preexisting vessels, is essential both for the growth of a primary tumor and for successful metastasis. As a result of intense research in this field, a number of antiangiogenic agents have been identified and have demonstrated varying degrees of success in inhibiting the growth of solid tumors and metastases in preclinical and clinical studies. The real potential of antiangiogenic agents for cancer therapy resides in strategic combinations with each other, with chemotherapy, with radiation, and with tumor-targeting agents, such as radioimmunotherapy. Along with this new opportunity to develop synergistic therapy comes the challenging complexities of the physiologic systems regulating angiogenesis. These multifaceted systems could intimidate investigators seeking to take advantage of the potential synergy in combined cancer therapy. To aid in these efforts, this overview of key antiangiogenic agent mechanisms, combination strategies and initial studies of the potential synergy with chemotherapy, radiation and radioimmunotherapy is presented.

Induction of tumour cell apoptosis by matrix metalloproteinase inhibitors: new tricks from a (not so) old drug

Matrix metalloproteinases (MMPs) regulate the turnover of extracellular matrix (ECM) components and play an important role in embryo development, morphogenesis and tissue remodelling, as well as in tumour invasion and metastasis. Synthetic MMP inhibitors (MMPIs) were designed to prevent tumour cell-induced changes in ECM and thereby achieve antitumour activity. Several MMPIs have entered clinical trials but the preliminary results did not meet the expectations. Recent evidence suggests that MMPs may have more diverse roles than originally believed, influencing angiogenesis, cytokine secretion, as well as tumour cell growth and survival. In particular, synthetic MMPIs may directly induce apoptosis of cancer cells via their inhibitory effect on the shedding of Fas Ligand (FasL), a transmembrane member of the TNF superfamily that kills susceptible cells through its receptor, Fas. Several types of cancers have been shown to express FasL and to shed it from their surface as a soluble form, which is significantly less potent in promoting apoptosis. MMP-7 was recently reported to catalyse this process. Conversely, inhibition of FasL-shedding by a synthetic MMPI results in apoptosis of Fas-sensitive cancer cells. More importantly, DNA-damaging anticancer agents, such as adriamycin, kill cancer cells, at least in part, by upregulating FasL. By inhibiting the proteolytic cleavage of FasL, MMPIs can potentiate the killing effect of traditional chemotherapeutic drugs. These studies therefore demonstrate a direct link between DNA-damaging chemotherapeutic drugs, the apoptosis-inducing Fas/FasL system and the proteolytic activity of MMPs and have important therapeutic implications. For example, the proteolytic activity of MMP-7, which is broadly expressed in primary and especially metastatic human malignancies, may contribute to tumour resistance to cytotoxic agents; targeting and inactivating MMP-7 may, therefore, enhance the efficacy of conventional cancer chemotherapy.

In vivo molecular target assessment of matrix metalloproteinase inhibition

A number of different matrix metalloproteinase (MMP) inhibitors have been developed as cytostatic and anti-angiogenic agents and are currently in clinical testing. One major hurdle in assessing the efficacy of such drugs has been the inability to sense or image anti-proteinase activity directly and non-invasively in vivo. We show here that novel, biocompatible near-infrared fluorogenic MMP substrates can be used as activatable reporter probes to sense MMP activity in intact tumors in nude mice. Moreover, we show for the first time that the effect of MMP inhibition can be directly imaged using this approach within hours after initiation of treatment using the potent MMP inhibitor, prinomastat (AG3340). The developed probes, together with novel near-infrared fluorescence imaging technology will enable the detailed analysis of a number of proteinases critical for advancing the therapeutic use of clinical proteinase inhibitors.

