Synthesis and Biological Evaluation of a Novel Series of Heterobivalent Muscarinic Ligands Based on Xanomeline and 1‑[3-(4-Butylpiperidin-1-yl)propyl]-1,2,3,4-tetrahydroquinolin-2-one (77-LH-28-1)

Novel bitopic hybrids, based on the M₁/M₄ muscarinic acetylcholine receptor (mAChR) orthosteric agonist xanomeline (<b>1</b>) and the putative M₁ mAChR allosteric agonist 1-[3-(4-butylpiperidin-1-yl)­propyl]-1,2,3,4-tetrahydroquinolin-2-one (77-LH-28-1, <b>3</b>) connected by an aliphatic linker of variable length, were prepared. The novel heterobivalent hybrids <b>4a</b>–<b>f</b> along with the intermediate alcohols <b>5a</b>–<b>f</b> were pharmacologically evaluated in radioligand binding assays and some of them for their functional efficacies in bioluminescence resonance energy transfer (BRET)-based assays to give an insight into the structure–activity relationships of bivalent and linker-attached compounds in mAChRs. The hybrid <b>4d</b> exhibited high efficacy for β-arrestin2 engagement in M₁ mAChR and alcohol <b>5c</b> behaved much like <b>3</b> at M₁ mAChR and showed full antagonism in both G_i activation and β-arrestin2 engagement at M₄ mAChR. Moreover, docking simulations on the M₁ mAChR model were performed to elucidate how the binding mode of the proposed compounds is influenced by the linker length

1,4-Dioxane, a Suitable Scaffold for the Development of Novel M₃ Muscarinic Receptor Antagonists

In this study the modulation of the pharmacological profile from agonist to antagonist was successfully obtained by replacing the methyl group in position 6 of the 1,4-dioxane scaffold of the potent M₂/M₃ muscarinic agonist <b>1</b> with bulkier groups. In particular, the 6,6-diphenyl substitution provided the potent M₃ preferring antagonist (±)-<b>17</b>, which in in vivo study proved to be effective in reducing the volume-induced contractions of rat urinary bladder and was devoid of cardiovascular effects

Structure–Activity Relationships in 1,4-Benzodioxan-Related Compounds. 11. Reversed Enantioselectivity of 1,4-Dioxane Derivatives in α₁‑Adrenergic and 5‑HT_1A Receptor Binding Sites Recognition

5-HT_1A receptor and α₁-adrenoreceptor (α₁-AR) binding sites recognized by the 1,4-dioxanes <b>2</b>–<b>4</b> display reversed stereochemical requirements. (<i>S</i>)-<b>2</b> proved to be a potent 5-HT_1A receptor agonist highly selective over α₁-AR subtypes. Chirality influenced the anticancer activity of <b>3</b> and <b>4</b> in human prostate cancer cells (PC-3): (<i>R</i>)-<b>4</b>, eutomer at the α_1d-AR subtype, was the most potent. The decreased effect of <b>4</b> and (<i>R</i>)-<b>4</b> in α_1d-AR silenced PC-3 cells confirmed that their anticancer activity was α_1d-AR-dependent

Low Doses of Allyphenyline and Cyclomethyline, Effective against Morphine Dependence, Elicit an Antidepressant-like Effect

This study demonstrated that cyclomethyline (<b>2</b>) and the corresponding enantiomers (<i>R</i>)-(−)-<b>2</b> and (<i>S</i>)-(+)-<b>2</b>, displaying α_2C-adrenoreceptor (AR) agonism/α_2A-AR antagonism, similarly to allyphenyline (<b>1</b>) and its enantiomers, significantly decreased the naloxone-precipitated withdrawal symptoms in mice at very low doses. It also highlighted that such positive effects on morphine dependence can even be improved by additional serotoninergic 5-HT_1A receptor (5-HT_1A-R) activation. Indeed, <b>1</b> or the single (<i>S</i>)-(+)-<b>1</b>, <b>2</b>, or both its enantiomers, all behaving as α_2C-AR agonists/α_2A-AR antagonists/5-HT_1A-R agonists, alone and at the same low dose, improved morphine withdrawal syndrome and exerted a potent antidepressant-like effect. Therefore, considering the elevated comorbidity between opiate abuse and depressed mood and the benefit of these multifunctional compounds to both disorders, it is possible that they prove more efficacious and less toxic than a cocktail of drugs in managing opioid addiction

1‑[3-(4-Butylpiperidin-1-yl)propyl]-1,2,3,4-tetrahydroquinolin-2-one (77-LH-28-1) as a Model for the Rational Design of a Novel Class of Brain Penetrant Ligands with High Affinity and Selectivity for Dopamine D₄ Receptor

In the present article, the M₁ mAChR bitopic agonist 1-[3-(4-butylpiperidin-1-yl)­propyl]-1,2,3,4-tetrahydroquinolin-2-one (77-LH-28-1, <b>1</b>) has been demonstrated to show unexpected D₄R selectivity over D₂R and D₃R and to behave as a D₄R antagonist. To better understand the structural features required for the selective interaction with the D₄R and to obtain compounds unable to activate mAChRs, the aliphatic butyl chain and the piperidine nucleus of <b>1</b> were modified, affording compounds <b>2</b>–<b>14</b>. The 4-benzylpiperidine <b>9</b> and the 4-phenylpiperazine <b>12</b> showed high D₄R affinity and selectivity not only over the other D₂-like subtypes, but also over M₁–M₅ mAChRs. Derivative <b>12</b> was also highly selective over some selected off-targets. This compound showed biased behavior, potently and partially activating G_i protein and inhibiting β-arrestin2 recruitment in functional studies. Pharmacokinetic studies demonstrated that it was characterized by a relevant brain penetration. Therefore, <b>12</b> might be a useful tool to better clarify the role played by D₄R in disorders in which this subtype is involved

