2,4-Diaminopyrimidines as dual ligands at the histamine H1 and H4 receptor-H1/H4-receptor selectivity

Discovery of CDC42 Inhibitors with a Favorable Pharmacokinetic Profile and Anticancer In Vivo Efficacy

We previously reported trisubstituted pyrimidine lead compounds, namely, ARN22089 and ARN25062, which block the interaction between CDC42 with its specific downstream effector, a PAK protein. This interaction is crucial for the progression of multiple tumor types. Such inhibitors showed anticancer efficacy in vivo. Here, we describe a second class of CDC42 inhibitors with favorable drug-like properties. Out of the 25 compounds here reported, compound 15 (ARN25499) stands out as the best lead compound with an improved pharmacokinetic profile, increased bioavailability, and efficacy in an in vivo PDX tumor mouse model. Our results indicate that these CDC42 inhibitors represent a promising chemical class toward the discovery of anticancer drugs, with ARN25499 as an additional lead candidate for preclinical development.

A Pd-Catalyzed Annulation Strategy to Linearly Fused Functionalized N-Heterocycles

Linearly fused polycyclic piperidines represent common substructures in natural products and biologically active small molecules. We have devised a Pd-catalyzed annulation strategy to these compounds that converts readily available 2-tetralones and indanones into these scaffolds with the potential for control of both enantio- and diastereoselectivity. Importantly, these compounds can be chemoselectively functionalized, providing an efficient and robust methodology to these important nitrogen-containing molecules.

Design, synthesis and biological evaluation of novel cyclic malonamide derivatives as selective RIPK1 inhibitors

Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) plays a key role in cell death and inflammation. RIPK1 is a well-established therapeutic target, due to the presence of a unique kinase-regulating allosteric pocket, which enables selective inhibition. Herein we used GSK2982772 as our starting point in our discovery campaign. Applying isosteric replacement, we successfully identified the malonamide scaffold, instead of the well-established serine template. Further structural optimization led to the design and synthesis of a series of analog inhibitors. The enantiomers of the most promising compound were tested on 97 different kinases. The active enantiomer proved to be kinase selective.

Molecular Modeling of Histamine Receptors-Recent Advances in Drug Discovery

The recent developments of fast reliable docking, virtual screening and other algorithms gave rise to discovery of many novel ligands of histamine receptors that could be used for treatment of allergic inflammatory disorders, central nervous system pathologies, pain, cancer and obesity. Furthermore, the pharmacological profiles of ligands clearly indicate that these receptors may be considered as targets not only for selective but also for multi-target drugs that could be used for treatment of complex disorders such as Alzheimer's disease. Therefore, analysis of protein-ligand recognition in the binding site of histamine receptors and also other molecular targets has become a valuable tool in drug design toolkit. This review covers the period 2014-2020 in the field of theoretical investigations of histamine receptors mostly based on molecular modeling as well as the experimental characterization of novel ligands of these receptors.

Light-Switchable Antagonists for the Histamine H1 Receptor at the Isolated Guinea Pig Ileum

The histamine H₁ G protein-coupled receptor (GPCR) plays an important role in allergy and inflammation. Existing drugs that address the H₁ receptor differ in their chemical structure, pharmacology, and side effects. Light-controllable spatial and temporal activity regulation of photochromic H₁ ligands may contribute to a better mechanistic understanding and the development of improved correlations between ligand structure and pharmacologic effects. We report photochromic H₁ receptor ligands, which were investigated in an organ-pharmacological assay. Initially, five photochromic azobenzene derivatives of reported dual H₁ -H₄ receptor antagonists were designed, synthesized, photochemically characterized, and organ-pharmacologically tested on the isolated guinea pig ileum. Among them, one compound [trans-19: (Z)-1-(4-chlorophenyl)-1-(4-methylpiperazin-1-yl)-N-(4-((E)-phenyldiazenyl)phenyl)methanimine] retained the antagonistic activity of its non-photochromic lead, and trans-cis isomerization by irradiation induced a fourfold difference in the pharmacological response. Further structural optimization resulted in two bathochromically shifted derivatives of 19 [NO₂ -substituted 35 {(Z)-1-(4-chlorophenyl)-1-(4-methylpiperazin-1-yl)-N-(4-((E)-(4-nitrophenyl)diazenyl)phenyl)methanimine} and SO₃ ^- -substituted 41 {4-((E)-(4-(((Z)-(4-chlorophenyl)(4-methylpiperazin-1-yl)methylene)amino)phenyl)diazenyl)benzenesulfonate}], which do not require the use of UV light for photoisomerization and which also have improved solubility and show reduced tissue impairment. The trans isomers of both compounds showed a remarkable increase in antagonistic activity relative to their lead trans-19; furthermore, a 46-fold difference in activity on the isolated guinea pig ileum was observed between trans- and cis-35.