The role of matrix metalloproteinase genes in glioma invasion: co-dependent and interactive proteolysis

Matrix metalloproteinases (MMPs) are cation-dependent endopeptidases which have been implicated in the malignancy of gliomas. It is thought that the MMPs play a critical role in both metastasis and angiogenesis, and that interference with proteases might therefore deter local tumor dissemination and neovascularization. However, the attempt to control tumor-associated proteolysis will rely on better definition of the normal tissue function of MMPs, an area of study still in its infancy in the central nervous system (CNS). Understanding the role of MMP-mediated proteolysis in the brain relies heavily on advances in other areas of molecular neuroscience, most notably an understanding of extracellular matrix (ECM) composition and the function of cell adhesion molecules such as integrins, which communicate knowledge of ECM composition intracellularly. Recently, protease expression and function has been shown to be strongly influenced by the functional state and signaling properties of integrins. Here we review MMP function and expression in gliomas and present examples of MMP profiling studies in glioma tissues and cell lines by RT-PCR and Western blotting. Co-expression of MMPs and certain integrins substantiates the gathering evidence of a functional intersection between the two, and inhibition studies using recombinant TIMP-1 and integrin antisera demonstrate significant inhibition of glioma invasion in vitro. Use of promising new therapeutic compounds with anti-MMP and anti-invasion effects are discussed. These data underline the importance of functional interaction of MMPs with accessory proteins such as integrins during invasion, and the need for further studies to elucidate the molecular underpinnings of this process.

Evaluation of intraocular pharmacokinetics and toxicity of prinomastat (AG3340) in the rabbit

To determine the ocular pharmacokinetics, physiological and histological effects of prinomastat (a matrix metalloprotease inhibitor), a total of seventy-seven eyes of New Zealand White rabbits received intravitreous and subtenon injections of prinomastat or of acidified water vehicle as control, Doses of 0.5 mg in 0.05 mL of prinomastat or acidified water were used for intravitreal injection. For the subtenon injections, doses of 5 mg prinomastat in 0.5 mL of acidified water were administered in the superotemporal quadrant. Intraocular pharmacokinetics were determined by analyzing vitreous samples at different postinjection time points using Liquid Chromatography-Mass Spectroscopy/Mass Spectroscopy (LC-MS/MS). The toxicity was evaluated by biomicroscopy, electroretinography (ERG), pneumatonometry, and histology. No toxicity was found with either administration method. At day 14 after intravitreal injection, levels of prinomastat in the vitreous and choroid were 1.4 ng/mg and 7.8 ng/mg, respectively. The retinal levels of prinomastat were 22 ng/mg at 24 hr and dropped below 1 ng/mg at 48 hr. Prinomastat remained well above minimum effective concentration in the choroid for at least four weeks after a single intravitreal injection, suggesting that local intravitreal injection may have potential in treating choroidal neovascularization.

Biological considerations in lung cancer

Our understanding of lung cancer biology has rapidly expanded in recent years. Lung cancer, unlike most human cancers, can be traced to an environmental risk factor in the majority of cases, and this fact is reflected in the vast number of genetic alterations discovered in lung tumors whose pathogenesis is believed to be mediated by carcinogen exposure. The discovery of these alterations has led to a greater understanding of tumor development. The dramatic progress in the understanding of the genetic and molecular basis of oncogenesis and the induction of immunity has led to a rejuvenation of efforts to apply this new knowledge to this common and refractory disease. Further, the resurgent interest in cancer immunology and tumor-host interactions holds promise for the development of new approaches to treatment based on harvesting the immune systems ability to recognize these alterations. Hopefully, this understanding will lead to novel approaches with real and convincing clinical efficacy once some of these strategies are tested in carefully performed randomized clinical trials with appropriate power to detect meaningful differences.

Inhibitory effect of a matrix metalloproteinase inhibitor on growth and spread of human pancreatic ductal adenocarcinoma evaluated in an orthotopic severe combined immunodeficient (SCID) mouse model

The present study was aimed at evaluating the effect of the matrix metalloproteinase (MMP) inhibitor prinomastat (AG3340) on tumor progression using an orthotopic pancreatic carcinoma model in severe combined immunodeficient mice. In controls, receiving vehicle only, the poorly differentiated ductal adenocarcinoma invaded into adjacent organs and metastasized to different sites in the abdomen and to the lungs. Treatment with prinomastat, intraperitoneally twice daily for 21 days, reduced primary tumor volume significantly to 19.0 (+/-7.7)% of control, with induction of necrosis, differentiation, and fibrotic tissue in the pancreatic tumors. Invasion was not observed in 63% of prinomastat-treated mice, and metastases were reduced markedly. Surprisingly, prinomastat-treated tumors had on average higher microvessel densities as a consequence of an increased angiogenesis in perinecrotic tumor areas. We conclude that prinomastat is highly effective in inhibiting pancreatic carcinoma growth and progression in an orthotopic cancer model. This model appears to be a valuable tool to investigate the potency of novel antimetastatic strategies in pancreatic ductal adenocarcinoma by specifically targeting certain MMPs.

