Comprehensive Review on Recent Strategies for Management of Prostate Cancer: Therapeutic Targets and SAR

Prostate cancer is a disease that is affecting a large population worldwide. Androgen deprivation therapy (ADT) has become a foundation for the treatment of advanced prostate cancer, as used in most clinical settings from neo-adjuvant to metastatic stage. In spite of the success of ADT in managing the disease in the majority of men, hormonal manipulation fails eventually. New molecules are developed for patients with various hormone-refractory diseases. Advancements in molecular oncology have increased understanding of numerous cellular mechanisms which control cell death in the prostate and these insights can lead to the development of more efficacious and tolerable therapies for carcinoma of the prostate. This review is focused on numerous therapies that might be a boon for prostate therapy like signaling inhibitors, vaccines, and inhibitors of androgen receptors. Along with these, various bioactive molecules and their derivatives are highlighted, which act as potential anti-prostate cancer agents. This article also emphasized the recent advances in the field of medicinal chemistry of prostate cancer agents.

Design, synthesis, and biological evaluation of N-arylpiperazine derivatives as interferon inducers

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We designed and synthesized a series of arylpiperazine derivatives as interferon inducers.

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We tested different linker system and carbonyl moiety resulted in increase of potency.

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5i exhibited the activity of interferon inducer with EC₅₀ of 13.1 μM and no cytotoxicity.

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5i initiated immune responses by mediating type I IFN signaling.

Type I Interferon (IFN) signaling plays an important role in the immune defense system against virus infection and in the innate immune response, thus IFNs are widely used as anti-viral agents and treatment for immune disorder or cancer. However, there is a growing demand for novel small-molecule IFN inducer due to tolerance, toxicity, or short duration of action following direct administration of IFNs. In this study, we assessed arylpiperazine (ARP) as a new core skeleton of IFN inducer. To investigate structure–activity relationship, we designed and synthesized a series of ARP analogues and evaluated the ability to stimulate IFN response in THP-1 human monocyte cells. Compound 5i was identified as a potent type I IFN inducer as it significantly increased cytokine secretion and increased expression of various IFN-stimulating genes which are representative biomarkers of type I IFN pathway. Our results suggested a beneficial therapeutic potential of 5i as an anti-viral agent.

The relationship between stereochemical and both, pharmacological and ADME-Tox, properties of the potent hydantoin 5-HT7R antagonist MF-8

This study concerns synthesis and evaluation of pharmacodynamic and pharmacokinetic profile for all four stereoisomers of MF-8 (5-(4-fluorophenyl)-3-(2-hydroxy-3-(4-(2-methoxyphenyl)piperazin-1-yl)propyl)-5-methylimidazolidine-2,4-dione), the previously described, highly potent 5-HT₇R ligand with antidepressant activity on mice. The combination of DFT calculations of ¹H NMR chemical shifts with docking and dynamic simulations, in comparison to experimental screening results, provided prediction of the configuration for one of two present stereogenic centers. The experimental data for stereoisomers (MF-8A-MF-8D) confirmed the significant impact of stereochemistry on both, 5-HT₇R affinity and antagonistic action, with K_i and K_b values in the range of 3-366 nM and 0.024-99 μM, respectively. We also indicated the stereochemistry-dependent influence of the tested compounds on P-glycoprotein efflux, absorption in Caco-2 model, metabolic pathway as well as CYP3A4 and CYP2C9 activities.

Privileged scaffold-based design to identify a novel drug-like 5-HT7 receptor-preferring agonist to target Fragile X syndrome

Recent preclinical studies have shown that activation of the serotonin 5-HT₇ receptor has the potential to treat neurodevelopmental disorders such as Fragile X syndrome, a rare disease characterized by autistic features. With the aim to provide the scientific community with diversified drug-like 5-HT₇ receptor-preferring agonists, we designed a set of new long-chain arylpiperazines by exploiting structural fragments present in clinically approved drugs or in preclinical candidates (privileged scaffolds). The new compounds were synthesized, tested for their affinity at 5-HT₇ and 5-HT_1A receptors, and screened for their in vitro stability to microsomal degradation and toxicity. Selected compounds were characterized as 5-HT₇ receptor-preferring ligands, endowed with high metabolic stability and low toxicity. Compound 7g emerged as a drug-like 5-HT₇ receptor-preferring agonist capable to rescue synaptic plasticity and attenuate stereotyped behavior in a mouse model of Fragile X syndrome.

Design, synthesis and biological evaluation of isochroman-4-one hybrids bearing piperazine moiety as antihypertensive agent candidates

7,8-Dihydroxy-3-methyl-isochromanone-4 (XJP), is a polyphenolic natural product with moderate antihypertensive activity. To obtain new agents with stronger potency and safer profile, we employed XJP and naftopidil as the lead compounds to design and synthesize a novel class of hybrids as antihypertensive agent candidates. In the present study, a series of hybrids (6a-r) of XJP bearing arylpiperazine moiety, which is identified as the pharmacophore of naftopidil, were designed and synthesized as novel α₁-adrenergic receptor antagonists. The biological evaluation showed that target compounds 6c, 6e, 6f, 6g, 6h, 6m and 6q possessed potent in vitro vasodilation potency and α₁-adrenergic receptor antagonistic activity. Furthermore, the most potent compound 6e significantly reduced the systolic and diastolic blood pressure in spontaneously hypertensive rats (SHRs), which was comparable to that of naftopidil, and it had no observable effects on the basal heart rate, suggesting that 6e deserves to be further investigated as a potential clinical candidate for the treatment of hypertension.

