Lead identification and structure-activity relationships of heteroarylpyrazole arylsulfonamides as allosteric CC-chemokine receptor 4 (CCR4) antagonists

Streamlined Synthesis of Diaminopyridines by Pd-Catalyzed Ammonia Coupling with Deactivated Amino-Chloropyridines

An efficient and cost-effective two-step synthesis of diaminopyridines, fundamental building blocks of biologically active compounds, is reported. The advantages over previously reported routes include cost and wider availability of the bromo-chloropyridine starting materials and the straightforward accessibility to an extended array of diaminopyridine regioisomers. The key enabler of this synthetic strategy is the development of an unprecedented palladium-catalyzed coupling reaction of ammonia with chloropyridines deactivated by the presence of an alkylamino substituent. The coupling reaction was accomplished with very low catalyst loadings under remarkably mild reaction conditions, making the system particularly suitable for both academic and industrial applications. The utility of this methodology is exemplified by the application to the synthesis of highly relevant scaffolds, including the synthetic intermediates of the marketed drugs Ribociclib and Palbociclib.

Allosteric Modulation of Class A GPCRs: Targets, Agents, and Emerging Concepts

G-protein-coupled receptors (GPCRs) have been tractable drug targets for decades with over one-third of currently marketed drugs targeting GPCRs. Of these, the class A GPCR superfamily is highly represented, and continued drug discovery for this family of receptors may provide novel therapeutics for a vast range of diseases. GPCR allosteric modulation is an innovative targeting approach that broadens the available small molecule toolbox and is proving to be a viable drug discovery strategy, as evidenced by recent FDA approvals and clinical trials. Numerous class A GPCR allosteric modulators have been discovered recently, and emerging trends such as the availability of GPCR crystal structures, diverse functional assays, and structure-based computational approaches are improving optimization and development. This Perspective provides an update on allosterically targeted class A GPCRs and their disease indications and the medicinal chemistry approaches toward novel allosteric modulators and highlights emerging trends and opportunities in the field.

Structure-based design of nucleoside-derived analogues as sulfotransferase inhibitors

Regulated sulfation of biomolecules by sulfotransferases (STs) plays a role in many biological processes with implications for a number of disease areas. A structure-based approach and molecular docking were used to design a library of ST inhibitors.

Identification of pyrazolopyrimidine arylsulfonamides as CC-chemokine receptor 4 (CCR4) antagonists

A novel 4-aminoindazole sulfonamide hit (13) was identified as a human CCR4 antagonists from testing a focussed library of compounds in the primary GTPγS assay. Replacing the indazole core with a pyrazolopyrimidine, and introduction of a methoxy group adjacent to the sulfonamide substituent, resulted in the identification of pyrazolopyrimidine 37a, which exhibited good binding affinity in the GTPγS assay (pIC₅₀=7.2), low lipophilicity (clogP=2.2, chromlogD_7.4=2.4), high LE (0.41), high solubility (CLND solubility ≥581µM), and an excellent PK profile in both the rat (F=62%) and the dog (F=100%). Further SAR investigation of the pyrazolopyrimidine suggested that substitution at N1 is tolerated, providing a suitable vector to modulate the properties, and increase the potency in a lead optimisation campaign.

Intramolecular Hydrogen Bond Expectations in Medicinal Chemistry

Design strategies centered on intramolecular hydrogen bonds are sometime used in drug discovery, but their general applicability has not been addressed beyond scattered examples or circumstantial evidence. A total of 1053 matched molecular pairs where only one of the two molecules is able to form an intramolecular hydrogen bond via monatomic transformations have been identified across the ChEMBL database. These pairs were used to investigate the effect of intramolecular hydrogen bonds on biological activity. While cases of extreme, conflicting variation of effect emerge, the mean biological activity difference for a pair is close to zero and does not exceed ±0.5 log biological activity for over 50% of the analyzed sample.

2,8-Diazaspiro[4.5]decan-8-yl)pyrimidin-4-amine potent CCR4 antagonists capable of inducing receptor endocytosis

A number of potent 2,8-diazaspiro[4.5]decan-8-yl)pyrimidin-4-amine CCR4 antagonists binding to the extracellular allosteric site were synthesised. (R)-N-(2,4-Dichlorobenzyl)-2-(2-(pyrrolidin-2-ylmethyl)-2,8-diazaspiro[4.5]decan-8-yl)pyrimidin-4-amine (R)-(18a) has high affinity in both the [(125)I]-TARC binding assay with a pKi of 8.8, and the [(35)S]-GTPγS functional assay with a pIC50 of 8.1, and high activity in the human whole blood actin polymerisation assay (pA2 = 6.7). The most potent antagonists were also investigated for their ability to induce endocytosis of CCR4 and were found to internalise about 60% of the cell surface receptors, a property which is not commonly shared by small molecule antagonists of chemokine receptors.