Quantification of matrix metalloproteinase activity in plasma of patients enrolled in a BAY 12-9566 phase I study

The expression of matrix metalloproteinases (MMPs) is often associated with invasiveness or grade of tumours. Increased blood levels of MMP proteins, including MMP-1, MMP-2, MMP-3 and MMP-9 have been detected in various types of cancers. With the exception of one study, MMPs in serum and plasma have been determined using ELISA. In the present study we measured the activity of the MMPs found in human plasma samples using gelatin enzymography and fluorimetric degradation assays. We used plasma samples from healthy control subjects and cancer patients enrolled in a dose-finding study for the MMP inhibitor, BAY 12-9566, to assess the activity of MMPs found in plasma and screen for efficacy of the MMP inhibitor. BAY 12-9566 has inhibitory activity toward MMP-2, MMP-3 and MMP-9. Patients with advanced solid tumours were enrolled in our study and plasma was collected on day 1 before dosing and at steady-state of the drug on day 15. Our results show that BAY 12-9566 was effective in lowering the plasma gelatinolytic activity in the group of 29 patients when considering the data obtained from a fluorimetric gelatinase assay. The data obtained from gelatin enzymography, however, did not reach significance. The fluorimetric degradation assay could be a useful tool to screen plasma from cancer patients in other clinical trials assessing MMP inhibitors.

Tumor gelatinases and invasion inhibited by the green tea flavanol epigallocatechin-3-gallate

BACKGROUND

Given the association of consumption of green tea with prevention of cancer development, metastasis, and angiogenesis, the effect of the main flavanol present, epigallocatechin-3-gallate (EGCG), on two gelatinases most frequently overexpressed in cancer and angiogenesis (MMP-2 and MMP-9) and on tumor cell invasion and chemotaxis were examined.

METHODS

Zymography, Western blotting, and enzyme linked immuoadsorbent assay were used to analyze the effect of EGCG on MMP-2 and MMP-9 activity, whereas its effect on tumor cell invasion and chemotaxis was examined using modified Boyden chamber assays.

RESULTS

A Zn2+ chelation-independent, dose-dependent, noncompetitive inhibition by EGCG of both gelatinases was found at concentrations 500 times lower than that reported to inhibit urokinase. Tumor cell invasion of a reconstituted basement membrane matrix, but not chemotaxis, was reduced by 50% with EGCG concentrations equivalent to that in the plasma of moderate green tea drinkers, and 2 orders of magnitude below those of tissue inhibitors of MMPs. Although higher concentrations of EGCG were associated with increased levels of both cell-associated gelatinases and their activator MT1-MMP, no increased gelatinase activation was found, and TIMP-1 and TIMP-2 inhibitors were up-regulated. Finally, concentrations of EGCG active in restraining proliferation and inducing apoptosis of transformed cells were more than 100 times lower than those reported for normal cells.

CONCLUSIONS

Epigallocatechin-3-gallate is a potent inhibitor of gelatinases and an orally available pharmacologic agent that may confer the antiangiogenic and antimetastatic activity associated with green tea.

Development of matrix metalloproteinase inhibitors in cancer therapy

The matrix metalloproteinases (MMPs) are a family of zinc-dependent proteinases involved in the degradation of the extracellular matrix. The MMPs have been implicated in the processes of tumor growth, invasion, and metastasis; are frequently overexpressed in malignant tumors; and have been associated with an aggressive malignant phenotype and adverse prognosis in patients with cancer. A number of MMP inhibitors are being developed for the treatment of cancer. The most extensively studied class of MMP inhibitors includes collagen peptidomimetics and nonpeptidomimetic inhibitors of the MMP active site, tetracycline derivatives, and bisphosphonates. The hydroxamate peptidomimetic inhibitor batimastat and its orally bioavailable analogue marimastat, which bind covalently to the zinc atom at the MMP-active site, were the first MMP inhibitors to be studied in detail. Marimastat is currently being studied in randomized clinical trials. The nonpeptidic MMP inhibitors were synthesized in an attempt to improve the oral bioavailability and pharmaceutical properties of the peptidic inhibitors. Several members of this class of compounds are undergoing evaluation in phase III clinical trials. The tetracyclines and, particularly, the nonantibiotic chemically modified tetracyclines, interfere with several aspects of MMP expression and activation and inhibit tumor growth and metastases in preclinical models. A representative agent of this class, Col-3, is currently undergoing phase I clinical trials. The development of the MMP inhibitors, like that of other targeted and predominantly antiproliferative compounds, poses a challenge because the paradigms that have governed the design of clinical oncology trials may not be relevant to this new class of agents. The anticipated need for long-term administration of these drugs, together with their cytostatic mechanism of action, will require novel clinical trial design strategies.

