Identification of highly potent and selective PI3Kδ inhibitors

Selective PI3Kδ inhibitors have recently been hypothesized to be appropriate immunosuppressive agents for the treatment of immunological disorders such as rheumatoid arthritis. However, few reports have highlighted molecules that are highly selective for PI3Kδ over the other PI3K isoforms. In this letter, isoform and kinome selective PI3Kδ inhibitors are presented. The Structural Activity Relationship leading to such molecules is outlined.     

Identification of GNE-293, a potent and selective PI3Kδ inhibitor: Navigating in vitro genotoxicity while improving potency and selectivity

In an effort to identify potent and isoform selective inhibitors of PI3Kδ, GNE-293 (34) was identified. Inhibitor 2 was found to induce micronuclei formation in both the MNT and HCA in vitro assays. Compounds testing negative for genotoxicity were successfully identified through modifications of the 2-benzimidazole substituent and the methylene moiety to disrupt planarity. A variety of heteroatom linkers were explored to examine their effect on potency and isoform selectivity by restricting torsional angles to favor ligand interactions with PI3Kδ’s Trp760. These modifications also resulted in an improved in vivo pharmacokinetic profile.     

Discovery of potent and orally bioavailable 17β-hydroxysteroid dehydrogenase type 3 inhibitors

We have previously reported the discovery of a new class of potent inhibitors of 17β-hydroxysteroid dehydrogenase type 3 (17β-HSD3) derived from benzylidene oxazolidinedione and thiazolidinedione scaffolds. In this study, these analogs were designed, synthesized, and evaluated in a human cell-based assay. The detailed structure-activity relationship (SAR) surrounding this pharmacophore were developed, and consequently a number of compounds from this series demonstrated single-digit nanomolar 17β-HDS3 inhibitory activity in vitro. Subsequent optimization work in pursuit of the improvement of oral bioavailability demonstrated in vivo proof-of-concept by prodrug strategy based on phosphate esters for these 17β-HSD3 inhibitors. When a phosphate ester 16 was administered orally at a high dose of 100mg/kg, 16 showed approximately two times more potent testosterone (T)-lowering effect against a positive control in the luteinizing hormone-releasing hormone (LH-RH)-induced T production assay. The T-lowering effect continued at ca 10% level of control over 4h after administration. The nonsteroidal molecules based on this series have the potential to provide unique and effective clinical opportunities for treatment of prostate cancer.     

Optimization and in vivo evaluation of pyrazolopyridines as a potent and selective PI3Kδ inhibitor

Chemical optimization of pyrazolopyridine 1, focused on cellular potency, isoform selectivity and microsomal stability, led to the discovery of the potent, selective and orally available PI3Kδ inhibitor 5d. On the basis of its desirable potency, selectivity and pharmacokinetic profiles, 5d was tested in the trinitrophenylated aminoethylcarboxymethyl-Ficoll (TNP-Ficoll)-induced antibody production model, and showed higher antibody inhibition than a 4-fold oral dose of the starting compound 1. These excellent results suggest that 5d is a potential candidate for further studies in the treatment of autoimmune diseases and leukocyte malignancies.     

Identification of the first potent,selective and bioavailable PPARα antagonist

The discovery and SAR of a novel series of potent and selective PPARα antagonists are herein described. Exploration of replacements for the labile acyl sulfonamide linker led to a biaryl sulfonamide series of which compound 33 proved to be suitable for further profiling in vivo. Compound 33 demonstrated excellent potency, selectivity against other nuclear hormone receptors, and good pharmacokinetics in mouse.     

Design and synthesis of a novel pyrrolidinyl pyrido pyrimidinone derivative as a potent inhibitor of PI3Kα and mTOR

Lead optimization efforts that employed structure base drug design and physicochemical property based optimization leading to the discovery of a novel series of 4-methylpyrido pyrimidinone (MPP) are discussed. Synthesis and profile of 1, a PI3Kα/mTOR dual inhibitor, is highlighted.     

Discovery and biological evaluation of novel pyrazolopyridine derivatives as potent and orally available PI3Kδ inhibitors

Phosphatidylinositol-3-kinase (PI3K)δ inhibition is one of the most attractive approaches to the treatment of autoimmune diseases and leukocyte malignancies. Through the exploration of pyrazolopyridine derivatives as potential PI3Kδ inhibitors, compound 12a was identified as a potent PI3Kδ inhibitor but suffered from poor oral exposure in mice. With a modified amide linkage group, compound 15a was developed as an orally available PI3Kδ inhibitor with reduced selectivity against other PI3Ks. To improve the trade-off between selectivity and PK profile, structure–activity relationship (SAR) studies of terminal substituents on the pyrolidine ring were conducted. As a result, we developed potent PI3Kδ inhibitors with good oral availability. In particular, the representative compound 15j showed excellent selectivity for PI3Kδ over other PI3Ks with good oral exposure in mice.     

