Novel, potent P2–P3 pyrrolidine derivatives of ketoamide-based cathepsin K inhibitors

Synthesis, spectroscopic investigation, molecular docking and DFT studies of novel (2Z,4Z)-2,4-bis(4-chlorobenzylidene)-5-oxo-1-phenylpyrrolidine-3-carboxylic acid (BCOPCA)

The synthesized compound (2Z,4Z)-2,4-bis(4-chlorobenzylidene)-5-oxo-1-phenylpyrrolidine-3-carboxylic acid (BCOPCA) was characterised by Ultraviolet, FT-Infra Red, ¹H, ¹³C Nuclear Magnetic Resonance and mass spectroscopy. The compound was further subjected to quantum chemical calculations at the level of density functional theory (DFT) using 6-31G (d,p) basis sets method with B3LYP and CAM-B3LYP hybrid functionals. The intramolecular interactions, polarizability, hyperpolarizability and nonlinear optical properties of the title compound were also incorporated in the study. The total first static hyperpolarizability (β₀ = 19.477 × 10⁻³⁰ and 16.924 × 10⁻³⁰ esu) value was also computed and indicated the title molecule as an interesting forthcoming NLO material. The other thermodynamic properties (entropy, heat capacity and zero vibrational energy) were also discussed. The study also includes NBO computations, complete vibrational assignments, Mulliken charges, UV–Visible spectral analysis and HOMO–LUMO energies. The regions of low and high electron density were obtained from MESP and ESP maps. The calculated parameters for BCOPCA using aforementioned functions are harmonious with the experimental findings. The in-vitro antimicrobial activity and molecular docking studies of BCOPCA were also done and showed a good correlation.

Structure-based virtual screening approach for discovery of covalently bound ligands

We present a fast and effective covalent docking approach suitable for large-scale virtual screening (VS). We applied this method to four targets (HCV NS3 protease, Cathepsin K, EGFR, and XPO1) with known crystal structures and known covalent inhibitors. We implemented a customized "VS mode" of the Schrödinger Covalent Docking algorithm (CovDock), which we refer to as CovDock-VS. Known actives and target-specific sets of decoys were docked to selected X-ray structures, and poses were filtered based on noncovalent protein-ligand interactions known to be important for activity. We were able to retrieve 71%, 72%, and 77% of the known actives for Cathepsin K, HCV NS3 protease, and EGFR within 5% of the decoy library, respectively. With the more challenging XPO1 target, where no specific interactions with the protein could be used for postprocessing of the docking results, we were able to retrieve 95% of the actives within 30% of the decoy library and achieved an early enrichment factor (EF1%) of 33. The poses of the known actives bound to existing crystal structures of 4 targets were predicted with an average RMSD of 1.9 Å. To the best of our knowledge, CovDock-VS is the first fully automated tool for efficient virtual screening of covalent inhibitors. Importantly, CovDock-VS can handle multiple chemical reactions within the same library, only requiring a generic SMARTS-based predefinition of the reaction. CovDock-VS provides a fast and accurate way of differentiating actives from decoys without significantly deteriorating the accuracy of the predicted poses for covalent protein-ligand complexes. Therefore, we propose CovDock-VS as an efficient structure-based virtual screening method for discovery of novel and diverse covalent ligands.

Application of EMBM to Structure-Based Design of Warheads for Protease Inhibitors

Most CADD tools handle non-covalent enzyme inhibitors, despite the growing interest of the pharma industry in covalent inhibitors. We have recently introduced an enzyme mechanism-based method, EMBM, as a computational tool for binding trend analysis and prediction of chemical sites (CS) of reversible covalent enzyme inhibitors. In the current study we demonstrate the utility of EMBM to structure-based applications. In this mode, the energy of the enzyme-inhibitor covalent bond is accounted for by the W1 and W2 covalent descriptors we have developed, whereas the non-covalent interactions between the inhibitor CS and the enzyme active site can be estimated directly on the 3D structure of the enzyme-inhibitor complex.

Convergent synthesis of alpha-ketoamide inhibitors of Pin1

A convergent synthesis of alpha-ketoamide inhibitors of Pin1 is described. An alpha-hydroxyorthothioester derivative of Ser was reacted directly with an amine synthon. The reaction was catalyzed by HgO and HgCl(2) to form alpha-hydroxyamide. Thus, hydrolysis and coupling were combined in one step with 80% yield. Two diastereomers of a phospho-Ser-Pro alpha-ketoamide analogue were synthesized. The IC(50) values of 100 and 200 microM were surprisingly weak for Pin1 peptidyl prolyl isomerase.

Biochemical properties and regulation of cathepsin K activity

Cysteine cathepsins (11 in humans) are mostly located in the acidic compartments of cells. They have been known for decades to be involved in intracellular protein degradation as housekeeping proteases. However, the discovery of new cathepsins, including cathepsins K, V and F, has provided strong evidence that they also participate in specific biological events. This review focuses on the current knowledge of cathepsin K, the major bone cysteine protease, which is a drug target of clinical interest. Nevertheless, we will not discuss recent developments in cathepsin K inhibitor design since they have been extensively detailed elsewhere. We will cover features of cathepsin K structure, cellular and tissue distribution, substrate specificity, and regulation (pH, propeptide, glycosaminoglycans, oxidants), and its putative roles in physiological or pathophysiological processes. Finally, we will review the kinetic data of its inhibition by natural endogenous inhibitors (stefin B, cystatin C, H- and L-kininogens).

Enantiomeric separation and determination of absolute stereochemistry of asymmetric molecules in drug discovery—Building chiral technology toolboxes

The application of Chiral Technology, or the (extensive) use of techniques or tools for the determination of absolute stereochemistry and the enantiomeric or chiral separation of racemic small molecule potential lead compounds, has been critical to successfully discovering and developing chiral drugs in the pharmaceutical industry. This has been due to the rapid increase over the past 10-15 years in potential drug candidates containing one or more asymmetric centers. Based on the experiences of one pharmaceutical company, a summary of the establishment of a Chiral Technology toolbox, including the implementation of known tools as well as the design, development, and implementation of new Chiral Technology tools, is provided.