Angiogenesis: regulators and clinical applications

Angiogenesis is a fundamental process in reproduction and wound healing. Under these conditions, neovascularization is tightly regulated. Unregulated angiogenesis may lead to several angiogenic diseases and is thought to be indispensable for solid tumor growth and metastasis. The construction of a vascular network requires different sequential steps including the release of proteases from "activated" endothelial cells with subsequent degradation of the basement membrane surrounding the existing vessel, migration of endothelial cells into the interstitial space, endothelial cell proliferation, and differentiation into mature blood vessels. These processes are mediated by a wide range of angiogenic inducers, including growth factors, chemokines, angiogenic enzymes, endothelial specific receptors, and adhesion molecules. Finally, when sufficient neovascularization has occurred, angiogenic factors are down-regulated or the local concentration of inhibitors increases. As a result, the endothelial cells become quiescent, and the vessels remain or regress if no longer needed. Thus, angiogenesis requires many interactions that must be tightly regulated in a spatial and temporal manner. Each of these processes presents possible targets for therapeutic intervention. Synthetic inhibitors of cell invasion (marimastat, Neovastat, AG-3340), adhesion (Vitaxin), or proliferation (TNP-470, thalidomide, Combretastatin A-4), or compounds that interfere with angiogenic growth factors (interferon-alpha, suramin, and analogues) or their receptors (SU6668, SU5416), as well as endogenous inhibitors of angiogenesis (endostatin, interleukin-12) are being evaluated in clinical trials against a variety of solid tumors. As basic knowledge about the control of angiogenesis and its role in tumor growth and metastasis increases, it may be possible in the future to develop specific anti-angiogenic agents that offer a potential therapy for cancer and angiogenic diseases.

HIV-1 Tat neurotoxicity is prevented by matrix metalloproteinase inhibitors

The release of potentially neurotoxic molecules by HIV-infected brain macrophages is accompanied by neuronal injury and death that results in the development of HIV-associated dementia (HAD). Among the potential neurotoxins implicated in the development of HAD is the HIV-1 transactivating protein, Tat. To investigate the mechanism by which Tat causes neurotoxicity, brain-derived Tat sequences from nondemented (Tat-ND) and demented (Tat-HAD) AIDS patients, which differed primarily in the augmenting region of Tat, were expressed in U937 monoblastoid cells and primary human macrophages. Cells expressing Tat-HAD protein exhibited elevated matrix metalloproteinase (MMP)-2 and -7 release and activation, but cells expressing Tat-ND did not exhibit enhanced MMP expression. Conditioned media from Tat-HAD-transfected cells caused significantly greater neuronal death (15.4 +/- 4.3%) than did Tat-ND (4.4 +/- 2.1%) or nontransfected (2.1 +/- 0.8%) cell-derived conditioned media. The neurotoxicity induced by Tat-HAD was inhibited by anti-MMP-2 or -7 antibodies (p < 0.005) but not by antibodies against MMP-9 or Tat. Similarly, scid/nod mice receiving striatal implants of Tat-HAD-transfected cells exhibited greater neurobehavioral abnormalities and neuronal loss (p < 0.005) than did animals receiving Tat-ND or nontransfected cells, which were reduced by treatment with the MMP inhibitor prinomastat (p < 0.005). These findings indicate that Tat causes neuronal death through an indirect mechanism that is Tat sequence dependent and involves the induction of MMPs.