Virtual ligand screening of α-glucosidase: Identification of a novel potent noncarbohydrate mimetic inhibitor

5-Thiazoleacetamide derivatives of AR122 and AR125 were screened as α-glucosidase inhibitors by in silico high-throughput screening from commercial drug-like small compound libraries. Inhibition of α-glucosidase with AR122 and AR125 is time dependent: with no preincubation, AR122 and AR125 are relatively moderate inhibitors, but interestingly, after a 120 min incubation, they were 50-fold more potent (AR122: IC(50)=2.47 μM and AR125: IC(50)=27.1 μM). Plots of ln [residual α-glucosidase activity %] versus preincubation time show a pseudo-first order kinetics for both inhibitors. Through dialysis of enzyme-inhibitor complexes, no activity recovery was shown. These results suggest that AR122 and AR125 constitute a new class of noncarbohydrate mimetic inhibitor with an irreversible mechanism.     

Discovery and lead optimisation of a potent,selective and orally bioavailable RARβ agonist for the potential treatment of nerve injury

Oxadiazole replacement of an amide linkage in an RARα agonist template 1, followed by lead optimisation, has produced a highly potent and selective RARβ agonist 4-(5-(4,7-dimethylbenzofuran-2-yl)-1,2,4-oxadiazol-3-yl)benzoic acid (10) with good oral bioavailability in the rat and dog. This molecule increases neurite outgrowth in vitro and induces sensory axon regrowth in vivo in a rodent model of avulsion and crush injury, and thus has the potential for the treatment of nerve injury.     

Discovery of potent and bioavailable GSK-3β inhibitors

Here we report on the discovery of a series of maleimides which have high potency and good selectivity for GSK-3β. The incorporation of polar groups afforded compounds with good bioavailability. The most potent compound 34 has an IC₅₀ of 0.6 nM for GSK-3β, over 100-fold selectivity against a panel of other kinases, and shows efficacy in rat osteoporosis models. The X-ray structure of GSK-3β protein with 34 bound revealed the binding mode of the template and provided insights for future optimization opportunities.     

Discovery of O6-benzyl glaziovianin A,a potent cytotoxic substance and a potent inhibitor of α,β-tubulin polymerization

We have discovered O⁶-benzyl glaziovianin A, which showed stronger inhibition of microtubule polymerization (IC₅₀ = 2.1 μM) than known α,β-tubulin inhibitors, such as colchicine and glaziovianin A. Also, we performed competition binding experiments of O⁶-benzyl glaziovianin A and revealed that O⁶-benzyl glaziovianin A binds to the colchicine binding site with high affinity. It is interesting that glaziovianin A derivatives change their mode of action in benzylation at the O⁶ (α,β-tubulin inhibitor) or O⁷ (γ-tubulin-specific inhibitor) position.     

Identification of potent,selective and orally bioavailable phenyl ((R)-3-phenylpyrrolidin-3-yl)sulfone analogues as RORγt inverse agonists

An X-ray crystal structure of one of our previously discovered RORγt inverse agonists bound to the RORγt ligand binding domain revealed that the cyclohexane carboxylic acid group of compound 2 plays a significant role in RORγt binding, forming four hydrogen bonding and ionic interactions with RORγt. SAR studies centered around the cyclohexane carboxylic acid group led to identification of several structurally diverse and more potent compounds, including new carboxylic acid analogues 7 and 20, and cyclic sulfone analogues 34 and 37. Notably, compounds 7 and 20 were found to maintain the desirable pharmacokinetic profile of 2.     

Discovery of a potent,selective, and orally bioavailable histamine H3 receptor antagonist SAR110068 for the treatment of sleep–wake disorders

Previous studies have shown that compound 1 displayed high affinity towards histamine H₃ receptor (H₃R), (human (h-H₃R), K_i = 8.6 nM, rhesus monkey (rh-H₃R), K_i = 1.2 nM, and rat (r-H₃R), K_i = 16.5 nM), but exhibited high affinity for hERG channel. Herein, we report the discovery of a novel, potent, and highly selective H₃R antagonist/inverse agonist 5a(SS) (SAR110068) with acceptable hERG channel selectivity and desirable pharmacological and pharmacokinetic properties through lead optimization sequence. The significant awakening effects of 5a(SS) on sleep–wake cycles studied by using EEG recording in rats during their light phase support its potential therapeutic utility in human sleep–wake disorders.     

