Discovery of WLB-89462, a New Drug-like and Highly Selective σ2 Receptor Ligand with Neuroprotective Properties

Recent Advances in the Development of Sigma Receptor (Radio)Ligands and Their Application in Tumors

Cancer ranks among the top triumvirate leading causes of human deaths worldwide. The pathological mechanisms are notably intricate, demonstrating proliferative and metastatic capabilities, which complicate therapeutic interventions. The sigma-1 receptor (σ1R) plays a crucial role in tumor survival and migration, while the sigma-2 receptor (σ2R) is intimately associated with tumor proliferation. This review encapsulated the investigation concerning σ1R and σ2R in neoplasms and rigorously summarized the ligands and radio-ligands development and their tumor applications, such as antitumor cell proliferation and PET/SPECT imaging in tumors. A comprehensive classification discussion was undertaken regarding the chemical structures and emphasized the possibility of dual/multitargeted ligands. Ultimately, we discussed the effects of chiral structures and the pharmacological characteristics of ligands on affinity and pharmacokinetic features in vivo, particularly concerning radiopharmaceuticals. This review functions as a beneficial resource, fostering ligand deployment and stimulating the generation of innovative ideas for developing innovative radiopharmaceuticals.

Synthesis of Azirinyl Ethynyl Ketones and Their Use in the Preparation C(O)C≡CR-Substituted NH-Pyrroles/NH-Imidazoles and Azole-Azine/Azole-Azole Heterocyclic Hybrids

Azirinyl-substituted conjugated ynones were first synthesized by the reaction of lithiated acetylenes with 2H-azirine-2-carbonyl chlorides. Azirinyl ethynyl ketones containing only a C(O)C≡CR substituent at position 2 of the azirine ring are good precursors for obtaining α-C(O)C≡CR substituted NH-pyrroles and 5-[C(O)C≡CR]-substituted NH-imidazoles, reacting selectively only at the azirine moiety with 1,3-diketones and arylamidines, respectively. Various N-heterocyclic hybrids (pyrrole-pyrimidine, imidazole-pyrimidine, pyrrole-isoxazole, imidazole-isoxazole, pyrimidine-pyrrole-thiophene, pyrrole-pyrimidine-thiophene, imidazole-pyrimidine-thiophene, isoxazole-pyrrole-thiophene) have been prepared based on orthogonal or domino reactions of an azirine and C(O)C≡CR moieties of azirinyl ethynyl ketones.

Compound (E)-2-(3,4-dihydroxystyryl)-3-hydroxy-4H-pyran-4-one downregulation of Galectin-3 ameliorates Aβ pathogenesis-induced neuroinflammation in 5 × FAD mice

AIMS

Alzheimer's disease (AD) is characterized by β-amyloid (Aβ) aggregation and neuroinflammation, leading to progressive synaptic loss and cognitive decline. Recent evidence suggests that Galectin-3 (Gal-3) plays a critical role in Aβ pathogenesis. However, strategies to simultaneously target Gal-3 and Aβ are currently insufficient. This study evaluates the therapeutic efficacy of (E)-2-(3,4-dihydroxystyryl)-3-hydroxy-4H-pyran-4-one (D30), in reducing Gal-3 and Aβ pathogenesis.

MATERIALS AND METHODS

We applied exogenous oligomeric Aβ and used 5 × FAD mice to assess the impact of Aβ on Gal-3 deposition, microglial activation, and cognitive function. Thy1-EGFP mice were employed to observe dendritic spines. Comprehensive evaluations of D30's effects included behavioral studies, transcriptomic analysis, Western blotting, and immunofluorescent staining. The interaction between D30 and Gal-3 was examined using fluorescence resonance energy transfer (FRET) and microscale thermophoresis (MST).

KEY FINDINGS

D30 effectively reduced Aβ monomer production by inhibiting Amyloid Precursor Protein (APP) and presenilin 1 (PS1) expression, and decreased Aβ aggregation. Treatment with D30 improved cognitive functions, reversed dendritic spine loss, and increased PSD95 expression in 5 × FAD mice. Additionally, D30 significantly lowered Gal-3 levels in both plasma and hippocampal tissues. D30 binds to Gal-3 and disrupts the interaction between Gal-3 and TREM2, as confirmed by FRET and MST.

SIGNIFICANCE

Our findings underscore the interaction between Gal-3 and Aβ in AD and its role in systemic inflammation using the 5 × FAD mouse model. Being able to target and regulate Gal-3 together with Aβ is crucial for preventing neuroinflammation and protecting synapses, D30 emerged as a novel compound with promising potential for AD treatment.

WLB-87848, a Selective σ1 Receptor Agonist, with an Unusually Positioned NH Group as Positive Ionizable Moiety and Showing Neuroprotective Activity

The synthesis and pharmacological activity of a new series of thieno[2,3-d]pyrimidin-4(3H)-one derivatives as sigma-1 receptor (σ1R) ligands are reported. A hit from a high-throughput screening program was evolved into a highly potent and selective σ1R agonist (14qR) that contains a free NH group as positive ionizable moiety, not fulfilling the usual pharmacophoric features of the σ1R. The compound shows good physicochemical and ADMET characteristics, displays an agonist profile in the binding immunoglobulin protein/σ1R association assay, induces neuron viability in an in vitro model of β-amyloid peptide intoxication, and presents positive results against recognition memory impairment induced by hippocampal injection of Aβ peptide in rats after oral treatment, altogether making 14qR (WLB-87848) an interesting candidate for neuroprotection.

Structure-Affinity relationships of novel σ2R/TMEM97 ligands

The sigma 2 receptor (σ2R), which was recently identified as the transmembrane protein 97 (TMEM97), is increasingly attracting interest as a possible therapeutic target for indications in neuroscience. Toward identifying novel modulators of σ2R/TMEM97, we prepared a collection of benzoxazocine, benzomorphan, and methanobenzazepine ligands related to the known bioactive norbenzomorphans DKR-1677, FEM-1689, and EES-1686 and determined their Ki values for σ2R/TMEM97 and the sigma 1 receptor (σ1R). The σ2R/TMEM97 binding affinities and selectivities relative to σ1R of these new benzoxazocine, benzomorphan, and methanobenzazepine analogs are lower, often significantly lower, than their respective norbenzomorphan counterparts, suggesting the spatial orientation of pharmacophoric substituents is critical for binding to the two proteins. The benzoxazocine, benzomorphan, and methanobenzazepine congeners of DKR-1677 and FEM-1689 tend to be weakly selective for σ2R/TMEM97 versus σ1R, whereas EES-1686 derivatives exhibit the greatest selectivity, suggesting the size and/or nature of the substituent on the nitrogen atom of the scaffold may be important for selectivity. Computational docking studies were performed for the 1S,5R-and 1R,5S-enantiomers of DKR-1677, FEM-1689, and EES-1686 and their benzoxazocine, benzomorphan, and methanobenzazepine counterparts. These computations predict that the protonated amino group of each ligand forms a highly conserved salt bridge and a H-bonding interaction with Asp29 as well as a cation-π interaction with Tyr150 of σ2R/TMEM97. These electrostatic interactions are major driving forces for binding to σ2R/TMEM97 and are similar, though not identical, for each ligand. Other interactions within the well-defined binding pocket also tend to be comparable, but there are some major differences in how the hydrophobic aryl groups of various ligands interact with the protein surface external to the binding pocket. Overall, these studies show that the orientations of aryl and N-substituents on the norbenzomorphan and related scaffolds are important determinants of binding affinity of σ2R/TMEM97 ligands, and small changes can have significant effects upon binding profiles.