Substituted Pyridazin-3(2 H)-ones as Highly Potent and Biased Formyl Peptide Receptor Agonists.

Herein we describe the development of a focused series of functionalized pyridazin-3(2 H)-one-based formyl peptide receptor (FPR) agonists that demonstrate high potency and biased agonism. The compounds described demonstrated biased activation of prosurvival signaling, ERK1/2 phosphorylation, through diminution of the detrimental FPR1/2-mediated intracellular calcium (Cai2+) mobilization. Compound 50 showed an EC50 of 0.083 µM for phosphorylation of ERK1/2 and an approximate 20-fold bias away from Cai2+ mobilization at the hFPR1.

Clickable Photoaffinity Ligands for Metabotropic Glutamate Receptor 5 Based on Select Acetylenic Negative Allosteric Modulators.

G protein-coupled receptors (GPCRs) represent the largest class of current drug targets. In particular, small-molecule allosteric modulators offer substantial potential for selectively "tuning" GPCR activity. However, there remains a critical need for experimental strategies that unambiguously determine direct allosteric ligand-GPCR interactions, to facilitate both chemical biology studies and rational structure-based drug design. We now report the development and use of first-in-class clickable allosteric photoprobes for a GPCR based on metabotropic glutamate receptor 5 (mGlu5) negative allosteric modulator (NAM) chemotypes. Select acetylenic mGlu5 NAM lead compounds were rationally modified to contain either a benzophenone or an aryl azide as a photoreactive functional group, enabling irreversible covalent attachment to mGlu5 via photoactivation. Additionally, a terminal alkyne or an aliphatic azide was incorporated as a click chemistry handle, allowing chemoselective attachment of fluorescent moieties to the irreversibly mGlu5-bound probe via tandem photoaffinity labeling-bioorthogonal conjugation. These clickable photoprobes retained submicromolar affinity for mGlu5 and negative cooperativity with glutamate, interacted with the "common allosteric-binding site," displayed slow binding kinetics, and could irreversibly label mGlu5 following UV exposure. We depleted the number of functional mGlu5 receptors using an irreversibly bound NAM to elucidate and delineate orthosteric agonist affinity and efficacy. Finally, successful conjugation of fluorescent dyes via click chemistry was demonstrated for each photoprobe. In the future, these clickable photoprobes are expected to aid our understanding of the structural basis of mGlu5 allosteric modulation. Furthermore, tandem photoaffinity labeling-bioorthogonal conjugation is expected to be a broadly applicable experimental strategy across the entire GPCR superfamily.

De-novo designed library of benzoylureas as inhibitors of BCL-XL: synthesis, structural and biochemical characterization.

The prosurvival BCL-2 proteins are attractive yet challenging targets for medicinal chemists. Their involvement in the initiation and progression of many, if not all, tumors makes them prime targets for developing new anticancer therapies. We present our approach based on de novo structure-based drug design. Using known structural information from complexes engaging opposing members of the BCL-2 family of proteins, we designed peptidomimetic compounds using a benzoylurea scaffold to reproduce key interactions between these proteins. A library stemming from the initial de novo designed scaffold led to the discovery of ligands with low micromolar potency (KD = 4 µM) and selectivity for BCL-XL. These compounds bind in the canonical BH3 binding groove in a binding mode distinct from previously known BCL-2 inhibitors. The results of our study provide insight into the design of a new class of antagonists targeting a challenging class of protein-protein interactions.

Strategies for the development of conotoxins as new therapeutic leads.

Peptide toxins typically bind to their target ion channels or receptors with high potency and selectivity, making them attractive leads for therapeutic development. In some cases the native peptide as it is found in the venom from which it originates can be used directly, but in many instances it is desirable to truncate and/or stabilize the peptide to improve its therapeutic properties. A complementary strategy is to display the key residues that make up the pharmacophore of the peptide toxin on a non-peptidic scaffold, thereby creating a peptidomimetic. This review exemplifies these approaches with peptide toxins from marine organisms, with a particular focus on conotoxins.

De novo design and synthesis of a µ-conotoxin KIIIA peptidomimetic.

µ-Conotoxin KIIIA blocks voltage-gated sodium channels and displays potent analgesic activity in mice models for pain. Structure-activity studies with KIIIA have shown that residues important for sodium channel activity are presented on an α-helix. Herein, we report the de novo design and synthesis of a three-residue (Lys7, Trp8, His12) peptidomimetic based on a novel diketopiperazine (DKP) carboxamide scaffold.

Synthesis of conformationally constrained benzoylureas as BH3-mimetics.

The design of small molecules that mimic the BH3 domain and bind to Bcl-2 proteins has emerged as a promising approach to discovering novel anti-cancer therapeutics. We reveal the design and synthesis of conformationally constrained benzoylurea scaffolds as conformational probes. Central to helix mimicry, the intramolecular hydrogen bond in the benzoylurea plays a key role in the pre-organisation of the acyclic substrates for cyclisation via ring closing metathesis, providing efficient access to the constrained mimetics.

Benzoylureas as removable cis amide inducers: synthesis of cyclic amides via ring closing metathesis (RCM).

Rapid and high yielding synthesis of medium ring lactams was made possible through the use of a benzoylurea auxiliary that serves to stabilize a cisoid amide conformation, facilitating cyclization. The auxiliary is released after activation under the mild conditions required to deprotect a primary amine, such as acidolysis of a Boc group in the examples given here. This methodology is a promising tool for the synthesis of medium ring lactams, macrocyclic natural products and peptides.