Synthesis of benzothiazole derivatives as a potent α-glucosidase inhibitor

Diabetes is one of the pre-dominant metabolic disorders all over the world. It is the prime reason of mortality and morbidity due to hyperglycemia which is link with numerus obstacles. Delaying absorption and digestion of carbohydrate has great therapeutic impact for governing postprandial hyperglycemia. Consequently, alpha glucosidase is one of the potential therapeutic approaches that reduce absorption of glucose and delay carbohydrate digestion hence maintaining blood glucose level. In this regard we have synthesized benzothiazole based oxadiazole in search of potent anti-diabetic agent as α-glucosidase Inhibitors. Benzothiazole based oxadiazole derivatives 1–23 have been synthesized, characterized by ¹HNMR, ¹³CNMR, and MS and evaluated for α-glucosidase Inhibition. All analogs exhibited a varying degree of α-glucosidase inhibitory activity with IC₅₀ values ranging in between 0.5 ± 0.01–30.90 ± 0.70 μM when compared with the standard acarbose (IC₅₀ = 866.30 ± 3.20 μM). Structure activity relationship has been established for all compounds. Molecular docking studies were performed to predict the binding interaction of the compounds with the active site of enzyme.     

Identification of DK419, a potent inhibitor of Wnt/β-catenin signaling and colorectal cancer growth

The Wnt signaling pathway is critical for normal tissue development and is an underlying mechanism of disease when dysregulated. Previously, we reported that the drug Niclosamide inhibits Wnt/β-catenin signaling by decreasing the cytosolic levels of Dishevelled and β-catenin, and inhibits the growth of colon cancers both in vitro and in vivo. Since the discovery of Niclosamide’s anthelmintic activity, a growing body of literature indicates that Niclosamide is a multifunctional drug. In an effort to identify derivatives of Niclosamide with improved pharmacokinetic properties that maintain the multifunctional drug activity of Niclosamide for clinical evaluation, we designed DK419, a derivative containing a 1H-benzo[d]imidazole-4-carboxamide substructure, using the structure-activity relationships (SAR) of the Niclosamide salicylanilide chemotype. Similar to Niclosamide, we found DK419 inhibited Wnt/β-catenin signaling, altered cellular oxygen consumption rate and induced production of pAMPK. Moreover, we found DK419 inhibited the growth of CRC tumor cells in vitro, had good plasma exposure when dosed orally, and inhibited the growth of patient derived CRC240 tumor explants in mice dosed orally. DK419, a derivative of Niclosamide with multifunctional activity and improved pharmacokinetic properties, is a promising agent to treat colorectal cancer, Wnt-related diseases and other diseases in which Niclosamide has demonstrated functional activity.     

Discovery of a series of potent,orally active α,α-disubstituted piperidine NK1 antagonists

Modification of prototype NK₁ antagonist 2 resulted in the synthesis of a series of simple amides 6 and retroamides 9. These compounds were shown to be potent and orally active NK₁ antagonists.     

Discovery of potent,selective, and orally bioavailable 3H-spiro[isobenzofuran-1,4′-piperidine] based melanocortin subtype-4 receptor agonists

Design, synthesis, and SAR of a series of 3H-spiro[isobenzofuran-1,4′-piperidine] based compounds as potent, selective and orally bioavailable melanocortin subtype-4 receptor (MC4R) agonists are disclosed.     

Discovery of triazole aminopyrazines as a highly potent and selective series of PI3Kδ inhibitors

A novel class of potent PI3Kδ inhibitors with >1000-fold selectivity against other class I PI3K isoforms is described. Optimization of the substituents on a triazole aminopyrazine scaffold, emerging from an in-house PI3Kα program, turned moderately selective PI3Kδ compounds into highly potent and selective PI3Kδ inhibitors. These efforts resulted in a series of aminopyrazines with PI3Kδ IC₅₀ ? 1 nM in the enzyme assay, some of the most selective PI3Kδ inhibitors published to date, with a cell potency in a JeKo-cell assay of 20–120 nM.     

SAR studies around a series of triazolopyridines as potent and selective PI3Kγ inhibitors

Herein we describe the SAR of a novel series of 6-aryl-2-amino-triazolopyridines as potent and selective PI3Kγ inhibitors. The 6-aryl-triazolopyridine core was identified by chemoproteomic screening of a kinase focused library. Rapid chemical expansion around a bi-functional core identified the key features required for PI3Kγ activity and selectivity. The series was optimized to afford 43 (CZC19945), a potent PI3Kγ inhibitor with high oral bioavailability and selectivity over PI3Kα and PI3Kδ. Modification to the core afforded 53 (CZC24832) which showed increased selectivity over the entire kinome in particular over PI3Kβ.