The pyridazine heterocycle in molecular recognition and drug discovery

Novel Dual Acetyl- and Butyrylcholinesterase Inhibitors Based on the Pyridyl-Pyridazine Moiety for the Potential Treatment of Alzheimer's Disease

Background: Alzheimer's disease (AD) is characterized by cholinergic dysfunction, making the inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) critical for improving cholinergic neurotransmission. However, the development of effective dual inhibitors remains challenging. Objective: This study aims to synthesize and evaluate novel pyridazine-containing compounds as potential dual inhibitors of AChE and BuChE for AD treatment. Methods: Ten novel pyridazine-containing compounds were synthesized and characterized using IR, 1H NMR, and 13C NMR. The inhibitory activities against AChE and BuChE were assessed in vitro, and pharmacokinetic properties were explored through in silico ADME studies. Molecular dynamics simulations were performed for the most active compound. Results: Compound 5 was the most potent inhibitor, with IC50 values of 0.26 µM for AChE and 0.19 µM for BuChE, outperforming rivastigmine and tacrine, and showing competitive results with donepezil. Docking studies revealed a binding affinity of -10.21 kcal/mol to AChE and -13.84 kcal/mol to BuChE, with stable interactions confirmed by molecular dynamics simulations. In silico ADME studies identified favorable pharmacokinetic properties for compounds 5, 8, and 9, with Compound 5 showing the best activity. Conclusions: Compound 5 demonstrates strong potential as a dual cholinesterase inhibitor for Alzheimer's disease, supported by both in vitro and in silico analyses. These findings provide a basis for further optimization and development of these novel inhibitors.

Recent contributions of pyridazine as a privileged scaffold of anticancer agents in medicinal chemistry: An updated review

Pyridazine, as a privileged scaffold, has been extensively utilized in drug development due to its multiple biological activities. Especially around its distinctive anticancer property, a massive number of pyridazine-containing compounds have been synthesized and evaluated that target a diverse array of biological processes involved in cancer onset and progression. These include glutaminase 1 (GLS1) inhibitors, tropomyosin receptor kinase (TRK) inhibitors, and bromodomain containing protein (BRD) inhibitors, targeting aberrant tumor metabolism, cell signal transduction and epigenetic modifications, respectively. Pyridazine moieties functioned as either core frameworks or warheads in the above agents, exhibiting promising potential in cancer treatment. Therefore, the review aims to summarize the recent contributions of pyridazine derivatives as potent anticancer agents between 2020 and 2024, focusing mainly on their structure-activity relationships (SARs) and development strategies, with a view to show that the application of the pyridazine scaffold by different medicinal chemists provides new insights into the rational design of anticancer drugs.

Development of Brain Penetrant Pyridazine Pantothenate Kinase Activators

Conversion of pantothenate to phosphopantothenate in humans is the first dedicated step in the coenzyme A (CoA) biosynthesis pathway and is mediated by four isoforms of pantothenate kinase. These enzymes are allosterically regulated by acyl-CoA levels, which control the rate of CoA biosynthesis. Small molecule activators of the PANK enzymes that overcome feedback suppression increase CoA levels in cultured cells and animals and have shown great potential for the treatment of pantothenate kinase-associated neurodegeneration and propionic acidemias. In this study, we detail the further optimization of PANK pyridazine activators using structure-guided design and focus on the cellular CoA activation potential, metabolic stability, and solubility as the primary drivers of the structure-activity relationship. These studies led to the prioritization of three late-stage preclinical lead PANK modulators with improved pharmacokinetic profiles and the ability to substantially increase brain CoA levels. Compound 22 (BBP-671) eventually advanced into clinical testing for the treatment of PKAN and propionic acidemia.

