Potent, selective spiropyrrolidine pyrimidinetrione inhibitors of MMP-13

Selective MMP-13 Inhibitors: Promising Agents for the Therapy of Osteoarthritis

Osteoarthritis (OA) is an age-related degenerative disease, which is characterized by chronic joint pain, inflammation and the damage of joint cartilage. At present, steroidal drugs and nonsteroidal anti-inflammatory drugs (NSAIDS), selective cyclooxygenase-2 (COX-2) inhibitors, are the first-line drugs for the treatment of OA. However, these drugs could lead to some cardiovascular side effects. Therefore, it is urgent to develop novel agents for the treatment of OA. Matrix metalloproteinase-13 (MMP-13), an important member of matrix metalloproteinases (MMPs) family, plays a vital role by degrading type II collagen in articular cartilage and bone in OA. It is noted that MMP-13 is specially expressed in the OA patients, and not in normal adults. In addition, broadspectrum MMP inhibitors could result in some painful and joint-stiffening side effects, called musculoskeletal syndrome (MSS) in the clinical trials. Thus, developing selective MMP-13 inhibitors is a potential strategy for the therapy of OA. In this review, we summarize the recent progress of selective MMP-13 inhibitors including two subfamilies, namely zinc-binding and non-zinc-binding selective MMP-13 inhibitors.

Matrix Metalloproteinase Inhibitors as Investigational and Therapeutic Tools in Unrestrained Tissue Remodeling and Pathological Disorders

Matrix metalloproteinases (MMPs) are zinc-dependent proteolytic enzymes that degrade various proteins in the extracellular matrix (ECM). MMPs may also regulate the activity of membrane receptors and postreceptor signaling mechanisms and thereby affect cell function. The MMP family includes collagenases, gelatinases, stromelysins, matrilysins, membrane-type MMPs, and other MMPs. Inactive proMMPs are cleaved by other MMPs or proteases into active MMPs, which interact with various protein substrates in ECM and cell surface. MMPs regulate important biological processes such as vascular remodeling and angiogenesis and may be involved in the pathogenesis of cardiovascular disorders such as hypertension, atherosclerosis, and aneurysm. The role of MMPs is often assessed by measuring their mRNA expression, protein levels, and proteolytic activity using gel zymography. MMP inhibitors are also used to assess the role of MMPs in different biological processes and pathological conditions. MMP activity is regulated by endogenous tissue inhibitors of metalloproteinases (TIMPs), and the MMP/TIMP balance could determine the net MMP activity, ECM turnover, and tissue remodeling. Also, several synthetic MMP inhibitors have been developed. Synthetic MMP inhibitors include a large number of zinc-binding globulins (ZBGs), in addition to non-ZBGs and mechanism-based inhibitors. MMP inhibitors have been proposed as potential tools in the management of osteoarthritis, cancer, and cardiovascular disorders. However, most MMP inhibitors have broad-spectrum actions on multiple MMPs and could cause undesirable musculoskeletal side effects. Currently, doxycycline is the only MMP inhibitor approved by the Food and Drug Administration. New generation biological and synthetic MMP inhibitors may show greater MMP specificity and fewer side effects and could be useful in targeting specific MMPs, reducing unrestrained tissue remodeling, and the management of MMP-related pathological disorders.

Design, synthesis, and biological activity of novel, potent, and highly selective fused pyrimidine-2-carboxamide-4-one-based matrix metalloproteinase (MMP)-13 zinc-binding inhibitors

Matrix metalloproteinase-13 (MMP-13), a member of the collagenase family of enzymes, has been implicated to play a key role in the pathology of osteoarthritis. Recently, we have reported the discovery of a series of quinazoline-2-carboxamide based non-zinc-binding MMP-13 selective inhibitors, as exemplified by compound 1. We then continued our research of a novel class of zinc-binding inhibitors to obtain follow-up compounds with different physicochemical, pharmacokinetic, and biological activity profiles. In order to design selective MMP-13 inhibitors, we adopted a strategy of connecting a zinc-binding group with the quinazoline-2-carboxamide system, a unique S1' binder, by an appropriate linker. Among synthesized compounds, a triazolone inhibitor 35 exhibited excellent potency (IC₅₀=0.071nM) and selectivity (greater than 170-fold) over other MMPs (MMP-1, 2, 3, 7, 8, 9, 10, 12, and 14) and tumor necrosis factor-α converting enzyme (TACE). In this article, the design, synthesis, and biological activity of novel zinc-binding MMP-13 inhibitors are described.

Advances in studies on collagenase inhibitors

Matrix metalloproteinases (MMPs) play an important role in many physiological and pathological processes. Development of MMP inhibitors, in particular collagenase inhibitors, for the treatment of arthritis has been more challenging, undoubtedly. Small-molecular-weight collagenase inhibitors may be classified into several different arbitrary structural classes, depending on the catalytic zinc-binding function as well as other structural elements of the inhibitors. This chapter tries to make an attempt in providing the reader with an overall flavor of the type of scaffolds reported in the past few years along with the molecular modeling studies.