Molecular docking, dynamics simulations and 3D-QSAR modeling of arylpiperazine derivatives of 3,5-dioxo-(2H,4H)-1,2,4-triazine as 5-HT1AR agonists

Serotonin receptor, 5-HT_1AR, agonists and partial agonists have established drug candidates for psychiatric and neurologic disorders. Recently, we reported the synthesis and evaluation of arylpiperazine derivatives of 3,5-dioxo-(2H,4H)-1,2,4-triazine as 5-HT_1AR ligands. Herein, we generated a homology model of the receptor and docked the ligands against it, predicted the stability of the receptor model and complexes by molecular dynamics and generated a 3D-QSAR model for the arylpiperazine derivatives of 3,5-dioxo-(2H,4H)-1,2,4-triazine. The model suggests the hydrophobic part that arises from the aromatic region and the electron withdrawing parts play a vital role in the agonist activity of the lead molecules.

Pharmacophore Comparison and Development of Recently Discovered Long Chain Arylpiperazine and Sulfonamide Based 5-HT7 Ligands

The serotonin system exerts its effects on the CNS and many peripheral systems. Of the 14 serotonin receptors, the 5-HT7 receptor is the most recently discovered. The 5-HT7 receptor has been shown to be involved in stress reduction, depression, and nociceptive control. Despite the 20 years since the discovery of 5-HT7R, there are still few truly selective ligands. Two of the common scaffolds for 5-HT7R ligands are long chain arylpiperazines (LCAPs) and sulfonamide containing compounds. This review focuses on recently developed (2014-2016) 5-HT7R ligands, their selectivity for the receptor, and suggests the possible new pharmacophore models for these ligands.

Design, synthesis, crystal structure, biological evaluation and molecular docking studies of carbazole-arylpiperazine derivatives

Subtype-selective α₁-adrenoceptor (AR) antagonists display optimum therapeutic efficacies for the treatment of benign prostatic hyperplasia (BPH). In this study, we designed and synthesized novel carbazole-arylpiperazines derivatives (1 and 2) on the basis of the proposed pharmacophore model for α₁-AR antagonists. Structural properties were investigated using single-crystal X-ray diffraction analysis. Comparison of crystal structures with ligand-based pharmacophore models revealed that the two agents may possess antagonistic effects on α_1D subtype. Tissue functional assay in vitro showed that compound 2 exerted strong antagonistic activity on α_1B-AR (pA₂ 7.13) with a poor selectivity for α_1A and α_1D subtypes. Compound 1 exhibited enhanced antagonistic effect on α_1D subtype (pA₂ 7.06) and excellent selectivity for α_1D over α_1B (α_1D/α_1B ratio=79.4). To illustrate the relationship between antagonistic activity and chemical structure, molecular docking studies were performed using the homology models of α₁ receptors. Binding mechanism indicated that small hydrophobic substituents attached to the arylpiperazine moiety were essential for rational design of α_1D-selective antagonists.

Structural modifications of the serotonin 5-HT7 receptor agonist N-(4-cyanophenylmethyl)-4-(2-biphenyl)-1-piperazinehexanamide (LP-211) to improve in vitro microsomal stability: A case study

The 5-HT7 serotonin receptor is revealing a promising target for innovative therapeutic strategies of neurodevelopmental and neuropsychiatric disorders. Here, we report the synthesis of thirty long-chain arylpiperazine analogs of the selective and brain penetrant 5-HT7 receptor agonist LP-211 (1) designed to enhance stability towards microsomal oxidative metabolism. Commonly used medicinal chemistry strategies were used (i.e., reduction of overall lipophilicity, introduction of electron-withdrawing groups, blocking of potential vulnerable sites of metabolism), and in vitro microsomal stability was tested. The data showed that the adopted design strategy does not directly translate into improvements in stability. Instead, the metabolic stability of the compounds was related to the presence of specific substituents in well-defined regions of the molecule. The collected data allowed for the construction of a machine learning model that, in a given chemical space, is able to describe and quantitatively predict the metabolic stability of the compounds. The majority of the synthesized compounds maintained high affinity for 5-HT7 receptors and showed selectivity towards 5-HT6 and dopamine D2 receptors and different selectivity for 5-HT1A and α1 adrenergic receptors. Compound 50 showed 3-fold higher in vitro stability towards oxidative metabolism than 1 and was able to stimulate neurite outgrowth in neuronal primary cultures through the 5-HT7 receptor in a shorter time and at a lower concentration than the agonist 1. A preliminary disposition study in mice revealed that compound 50 was metabolically stable and was able to pass the blood-brain barrier, thus representing a new tool for studying the pharmacotherapeutic potential of 5-HT7 receptor in vivo.

Synthesis and evaluation of arylpiperazines derivatives of 3,5-dioxo-(2H,4H)-1,2,4-triazine as 5-HT1AR ligands

5-HT1AR agonist or partial agonists are established drug candidates for psychiatric and neurological disorders. We have reported the synthesis and evaluation of a series of high affinity 5-HT1AR partial agonist PET imaging agents with greater selectivity over α-1AR. The characteristic of these molecules are 3,5-dioxo-(2H,4H)-1,2,4-triazine skeleton tethered to an arylpiperazine unit through an alkyl side chain. The most potent 5-HT1AR agonistic properties were found to be associated with the molecules bearing C-4 alkyl group as the linker. Therefore development of 3,5-dioxo-(2H,4H)-1,2,4-triazine bearing arylpiperazine derivatives may provide high affinity selective 5-HT1AR ligands. Herein we describe the synthesis and evaluation of the binding properties of a series of arylpiperazine analogues of 3,5-dioxo-(2H,4H)-1,2,4-triazine.