Pyridazine-Promoted Construction of Vinylene-Linked Covalent Organic Frameworks with Exceptional Capability of Stepwise Water Harvesting

In this study, we successfully developed two novel vinylene-linked covalent organic frameworks (COFs) using 2-connected 3,6-dimethylpyridazine through Knoevenagel condensation. These COFs featured finely tailored micro-/nano-scale pore sizes, high surface areas and stable non-polar vinylene linkages. Finely resolved powder X-ray diffraction patterns demonstrated highly crystalline structures with a hexagonal lattice in the AA layer stacking. The resulting one-dimensional channels possess strong hydrogen-bond accepting sites arising from the decorated cis-azo/azine units with two pairs of fully exposed lone pair electrons, endowing the as-prepared COFs with exceptional water absorption properties. The g-DZPH-COF exhibited successive steep water uptake steps starting from low relative pressures (P/PSTA=0.1), with the remarkable water uptake capacity of 0.26 g/g at P/PSTA=0.2 (25 °C), which is the optimal value recorded among the reported COFs. Dynamic vapour sorption measurements revealed the fast kinetics of these COFs, even in the cluster formation process. Water uptake and release cycling tests demonstrated their outstanding hydrolytic stability, durability, and adsorption-desorption retention ability.

The role of the methoxy group in approved drugs

The methoxy substituent is prevalent in natural products and, consequently, is present in many natural product-derived drugs. It has also been installed in modern drug molecules with no remnant of natural product features because medicinal chemists have been taking advantage of the benefits that this small functional group can bestow on ligand-target binding, physicochemical properties, and ADME parameters. Herein, over 230 methoxy-containing small-molecule drugs, as well as several fluoromethoxy-containing drugs, are presented from the vantage point of the methoxy group. Biochemical mechanisms of action, medicinal chemistry SAR studies, and numerous X-ray cocrystal structures are analyzed to identify the precise role of the methoxy group for many of the drugs and drug classes. Although the methoxy substituent can be considered as the hybridization of a hydroxy and a methyl group, the combination of these functionalities often results in unique effects that can amount to more than the sum of the individual parts.

The effect of novel aromatic heterocycle substituted aminamidine derivatives on Necator americanus

BACKGROUND

The efficacy of current drugs against hookworms at a single dose is highly variable across regions, age groups and infection intensity. Extensive and repeated use of these drugs also leads to potential drug resistance. Therefore, novel drugs are required for sustained disease control.

OBJECTIVES

Novel aromatic heterocycle substituted aminamidine derivatives (AADs) were synthesized based on tribendimine (TBD), and their in vivo potency against Necator americanus was tested.

METHODS

The efficacy of the AADs was tested in male hamsters. Oral and IV pharmacokinetic parameters were determined in male Sprague-Dawley rats. The proteomic profiles of N. americanus samples treated with AADs were compared using tandem mass tag-based quantitative proteomic analyses.

RESULTS

Most AADs exhibited better anthelmintic activity than TBD at a single oral dose. Compound 3c exhibited improved solubility (>50×), and the curative dose was as low as 25 mg/kg. Similar to TBD, 3c was rapidly metabolized after oral administration and transformed into p-(1-dimethylamino ethylimino)aniline (dADT), an active metabolite against intestinal nematodes. dADT from 3c had better pharmacokinetic profiles than that from TBD and achieved an oral bioavailability of 99.5%. Compound 3c possessed rapid anthelmintic activity, clearing all worms within 24 h after an oral dose of 50 mg/kg. Quantitative proteomic analysis indicated that it might be related to ATP metabolism and cuticle protein synthesis.

CONCLUSIONS

Compound 3c is a novel and promising compound against N. americanus in vivo.

Triazoles in Medicinal Chemistry: Physicochemical Properties, Bioisosterism, and Application

Triazole demonstrates distinctive physicochemical properties, characterized by weak basicity, various dipole moments, and significant dual hydrogen bond acceptor and donor capabilities. These features are poised to play a pivotal role in drug-target interactions. The inherent polarity of triazole contributes to its lower logP, suggesting the potential improvement in water solubility. The metabolic stability of triazole adds additional value to drug discovery. Moreover, the metal-binding capacity of the nitrogen atom lone pair electrons of triazole has broad applications in the development of metal chelators and antifungal agents. This Perspective aims to underscore the unique physicochemical attributes of triazole and its application. A comparative analysis involving triazole isomers and other heterocycles provides guiding insights for the subsequent design of triazoles, with the hope of offering valuable considerations for designing other heterocycles in medicinal chemistry.