Specificity of binding with matrix metalloproteinases

Matrix metalloproteinases (MMPs) regulate a wide range of biological functions; hence, they have invited great attention for the studies on their structures and functions, and since their overactivation leads to several diseases, the design and discovery of their potent inhibitors have become the need of the day. Since there have been so far discovered 28 different types of human MMPs, the specificity of binding of inhibitors with each different MMP needs special attention. The chapter presents the X-ray crystallographic and NMR studies on three-dimensional structures of a number of MMPs to reveal their catalytic site, subsites, specificity of binding with substrate and inhibitors, and catalytic mechanism. In addition to catalytic site, MMPs possess some subsites designated by unprimed and primed S, e.g., S1, S2, S3 and S1', S2', S3'. Among these, the S1' pocket varies the most among the different MMPs varying in both the amino acid makeup and depth of the pocket (shallow, intermediate, and deep pocket MMPs). This, along with the flexibility in the structures of MMPs, could be of great help in the design and the development of selective MMP inhibitors (MMPIs). The determination of affinity of inhibitors and the cleavage position of peptide substrates is mainly based on P1'-S1' interaction (P1', the group in inhibitor or substrate binding to S1' pocket of the enzyme), and it is the main determinant for the affinity of inhibitors and the cleavage position of peptide substrates.

Matrix metalloproteinase inhibitors as investigative tools in the pathogenesis and management of vascular disease

Matrix metalloproteinases (MMPs) are proteolytic enzymes that degrade various components of the extracellular matrix (ECM). MMPs could also regulate the activity of several non-ECM bioactive substrates and consequently affect different cellular functions. Members of the MMPs family include collagenases, gelatinases, stromelysins, matrilysins, membrane-type MMPs, and others. Pro-MMPs are cleaved into active MMPs, which in turn act on various substrates in the ECM and on the cell surface. MMPs play an important role in the regulation of numerous physiological processes including vascular remodeling and angiogenesis. MMPs may also be involved in vascular diseases such as hypertension, atherosclerosis, aortic aneurysm, and varicose veins. MMPs also play a role in the hemodynamic and vascular changes associated with pregnancy and preeclampsia. The role of MMPs is commonly assessed by measuring their gene expression, protein amount, and proteolytic activity using gel zymography. Because there are no specific activators of MMPs, MMP inhibitors are often used to investigate the role of MMPs in different physiologic processes and in the pathogenesis of specific diseases. MMP inhibitors include endogenous tissue inhibitors (TIMPs) and pharmacological inhibitors such as zinc chelators, doxycycline, and marimastat. MMP inhibitors have been evaluated as diagnostic and therapeutic tools in cancer, autoimmune disease, and cardiovascular disease. Although several MMP inhibitors have been synthesized and tested both experimentally and clinically, only one MMP inhibitor, i.e., doxycycline, is currently approved by the Food and Drug Administration. This is mainly due to the undesirable side effects of MMP inhibitors especially on the musculoskeletal system. While most experimental and clinical trials of MMP inhibitors have not demonstrated significant benefits, some trials still showed promising results. With the advent of new genetic and pharmacological tools, disease-specific MMP inhibitors with fewer undesirable effects are being developed and could be useful in the management of vascular disease.

Orally active MMP-1 sparing α-tetrahydropyranyl and α-piperidinyl sulfone matrix metalloproteinase (MMP) inhibitors with efficacy in cancer, arthritis, and cardiovascular disease

α-Sulfone-α-piperidine and α-tetrahydropyranyl hydroxamates were explored that are potent inhibitors of MMP's-2, -9, and -13 that spare MMP-1, with oral efficacy in inhibiting tumor growth in mice and left-ventricular hypertrophy in rats and in the bovine cartilage degradation ex vivo explant system. α-Piperidine 19v (SC-78080/SD-2590) was selected for development toward the initial indication of cancer, while α-piperidine and α-tetrahydropyranyl hydroxamates 19w (SC-77964) and 9i (SC-77774), respectively, were identified as backup compounds.

Selective MMP13 inhibitors

Pharmacology of MMP13 and MMP13 selective inhibitors is reviewed.

Sequential five-component synthesis of spiropyrrolidinochromanones

Herein we report a novel, diastereoselective, one-pot, two-step, sequential synthesis of highly functionalized natural product-like spiropyrrolidinochromanones. The process consists of an Ugi four-component condensation of 3-formylchromones with amines, isocyanides, and glyoxylic acids followed by a nucleophilic conjugate addition and intramolecular cyclization. The experimental simplicity and tolerance to a wide variety of substituents makes this method suitable for combinatorial synthesis.

To bind zinc or not to bind zinc: an examination of innovative approaches to improved metalloproteinase inhibition

This short review highlights some recent advances in matrix metalloproteinase inhibitor (MMPi) design and development. Three distinct approaches to improved MMP inhibition are discussed: (1) the identification and investigation of novel zinc-binding groups (ZBGs), (2) the study of non-zinc-binding MMPi, and (3) mechanism-based MMPi that form covalent adducts with the protein. Each of these strategies is discussed and their respective advantages and remaining challenges are highlighted. The studies discussed here bode well for the development of ever more selective, potent, and well-tolerated MMPi for treating several important disease pathologies.

Charting the chemical space of target sites: insights into the binding modes of amine and amidine groups

Nowadays there is growing awareness that the translation of the increasing number of lead compounds into clinical candidates is still a slow and often inefficient process. In order to facilitate the lead optimization procedure, due consideration must be given to the use of the right bioisosteric replacements. Very recently, we reported that exploring a chemical space of binding sites is a more effective strategy for studying the bioisosteric relationships existing among functional groups. As a continuation of our work in this field, we report herein the construction of a chemical space covered by binding sites of small molecules containing diverse amine and amidine groups. The analysis of the differences in some properties of the binding sites of these functional groups allow for gaining insights into the binding modes of positively charged groups. In addition, this study pinpoints that different types of interactions and bioisosteric relationships exist among primary, secondary, tertiary, quaternary amine, and amidine moieties.