Exploring Multitarget Interactions to Reduce Opiate Withdrawal Syndrome and Psychiatric Comorbidity

Opioid addiction is often characterized as a chronic relapsing condition due to the severe somatic and behavioral signs, associated with depressive disorders, triggered by opiate withdrawal. Since prolonged abstinence remains a major challenge, our interest has been addressed to such objective. Exploring multitarget interactions, the present investigation suggests that <b>3</b> or its (<i>S</i>)-enantiomer and <b>4</b>, endowed with effective α_2C-AR agonism/α_2A-AR antagonism/5-HT_1A-R agonism, or <b>7</b> and <b>9</b>–<b>11</b> producing efficacious α_2C-AR agonism/α_2A-AR antagonism/I₂–IBS interaction might represent novel multifunctional tools potentially useful for reducing withdrawal syndrome and associated depression. Such agents, lacking in sedative side effects due to their α_2A-AR antagonism, might afford an improvement over current therapies with clonidine-like drugs

Novel Potent <i>N</i>‑Methyl‑d‑aspartate (NMDA) Receptor Antagonists or σ₁ Receptor Ligands Based on Properly Substituted 1,4-Dioxane Ring

Two series of 1,4-dioxanes (<b>4</b>–<b>11</b> and <b>12</b>–<b>19</b>) were rationally designed and prepared to interact either with the phencyclidine (PCP) binding site of the <i>N</i>-methyl-d-aspartate (NMDA) receptor or with σ₁ receptors, respectively. The biological profiles of the novel compounds were assessed using radioligand binding assays, and the compounds with the highest affinities were investigated for their functional activity. The results were in line with the available pharmacophore models and highlighted that the 1,4-dioxane scaffold is compatible with potent antagonist activity at NMDA receptor or high affinity for σ₁ receptors. The primary amines <b>6b</b> and <b>7</b> bearing a cyclohexyl and a phenyl ring or two phenyl rings in position 6, respectively, were the most potent noncompetitive antagonists at the NMDA receptor with IC₅₀ values similar to those of the dissociative anesthetic (<i>S</i>)-(+)-ketamine. The 5,5-diphenyl substitution associated with a benzylaminomethyl moiety in position 2, as in <b>18</b>, favored the interaction with σ₁ receptors

Combined Interactions with I₁‑, I₂‑Imidazoline Binding Sites and α₂‑Adrenoceptors To Manage Opioid Addiction

Tolerance and dependence associated with chronic opioid exposure result from molecular, cellular, and neural network adaptations. Such adaptations concern opioid and nonopioid systems, including α₂-adrenoceptors (α₂-ARs) and I₁- and I₂-imidazoline binding sites (IBS). Agmatine, one of the hypothesized endogenous ligands of IBS, targeting several systems including α₂-ARs and IBS, proved to be able to regulate opioid-induced analgesia and to attenuate the development of tolerance and dependence. Interested in the complex pharmacological profile of agmatine and considering the nature of its targets, we evaluated two series of imidazolines, rationally designed to simultaneously interact with I₁-/I₂-IBS or I₁-/I₂-IBS/α₂-ARs. The compounds showing the highest affinities for I₁-/I₂-IBS or I₁-/I₂-IBS/α₂-ARs have been selected for their <i>in vivo</i> evaluation on opiate withdrawal syndrome. Interestingly, <b>9</b>, displaying I₁-/I₂-IBS/α₂-ARs interaction profile, appears more effective in reducing expression and acquisition of morphine dependence and, therefore, might be considered a promising tool in managing opioid addiction

Antagonism/Agonism Modulation to Build Novel Antihypertensives Selectively Triggering I₁‑Imidazoline Receptor Activation

Pharmacological studies have suggested that I₁-imidazoline receptors are involved in the regulation of cardiovascular function and that selective I₁-agonists, devoid of the side effects associated with the common hypotensive α₂-adrenoreceptor agonists, might be considered as a second generation of centrally acting antihypertensives. Therefore, in the present study, inspired by the antihypertensive behavior of our selective I₁-agonist <b>4</b>, we designed, prepared, and studied the novel analogues <b>5</b>–<b>9</b>. A selective I₁-profile, associated with significant hemodinamic effects, was displayed by <b>5</b>, <b>8</b>, and <b>9</b>. Interestingly, the highest potency and longest lasting activity displayed by <b>8</b> (carbomethyline) suggested that van der Waals interactions, promoted by the ortho methyl decoration of its aromatic moiety, are particularly advantageous. In addition, in analogy to what was noted for (<i>S</i>)-(+)-<b>4</b>, the observation that only (<i>S</i>)-(+)-<b>8</b> displayed significant hemodynamic effects unequivocally confirmed the stereospecific nature of the I₁ proteins