Critical appraisal of the use of matrix metalloproteinase inhibitors in cancer treatment

Experimental studies performed prior to 1990 led to the widely held belief that matrix metalloproteinases (MMPs) produced by cancer cells are of critical importance in tumor invasion and metastasis. Based on this evidence, the pharmaceutical industry produced several well tolerated, orally active MMP inhibitors (MMPIs) which demonstrated efficacy in mouse cancer models. Phase III clinical trials initiated in 1997-98 using marimastat, prinomastat (AG3340), and BAY 12-9566 alone or in combination with standard chemotherapy in patients with advanced cancers (lung, prostate, pancreas, brain, GI tract) have recently been reported; no clinical efficacy was demonstrated. Bayer and Agouron have discontinued their ongoing Phase III drug trials of MMPIs in advanced cancer. In retrospect, the failure of MMPIs to alter disease progression in metastatic cancer might have been anticipated since MMPs appear to be important in early aspects of cancer progression (local invasion and micrometastasis) and may no longer be required once metastases have been established. Our understanding of MMP pathophysiology in cancer has expanded considerably in the past 10 years. Current views indicate that: (1) most MMPs in tumors are made by stromal cells, not carcinoma cells; (2) cancer cells induce stromal cells to synthesize MMPs using extracellular matrix metalloproteinase inducer (EMMPRIN) and cytokine stimulatory mechanisms; and (3) MMPs promote cell migration and the release of growth factors sequestered in the extracellular matrix. MMPs have a dual function in tumor angiogenesis: MMP-2 and MT1-MMP are required in breaking down basement membrane barriers in the early stage of angiogenesis, while other MMPs are involved in the generation of an angiogenic inhibitor, angiostatin. In spite of considerable recent progress in identifying multiple roles of MMPs in disease, our understanding of MMP function in cancer is far from complete (see Table 1). Based on accumulated data, it is recommended that future MMPI trials focus on: (1) patients with early stage cancer; (2) the use of MMPIs along with chemotherapy; (3) the measurement of MMPs in tumor tissue and blood as a means of identifying patients who are more likely to respond to MMPI therapy; and (4) identification of biomarkers that reflect activation or inhibition of MMPs in vivo.

Matrix metalloproteinases: pro- and anti-angiogenic activities

Matrix metalloproteinases (MMP) are a family of structurally related proteinases most widely recognized for their ability to degrade extracellular matrix, although recent investigations have demonstrated other biologic functions for these enzymes. MMP are typically not constitutively expressed, but are regulated by: (1) cytokines, growth factors, and cell-cell and cell-matrix interactions that control gene expression; (2) activation of their proenzyme form; and (3) the presence of MMP inhibitors [tissue inhibitors of metalloproteinases, (TIMP)]. MMP have important roles in normal processes including development, wound healing, mammary gland, and uterine involution, but are also involved in angiogenesis, tumor growth, and metastasis. Angiogenesis, characteristically defined as the establishment of new vessels from pre-existing vasculature, is required for biologic processes such as wound healing and pathologic processes such as arthritis, tumor growth, and metastasis. Blocking of MMP activity has been studied for potential therapeutic efficacy in controlling such pathologic processes. Synthetic MMP inhibitors, most notably the hydroxymates, have been engineered for this purpose and are presently in clinical trial. These inhibitors may have broad versus specific MMP inhibitory activity. As increased non-matrix degrading capabilities of MMP are recognized, however, i.e., cytokine activation, processing of proteins to molecules of distinct biologic function, it becomes less clear whether the nonselective inhibition of MMP activity for all pathologic processes involving MMP is appropriate. This review focuses upon the contribution of MMP to the process of tumor invasion and angiogenesis, and discusses the design and use of MMP inhibitors as therapeutic agents in these processes.

