Synthesis, SAR and evaluation of [1,4']-bipiperidinyl-4-yl-imidazolidin-2-one derivatives as novel CCR5 antagonists

Discovery of Novel CCR5 Ligands as Anticolorectal Cancer Agents by Sequential Virtual Screening

C-C chemokine receptor type 5 (CCR5) is a member of the G protein-coupled receptor. CCR5 and its interaction with chemokine ligands have been crucial for understanding and tackling human immunodeficiency virus (HIV)-1 entry into target cells. In recent years, the change in CCR5 expression has been related to the progression of different cancer types. Patients treated with the CCR5 ligand, maraviroc (MVC), showed a deceleration in tumor development especially for metastatic colorectal cancer. Based on the crystal structure of CCR5, we herein describe a multistage virtual screening protocol including pharmacophore screening, molecular docking, and protein-ligand interaction fingerprint (PLIF) postdocking filtration for discovery of novel CCR5 ligands. The applied virtual screening protocol led to the identification of four hits with binding modes showing access to the major and minor pockets of the MVC binding site. Compounds 2-4 showed a decrease in cellular proliferation upon testing on the metastatic colorectal cancer cell line, SW620, displaying 12, 16, and 4 times higher potency compared to MVC, respectively. Compound 3 induced apoptosis by arresting cells in the G0/G1 phase of the cell cycle similar to MVC. Further in vitro assays showed compound 3 drastically decreasing the CCR5 expression and cellular migration 48 h post treatment, indicating its ability to inhibit metastatic activity in SW620 cells. The discovered hits represent potential leads for the development of novel classes of anticolorectal cancer agents targeting CCR5.

Trial Watch-Small molecules targeting the immunological tumor microenvironment for cancer therapy

Progressing malignancies establish robust immunosuppressive networks that operate both systemically and locally. In particular, as tumors escape immunosurveillance, they recruit increasing amounts of myeloid and lymphoid cells that exert pronounced immunosuppressive effects. These cells not only prevent the natural recognition of growing neoplasms by the immune system, but also inhibit anticancer immune responses elicited by chemo-, radio- and immuno therapeutic interventions. Throughout the past decade, multiple strategies have been devised to counteract the accumulation or activation of tumor-infiltrating immunosuppressive cells for therapeutic purposes. Here, we review recent preclinical and clinical advances on the use of small molecules that target the immunological tumor microenvironment for cancer therapy. These agents include inhibitors of indoleamine 2,3-dioxigenase 1 (IDO1), prostaglandin E2, and specific cytokine receptors, as well as modulators of intratumoral purinergic signaling and arginine metabolism.

Conformational restriction: an effective tactic in 'follow-on'-based drug discovery

The conformational restriction (rigidification) of a flexible ligand has often been a commonly used strategy in drug design, as it can minimize the entropic loss associated with the ligand adopting a preferred conformation for binding, which leads to enhanced potency for a given physiological target, improved selectivity for isoforms and reduced the possibility of drug metabolism. Therefore, the application of conformational restriction strategy is a core aspect of drug discovery and development that is widely practiced by medicinal chemists either deliberately or subliminally. The present review will highlight current representative examples and a brief overview on the rational design of conformationally restricted agents as well as discuss its advantages over the flexible counterparts.

Design of substituted imidazolidinylpiperidinylbenzoic acids as chemokine receptor 5 antagonists: potent inhibitors of R5 HIV-1 replication

The redesign of the previously reported thiophene-3-yl-methyl urea series, as a result of potential cardiotoxicity, was successfully accomplished, resulting in the identification of a novel potent series of CCR5 antagonists containing the imidazolidinylpiperidinyl scaffold. The main redesign criteria were to reduce the number of rotatable bonds and to maintain an acceptable lipophilicity to mitigate hERG inhibition. The structure-activity relationship (SAR) that was developed was used to identify compounds with the best pharmacological profile to inhibit HIV-1. As a result, five advanced compounds, 6d, 6e, 6i, 6h, and 6k, were further evaluated for receptor selectivity, antiviral activity against CCR5 using (R5) HIV-1 clinical isolates, and in vitro and in vivo safety. On the basis of these results, 6d and 6h were selected for further development.

Asymmetric hydroamination catalyzed by in situ generated chiral amidate and ureate complexes of zirconium — Probing the role of the tether in ligand design

Simple chiral proligands have been synthesized from inexpensive chiral starting materials. These amidate and ureate ligands support zirconium complexes that successfully catalyze intramolecular hydroamination with up to 26% ee. Several elements necessary for successful ligand design are highlighted and discussed. In particular, the strict control of metal geometry through multidentate tethered ligands is determined to be an essential aspect of future ligand development.

Prospective CCR5 small molecule antagonist compound design using a combined mutagenesis/modeling approach

The viral resistance of marketed antiviral drugs including the emergence of new viral resistance of the only marketed CCR5 entry inhibitor, maraviroc, makes it necessary to develop new CCR5 allosteric inhibitors. A mutagenesis/modeling approach was used (a) to remove the potential hERG liability in an otherwise very promising series of compounds and (b) to design a new class of compounds with an unique mutant fingerprint profile depending on residues in the N-terminus and the extracellular loop 2. On the basis of residues, which were identified by mutagenesis as key interaction sites, binding modes of compounds were derived and utilized for compound design in a prospective manner. The compounds were then synthesized, and in vitro evaluation not only showed that they had good antiviral potency but also fulfilled the requirement of low hERG inhibition, a criterion necessary because a potential approved drug would be administered chronically. This work utilized an interdisciplinary approach including medicinal chemistry, molecular biology, and computational chemistry merging the structural requirements for potency with the requirements of an acceptable in vitro profile for allosteric CCR5 inhibitors. The obtained mutant fingerprint profiles of CCR5 inhibitors were used to translate the CCR5 allosteric binding site into a general pharmacophore, which can be used for discovering new inhibitors.

Gold(I)-Catalyzed Intramolecular Hydroamination of N-Allylic,N'-Aryl Ureas to form Imidazolidin-2-ones

Treatment of N-allylic,N'-aryl ureas with a catalytic 1:1 mixture of di-tert-butyl-o-biphenylphoshphine gold(I) chloride and silver hexafluorophosphate (1 mol %) in chloroform at room temperature led to 5-exo hydroamination to form the corresponding imidazolidin-2-ones in excellent yield. In the case of N-allylic ureas that possessed an allylic alkyl, benzyloxymethyl, or acetoxymethyl substituent, gold(I)-catalyzed 5-exo hydroamination leads to formation of the corresponding trans-3,4-disubstituted imidazolidin-2-ones in excellent yield with ≥50:1 diastereoselectivity.