N-acyl-L-phenylalanine derivatives as potent VLA-4 antagonists that mimic a cyclic peptide conformation

Galantamine-Curcumin Hybrids as Dual-Site Binding Acetylcholinesterase Inhibitors

Galantamine (GAL) and curcumin (CU) are alkaloids used to improve symptomatically neurodegenerative conditions like Alzheimer's disease (AD). GAL acts mainly as an inhibitor of the enzyme acetylcholinesterase (AChE). CU binds to amyloid-beta (Aβ) oligomers and inhibits the formation of Aβ plaques. Here, we combine GAL core with CU fragments and design a combinatorial library of GAL-CU hybrids as dual-site binding AChE inhibitors. The designed hybrids are screened for optimal ADME properties and BBB permeability and docked on AChE. The 14 best performing compounds are synthesized and tested in vitro for neurotoxicity and anti-AChE activity. Five of them are less toxic than GAL and CU and show activities between 41 and 186 times higher than GAL.

Role of integrin alpha4 in drug resistance of leukemia

Chemotherapeutic drug resistance in acute lymphoblastic leukemia (ALL) is a significant problem, resulting in poor responsiveness to first-line treatment or relapse after transient remission. Classical anti-leukemic drugs are non-specific cell cycle poisons; some more modern drugs target oncogenic pathways in leukemia cells, although in ALL these do not play a very significant role. By contrast, the molecular interactions between microenvironment and leukemia cells are often neglected in the design of novel therapies against drug resistant leukemia. It was shown however, that chemotherapy resistance is promoted in part through cell–cell contact of leukemia cells with bone marrow (BM) stromal cells, also called cell adhesion-mediated drug resistance (CAM-DR). Incomplete response to chemotherapy results in persistence of resistant clones with or without detectable minimal residual disease (MRD). Approaches for how to address CAM-DR and MRD remain elusive. Specifically, studies using anti-functional antibodies and genetic models have identified integrin alpha4 as a critical molecule regulating BM homing and active retention of normal and leukemic cells. Pre-clinical evidence has been provided that interference with alpha4-mediated adhesion of ALL cells can sensitize them to chemotherapy and thus facilitate eradication of ALL cells in an MRD setting. To this end, Andreeff and colleagues recently provided evidence of stroma-induced and alpha4-mediated nuclear factor-κB signaling in leukemia cells, disruption of which depletes leukemia cells of strong survival signals. We here review the available evidence supporting the targeting of alpha4 as a novel strategy for treatment of drug resistant leukemia.

Modeling the molecular basis for α4β1 integrin antagonism

We report a 3D QSAR study of almost 300 structurally diverse small molecule antagonists of the integrin α4β1 whose biological activity spans six orders of magnitude. The alignment of the molecules was based on the conformation of a structurally related ligand bound to the αIIBβ3 and αvβ3 integrins in X-ray crystallographic studies. The molecular field method, CoMSIA, was used to generate the 3D QSAR models. The resulting models showed that the lipophilic properties were the most important, with hydrogen bond donor and steric properties less relevant. The models were highly significant (r(2)=0.89, q2(LOO)=0.67, r(2) (test set)=0.76), and could make robust predictions of the data (SEE=0.46, SEP=0.78, SEP (test set)=0.66). We predicted the antagonist activities of a further ten compounds with useful accuracy. The model appears capable of predicting α4β1 integrin antagonist activity to within a factor of five for compounds within its domain of applicability. The implications for design of improved integrin antagonists will be discussed.

A general method for discovering inhibitors of protein-DNA interactions using photonic crystal biosensors

Protein-DNA interactions are essential for fundamental cellular processes such as transcription, DNA damage repair, and apoptosis. As such, small molecule disruptors of these interactions could be powerful tools for investigation of these biological processes, and such compounds would have great potential as therapeutics. Unfortunately, there are few methods available for the rapid identification of compounds that disrupt protein-DNA interactions. Here we show that photonic crystal (PC) technology can be utilized to detect protein-DNA interactions, and can be used in a high-throughput screening mode to identify compounds that prevent protein-DNA binding. The PC technology is used to detect binding between protein-DNA interactions that are DNA-sequence-dependent (the bacterial toxin-antitoxin system MazEF) and those that are DNA-sequence-independent (the human apoptosis inducing factor (AIF)). The PC technology was further utilized in a screen for inhibitors of the AIF-DNA interaction, and through this screen aurin tricarboxylic acid was identified as the first in vitro inhibitor of AIF. The generality and simplicity of the photonic crystal method should enable this technology to find broad utility for identification of compounds that inhibit protein-DNA binding.