Inhibition of experimental lung metastasis by aerosol delivery of PEI-p53 complexes

Mutations in the p53 tumor suppressor gene and the pathways mediated by the p53 protein are common in many human cancers. Replacement of functional p53 by gene therapy is a potential way of combating these cancers and the associated drug resistance and tumor growth. Aerosol delivery of genes is a noninvasive way of targeting genes to the lung for gene therapy. Here we demonstrate, using a murine melanoma lung metastasis model, that aerosol delivery of polyethyleneimine-p53 (PEI-p53) complexes inhibits the growth of lung metastasis. A significantly reduced number of visible foci were observed in C57BL/6 mice injected with B16-F10 melanoma and treated with PEI-p53 complexes by aerosol for 3 weeks at twice a week. Fifty percent of the mice in the PEI-p53-treated group exhibited no visible tumor foci. There was a significant reduction in the lung weights of p53-treated mice (P < 0.01) compared to control groups. The tumor burden was also significantly lower (P < 0.001) in mice treated with PEI-p53 complexes. No extrapulmonary metastasis was observed in the groups treated with PEI-p53 complexes compared to 50% of the mice in control groups, which showed metastasis to lymph nodes in the neck or abdomen. Treatment with PEI-p53 aerosol also led to about a 50% increase in the mean length of survival of the mice injected with B16-F10 cells. These data suggest that delivery of the p53 gene by aerosol using PEI as the gene delivery vector can inhibit the growth of lung metastasis.

Prinomastat, a hydroxamate-based matrix metalloproteinase inhibitor. A novel pharmacological approach for tissue remodelling-related diseases

Prinomastat (formerly AG3340, Agouron Pharmaceuticals, Inc.) is a potent, selective oral inhibitor of matrix metalloproteinase-2, -9, -13 and -14. This peculiar selectivity should represent an advantage for prinomastat in terms of efficacy/tolerability. The drug has been shown to inhibit tumour growth and angiogenesis in a variety of preclinical models, including cancer of colon, breast, lung and intriguingly in melanoma and glioma models. Moreover, the combination of prinomastat and several chemotherapeutic agents was shown to induce additive effects. The drug is currently in Phase III clinical trials for patients with non-small cell lung cancer in combination with paclitaxel and carboplatin, as well as in advanced hormone refractory prostate cancer in combination with mitoxantrone. The most common side effects are musculoskeletal pain and stiffness. These side effects generally cease with treatment interruption. Finally, considering the pathophysiology of MMPs, Agouron is exploring the utility of prinomastat in ophthalmology and dermatology.

Ongoing trials with matrix metalloproteinase inhibitors

Excessive or poorly regulated matrix metalloproteinase (MMP) activity has been implicated as a pathogenic factor in a range of diseases where the extracellular matrix is degraded or remodelled. Synthetic, potent, low molecular weight MMP inhibitors (MMPIs) have been developed and, over the past five years, these agents have begun clinical testing in patients with cancer, rheumatoid arthritis, osteoarthritis and acute macular degeneration. The past year has seen a number of disappointments with the halting of clinical trials of Ro 32-3555 in patients with rheumatoid arthritis and of BAY 12-9566 in patients with cancer. There have, however, been some successes with perhaps the clearest indication of efficacy being seen in the results of a Phase III trial of marimastat in patients with advanced gastric cancer. Clinical trials are continuing with marimastat and other MMPIs, including prinomastat, solimastat, BMS 275291, metastat and neovastat. Results from these trials are expected in the next two years and it is likely that clinical trials with MMPIs will begin in patients with other diseases where MMPs are believed to be involved, such as restenosis, cerebral haemorrhage and multiple sclerosis. Future research is likely to focus on the identification of specific MMP targets in different diseases, both in order to improve efficacy and to reduce the musculoskeletal side effect profile that has characterised several of the first generation oral MMPIs.

New paradigms for the treatment of cancer: the role of anti-angiogenesis agents

Angiogenesis, the sprouting of new blood vessels, plays a role in diverse disease states including cancer, diabetic retinopathy, age-related macular degeneration, rheumatoid arthritis, psoriasis, atherosclerosis, and restenosis. With regard to cancer, the clinical association of tumor vascularity with tumor aggressiveness has been clearly demonstrated in numerous tumor types. The observation of increased microvessel density in tumors not only serves as an independent prognostic indicator, but also suggests that anti-angiogenic therapy may be an important component of treatment regimens for cancer patients. The complexity of the angiogenic process, which involves both positive and negative regulators, provides a number of targets for therapy. Many positive regulators, including growth factor receptors, matrix metalloproteinases, and integrins, have been correlated with increased vascularity of tumors and poor prognosis for patient survival. Thus, these serve as ideal targets for anti-angiogenesis therapy. Many inhibitors of these targets are currently undergoing clinical evaluation as potential anti-cancer agents. In this article, we discuss the role of positive regulators in angiogenesis and tumor growth and describe the anti-angiogenic agents under development.