Dual Inhibitors of PARPs and ROCKs

Recent network and system biology analyses suggest that most complex diseases are regulated by robust and highly interconnected pathways that could be better modulated by small molecules binding to multiple biological targets. These pieces of evidence recently led to devote efforts on identifying single chemical entities that bind to two different disease-relevant targets. Here, we first predicted in silico and later confirmed in vitro that UPF 1069, a known bioactive poly(ADP-ribose) polymerase-1/2 (PARP1/2) molecule, and hydroxyfasudil, a known bioactive Rho-associated protein kinase-1/2 (ROCK1/2) molecule, have low-micromolar cross-affinity for ROCK1/2 and PARP1/2, respectively. These molecules can now be regarded as chemical seeds from which pharmacological tools could be generated to study the impact of dual inhibition of PARPs and ROCKs in preclinical models of a variety of complex diseases where both targets are involved.

Substituent effects on stereoselectivity of dihalocarbene reactions with cyclohexadiene and on the reactivity of bis-dihalocyclopropanes in electrophilic nitrations en route to pyrimidine N-oxides

Tricyclic bis-adducts of cyclohexa-1,4-diene with bromofluorocarbene and non-symmetric adducts with both bromofluoro- and dichlorocarbenes were synthesised selectively. The treatment of the bis-adducts with nitrating reagents in acetonitrile affords the products of heterocyclization of a sole dihalogenocyclopropane into 4-fluoropyrimidine N-oxide. The difference in the reactivity of bis-cyclopropanes with different sets of halogen substituents leads to selective heterocyclization of bromofluorocyclopropanes without affecting the dichlorocyclopropane moiety.

Dibenzo[b,f][1,4]oxazepines and dibenzo[b,e]oxepines: Influence of the chlorine substitution pattern on the pharmacology at the H1R, H4R, 5-HT2AR and other selected GPCRs

Inspired by VUF6884 (7-Chloro-11-(4-methylpiperazin-1-yl)dibenzo[b,f][1,4]oxazepine), reported as a dual H₁/H₄ receptor ligand (pK_i: 8.11 (human H₁R (hH₁R)), 7.55 (human H₄R (hH₄R))), four known and 28 new oxazepine and related oxepine derivatives were synthesised and pharmacologically characterized at histamine receptors and selected aminergic GPCRs. In contrast to the oxazepine series, within the oxepine series, the new compounds showed high affinity to the hH₁R (pK_i: 6.8-8.7), but no or moderate affinity to the hH₄R (pK_i:≤5.3). For one oxepine derivative (1-(2-Chloro-6,11-dihydrodibenzo[b,e]oxepin-11-yl)-4-methylpiperazine), the enantiomers were separated and the R-enantiomer was identified as the eutomer at the hH₁R (pK_i: 8.83 (R), 7.63 (S)) and the guinea-pig H₁R (gpH₁R) (pK_i: 8.82 (R), 7.41 (S)). Molecular dynamic studies suggest that the tricyclic core of the compounds is bound in a similar mode into the binding pocket, as described for doxepine in the hH₁R crystal structure. Moreover, docking studies of all oxepine derivatives at the hH₁R indicate that the oxygen and the position of the chlorine in the tricyclic core determines, if the R- or the S-enantiomer is the eutomer. For some of the oxazepines and oxepines the affinity to other aminergic GPCRs is in the same range as to hH₁R or hH₄R, thus, those compounds have to be classified as dirty drugs. However, one oxazepine derivative (3,7-Dichloro-11-(4-methylpiperazin-1-yl)dibenzo[b,f][1,4]oxazepine was identified as dual hH₁/h5-HT_2A receptor ligand (pK_i: 9.23 (hH₁R), 8.74 (h5-HT_2AR), ≤7 at other analysed GPCRs), whereas one oxepine derivative (1-(3,8-Dichloro-6,11-dihydrodibenzo[b,e]oxepin-11-yl)-4-methylpiperazine) was identified as selective hH₁R antagonist (pK_i: 8.44 (hH₁R), ≤6.7 at other analyzed GPCRs). Thus, the pharmacological results suggest that the oxazepine/oxepine moiety and additionally the chlorine substitution pattern toggles receptor selectivity and specificity.