Expedient synthesis of N-Z-pyroglutamyl-amino acid derivatives

N-Z-pyroglutamyl pseudopeptides 3a-c are shown to be conveniently prepared from glutamyl-bis-Bt 1a by cyclization of an N-terminal glutamic acid residue. Structures are supported by 2D NMR studies and by comparison with the same products prepared by direct coupling of the C-terminus activated N-pGlu 1b and free amino acids 2a-c.

Protein-protein interactions as targets for small molecule drug discovery

Protein-protein interactions represent a highly populated class of targets for drug discovery. However, such systems present a number of unique challenges. This review presents an analysis of individual protein-protein interaction systems which have recently yielded success in discovering drug-like inhibitors. The structural characteristics of the protein binding sites and the attributes of the small molecule ligands are focused upon, in an attempt to derive commonly shared principles that may be of general usefulness in future drug discovery efforts within this target class.

2,6-Quinolinyl derivatives as potent VLA-4 antagonists

A new series of 2,6-quinolinyl derivatives was prepared leading to potent low nanomolar VLA-4/VCAM-1 antagonists.

2,3-Diphenylpropionic acids as potent VLA-4 antagonists

The discovery and SAR of 2,3-diphenylpropionic acid derivatives as highly potent VLA-4 antagonists are described. One representative compound, 9cc has inhibited intercellular adhesion by a VCAM-1/VLA-4 interaction with an IC(50) of 1.7 nM, and has good pharmacokinetics and oral bioavailability.

Efficient synthesis of 3-aminocyclobut-2-en-1-ones: squaramide surrogates as potent VLA-4 antagonists

A novel series of uniquely functionalized 3-aminocyclobut-2-en-1-ones has been prepared by facile condensation of a variety of cyclobuta-1,3-diones with a phenylalanine-derived primary amine. These systems subsequently lend themselves to substitution at C-2 by reaction with a variety of electrophilic reagents including N-halosuccinimides, sulfenyl chlorides, and Eschenmoser's salt. Compounds from this novel series are potent antagonists of VLA-4. [reaction: see text]

VLA-4 antagonists: potent inhibitors of lymphocyte migration

Circulating lymphocytes normally migrate through extravascular spaces in relatively low numbers as important members of the immunosurveillance process. That is until signals are received by endothelial cells that there is an underlying infection or inflammatory condition. These vascular surface cells in turn overexpress and present ligands to circulating lymphocyte adhesion molecules. Upon encountering this higher density of ligands, lymphocytes, which had been leisurely rolling along the vascular surface, now become more firmly attached, change shape, and migrate through tight junctions to the sites of infection or inflammation. If the initiating events are not resolved and the condition becomes chronic, there can be a sustained extravasation of lymphocytes that can exacerbate the inflammatory condition, which in turn will continue to recruit more inflammatory cells resulting in unwanted tissue destruction. It is for the attenuation of this cycle of sustained inflammatory cell recruitment that very late activating antigen-4 (VLA-4) antagonists are being developed. Most lymphocytes, except neutrophils, express VLA-4 on their surface and they interact with endothelial vascular cell adhesion molecule-1 (VCAM-1). It is this interaction that VLA-4 antagonists are intended to disrupt, thus, putting an end to the cycle of chronic inflammation, which is the hallmark of many diseases. This review will provide an update of VLA-4 antagonists that have appeared since early 2001 and will discuss some of the issues, both positive and negative, that may be encountered in their development.

Solid-phase synthesis of dual α4β1/α4β7 integrin antagonists: two scaffolds with overlapping pharmacophores

Two structural classes of dual alpha4beta1/alpha4beta7 integrin antagonists were investigated via solid-phase parallel synthesis. Using an acylated amino acid backbone, lead compounds containing biphenylalanine or tyrosine carbamate scaffolds were optimized for inhibition of alpha4beta1/VCAM and alpha4beta7/MAdCAM. A comparison of the structure-activity relationships in the inhibition of the alpha4beta7/MAdCAM interaction for substituted amines employed in both scaffolds suggests a similar binding mode for the compounds.

N-Aroyl-L-phenylalanine derivatives as VCAM/VLA-4 antagonists

A series of N-benzoyl-4-[(2,6-dichlorobenzoyl)amino]-L-phenylalanine derivatives was prepared in order to optimize the substitution on the N-benzoyl moiety for VCAM/VLA-4 antagonist activity. Disubstitution in the 2- and 6-positions is favored and a range of small alkyl and halogen are tolerated. A model of the bioactive conformation of these compounds is proposed.

Focused library approach for identification of new N-acylphenylalanines as VCAM/VLA-4 antagonists

A structure-based focused library approach was employed in an effort to identify more lipophilic replacements for the N-benzylpyroglutamyl group of the VCAM/VLA-4 antagonist 2. This effort led to the discovery of two new classes of potent antagonists characterized by the N-(alpha-phenylcyclopentanoyl- and the N-(2,6-dimethylbenzoyl)-derivatives 60 and 64.