Matrix metalloproteinases: multifunctional contributors to tumor progression

Matrix metalloproteinases (MMPs) are a family of extracellular matrix degrading proteinases. Owing to their matrix-degrading abilities and high expression in advanced tumors, MMPs were originally implicated in invasion and metastasis during cancer progression. However, recent work extends a role for MMPs during multiple stages of tumor progression to include other functions such as growth, angiogenesis and migration. Based on studies in animal models implicating MMP activity in cancer, synthetic MMP inhibitors are currently being tested in a clinical setting.

Protease inhibitors. Part 8: synthesis of potent Clostridium histolyticum collagenase inhibitors incorporating sulfonylated L-alanine hydroxamate moieties

A series of hydroxamates was prepared by reaction of alkyl/arylsulfonyl halides with N-2-chlorobenzyl-L-alanine, followed by conversion of the COOH moiety to the CONHOH group, with hydroxylamine in the presence of carbodiimides. Other structurally related compounds were obtained by reaction of N-2-chlorobenzyl-L-alanine with aryl isocyanates, arylsulfonyl isocyanates or benzoyl isothiocyanate, followed by the similar conversion of the COOH into the CONHOH moiety. The new compounds were assayed as inhibitors of the Clostridium histolyticum collagenase, ChC (EC 3.4.24.3), a bacterial zinc metallo-peptidase which degrades triple helical collagen as well as a large number of synthetic peptides. The prepared hydroxamate derivatives proved to be 100-500 times more active collagenase inhibitors than the corresponding carboxylates. Substitution patterns leading to best ChC inhibitors (both for carboxylates as well as for the hydroxamates) were those involving perfluoroalkylsulfonyl- and substituted-arylsulfonyl moieties, such as pentafluorophenylsulfonyl; 3- and 4-protected-aminophenylsulfonyl-; 3- and 4-carboxyphenylsulfonyl-; 3-trifluoromethyl-phenylsulfonyl; as well as 1- and 2-naphthyl-, quinoline-8-yl- or substituted-arylsulfonylamidocarboxyl moieties among others. Similarly to the matrix metalloproteinase (MMP) hydroxamate inhibitors, ChC inhibitors of the type reported here must incorporate hydrophobic moieties at the P2' and P3' sites, in order to achieve tight binding to the enzyme. This study also proves that the 2-chlorobenzyl moiety, investigated here for the first time, is an efficient P2' anchoring moiety for obtaining potent ChC inhibitors.

Antiangiogenic agents

A greater understanding of the complex process of tumor-induced angiogenesis, coupled with the notion that tumors require a blood supply to both grow and metastasize, has fueled the search for agents that block or disrupt the angiogenic process. Because normal vascular endothelial cells (ECs) turn over so slowly, conventional wisdom suggests that an antiangiogenic approach to cancer therapy should offer improved efficacy and reduced toxicity, without the potential for drug resistance. Numerous reports have identified small molecules or antibodies that can interfere with one or more key steps in EC signaling, migration or differentiation. Three new compounds, ZD4190, SU6668 and PD 0173073, have been reported during the past year to have significant and selective antiangiogenic activity, as well as antitumor activity.

Design, synthesis, and biological evaluation of potent thiazine- and thiazepine-based matrix metalloproteinase inhibitors

The synthesis and enzyme inhibition data for a series of thiazine- and thiazepine-based matrix metalloproteinase (MMP) inhibitors are described. The thiazine- and thiazepine-based inhibitors were discovered by optimization of hetererocyclic sulfonamide-based inhibitors. The most potent series of inhibitors was obtained by modification of the amino acid D-penicillamine. This amino acid provides a gem-dimethyl group on the thiazine or thiazepine ring which has a dramatic effect on the in vitro potency of this series. In particular, the sulfide 4a and the sulfone 5a were potent, broad-spectrum inhibitors of the MMPs with IC(50)'s against MMP-1 of 0.8 and 1.9 nM, respectively. The binding mode of this novel thiazepine-based series of MMP inhibitors was established based on X-ray crystallography of the complex of stromelysin and 4a.