Visualization of Modified Bisarylbutadiyne-Tagged Small Molecules in Live-Cell Nuclei by Stimulated Raman Scattering Microscopy

Visualizing the distribution of small-molecule drugs in living cells is an important strategy for developing specific, effective, and minimally toxic drugs. As an alternative to fluorescence imaging using bulky fluorophores or cell fixation, stimulated Raman scattering (SRS) imaging combined with bisarylbutadiyne (BADY) tagging enables the observation of small molecules closer to their native intracellular state. However, there is evidence that the physicochemical properties of BADY-tagged analogues of small-molecule drugs differ significantly from those of their parent drugs, potentially affecting their intracellular distribution. Herein, we developed a modified BADY to reduce deviations in physicochemical properties (in particular, lipophilicity and membrane permeability) between tagged and parent drugs, while maintaining high Raman activity in live-cell SRS imaging. We highlight the practical application of this approach by revealing the nuclear distribution of a modified BADY-tagged analogue of JQ1, a bromodomain and extra-terminal motif inhibitor with applications in targeted cancer therapy, in living HeLa cells. The modified BADY, methoxypyridazyl pyrimidyl butadiyne (MPDY), revealed intranuclear JQ1, while BADY-tagged JQ1 did not show a clear nuclear signal. We anticipate that the present approach combining MPDY tagging with live-cell SRS imaging provides important insight into the behavior of intracellular drugs and represents a promising avenue for improving drug development.

Stereoselective Amine Synthesis Mediated by a Zirconocene Hydride to Accelerate a Drug Discovery Program

Chiral amine synthesis remains a significant challenge in accelerating the design cycle of drug discovery programs. A zirconium hydride, due to its high oxophilicity and lower reactivity, gave highly chemo- and stereoselective reductions of sulfinyl ketimines. The development of this zirconocene-mediated reduction helped to accelerate our drug discovery efforts and is applicable to several motifs commonly used in medicinal chemistry. Computational investigation supported a cyclic half-chair transition state to rationalize the high selectivity in benzyl systems.

The progress of small molecules against cannabinoid 2 receptor (CB2R)

The two subtypes of cannabinoid receptors (CBR), namely CB1R and CB2R, belong to the G protein-coupled receptor (GPCR) superfamily and are confirmed as potential therapeutic targets for a variety of diseases such as inflammation, neuropathic pain, and immune-related disorders. Since CB1R is mainly distributed in the central nervous system (CNS), it could produce severe psychiatric adverse reactions and addiction. In contrast, CB2R are predominantly distributed in the peripheral immune system with minimal CNS-related side effects. Therefore, more attention has been devoted to the discovery of CB2R ligands. In view of the favorable profile of CB2R, many high-binding affinity and selectivity CB2R ligands have been developed recently. This paper reviews recent research progress on CB2R ligands, including endogenous CB2R ligands, natural compounds, and novel small molecules, in order to provide a reference for subsequent CB2R ligand development.

Exploring Three Avenues: Chemo- and Regioselective Transformations of 1,2,4-Triketone Analogs into Pyrazoles and Pyridazinones

A convenient approach to substituted pyrazoles and pyridazinones based on 1,2,4-triketones is presented. Chemo- and regiocontrol in condensations of t-Bu, Ph-, 2-thienyl-, and CO2Et-substituted 1,2,4-triketone analogs with hydrazines are described. The direction of preferential nucleophilic attack was shown to be switched depending on the substituent nature in triketone as well as the reaction conditions. The acid and temperature effects on the selectivity of condensations were revealed. Regiochemistry of heterocyclic core formation was confirmed by NMR and XRD studies. The facile construction of heterocyclic motifs bearing acetyl and (or) carbethoxy groups suggests them as promising mono- or bifunctional building blocks for subsequent transformations.