Synthesis and structure-activity relationships of novel arylpiperazines as potent antagonists of α1-adrenoceptor

The Therapeutic Potential of 2-{[4-(2-methoxyphenyl)piperazin-1-yl]alkyl}-1H-benzo[d]imidazoles as Ligands for Alpha1-Adrenergic Receptor - Comparative In Silico and In Vitro Study

Adrenergic receptors are among the most studied G protein-coupled receptors. Activation or blockade of these receptors is a major therapeutic approach for the treatment of numerous disorders such as cardiac hypertrophy, congestive heart failure, hypertension, angina pectoris, cardiac arrhythmias, depression, benign prostate hyperplasia, anaphylaxis, asthma, and hyperthyroidism. Among all nine cloned adrenoceptor subtypes and the subsequent development of animal models, a significant target for various neurological conditions treatment is alpha1-adrenergic receptors. 2-{[4-(2-Methoxyphenyl)piperazin-1-yl]alkyl}-1H-benzo[d]imidazoles, their 5 substituted derivatives, and structurally similar, arylpiperazine based alpha1-adrenergic receptors antagonists (trazodone, naftopidil, and urapidil) have been subjects of comparative analysis. Most of the novel compounds showed alpha1-adrenergic affinity in the range from 22 nM to 250 nM. The in silico docking and molecular dynamics simulations, binding data together with absorption, distribution, metabolism, and excretion (ADME) calculations identified the promising lead compounds. The results brought out the conclusions which allowed us to propose a rationale for the activity of these molecules and to highlight six compounds (2-5, 8, and 12) that exhibited an acceptable pharmacokinetic profile to the advanced investigation as the potential alpha1-adrenergic receptor antagonists.

The affinity and selectivity of α-adrenoceptor antagonists, antidepressants, and antipsychotics for the human α1A, α1B, and α1D-adrenoceptors

α1-adrenoceptor antagonists are widely used for hypertension (eg, doxazosin) and benign prostatic hypertrophy (BPH, eg, tamsulosin). Some antidepressants and antipsychotics have been reported to have α1 affinity. This study examined 101 clinical drugs and laboratory compounds to build a comprehensive understanding of α1-adrenoceptor subtype affinity and selectivity. [3H]prazosin whole-cell binding was conducted in CHO cells stably expressing either the full-length human α1A, α1B, or α1D-adrenoceptor. As expected, doxazosin was a high-affinity nonselective α1-antagonist although other compounds (eg, cyclazosin, 3-MPPI, and ARC239) had higher affinities. Several highly α1A-selective antagonists were confirmed (SNAP5089 had over 1700-fold α1A selectivity). Despite all compounds demonstrating α1 affinity, only BMY7378 had α1D selectivity and no α1B-selective compounds were identified. Phenoxybenzamine (used in pheochromocytoma) and dibenamine had two-component-binding inhibition curves at all three receptors. Incubation with sodium thiosulfate abolished the high-affinity component suggesting this part is receptor mediated. Drugs used for hypertension and BPH had very similar α1A/α1B/α1D-adrenoceptor pharmacological profiles. Selective serotonin reuptake inhibitors (antidepressants) had poor α1-adrenoceptor affinity. Several tricyclic antidepressants (eg, amitriptyline) and antipsychotics (eg, chlorpromazine and risperidone) had high α1-adrenoceptor affinities, similar to, or higher than, α blockers prescribed for hypertension and BPH, whereas others had poor α1 affinity (eg, protriptyline, sulpiride, amisulpiride, and olanzapine). The addition of α blockers for the management of hypertension or BPH in people already taking tricyclic antidepressants and certain antipsychotics may not be beneficial. Awareness of the α-blocking potential of different antipsychotics may affect the choice of drug for those with delirium where additional hypotension (eg, in sepsis) may be detrimental.