Structural Insight into the Stereoselective Inhibition of MMP-8 by Enantiomeric Sulfonamide Phosphonates

An Overview of Stereoselective Synthesis of α-Aminophosphonic Acids and Derivatives

An overview of all methodologies published during the last few years focused to the stereoselective (diastereoselective or enantioselective) synthesis of α-aminophosphonic acids and derivatives is reported. The procedures have been classified according a retrosynthetic strategy and taking into account the formation of each one of the bonds connected to the chiral centre.

Crystal structures of human ADAMTS-1 reveal a conserved catalytic domain and a disintegrin-like domain with a fold homologous to cysteine-rich domains

The ADAMTS (a disintegrin-like and metalloproteinase domain with thrombospondin type I motifs) family of proteases plays a role in pathological conditions including arthritis, cancer, thrombotic thrombocytopenic purpura and the Ehlers-Danlos type VIIC and Weill-Marchesani genetic syndromes. Here, we report the first crystal structures for a member of the ADAMTS family, ADAMTS-1. Originally cloned as an inflammation-associated gene, ADAMTS-1 has been shown to be involved in tissue remodelling, wound healing and angiogenesis. The crystal structures contain catalytic and disintegrin-like domains, both in the inhibitor-free form and in complex with the inhibitor marimastat. The overall fold of the catalytic domain is similar to related zinc metalloproteinases such as matrix metalloproteinases and ADAMs (a disintegrin and metalloproteinases). The active site contains the expected organisation of residues to coordinate zinc but has a much larger S1' selectivity pocket than ADAM33. The structure also unexpectedly reveals a double calcium-binding site. Also surprisingly, the previously named disintegrin-like domain showed no structural homology to the disintegrin domains of other metalloproteinases such as ADAM10 but is instead very similar in structure to the cysteine-rich domains of other metalloproteinases. Thus, this study suggests that the D (for disintegrin-like) in the nomenclature of ADAMTS enzymes is likely to be a misnomer. The ADAMTS-1 cysteine-rich domain stacks against the active site, suggesting a possible regulatory role.

Novel hydroxamic acid-related phosphinates: inhibition of neutral aminopeptidase N (APN)

Here we describe the inhibitory activity toward neutral aminopeptidase of three new families of phosphinate inhibitors related in structure to hydroxamic acids. These compounds, even as racemic mixtures, are good inhibitors of APN and show strong structure activity relationship (SAR) depending on the substituents in P1 and P1' positions.

α-Biphenylsulfonylamino 2-methylpropyl phosphonates: Enantioselective synthesis and selective inhibition of MMPs

(R)-alpha-Biphenylsulfonylamino 2-methylpropyl phosphonates attain nM potency against several MMPs and are the most effective inhibitors based on phosphonate as zinc binding group. Since their preparation by direct N-acylation of expensive, enantiopure, alpha-aminophosphonic acids proceeds in low yields, we devised and evaluated a stereoselective and straightforward method of synthesis that avoids the unfavourable step of N-acylation. The key intermediate (R)-4-bromophenylsulfonylamino 2-methylpropyl phosphonate 9 was obtained by highly stereoselective addition of dibenzylphosphite to the enantiopure (S)-N-isobutylidene-p-bromobenzenesulfinamide 3, followed by oxidation with m-CPBA. Suzuki coupling of 9 with the desired arylboronic acids, gave the expected biphenylsulfonylamino derivatives in satisfactory yields. Liberation of the phosphonic group by hydrogenolysis led to the desired (R)-alpha-biphenylsulfonylamino 2-methylpropyl phosphonates 14a-i. Screening of the new compounds on MMP-1, -2, -3, -7, -8, -9, -13 and -14 showed IC(50) in the range of nM in most cases.

Human neutrophil elastase and collagenase sequestration with phosphorylated cotton wound dressings

The design and preparation of wound dressings that redress the protease imbalance in chronic wounds is an important goal of wound healing and medical materials science. Chronic wounds contain high levels of tissue and cytokine-destroying proteases including matrix metalloprotease and neutrophil elastase. Thus, the lowering of excessive protease levels in the wound environment by wound dressing sequestration prevents the breakdown of extracellular matrix proteins and growth factors necessary for wound healing. Phosphorylated cotton wound dressings were prepared to target sequestration of proteases from chronic wound exudate through a cationic uptake binding mechanism involving salt bridge formation of the positively charged amino acid side chains of proteases with the phosphate counterions of the wound dressing fiber. Dressings were prepared by applying sodium hexametaphosphate and diammonium phosphate in separate formulations to cotton gauze by pad/dry/cure methods. Phosphorylated cotton dressings were assessed for their ability to lower elastase and collagenase activity. The phosphorylated cotton dressings lowered elastase and collagenase activity 40-80% more effectively than the untreated cotton wound dressings under conditions that mimic chronic wound exudate. Efficacy of the phosphorylated cotton was found to be related to the level of phosphorylation and a lower pH due to protonated phosphate at the surface of the dressing. The capacity of the modified gauze to sequester continued elastase secretions similar to that found in a chronic wound over a 24-h period was retained within a 80% retention of elastase sequestration and was dose-dependent.

Stereoselectivity by Enantiomeric Inhibitors of Matrix Metalloproteinase-8: New Insights from Molecular Dynamics Simulations

Molecular Dynamics simulations in aqueous solution were performed for the matrix metalloproteinase-8 (MMP-8) free catalytic domain and for its complexes with the (R)- and (S)-[1-(4'-methoxybiphenyl-4-sulfonylamino)-2-methylpropyl] phosphonate. The 144-155 loop of the enzyme undergoes a drastic decrease of mobility once complexed with both enantiomers. The two enantiomers induce a different decrease of conformational entropy upon complexation. The higher affinity of the R-enantiomer can be related to the lower loss of conformational entropy accompanying its binding. The differences in the dynamical behavior of the protein induced by the two enantiomers are discussed at molecular level and the mode of binding of the simulated complexes is compared with that previously determined by X-ray crystallography.

Recent advances in MMP inhibitor design

The search for an MMP inhibitor with anticancer efficacy is a nearly three-decade endeavor. This inhibitor is yet to be found. The reasons for this failure include shortcomings in the chemistry of these compounds (including broad MMP sub-type selectivity, metabolic lability, and toxicity) as well as the emerging, and arguably extraordinary, complexity of MMP cell (and cancer) biology. Together these suggest that the successful anticancer inhibitor must possess MMP selectivity against the MMP subtype whose involvement is critical, yet highly temporally (with respect to metastatic progression) and mechanistically (with respect to matrix degradation) regulated. This review summarizes the progression of chemical structure and mechanistic thinking toward these objectives, with emphasis on the disappointment, the perseverance, and the resilient optimism that such an inhibitor is there to be discovered.